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WO2018081340A1 - Émetteur-récepteur optique ayant un module d'alignement - Google Patents

Émetteur-récepteur optique ayant un module d'alignement Download PDF

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Publication number
WO2018081340A1
WO2018081340A1 PCT/US2017/058402 US2017058402W WO2018081340A1 WO 2018081340 A1 WO2018081340 A1 WO 2018081340A1 US 2017058402 W US2017058402 W US 2017058402W WO 2018081340 A1 WO2018081340 A1 WO 2018081340A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical
alignment
recited
waveguide
holder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2017/058402
Other languages
English (en)
Inventor
Marc Epitaux
Eric Zbinden
John L. Nightingale
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Samtec Inc
Original Assignee
Samtec Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Samtec Inc filed Critical Samtec Inc
Publication of WO2018081340A1 publication Critical patent/WO2018081340A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
    • G02B6/4228—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements
    • G02B6/423—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements using guiding surfaces for the alignment
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4249—Packages, e.g. shape, construction, internal or external details comprising arrays of active devices and fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
    • G02B6/3648—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures
    • G02B6/3652—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures the additional structures being prepositioning mounting areas, allowing only movement in one dimension, e.g. grooves, trenches or vias in the microbench surface, i.e. self aligning supporting carriers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
    • G02B6/3684—Mechanical coupling means for mounting fibres to supporting carriers characterised by the manufacturing process of surface profiling of the supporting carrier
    • G02B6/3692—Mechanical coupling means for mounting fibres to supporting carriers characterised by the manufacturing process of surface profiling of the supporting carrier with surface micromachining involving etching, e.g. wet or dry etching steps
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4246—Bidirectionally operating package structures

Definitions

  • Photonic integrated circuits provide for high bandwidth data transfer rates and transmission distances associated with modem communication systems. While photonic integrated circuits can generate and manipulate the data stream, the optically transmitted data is generally first coupled into optical fibers for transmission between various nodes of the communication network. Since photonic integrated circuits can more easily manipulate single mode light than multimode light, it is generally desirable to couple light to and from a photonic integrated circuit with single mode optical fiber. For the typically used transmission wavelengths in the 1200 to 1600 nm wavelength range, optical fibers typically have a mode field diameter of approximately 9 microns. PIC single mode w aveguides tend to have a smaller and asymmetric mode field size, such as approximately 0.3 x 0.4 microns.
  • optical fiber cores are suitably aligned with the photonic integrated circuit waveguides in order to efficiently couple light between the optical fibers and the photonic integrated circuit waveguides. Additionally, the optical coupling between the PIC waveguides and the optical fiber core must accommodate the different mode field size, so there is not a large optical loss due to the mismatch in the mode sizes.
  • an optical engine can include a photonic integrated circuit that is configured to be supported by a substrate, the photonic integrated circuit carrying first alignment indicator.
  • Tire optical engine can further include an alignment module having an alignment channel configured to receive an optical waveguide, the alignment module carrying second alignment indicator configured to be aligned with the first alignment indicator, w herein when the first and second alignment indicators are aligned with each other and the alignment channel receives the optical waveguide, the optical waveguide is butt coupled to the photonic integrated circuit in optical alignment with a corresponding waveguide of the photonic integrated circuit.
  • FIG. 1 is a perspective view of an optical transceiver constructed in accordance with one example of the present disclosure, including a transmitter and a receiver mounted onto a substrate;
  • FIG. 2 is an exploded perspective view of the optical transceiver illustrated in
  • FIG. 3 is another exploded perspective view of the optical transceiver illustrated in Fig. 2, showing optical fibers mounted to a fiber holder, and further showing an alignment module mounted to a photonic integrated circuit;
  • Fig. 4 is a perspective view of the fiber holder illustrated in Fig. 3;
  • Fig. 5 is a perspective view of a photonic integrated circuit aligned to be attached to an alignment module illustrated in Fig. 3;
  • Fig. 6 is an enlarged perspective view of the alignment module illustrated in Fig.
  • Fig. 7A is a schematic end elevation view showing a plurality of optical fibers seated in the alignment module in accordance with one embodiment:
  • Fig. 7B is a schematic end elevation view showing an optical fiber seated in the waveguide holder and the alignment module in accordance with another embodiment
  • Fig. 7C is a schematic end elevation view showing an optical fiber seated in the alignment module in accordance with another embodiment
  • Fig. 7D is a schematic end elevation view showing an optical fiber seated in the alignment module in accordance with another embodiment
  • Fig. 7E is a schematic end elevation view showing an optical fiber seated in the alignment module in accordance with another embodiment
  • Fig, 7F is a schematic side view, showing an optical fiber seated in the alignment module in accordance with another embodiment
  • Fig. 7G is a schematic end elevation view showing a plurality of optical fibers seated in the waveguide holder and the waveguide holder registered against the alignment module in accordance with one embodiment
  • FIG. 8 is a perspective view of the photonic integrated circuit of the transmitter illustrated in Fig. 2;
  • Fig, 9A is a schematic side elevation view of a portion of the transmitter illustrated in Fig. 1;
  • Fig. 9B is a schematic side elevation view of a portion of the receiver illustrated in Fig, 1;
  • Fig. 10 is a side view of a carrier configured to support at least one of the transmitter and the receiver illustrated in Fig. 1, the carrier shown in accordance with one embodiment;
  • Fig, 11 is a top plan view of the carrier illustrated in Fig. 10;
  • Fig. 12 is a schematic end view of an optical fiber seated in an alignment channel of the carrier illustrated in Fig. 10 in accordance with one embodiment
  • Fig. 13 is a schematic end view of an optical fiber seated in an alignment channel of the carrier illustrated in Fig. 10 in accordance with another embodiment
  • Fig. 14 is a sectional side elevation view of an optical engine mounted onto the earner illustrated in Fig. 10;
  • Fig. 15 is a top plan view of a carrier shown aligned with a waveguide holder in accordance with an alternative embodiment:
  • Fig. 16 is a schematic end view- of an alignment pin shown coupled to the carrier illustrated in Fig. 15.
  • photonic integrated circuits can be configured to receive electrical signals from a first electrical component, convert the electrical signals to optical signals, and output the optical signals to one or more optical waveguides, which can be configured as optical fibers, for communication to a second component.
  • Photonic integrated circuits can further be configured to receive optical receive signals from the second component, convert the received optical signals to received electrical signals, and the received electrical signals can be communicated to the first electrical component.
  • a photonic integrated circuit can be integrated into an optical transmitter.
  • a photonic integrated circuit can further be integrated into an optical receiver.
  • the photonic integrated circuit of the optical transmitter can be separate from the photonic integrated circuit of the optical receiver.
  • the optical transmitter and the optical receiver can include the same single photonic integrated circuit.
  • Photonic integrated circuits are being configured as silicon photonic chips with increasing prevalence.
  • PICs are commonly implemented using a silicon substrate in which waveguides are formed on the surface of the silicon substrate using continuous or patterned layers of various materials, such as indium phosphide, silicon, silicon oxide, and silicon nitride.
  • PICs can be fabricated in other substrates, such as, but not limited to, InP, GaAs, LiNbO.s .
  • the waveguides of the PICs are placed in alignment with optical fibers using an active alignment system.
  • transmission of data signals between the optical fibers and the PIC waveguides are monitored to ensure that the PIC waveguides are in suitable optical alignment with the optical fibers.
  • the present disclosure provides a passive alignment system that places at least one optical fiber in optical alignment with a PIC waveguide during fabrication of the optical engine without the need for monitoring the transmission of data signals therebetween.
  • an optical transceiver 20 is configured to be coupled between a first electrical component and a second component.
  • the optical transceiver 20 is configured to receive electrical receive signals from the first electrical component, convert the electrical receive signals to optical receive signals, and output the converted optical receive signals for transmission to the second component.
  • the optical transceiver 20 is configured to receive optical receive signals from the second component, convert the optical receive signals to electrical receive signals, and output the converted electrical receive signals for transmission to the first electrical component.
  • an electrical communication system can include the optical transceiver 20, the first electrical component, and the second component.
  • the optical transceiver 20 can be included in an active optical cable that is configured to provide electro-optical conversion and optical transmission.
  • the active optical cable can replace a pluggable electronic cable and connector that is mated with a first complementary electrical component, such that the form factor of the active optical cable mirrors that of the electronic cable and connector that it replaces.
  • the optical transceiver 20 may also be configured to unmate with the first
  • the optical transceiver 20 can be encased in a housing of the active optical cable.
  • the optical transceiver 20 can include an optical transmitter 22, and an optical receiver 24 that are each coupled between the first electrical component and the second component.
  • the optical transmitter 22 can be configured to receive electrical receive signals from the first electrical component, convert the electrical receive signals to optical receive signals, and output the converted optical receive signals for transmission to the second component.
  • the optical receiver 24 can be configured to receive optical receive signals from the second component, convert the optical receive signals to electrical receive signals, and output the converted electrical receive signals for transmission to the first electrical component.
  • the optical transceiver 20 can be configured to be mounted to a substrate 26. Thus, both the optical transmitter 22 and the optical receiver 24 can be mounted to the substrate 26. Alternatively, the optical transmitter 22 and the optical receiver 24 can be mounted to respective first and second different substrates 26.
  • the substrate 26 is intended to refer both to a common substrate to which both the optical transmitter 22 and the optical receiver 24 are mounted, and a substrate to which only one of the optical transmitter 22 and the optical receiver 24 can be mounted.
  • one or both of the optical transmitter 22 and the optical receiver 24 can include a carrier (see, e.g., carrier 29 at Figs. 10 and 15) that is in turn mounted to the substrate 26.
  • the optical transmitter 22 and the optical receiver 24 are mounted to respective carriers that, in turn, are mounted to the substrate 26.
  • the optical transmitter 22 and the optical receiver 24 can be mounted to a common carrier that, in turn, is mounted to the substrate 26.
  • the substrate 26 can be configured as a printed circuit board as desired.
  • the substrate 26 can be configured to be placed in electrical communication with the first electrical component.
  • the substrate 26 can define a plurality of electrical contacts 28, and a first plurality of electrical conductors that extend from a first plurality of the electrical contacts 28 to the optical transmitter 22.
  • the substrate can further include a second plurality of electrical conductors that extend from a second plurality of the electrical contacts 28 to the optical receiver 24.
  • the electrical contacts 28 can include electrical signal contacts alone or in combination with electrical ground contacts in any arrangement as desired. Adjacent ones of the signal contacts can define differential signal pairs. Alternatively, the electrical signal contacts can be single- ended. In an alternative embodiment, the electrical contacts 28 can be unassigned.
  • the electrical contacts 28 can include contact pads that are configured to be placed in electrical communication with complementar ' electrical contacts of the first electrical component when the substrate 26 is mated with the first electrical component. For instance, the edge of the substrate 26 that carries the contact pads can be plugged into a receptacle of the first electrical component so as to place the optical transceiver 20 in electrical communication with the first electrical component.
  • the optical transceiver further includes a plurality of optical transmit waveguides 36 and optical receive waveguides 60 that can each be in communication with the second component.
  • the optical receive waveguides 60 can be configured as optical fibers, or any suitable waveguide structure as desired.
  • the optical transmit waveguides 36 may be permanently affixed to the optical transceiver 20, commonly referred to as pigtailed, or may be detachable.
  • the optical receive waveguides 60 may be permanently affixed to the optical transceiver 20, commonly referred to as pigtailed, or may be detachable.
  • the optical transmit waveguides 36 can be configured as optical transmit fibers or any suitable alternatively constructed optical waveguide structure.
  • the optical receive waveguides 60 can be configured as optical transmit fibers or any suitable alternatively constructed optical waveguide structure.
  • the optical transmit waveguides 36 and the optical receive waveguides 60 can be bundled into a cable that is placed in optical communication with the second component.
  • at least some, up to all, of the optical transmit waveguides 36 and the optical receive waveguides 60 can be placed in optical communication with the second component.
  • the substrate 26 can further include a second plurality of electrical conductors that extend from a second plurality of the electrical contacts 28 to the optical receiver 24. When the electrical contacts 28 are placed in electrical communication with the first electrical
  • the first electrical component is placed in electrical communication with each of the optical transmitter 22 and the optical receiver 24.
  • the electrical contacts 28 can be configured as contact pads earned by an outer surface of the substrate 26. The contact pads can be disposed at an end of the substrate 26 that is configured to be received by the first electrical component, thereby placing the electrical contacts 28 in electrical communication with the first electrical component.
  • the substrate 26 can be placed in electrical communication with the first electrical component in accordance with any suitable alternative embodiment as desired.
  • the electrical contacts 28 can be configured as plated holes that are configured to receive press-fit mounting tails of electrical contacts of the first electrical component.
  • the optical transmitter 22 can also be referred to as an optical engine that can be configured as an optical transmitter engine 30.
  • the optical transmitter 22 can include at least one transmit PIC (photonic integrated circuit) 32 configured to be placed in communication with the optical transmit waveguides 36.
  • the transmit PIC 32 can be configured as a silicon photonics chip.
  • the transmit PIC 32, and thus the optical transmitter engine 30, can be supported by the substrate 26.
  • the substrate 26 defines a first substrate surface 26a and a second substrate surface 26b that is opposite the first substrate surface 26a along a transverse direction T.
  • the transmit PIC 32 defines a first transmit PIC surface 32a and a second transmit PIC surface 32b that is opposite the first transmit PIC surface 32a along a transverse direction T.
  • the transmit PIC 32 can be configured to be mounted to the substrate 26 such that the second transmit PIC surface 32b faces the fi rst substrate surface 26a.
  • the transmit PIC 32 includes a photonic layer, which can include any number of optical and electro-optical elements such as, but not limited to, modulators, splitters,
  • the photonic layer defines a plurality of waveguides that can be disposed adjacent the second surface 32b of the transmit PIC 32. For instance, the waveguides of the transmit PIC 32 can be disposed closer to the second surface 32b than the first PIC surface 32a along the transverse direction T.
  • the waveguides of the transmit PIC 32 can be disposed closer to the second surface 32b than to a midplane that is equidistantly spaced from, the first and second PIC surfaces 32a and 32b.
  • the waveguides of the transmit PIC 32 can be spaced no more than approximately 20 microns from the second surface 32b of the transmit PIC 32.
  • the waveguides of the transmit PIC 32 can be spaced no more than approximately 10 microns from the second surface 32b of the transmit PIC 32.
  • the waveguides of the transmit PIC 32 can be spaced no more than approximately 1 or 2 microns from the second surface 32 b of the transmit PIC 32.
  • the second surface 32b can be defined by a bottom, surface of the transmit PIC 32.
  • the second surface 32b of the transmit PIC 32 can be the surface of the transmit PIC 32 that faces the substrate 26.
  • the second surface 32b can be mounted to the substrate 26.
  • the second surface 32b of the transmit PIC 32 can be mounted to a carrier that is, in turn, mounted to the substrate 26, Either way, the second surface 32b of the transmit PIC 32 can be said to be supported by the substrate 26.
  • the transmit PIC 32 can be said to be supported by the substrate 26.
  • the optical transmitter 22 can be mounted to the first surface 26a so as to place the transmit PIC 32 in electrical communication with respective ones of the first plurality of electrical conductors of the substrate 26.
  • flip-chip technology such as use of a ball grid array, copper pillars, or stud bumps, may be used to mount the transmit PIC 32 and the modulator driver 25 to the substrate 26.
  • the transmit PIC 32 may include a plurality of electrical contacts 33 (see Fig. 8), which transmit electrical signals and power on and off the transmit PIC 32.
  • the electrical contacts 33 are configured for flip-chip mounting to the substrate 26.
  • the electrical contacts 33 can be disposed on the same second transmit PIC surface 32b as the photonic layer.
  • the transmit PIC 32 can define a coupling edge, and the waveguides of the transmit PIC 32 can terminate at the coupling edge 35.
  • the coupling edge 35 can be a polished edge.
  • the coupling edge 35 can be configured as an optical output surface 41 , such that the optical transmit signals travel from the output surface 35 and into the transmit waveguides 36.
  • the optical output surface 41 can extend between the first transmit PIC surface 32a and the second transmit PIC surface 32b.
  • the optical output surface 41 can extend from the first transmit PIC surface 32a to the second transmit PIC surface 32b.
  • the optical output surface 41 can be oriented along the transverse direction T. Alternatively, the optical output surface 41 can be sloped with respect to the transverse direction T.
  • the slope can be in a range between 0 degrees and 8 degrees with respect to the transverse direction T.
  • the optical output surface 41 can slope away from the transmit waveguides 36 at an angle ⁇ as it extends from the first transmit PIC surface 32a to the second transmit PIC surface 32b.
  • the angle ⁇ can be between 0 degrees and 8 degrees.
  • the central axis of the transmit waveguide 36 can define an angle a with respect to the longitudinal direction L when the output end of the transmit waveguide 36 is aligned with the optical output surface 41.
  • the angle a can be between 0 degrees and 8 degrees.
  • the angle ⁇ can be equal to the angle a.
  • the angle ⁇ can be less than to the angle a.
  • the angle ⁇ can be greater than the angle a.
  • the core of the transmit waveguide 36 can be angularly offset with respect to the waveguide of the transmit PIC 32 in some embodiments. This allows the transmit waveguides 36 to extend upwards away from the substrate 26 as they extend rearward from the transmit PIC 32, thereby allowing the fibers to be disposed above an apparatus that may be disposed rearward of the transceiver 20. Extending the waveguides 36 upwards in this manner can limit coupling of back reflections from the interface between the PIC 32 and waveguides 36 into the PIC waveguides.
  • the transmit PIC 32 can be configured to receive at least one electrical transmit signal from the first electrical component, convert the electrical transmit signal to an optical transmit signal, and output the optical transmit signal.
  • the waveguides of the transmit PIC 32 can emit respective cones of light in an optical emission pattern having a generally Gaussian intensity distribution.
  • the cone need not be circularly symmetric, but may have a different diameter in the transverse direction T and a lateral direction A that is oriented substantially perpendicular to the transverse direction T, the diameters denoted as 2WT and 2WA, respectively.
  • the optical emission direction is along a direction that is substantially perpendicular to the optical output surface 41.
  • the optical emission direction can be along a longitudinal direction L that is substantially perpendicular to each of the transverse direction T and the lateral direction A when the optical output surface 41 extends along the transverse direction T and the lateral direction A.
  • the emission direction will deviate from the longitudinal direction L as defined by Snell's Law.
  • the photonics layer may optionally include alignment indicator 80, which may aid in alignment of the optical waveguides, which can be configured as optical fibers, to the waveguides of the transmit PIC 32 as described herein. While the optical emission from only a single waveguide is shown in Fig. 8, it should be appreciated that the transmit PIC 32 can include a plurality of waveguides that terminate on the optical output surface 41 .
  • the photonic integrated circuit can include both transmit waveguides and receive waveguides that terminate at the coupling edge.
  • the optical transmitter engine 30, and thus the optical transmitter 22, can further include at least one light source 34 (see Fig. 8) such as a plurality of light sources 34 that emit light, which is coupled into the transmit PIC 32.
  • the substrate 26 can include a pocket 39 in the first substrate surface 26a that receives the light source 34.
  • the optical transmitter 22 can include a coupler that causes the light source to be directed into the transmit PIC 32. If a plurality of light sources 34 are present, each light source may operate at a different wavelength.
  • the at least one light source 34 may be mounted directly on the transmit PIC 32 or may be mounted at some other location in the optical transceiver 20.
  • the at least one light source 34 is mounted to the transmit PIC 32, in one example the at least one light source 34 can be mounted to the second transmit PIC surface 32 b. If the light source 34 is located off the transmit PIC 32, the transmitter 22 can include optical waveguides that can direct light from the light source 34 to the transmit PIC 32. If the transmit PIC 32 is formed from silicon, a separate laser may be mounted onto the transmit PIC 32. The laser may operate in a steady-state manner and couple light into the photonic layer where it is manipulated into an optical data stream. [0042] The transmit PIC 32 can receive light from the light source 34, and can modulate the light based on the received electrical transmit signals so as to produce the optical transmit signals that correspond to the received electrical transmit signals.
  • the transmitter 22 can include at least one modulator driver 25 that defines a modulation protocol that determines the modulation of the light based on the electrical signals received from the first electrical component.
  • the transmitter 22 can include a plurality of modulator drivers 25, with each modulator driver being dedicated to a respective channel that receives the electrical transmit signal to be converted into a respective optical transmit signal in the transmit PIC 32.
  • the modulator drivers may be fabricated on a single die.
  • Each modulator driver 25 can be configured to provide an electrical input to the transmit PIC 32 appropriate for driving the optical modulators located there.
  • the at least one optical modulator may take many forms, such as, but not limited to, an electro-absorption modulator, a Mach-Zehnder modulator, and a ring resonator modulator.
  • the modulator d river 25 generates electrical signals appropriate for that modulator.
  • a drive signal for a Mach-Zehnder modulator can include a constant or slowly varying offset voltage to bias the two modulator arms for increased or maximum modulation depth.
  • a multi-level modulation protocol such as PAM4
  • the transmit PIC 32 can be configured to convert the received electrical transmit signals into optical transmit signals.
  • the light source can be configured as any suitable diode laser.
  • the light source can be configured as a laser, preferably emitting wavelengths between 1200 nm to 160 nm.
  • the laser may be configured as vertical- cavity surface-emitting laser (VCSEL), a distributed feedback (DFB) laser, or a Fabry -Perot (FP) laser.
  • VCSEL vertical- cavity surface-emitting laser
  • DFB distributed feedback
  • FP Fabry -Perot
  • a coupling structure may be integrated with the laser so that light is emitted from the surface, rather than the edge of the die.
  • the optical transmit signals can be output to the second component.
  • the optical transmitter 22 can include a transmit waveguide assembly 37 that can include a plurality of optical transmit waveguides 36 that are in optical alignment with the transmit PIC 32.
  • the optical transmit waveguides 36 are configured to receive the optical transmit signals that are output by the transmit PIC 32, and carry the optical transmit signals to the second component.
  • the transmit waveguide assembly 37 can be referred to as a transmit fiber assembly when the optical transmit waveguides 36 are configured as optical fibers.
  • the transmit waveguide assembly 37 can further include a transmit waveguide holder 38 that is configured to support the optical transmit waveguides 36 such that an input end of the optical transmit waveguides 36 are in optical alignment with the waveguides of the transmit PIC 32 at the optical output surface 41 of the transmit PIC 32, Thus, the input ends of the optical transmit waveguides 36 are configured to receive the optical transmit signals from the transmit PIC 32.
  • the transmit waveguide holder 38 can be referred to as a transmit fiber holder when the optical transmit waveguides 36 are configured as optical fibers.
  • the transmit waveguide holder 38 can be made from glass, silicon, ceramic, plastic or any suitable alternative material.
  • the transmit waveguide holder 38 can be configured as a molded optical structure (MOS) that couples the substrate 26 to the optical transmit waveguides 36.
  • the transmit waveguide holder 38 can be supported by the substrate 26.
  • the transmit PIC 32 can be optically coupled to the optical transmit waveguides 36.
  • the input ends of the transmit waveguides 36 can be placed adjacent, i ,e, edge coupled to, an edge of the transmit PIC 32.
  • an edge of the transmit PIC 32 can define an optical output surface.
  • This type of coupling is known as butt coupling.
  • the optical transmit signals can be directly coupled between the transmit PIC 32 and optical transmit waveguide 36 without passing through any intervening structure.
  • the optical signal propagation from the transmit PIC 32 to the optical transmit waveguides 36 can be referred to as free space propagation
  • provisions can be made in at least one of the transmit PIC 32 waveguides and optical transmit waveguides 36 to mode match the light between the different waveguides.
  • one or more intervening optical elements may be situated between the waveguides of the transmit PIC 32 and the optical transmit waveguides 36 to facilitate mode matching.
  • These intervening optical elements may include one or more of mirrors, lenses, transparent substrates, transparent couplers, and optical waveguides that collectively serve to provide an optical path between the transmit PIC 32 waveguides and optical transmit waveguides 36. While the optical path is more complex in the embodiments using multiple optical elements, they may improve mode matching and relax alignment tolerances between the transmit PIC 32 and optical transmit waveguide 36. The high coupling efficiency may advantageously be maintained over a large operating temperature range. Optical alignment of the waveguides of the transmit PIC 32 with the transmit waveguides 36 is described in more detail below.
  • ihe transmit PIC 32 can be placed in electrical communication with a controller 42, which can be configured as a microprocessor.
  • the controller 42 can be mounted to the substrate 26, and can be programmed to control the operation of either or both of the opticai transmitter 22 and the optical receiver 24.
  • the controller 42 can control the light modulation characteristic of the modulator driver 25.
  • Such characteristics include, but are not limited to, the high/low extinction ratio, signal pre-compensation, and balancing phases in the arms of a Mach Zehnder modulator.
  • the optical receiver 24 is configured to receive opticai receive signals from the second component, convert the optical signals to electrical signals, and output the electrical signals to the first electrical component when the optical transceiver 20 is mated with the first electrical component.
  • the receiver 24 can be referred to as an optical engine that is configured as an optical receiver engine 62.
  • the receiver 62 can include at least one receive PIC (photonic integrated circuit) 64 configured to be placed in communication with the optical receive waveguides 60.
  • the receive PIC 64 can be configured as a silicon photonics chip.
  • the receive PIC 64 can be separate from the transmit PIC 32. Alternatively, a single PIC can include both the receive PIC 64 and the transmit PIC 32.
  • the receive PIC 64 includes a plurality of receive PIC waveguides that are configured to be optically aligned with the plurality of optical receive waveguides 60.
  • the receive PIC 64 receives the optical receive signals, and is configured to convert the optical receive signals to corresponding electrical receive signals.
  • the electrical receive signals can have current levels that are proportional with the intensity or rate of optical photon arrival of the optical receive signal.
  • the current of the electrical receive signals generated by the receive PIC 64 increases as the intensity of the incoming optical receive signal increases, and decreases as the intensity of the incoming optical receive signal decreases. It is recognized that the current levels of the electrical receive signals are not necessarily linearly proportional to the quantity of opticai photons of the received opticai receive signal, and that often the
  • optical receive signals having a high delivery rate of opticai photons will be converted to an electrical signal having higher current levels than optical receive signals having a lower deliver ⁇ ' rate of optical photons.
  • Data may be transmitted by this modulated optical and electrical signal.
  • the optical receiver engine 62 can further include a current-to-voltage converter 66 that is in electrical communication with the receive PIC 64, such that the electrical receive signals output by the optical receive PIC 64 are received by the current-to-voltage converter 66. It can thus be said that the receive PIC 64 can place the optical receive waveguides 60 in data communication with the current-to-voltage converter 66.
  • the current-to-voltage converter 66 is a transimpedence amplifier (TIA) that amplifies the electrical receive signal to voltage levels that are usable for communication with the first electrical component.
  • TIA transimpedence amplifier
  • the electrical receive signals output by the current-to- voltage converter 66 are the electronic equivalent of the optical signals received by the receive PIC 64.
  • the electrical receive signals output by the current-to-voltage converter 66 can mimic the digital patterns of the received optical patterns in an electrical signal.
  • the receive PIC 64 and thus the optical receiver engine 62, can be supported by the substrate 26.
  • the substrate 26 defines a first substrate surface 26a and a second substrate surface 26b that is opposite the first substrate surface 26a along a transverse direction T.
  • the receive PIC 64 defines a first receive PIC surface 64a and a second receive PIC surface 64b that is opposite the first receive PIC surface 64a along a transverse direction T.
  • the receive PIC waveguides that can be disposed adjacent the second surface 64b of the receive PIC 64. For instance, the waveguides of the receive PIC 64 can be disposed closer to the second surface 64b than the first PIC surface 64a along the transverse direction T.
  • the waveguides of the receive PIC 64 can be disposed closer to the second surface 64b than to a midplane that is equidistantly spaced from the first and second surfaces 64a and 64b.
  • the waveguides of the receive PIC 64 can be spaced no more than approximately 20 microns from the second surface 64b of the receive PIC 64.
  • the waveguides of the transmit PIC 32 can be spaced no more than approximately 10 microns from the second surface 32b of the transmit PIC 32.
  • the waveguides of the transmit PIC 32 can be spaced no more than approximately 1 or 2 microns from the second surface 64b of the receive PIC 32.
  • the second surface 64b can be defined by a bottom surface of the receive PIC 64.
  • the second surface 64b of the receive PIC 64 can be the surface of the receive PIC 64 that faces the substrate 26.
  • the second surface 64b can be mounted to the substrate 26.
  • the second surface 64b of the receive PIC 64 can be mounted to a carrier that is, in turn, mounted to the substrate 26. Either way, the second surface 64b of the receive PIC 64 can be said to be supported by the substrate 26.
  • the receive PIC 64 can be said to be supported by the substrate 26.
  • the optical receiver 24 can be mounted to the first surface 26a, directly or via a carrier, so as to place the current-to-voltage converter 66 in electrical communication with respective ones of the second plurality of electrical conductors of the substrate 26,
  • flip-chip technology such as use of a ball grid array, copper pillars, or stud bumps, may be used to mount the receive PIC 64 and the current-to-voltage converter 66 to the substrate 26.
  • each of the receive PIC 64 and the current-to- voltage converter 66 can be surface mounted to the substrate 26 either directly or via a carrier.
  • the receiver 24 can include a receive waveguide assembly 70 that, in turn, can include the optical receive waveguides 60 and a receive waveguide holder 72 that supports the receive waveguides 60.
  • the receive waveguide holder 72 can support the optical receive waveguides 60 such that output ends of the optical receive waveguides 60 are in optical alignment with respective waveguides of the receive PIC 64.
  • the receive waveguide assembly 70 can be referred to as a receive fiber assembly when the optical receive waveguides 60 are configured as optical fibers.
  • the receive waveguide holder 72 can be referred to as a receive fiber holder when the optical receive waveguides 60 are configured as optical fibers.
  • the receive PIC 64 can be configured to receive optical receive signals from the respective optical receive waveguide 60. As will be appreciated from the description below, the optical receive signals can travel from the optical receive waveguides 60 to the receive PIC 64 without passing through any waveguides. Thus, the optical signal propagation from the optical receive waveguides 60 to the receive PIC 64 can be referred to as free space propagation.
  • the optical receive signals can be sent from, the second component to the optical transceiver 20.
  • the receive PIC 64 can define a coupling edge 35, and the waveguides of the receive PIC 64 can terminate at the coupling edge 35.
  • the coupling edge can be configured as an optical input surface 65, such that the optical transmit signals travel from the receive waveguides 60 to the optical input surface 65, and into the receive PIC waveguides.
  • the output ends of the receive waveguides 60 can be placed adjacent, i.e. edge coupled to, an edge of the receive PIC 64.
  • the edge can be defined by the optical input surface 65. This type of coupling is known as butt coupling.
  • the optical input surface 65 can extend between the first receive PIC surface 64a and the second receive PIC surface 64b.
  • the optical input surface 65 can extend from the first receive PIC surface 64a to the second receive PIC surface 64b.
  • the optical input surface 65 can be oriented along the transverse direction T.
  • the optical input surface 65 can be sloped with respect to the transverse direction T. The slope can be in a range between 0 degrees and 8 degrees with respect to the transverse direction T.
  • the optical input surface 65 can slope away from the receive waveguides 60 at an angle ⁇ as it extends from the first receive PIC surface 64a to the second receive PIC surface 64b.
  • the angle ⁇ can be between 0 degrees and 8 degrees.
  • the central axis of the receive waveguide 60 can define an angle a with respect to the longitudinal direction L when the input end of the receive waveguide 60 is aligned with the optical input surface 65.
  • the angle a can be between 0 degrees and 8 degrees.
  • the angle ⁇ can be equal to the angle .
  • the angle ⁇ can be less than to the angle a.
  • the angle ⁇ can be greater than the angle a.
  • the core of the receive waveguide 60 can be angularly offset with respect to the waveguide of the receive PIC 64 in some embodiments.
  • the optical receive signals can travel from the optical receive waveguides 60 to the optical input surface 65 without passing through any intervening structure.
  • one or more intervening optical elements may be situated between the optical receive waveguides 60 and the receive PIC 64.
  • These intervening optical elements may include one or more of mirrors, lenses, transparent substrates, transparent couplers, and optical waveguides that collectively serve to provide an optical path between the optical receive waveguides 60 and the receive PIC 64. While the optical path is more complex in the embodiments using multiple optical elements, they may improve mode matching and relax alignment tolerances between the optical receive waveguides 60 and the receive PIC 64.
  • the controller 42 can control the current-to-voltage converter 66 of the receiver 24 that conditions the optical receive signals. For example, the controller 42 can control operation of the current-to-voltage converter 66 thereby placing it in an operating state suitable to receive incoming receiver signals. The controller 42 may also communicate squelch signals arising from incoming receive electrical signals to other elements in the data processing system.
  • the input ends of the optical transmit waveguides 36 are in optical alignment with the respective transmit PIC waveguides of the transmit PIC 32.
  • the output ends of the optical receive waveguides 60 are in optical alignment with the respective ones of the respective receive PIC waveguides of the receive PIC 64.
  • One or both of the transmitter 22 and the receiver 24 can include an alignment module 74 configured such that when the alignment module 74 has a predetermined spatial relationship with the respective photonic integrated circuit 32 or 64, and receives the corresponding waveguides 36 or 60, the corresponding waveguides 36 or 60 are aligned with the corresponding waveguides of the photonic integrated circuit.
  • a photonic integrated circuit (PIC) 76 (labeled in Fig. 5) can apply to one or both of the transmit PIC 32 and the receive PIC 64 unless otherwise indicated to the contrary.
  • the PIC 76 can define a first or upper surface 76a and a second or lower surface 76b opposite the first surface 76a along the transverse direction T.
  • a fiber holder or waveguide holder 86 (labeled in Fig. 4) can apply to one or both of the transmit waveguide holder 38 and the receive waveguide holder 72 unless otherwise indicated to the contrary.
  • Reference to a fiber holder can apply to the waveguide holder when the optical waveguides are configured as optical fibers 85.
  • one or both of the optical transmitter engine 30 (and thus the optical transmitter 22) and the optical receiver engine 62 (and thus the optical receiver 24) can include an alignment module 74. It will be understood that reference to an optical engine can include the optical transmitter engine 30, the optical receiver engine 62, or both.
  • the alignment module 74 is configured to receive one or both of the respective transmit or receive waveguides 36, 60, and is configured to be aligned with the PIC 76 such that the optical waveguides, which can be configured as optical fibers, that are received by the alignment module 74 are butt coupled with the PIC 76 in optical alignment with the waveguides of the PIC 76.
  • the waveguides of the PIC 76 are generally smaller than the waveguide structure in the optical fiber.
  • the mode sizes are substantially matched for efficient coupling.
  • One approach utilizes 1 -dimensional and/or 2-dimensional waveguide tapers in the PIC 76 to enlarge the mode size to match that of the optical fiber.
  • a second approach uses free space propagation of light in a gap region to match the beam size between the PIC 76 and the optical fiber. For example, light emitted from the coupling edge of a transmitting PIC expands due to diffraction as it propagates thai free space a shown at Fig. 8.
  • the end face of an optical fiber can be situated so that it intersects the beam at the plane where the beam size substantially matches the fiber mode size. For example, for a waveguide of a PIC 76 having a mode field diameter of 3 microns propagation thru air a distance of approximately 14 microns will result in a beam diameter of 9.2 microns, matching the mode size of SMF28 single mode fiber for 1.3 micron wavelength light. Even though the beam size of the propagating light matches the mode size of the fiber, the light may not efficiently couple into the optical fiber because the light is highly diverging.
  • a correction element can be disposed on or near the end of the fiber to reduce the light divergence and in some instances collimate the light entering the fiber core.
  • the correction element may be made in many ways.
  • the fiber end may be melted forming a curved surface that may serve as the correction element.
  • a fiber splicer may be used to precisely heat the fiber end face to form the correction element.
  • a small quantity (e.g., a drop) of adhesive may be placed on the fiber end. Surface tension can cause the adhesive to form a curved surface, such that the curved adhesive can provide the correction element.
  • a GRIN lens, bail, or barrel lens may be placed in the alignment channel 84 (see below) adjacent the fiber end.
  • an index matching material may be used at some places in the optical path to alter the beam propagation properties and reduce back reflections.
  • the PIC 76 can carry at least one first alignment indicator 80
  • the alignment module 74 can carry at least one second alignment indicator 82 that is configured to be placed in alignment with the first alignment indicator 80.
  • the at least one fi rst alignment indicator 80 can include at least a pair of first alignment indicators 80 that are spaced from each other.
  • the at least one second alignment indicator 82 can include at least a pair of second alignment indicators 82 that are spaced from each other.
  • the alignment module 74 can include an inner module surface 74a and an outer module surface 74b that are opposite one another.
  • the alignment module 74 can define a plurality of alignment channels 84 that are configured to receive respective ones of the transmit waveguides 36, the receive waveguides 60, or both.
  • the alignment module 74 can define the alignment channels 84 adjacent the inner module surface 74a.
  • the alignment channels 84 can be elongate along the longitudinal direction L.
  • the alignment channels 84 can be spaced from each other along the lateral direction A. In some examples, the alignment channels 84 can be substantially parallel to one another.
  • the PIC 76 and the alignment module 74 define a predetermined relative position with respect to the longitudinal direction L and the lateral direction A.
  • the optical fibers 85 can be butt coupled to the photonic integrated circuit 76 in optical alignment with a
  • the alignment indicators 80 and 82 can be aligned with each other along the transverse direction T.
  • One or both of the first and second alignment indicators 80 and 82 can be configured as visual markings. The visual markings can be visible in ambient lighting conditions or visible with infrared light.
  • the first and second alignment indicators 80 and 82 can be visible alignment indicator.
  • the first and second alignment indicators 80 and 82 can be stmctures, wherein one of the first and second alignment indicators 80 and 82 is configured to mate with or receive the other of the first and second alignment indicators 80 and 82.
  • the first and second alignment indicators 80 and 82 can be structures each configured to receive or otherwise mate with at least one auxiliaiy alignment structure so as to align the PIC 76 with the alignment module 74.
  • the alignment module 74 can be configured to be adhesively attached or soldered to the PIC 76 while the first and second alignment indicators 80 and 82 are aligned with each other. Adhesively bonding and soldering planar surfaces of the alignment module 74 and the PIC 76 to one another can result in misalignments due to irregular adhesive or solder thickness and due to differential thermal expansion between the alignment module 74 and the solder or adhesive. Therefore, the alignment module 74 can alternatively be configured to be attached to the PIC 76 by molecular bonding, which does suffer from these issues. Preferably, when molecular bonding is performed, the surfaces that are bonded to one another are relatively flat and clean so as to improve the likelihood that bonding is successful.
  • At least one of the PIC 76 and alignment module 74 can be provided with standoffs (e.g., three or more) that provide a gap between the PIC 76 and the alignment module 74, and the PIC 76 and alignment module 74 can be adhesively attached or soldered to one another in the gap. Providing such a gap can also limit the effects of irregular adhesive or solder thickness.
  • the optical fibers 85 can be configured to be registered in the alignment channels 84 of the alignment module 74.
  • fiber cores 79 of the optical fibers 85 are spaced in optical alignment with the waveguides of the PIC 76 and butt coupled with the PIC 76 when the PIC 76 is aligned with, and attached to, the alignment module 74.
  • Each of the alignment channels 84 can be a groove that extends into an inner module surface 74a of the alignment module 74 so as to define an opening at the inner module surface 74a.
  • Each alignment channel 84 can extend from the inner module surface 74a towards the outer module surface 74b, and terminate before the outer module surface 74b.
  • Each alignment channel 84 can be configured to receive an optical fiber 85 through the opening in the inner module surface 74a.
  • the alignment channels 84 can be substantially v-shaped grooves that define an apex.
  • each alignment channel 84 may be a substantially truncated v-shape in which the v-shape is truncated at its vertex, may be a substantially u-shaped groove, or may have any other suitable groove shape, wherein the apex of the groove is open.
  • each alignment channel 84 has a shape that is configured to form a pair of line contacts 71 with a respective one of the optical fibers 85.
  • each alignment channel 84 may be defined as a hole formed in the alignment module 74 thai which a fiber is inserted.
  • the hole can have a closed shape in a plane that extends along the lateral direction A and the transverse direction T,
  • the hole may be formed by ablating material from the alignment module 74 by scanning a focused spot from an uitrafast laser into the alignment module 74.
  • the optical fibers 85 may be secured within the alignments channels 84.
  • the alignment channels 84 are configured to receive the optical fibers 85 at the respective apexes, such that the cores 79 of the optical fibers are in optical alignment with the respective waveguides of the photonic integrated circuit 76 when the alignment module 74 is attached to the PIC 76 (not shown in Fig. 7B).
  • Reference to receipt in apexes can include a spatial orientation whereby the optical fibers are substantially centered with respect to the apexes.
  • the waveguides of the PIC 76 are aligned with the apex of the alignment channels 84 along a plane that is oriented along the longitudinal direction L and the transverse direction T.
  • the alignment channels 84 are defined by side walls 93 that are opposite each other along the lateral direction A.
  • Each alignment channel 84 can define a midplane 77 that is equidistantly spaced between its side walls 93, each midplane 77 defined by the longitudinal direction L and the transverse direction T.
  • the waveguides of the PIC 76 are aligned with the respective midplanes 77 of the alignment channels 84.
  • the midplanes 77 can define the location of the cores 79 of the optical fibers 85 that are seated in the alignment channels 84 and aligned with the waveguides of the PIC 76.
  • each midplane 77 can be aligned with a core 79 of an optical fiber 85.
  • the cores 79 of the optical fibers 85 are aligned with one another along a plane that extends along the longitudinal direction L and the lateral direction A. The plane can be spaced above the inner surface 74a of the alignment module 74 with respect to the transverse direction T.
  • each alignment channel 84 can be configured to form at least one line contact 71 with its associated optical fiber 85.
  • each optical fiber 85 can form a line contact 71 with each of the first a d second side walls 93 so that each optical fiber 85 is registered into its associated alignment channel 84.
  • Each line contact 71 can extend in the longitudinal direction L, and thus, into the page in the view of Fig. 7A.
  • the optical fibers 85 can have a well-controlled mechanical tolerance, wherein the fiber diameter and the centering of the core 79 is controlled to micron or sub-micron accuracy. As a result, the fiber cores 79 can be accurately registered with respect to the alignment features 82 of the alignment module 74 (see Fig. 6).
  • the waveguide holder 86 can be configured to apply the force F to each of the optical fibers 85,
  • the waveguide holder 86 may be configured in a number of different manners so as to seat each optical fiber 85 into its associated alignment channel 84 as will be discussed in relation to Figs. 7B to 7F. In at least some of the
  • the waveguide holder 86 can combine with the alignment module 74 to form a kinematic mounting structure.
  • the optical fibers 85 may be supported by a waveguide holder 86.
  • the waveguide holder 86 can include an inner holder surface 86a and an outer holder surface 86b that are opposite one another.
  • the optical fibers 85 can be supported adjacent the inner holder surface 86a.
  • the waveguide holder 86 may be positioned relative to the alignment module 74 such that the inner holder surface 86a faces the inner module surface 74a.
  • the waveguide holder 86 may be positioned relative to the alignment module 74 so as to align the optical fibers 85 with the waveguides of the PIC 76.
  • the waveguide holder 86 may apply a force F to each of the optical fibers 85 so as to cause the optical fibers 85 to seat properly within the alignment channels 84 of the alignment module 74.
  • the waveguide holder 86 may support the optical fibers 85 with a mechanical accuracy that is sufficient to cause the optical fibers 85 to engage with the alignment channels 84 when the waveguide holder 86 is positioned adjacent the alignment module 74.
  • the ends of the optical fibers 85 adjacent the PIC 76 can be rigidly attached to the waveguide holder 86.
  • the ends of the optical fibers 85 can be rigidly attached by an adhesive, press-fitting, or any other suitable fastening mechanism.
  • the ends of the optical fibers 85 adjacent the PIC 76 may be supported by the waveguide holder 86 such that the ends are not rigidly attached to the waveguide holder 86. Consequently, the ends of the optical fibers 85 may move relative to the waveguide holder 86 when the waveguide holder 86 mates with the alignment module 74.
  • the waveguide holder 86 is configured to be mounted to the optical fibers 85, such that when the optical fibers 85 are mounted to the waveguide holder 86 and inserted into the alignment channels 84, the optical fibers 85 are butt coupled to the photonic integrated circuit 76 in optical alignment with the waveguides of the photonic integrated circuit 76.
  • the optical fibers can be configured as fibers each having a core, cladding surrounding the core, and a buffer surrounding the cladding.
  • the buffer is configured to be secured to the waveguide holder 86, such that the core and cladding extend from the buffer toward the photonic integrated circuit 76. Thus, the buffer can be stripped from the end of the optical fiber.
  • the waveguide holder 86 may include at least one holder channel 90,
  • the waveguide holder 86 can include a plurality of holder channels 90.
  • the holder channels 90 can each be elongate along the longitudinal direction L.
  • the holder channels 90 can be spaced from one another along the lateral direction A .
  • Each of the holder channels 90 can be a groove that extends into the inner holder surface 86a of the waveguide holder 86 so as to define an opening at the inner holder surface 86a.
  • Each holder channel 90 can extend from the inner holder surface 86a towards the outer holder surface 86b, and terminate before the outer holder surface 86b.
  • Each holder channel 90 can be configured to receive an optical fiber 85 through the opening in the inner holder surface 86a such that the cores 79 of the optical fibers 85 are in optical alignment with the respective waveguides of the PIC 76 when the alignment module 74 is positioned adjacent to the PIC 76 (not shown in Fig. 7B).
  • the waveguide holder 86 can define, for each holder channel 90, a first channel portion 90a that is configured to receive the buffer, and a second channel portion 90b configured to receive the cladding from regions of the optical fiber 85 that have been stripped of buffer.
  • the first channel portions 90a can be adjacent a first holder end 86c of the waveguide holder 86
  • the second channel portions 90b can be adjacent a second holder end 86d of the waveguide holder 86.
  • the first and second holder ends 86c and 86d can be opposite one another with respect to a longitudinal direction L that is oriented substantially perpendicular to the transverse direction T and the lateral direction A. Further, the second holder end 86d can be disposed closer to the PIC 76 when the waveguide holder 86 is positioned adjacent to the PIC 76.
  • the second channel portion 90b can be aligned with the first channel portion 90a with respect to the longitudinal direction L.
  • Each first channel portion 90a can define a width along the lateral direction A in a plane that extends along the lateral direction A and the longitudinal direction L.
  • the width of each first channel portion 90a is greater than a width of its associated second channel portion 90b along the lateral direction A in the same plane.
  • the first channel portions 90a can be spaced from each other along the lateral direction A.
  • the second channel portions 90b can be spaced from each other along the lateral direction A.
  • the first and second channel portions 90a and 90b can be elongate along the longitudinal direction L.
  • the waveguide holder 86 can define a plurality of line contacts 90a, in lieu of the first channel portions.
  • the line contacts 90a can be spaced from each other along the lateral direction A and can be aligned with the second channel portions 90b along the longitudinal direction L.
  • the waveguide holder 86 can be configured to form a line contact 90a with the buffer of h optical fiber 85.
  • the waveguide holder 86 can define a stop surface 92 that is disposed between the first channel portions 90a (or tine contacts) and the second channel portions 90b.
  • the stop surface 92 is configured to abut an end of the buffer, such that the cladding and core extend forward from the respective buffer along the longitudinal direction L into the second channel portions 90b.
  • the buffers can be adhesively attached to the waveguide holder 86 in the respective first channel portions 90a (or line contacts).
  • the second channel portions 90b can define respective apexes, and the buffers can be attached to the waveguide holder 86 in the first channel portions 90a (or line contacts) such that the core and cladding are disposed at the respective apexes of the second channel portions 90b.
  • the cladding can then be secured to the alignment module 74 in the alignment channels 84 in any manner as desired.
  • the second channel portions 90b can further be configured to face the alignment channels 84, such that the cladding is captured between the alignment module 74 and the waveguide holder 86 in the alignment channels 84 and the second channel portions 90b of the holder channels 90,
  • the alignment channels 84 can be defined by an inner surface 74a of the alignment module 74
  • the second channel portions 90b can be defined by an inner surface 86a of the waveguide holder 86.
  • Each of the optical fibers 85 may be supported within a respective one of the holder channels 90.
  • Each holder channel 90 can be configured to form at least one line contact 71 with its associated optical fiber 85.
  • the holder channels 90 can be substantially v-shaped grooves defined by first and second side wails 91.
  • Each optical fiber 85 can form, a line contact 71 with each of the first and second side walls 91 of its associated holder channel 90 so that each optical fiber 85 is registered into its associated holder channel 90.
  • Each line contact 71 can extend in the longitudinal direction L, and thus, into the page in the view of Fig. 7B.
  • the alignment module 74 and waveguide holder 86 are configured to support the optical fiber 85 at four contact lines, two contact lines 71 with the alignment module 74 and two contact lines 71 with the waveguide holder 86.
  • Figs. 4 and 7B depicts the holder channels 90 as v-shaped grooves
  • the holder channels may have other suitable shape.
  • each holder channel 90 may be a substantially truncated v-shape in which the v-shape is truncated at its vertex, may be a substantially u-shaped groove, or may have any other suitable groove shape that forms at least one line contact 71 with a respective one of the optical fibers 85.
  • the alignment module 74 and waveguide holder 86 can be configured such that, when the waveguide holder 86 is positioned adjacent the alignment module 74, the inner holder surface 86a of the waveguide holder 86 faces the inner module surface 74a of the alignment module 74. Further, the alignment module 74 and waveguide holder 86 can be configured such that, when the optical fibers 85 are registered in the alignment channels 84 and the holder channels 90, the inner holder surface 86a of the waveguide holder 86 is spaced from the inner module surface 74a of the alignment module 74 so as to define a gap 78 therebetween.
  • the cores 79 of the optical fibers 85 can be aligned along a plane that extends in the lateral d irection A and the longitudinal direction L, The plane can be aligned with the gap 78 between the waveguide holder 86 and the alignment module 74. Providing the gap 78 can increase the likelihood that four line contacts 71 are maintained with each of the optical fibers 85.
  • the alignment module 74 and waveguide holder 86 can be attached to one another via adhesive (not shown) disposed in the gap 78.
  • the adhesive can attach to both the inner holder surface 86a of the waveguide holder 86 and the inner module surface 74a of the alignment module 7 .
  • the adhesive can be configured such that, as the adhesive cures, the adhesive shrinks, thereby drawing the alignment module 74 and waveguide holder 86 towards one another. Drawing the alignment module 74 and waveguide holder 86 towards one another can increase the registration force applied by the waveguide holder 86 and the alignment module 74 on the optical fiber 85.
  • the alignment module 74 can define a distance for each alignment channel 84 from one of its contact lines 71 with the optical fiber 85 to its other contact line 71 along the lateral direction A.
  • the distance defined by the alignment module 74 for each alignment channel 84 can be dependent upon the angle between the side walls 93 of the alignment channel 84. For instance, as the angle is increased, the contact lines 71 of each alignment channel 84 move closer to one another, and as the angle is decreased, the contact lines 71 of each alignment channel 84 move away from one another.
  • the waveguide holder 86 can define a distance for each holder channel 90 from one of its contact lines 71 with the optical fiber 85 to its other contact line 71 along the lateral direction A that is less than, greater than, or equal to the distance defined by the alignment module 74.
  • the distance defined by the waveguide holders 86 for each holder channel 90 can be dependent upon the angle between the side walls 91 of the holder channel 90. For instance, as the angle is increased, the contact lines 71 of each holder channel 90 move closer to one another, and as the angle is decreased, the contact lines 71 of each holder channel 90 move away from one another. Taken to the logical extreme, the first and second side walls 91 of each holder channel 90 can be aligned with one another such that the contact lines 71 merge together into one contact line 71 as shown in Fig. 7C.
  • Bowing and/or warping of the alignment module 74 or the waveguide holder 86 can result in the holder channels 90 in Fig. 7B above not properly aligning with the alignment channels 84.
  • Bowing and/or warping of the alignment module 74 or the waveguide holder 86 can additionally or alternatively result in some of the holder channels 90 being spaced closer to their corresponding alignment channels 84 than others. For instance, bowing towards a center of the waveguide holder 86 can result in outer ones of the holder channels 90 being spaced a first distance to their corresponding alignment channels 84, and one or more inner holder channels 90 between the outer ones being spaced a second distance to their corresponding alignment channels 84, where the second distance is greater than the first distance.
  • the outer ones of the holder channels 90 might provide sufficient line contact with their respective optical fibers 85, while tlie inner holder channels 90 might not provide sufficient line contact with their respective optical fibers 85. Therefore, in some embodiments, at least a portion of the holder channels 90, such as the second portions 90b, can be eliminated to eliminate misalignments between the holder channels 90 and the alignment channels 84.
  • FIG. 7C an alternative embodiment is shown in which the waveguide holder 86 is configured to form a single line contact with each of the optical fibers 85.
  • Tlie waveguide holder 86 of Fig. 7C does not define the second channel portions 90b, and therefore, does not suffer from misalignments between the second channel portions 90b and tlie alignment channels 84.
  • the inner holder surface 86a of the waveguide holder 86 can define a planar surface that supports the optical fibers 85, rather than the second channel portions 90b discussed above.
  • the planar inner holder surface 86a can apply a single line contact 71 to the end of each optical fiber 85 adjacent tlie PIC 76.
  • Each line contact 71 may apply a force F that registers a respective one of the optical fibers 85 into a respective one of the alignment channels 84.
  • each optical fiber 85 may be secured to the waveguide holder 86 on the first holder end 86c of the waveguide holder 86 that is opposite the PIC 76.
  • the waveguide holder 86 can include first channel portions 90a that are configured to receive the buffer as discussed above in relation to Fig. 4.
  • the buffers of the optical fibers 85 can be secured to the first channel portions 90a.
  • Each optical fiber 85 can be constrained in the transverse direction T by the inner holder surface 86a of the waveguide holder 86.
  • each optical fiber 85 is not constrained in the lateral direction A by the waveguide holder 86 at the second end 86d of the waveguide holder 86 adjacent the PIC 76. Rather, each optical fiber 85 can be constrained in tlie lateral A direction by the side walls 93 of the alignment module 74.
  • This embodiment has the advantage in that the optical fibers 85 have fewer contact lines 71 , and therefore are not overly constrained.
  • the inner holder surface 86a can be made of a compliant or elastically deformable material that deforms so as to increase the likelihood that the inner holder surface 86a makes contact with all of the optical fibers 85.
  • the inner holder surface 86a of the waveguide holder 86 is made from an elastically deformable material.
  • the entire waveguide holder 86 can be made from the elastically deformable material.
  • the waveguide holder 86 can have a holder body 86e that is made from a rigid material, and the inner holder surface 86a can be a layer or coating of elastically deformable material that is attached to the holder body 86e and that is more flexible than the holder body 86e.
  • the inner holder surface 86a can apply surface contact 71 with each of the optical fibers 85, For example, as the waveguide holder 86 applies a force F onto the optical fibers 85, the inner holder surface 86a can elastically deform so as to conform to an upper portion of each of the optical fibers 85. The downward force urges the optical fibers 85 against the side walls 93 of the respective alignment channels 84 forming two line contacts 71 with the side walls 93, These contact lines 71 register the optical fiber core 79 with respect to the alignment module 74, which in turn registers the fiber core 79 with a waveguide on the PIC 76 (not shown in Fig. 7D).
  • each alignment channel 84 is a rectangular-shaped groove.
  • Each alignment channel 84 can have first and second side walls 93 that are spaced from one another along the lateral direction A.
  • Each alignment channel 84 can have a bottom surface 75 that extends between the first and second side walls 93.
  • Each alignment channel 84 can have a width along the lateral direction A that is greater than that of its corresponding optical fiber 85 along the lateral direction A.
  • each alignment channel 84 can have a height along the transverse direction T that is greater than that of its corresponding optical fiber 85.
  • the waveguide holder 86 can be configured to apply a registration force F to the optical fibers 85 so as to bias the optical fibers 85 against a pair of alignment surfaces of the alignment channel 84.
  • the pair of alignment surfaces may be one of the first and second side walls 93 and the bottom surface 75 , in one example, the waveguide holder 86 can apply the force F so as to bias the optical fibers 85 in a direction that is angularly offset from the lateral direction A and the transverse direction T.
  • the optical fibers 85 can be seated in the alignment channels 84 such that the fiber core 79 is offset from the midplane 77 by a distance d along the lateral direction A.
  • the waveguides of the PIC 76 are offset from the respective midplanes 77 of the alignment channels 84 by the distance d along the lateral direction A.
  • the midplanes 77 do not define the location of the cores 79 of the optical fibers 85 that are seated in the alignment channels 84 and are not aligned with the w aveguides of the PIC 76. Rather, each midplane 77 is offset from a core 79 of an optical fiber 85 by the distance d,
  • the waveguide holder 86 can include at least one biasing member 81 that extends from the inner holder surface 86a, such as a plurality of biasing members 81.
  • Each biasing member 81 can correspond to an alignment channel 84.
  • the biasing member 81 can be configured to extend into the alignment channel 84 so as to apply a biasing force to the optical fiber 85.
  • Each biasing member 81 can be monolithic with, or separately- attached to, the waveguide holder 86, or other elements of the optical transceiver.
  • each biasing member 81 can be configured as a wedge element that can urge a respective one of the optical fibers 85 against the alignment surfaces 75 and 93 of a respective one of the alignment channels 84 when the alignment indicators 80 and 82 are aligned with each other and the PIC 76 is attached to the alignment module 74.
  • the core 79 of each optical fiber 85 is thus disposed at an alignment location where it abuts a waveguide in the PIC 76 (not shown in Fig. 7E).
  • Each biasing member 81 can include a sloped surface 81a that is angled with respect to the lateral direction A and the transverse direction T.
  • Each sloped surface 1a can be configured to make a line contact 71 with a respective one of the optical fibers 85.
  • Each sloped surface 8 la can be configured to bias a respective one of the optical fibers 85 in a direction that is perpendicular to the sloped surface 81a.
  • FIG. 7F a schematic side view of a portion of an optical transceiver is shown according to one embodiment in which an optical fiber 85 seated in an alignment module 74.
  • the waveguide holder 86 is positioned adjacent to the alignment module 74 in a manner that elasticaiiy bends the optical fiber 85.
  • the optical fiber 85 is secured to the waveguide holder 86 over a portion of its length such that a terminal end 85a of the optical fiber 85 extends outwardly from the waveguide holder 86.
  • the terminal end 85a of the optical fiber 85 is not secured to the waveguide holder 86.
  • the waveguide holder 86 forms a first line contact 71a with the optical fiber 85
  • the alignment module 74 forms a second line contact 71b with the optical fiber 85.
  • the first line contact 71a is angularly offset from the line contact 71b. Consequently, the optical fiber is elastically bent so that the terminal end 85a of the optical fiber 85 adjacent the PIC 76 seats against the alignment module 74.
  • the optical fiber 85 can seat into an alignment channel 84 configured as shown in any one of Figs. 7 A to 7E or in any other suitably -configured alignment channel. In this manner, the fiber core 79 is abutted with a PIC waveguide 63 so that they are optically aligned.
  • the alignment module 74 extends past the PIC 76 in the longitudinal direction L so that alignment features 82 on the alignment module 74 can mate with matching alignment features 80 on the PIC 76 as previously described.
  • the alignment module 74 is designed and configured to support the core 79 of the received optical fiber 85 at a predetermined location, and the predetermined location is aligned with the waveg uides of the PIC 76 along a plane defined by the longitudinal direction L and the transverse direction T when the alignment indicators 80 and 82 are aligned with each other.
  • the waveguide holder 86 and alignment module 74 can be configured such that the terminal ends 85a one or more of the optical fibers 85 are not registered into a corresponding alignment channel 84 of the alignment module 74 when the waveguide holder 86 is disposed adjacent the alignment module 74.
  • the terminal ends 85a of the optical fibers 85 can be rigidly secured to the waveguide holder 86, and the waveguide holder 86 and the terminal ends 85a can be mechanically registered together to the alignment module 74, which in turn is mechanically registered to the PIC 76.
  • a schematic end elevation view of a waveguide holder 86 and alignment module 74 is shown according to one embodiment.
  • the waveguide holder 86 has a plurality of holder channels 90 that can be configured as described above in relation Figs. 4 and 7B.
  • Each optical fiber 85 may be registered to and secured in a holder channel 90 in the waveguide holder 86.
  • the waveguide holder 86 and alignment module 74 can be configured such that one or more, up to all, of the optical fibers 85 do not make direct mechanical contact with the alignment module 74.
  • the waveguide holder 86 can be configured to form two line contacts 71 with each optical fiber 85.
  • the terminal ends 85a of the optical fibers 85 can be fixedly secured to the holder channels 90 by with an adhesive or other suitable faster such that terminal ends 85a do not move relative to the waveguide holder 86.
  • the waveguide holder 86 and the optical fibers 85 form a subassembly 83 that can be mounted onto the alignment module 74.
  • the alignment module 74 can be configured to provide line contact with at least first and second ones of the optical fibers 85.
  • the first and second optical fibers 85(1) and 85(2) can be spaced from one another along the lateral direction A.
  • at least one other optical fiber 85(3), 85(4), and 85(5) can be disposed between the first and second optical fibers 85(1 ) and 85(2), where the alignment module is configured so as to not provide line contact with the at least one other optical fiber 85(3), 85(4), and 85(5).
  • the first and second optical fibers 85(1) and 85(2) can be outermost ones of the optical fibers 85(1) and 85(2) as shown such that all optical fibers 85 that transmit optical signals are situated between the first and second optical fibers 85(1) and 85(2), although embodiments of the disclosure are not so limited.
  • the alignment module 74 has an alignment channel 84 that is configured to align with one of the holder channels 90 along the transverse direction T.
  • the alignment channel 84 can be configured as described above in relation to Figs. 7A to 7F.
  • the alignment channel 84 can be a substantially v -shaped groove.
  • the alignment channel 84 can form two line contacts 71 with the first corresponding optical fiber 85(1).
  • the alignment module 74 can be configured such that the inner module surface 74a forms a line contact 71 with the second optical fiber 85(2).
  • the inner module 74a can be considered to be a reference surface.
  • the alignment module 74 can define a recess 89 that extends into the inner module surface 74a.
  • the recess 89 can extend towards the outer module surface 74b and terminate before the outer module surface 74b.
  • the waveguide holder 86 and alignment module 74 can be configured such that, when the waveguide holder and optical fiber subassembly 83 is mounted onto the alignment module 74 thereby forming line contacts with the first and second optical fibers 85(1 ) and 85(2), the at least one other optical fiber 85(3), 85(4), and 85(5) is disposed in the recess 89.
  • the waveguide holder and optical fiber subassembly 83 is aligned with a PIC (not shown in Fig. 7G) by placing the first side optical fiber 85(1) or some mechanical reference member, such as a cylindrical rod, into alignment channel 84 of the alignment module 74.
  • the second optical fiber 85(2) or equivalent mechanical reference may be placed against the inner module surface 74a of the alignment module 74.
  • the waveguide holder and optical fiber subassembly 83 and the alignment module 74 may be secured together with an adhesive or other suitable fastener to form a unitary structure.
  • the waveguide holder and optical fiber subassembly 83 and alignment module 74 may be held together by a compressive force, such as may be supplied by a clamp (not shown).
  • the alignment module 74 and waveguide holder and optical fiber subassembly 83 can be kinematically mounted together.
  • the three line contacts 71 where the first optical fiber 85(1) and the second optical fiber 85(2) contact the alignment module 74 deterministically fix the orientation of the waveguide holder and optical fiber subassembly 83 to the alignment module 74.
  • Fig. 7G only two of the optical fibers 85( 1) and 85(2) are registered with the alignment module 74. This is in contrast with other embodiments in which greater than two optical fibers are registered with the alignment module 74. As the number of optical fibers 85 that are registered increases above two, the likelihood that one or more optical fibers 85 might not register properly with the alignment module 74 increases.
  • the alignment module 74 and waveguide holder 86 of Fig. 7G can be less susceptible to registration errors due to insufficient manufacturing tolerances or mechanical deformation than other systems in which more than two optical fibers are registered into the alignment module. Additionally, increasing the lateral distance between first and second optical fibers 85( 1) and 85(2) can limit the likelihood of mis-orientation of the optical fibers 85.
  • a method of placing the PIC 76 in optical alignment with the optical fiber 85 can comprise a step of aligning the PIC 76 with the alignment module 74.
  • the method can further comprise attaching the PIC 76 to the alignment module 74 while the PIC 76 is aligned with the alignment module.
  • the method can yet further comprise aligning the alignment module 74 with the waveguide holder 86 that defines the holder channel 90 that supports the optical fiber 85 such that the core 79 of the optical fiber 85 is optically aligned with a corresponding waveguide of the PIC 76.
  • one of the first and second optical fibers 85(1 ) and 85(2) may be replaced by an alignment sphere or other suitably shaped marker. While the other optical fibers 85(3), 85(4), and 85(5) in Fig. 7G are shown as not contacting the alignment module 74, embodiments of the disclosure are not so limited.
  • the alignment module 74 may have a series of alignment channels, a reference flat, or compliant surface that urge the terminal ends 85a of the optical fibers 85 against alignment surfaces of the waveguide holder 86.
  • the waveguide holder 86 may bend the optical fibers 85 so that elastic deformation of the optical fibers 85 registers them against the appropriate surfaces in the waveguide holder 86.
  • the substrate 26 can define a recess 94 that extends into the first substrate surface 26a.
  • the recess 94 can be sized to receive a lower portion of the alignment module 74, such that when the alignment channels 84 receive the optical fibers 85 in the manner described above, the optical fibers 85 are butt coupled to the photonic integrated circuit 76 in optical alignment with the waveguides of the photonic integrated circuit 76.
  • a lower portion of the alignment module 74 can be seated in the recess 94, such that a portion of the alignment channels extend out from the first substrate surface 26a.
  • the optical engine can further include an auxiliary mounting structure 31 that is mounted to the photonic integrated circuit 76.
  • the auxiliasy mounting structure 31 can be mounted to an external-facing surface of the photonic integrated circuit 76.
  • the auxiliary mounting structure 31 can be mounted to the upper surface of the photonic integrated circuit 76 that faces away from the underlying substrate 26.
  • the auxiliasy mounting structure 31 can be located adjacent the edge of the photonic integrated circuit 76 that is coupled to the optical fibers 85.
  • the auxiliary mounting structure 31 can be substantially flush with the edge of the photonic integrated circuit 76.
  • the auxiliary mounting structure 31 can further be elongate al ong the l ateral direction A at the edge of the photonic integrated circuit 76.
  • the waveguide holder 86 can be mounted to the auxiliary mounting structure 31 while the optical fibers 85 are butt coupled with the photonic integrated circuit 76 in optical alignment with the waveguides of the photonic integrated circuit 76, thereby increasing the bonding strength of the edge coupling between the transmit photonic integrated circuit 76 and the optical fibers 85.
  • the auxiliary mounting structure 31 can reduce bowing of the transmit PIC 32 and provide increased attachment area for transmit waveguide holder 38, thereby further increasing the bonding strength of the edge coupling between the transmit PIC 32 and the transmit waveguides 36.
  • the auxiliar ' mounting structure 31 can be referred to as a stiffener that enhances the rigidity of the photonic integrated circuit 76.
  • the method can include the step of aligning the photonic integrated circuit 76 with the alignment module 74 that defines an alignment channel 84 designed to receive the optical fiber. While the photonic integrated circuit 76 is aligned with the alignment module 74, the method can include the step of attaching the photonic integrated circuit 76 to the alignment module 74 such that when the alignment channel 84 receives the optical fiber, the core of the optical fiber is optically aligned with the
  • the alignment channel 84 can define a pair of side walls 93 of the alignment module 74, and a midplane that is equidistantly spaced from the side walls 93.
  • the aligning step can place the waveguide of the photonic integrated circuit 76 in alignment with the midplane, such that the midplane passes through the waveguide at the coupling edge of the photonic integrated circuit 76.
  • the method can further comprise the step of placing the optical fiber in the alignment channel 84 after the attaching step.
  • the method can further include the step of attaching the optical fiber to a fiber holder 86 prior to placing the optical fiber in the alignment channel 84.
  • the step of attaching the optical fiber to the fiber holder 86 can include the step of securing the buffer layer of the optical fiber to the fiber holder 86 such that the core of the fiber extend s forward from the buffer in a channel of the holder 86, which can be defined by the second coupler channel 90.
  • the fiber holder 86 can be provide strain relief for the optical fiber.
  • the method can further include the step of capturing the core between the alignment module 74 and the fiber holder 86 such that the core is in optical alignment with the waveguide of the photonic integrated circuit 76.
  • the capturing step can include the step of placing an inner holder surface 86a that defines openings of the coupler channel portions 90a and 90b against an inner alignment module surface 74a that defines openings of the alignment channels 84.
  • the optical engine can be mounted on the substrate 26.
  • the optical engine can be mounted directly on the substrate 26.
  • the optical engine can be mounted onto a second substrate 27 that is configured as a carrier 29 (see, e.g., Figs. 10 and 15) that, in turn, is configured to be mounted onto a first substrate that is configured as the substrate 26 so as to place the carrier 29 in electrical communication with the substrate 26.
  • the carrier 29 can be placed in electrical communication with the substrate 26 when the carrier 29 is mounted to the substrate 26.
  • the carrier 29 can be replaced by the substrate 26 such that the optical engines or components thereof are mounted directly onto the substrate 26.
  • the description of the carrier 29 can equally apply to the substrate 26 when the optical engines are mounted directly to the substrate 26 as opposed to the carrier 29.
  • the substrate 26 can be replaced by the carrier 29 such that the optical engines or components thereof are mounted directly on the carrier 29 which, in turn, is mounted on the substrate 26.
  • One benefit of mounting the optical engine on a carrier 29 is to provide a modular optical engine that can be mounted to any suitable platform as desired, such as a mid- board module or a front panel mounted module.
  • the optical engine can be mounted on a daughter board, a multi-source-agreement (MSA) optical transceiver such as a quad small form factor pluggable (QSFP) transceiver, an application specific integrated circuit (ASIC) interposer, or in an on-board transceiver.
  • MSA multi-source-agreement
  • QSFP quad small form factor pluggable
  • ASIC application specific integrated circuit
  • the carrier 29 is configured to support a plurality of optical fibers 85 such that, when the PIC 76 is aligned with the carrier 29 and mounted to the carrier 29, the optical fibers 85 are butt coupled to the PIC 76 and aligned with the waveguides of the PIC 76.
  • reference to optical fibers 85 can include the optical transmit waveguides 36, the optical receive waveguides 60, or both.
  • the carrier 29 can define a first carrier surface 29a and a second carrier surface 29b opposite the first carrier surface 29a along the transverse direction T.
  • the carrier 29 is configured to be mounted to the substrate 26, such that the second carrier surface 29b faces the first substrate surface 26a.
  • the second carrier surface 29b can be mounted to the first substrate surface 26a.
  • the second carrier surface 29b can thus be referred to as a bottom or lower surface of the earner 29, and the first carrier surface 29a can be referred to as a top or upper surface of the carrier 29.
  • the carrier 29 can define a pocket 96 that extends into the first carrier surface 29a, such that the base 97 of the pocket 96 is recessed from the first carrier surface 29a by a distance d.
  • the carrier 29 can define a plurality of alignment channels 100 that are configured to receive the optical fibers 85 such that the cores are aligned with respective waveguides of the PIC 76 when the PIC is mounted to the carrier 29.
  • the alignment channels 100 can thus be disposed adjacent the pocket 96 along the longitudinal direction L.
  • the alignment channels 100 can be elongate along the longitudinal direction L.
  • the alignment channels 100 can be spaced from each other along the lateral direction A.
  • the alignment channels 100 can he constructed as described above with respect to the alignment channels 84 of the alignment module 74.
  • the carrier 29 can be referred to as an alignment module in that it is configured to place the optical fibers 85 in alignment with the PIC 76.
  • the carrier 29 differs from the alignment module 74 described above.
  • the transmit PIC 32 and receive PIC 64 can be mounted directly to the substrate 26.
  • the modulator driver 25 and the current-to-voltage converter 66 can be mounted directly to the substrate 26.
  • the carrier 29, on the contrary, can be configured as an electrical interposer having electrical conductors that are contigured to be placed in electrical communication both with an optical engine and the substrate 26, thereby placing the optical engine in electrical communication with the substrate 26.
  • the carrier 29 may also provide electrical connections thai go directly between the PIC 32 and a driver 25 and/or a PIC 64 and a current-to-voltage converter 66. These electrical connections will be described in greater detail below.
  • the carrier 29 thus provides both an optical alignment function and an electrical transmission function.
  • the carrier 29 can further include a strain relief platform 98.
  • the strain relief platform. 98 can be configured to attach to the buffer 85b of the optical fiber 85, such that the cladding 85c and core 79 extend from the strain relief platform 98 into the alignment channels 100 of the carrier 29.
  • the buffer end of the optical fiber 85 can be stripped from the cladding.
  • the stram relief platform 98 can include strain relief channels that can be configured as described above with respect to the first channel portions 90a of the waveguide holder 86, Thus, the strain relief channels of the strain relief platform 98 can attach to the buffer of the optical fibers 85, such that the core and cladding extend out from the strain relief platform and into the alignment channels 100 of the carrier 29.
  • the carrier 29 can define a shoulder 102 that extends up from the strain relief platform 98 at a location between the alignment channels 100 and the strain relief platform 98.
  • the alignment channels 100 can extend through the shoulder 102.
  • the buffer can be attached to the strain relief platform 98 such that ends of the buffers abut the shoulder 102.
  • the core and cladding can extend forward from the buffer, and thus from the shoulder 1 2, a distance equal to the length of the alignment channels 100.
  • the carrier 29 can be formed from a single element or from one or more individual elements, which are bonded together to form the pocket 96 present in the carrier 29.
  • the optical fibers 85 can be attached to the waveguide holder 86 in the manner described above, such that the cladding and core extend into the alignment channels 100 of the earn r 29.
  • the holder 86 can include only the first channel portion 90a and not the second channel portion 90b.
  • the inner holder surface 86a of the waveguide holder 86 can be mounted to the carrier 29. Thus, the open ends of the holder channels 90 can face away from the carrier 29.
  • the optical fibers 85 can be registered into the alignment channels 100 of the carrier 29 in the manner described above with respect to the alignment module 74, Each optical fiber 85 described herein can be configured as a single mode fiber having a core and cladding surrounded by the buffer.
  • the core diameter can be approximately 9 microns.
  • the outer diameter of the cladding can be approximately 125 microns. While these are standard dimensions of optical fibers, it should be appreciated that the present disclosure is not limited to tins type of optical fiber.
  • the alignment channels 100 of the carrier 29 can be formed by anisotropically etching silicon, for instance, when the carrier 29 is made of silicon.
  • the alignment channels 84 of the alignment module 74 described above can be formed by anisotropically etching silicon, for instance, when the alignment module 74 is made of silicon.
  • the carrier 29 and the alignment module 74 may be formed from silicon, glass, ceramic, or a polymer. It is recognized , of course, that the alignment channels 84 and 100 can be formed by any suitable alternative method.
  • the side walls 93 that define the alignment channels can have a width w that can be defined photolithographically. If the alignment channels are fonned by anisotropically etching silicon, then the side wall 93 and a line oriented along the lateral direction A can define an angle a that is between 30 degrees and 80 degrees, such as between 40 degrees and 70 degrees, such as between 50 degrees and 60 degrees. In one example, the angle a can be approximately 54.7 degrees.
  • the fibers When the optical fibers are inserted into the alignment channels, the fibers may be spaced apart by a pitch. In one example, the pitch can be a constant pitch between adjacent ones of the optical fibers that are disposed in the alignment channels. In one example, the pitch can be between 150 microns and 400 microns, or a multiple thereof. For instance, in one example, the pitch can be approximately 250 microns or some multiple thereof, such as approximately 500 microns or approximately 750 microns.
  • the w idth w of the alignment channel and the angle of the side wall with respect to the line oriented along the lateral direction A can determine the height of the received optical fiber cores with respect to the first carrier surface 29a along the transverse direction T.
  • the core can be disposed above the first carrier surface 29a, such that the first carrier surface 29a is disposed between the core and the second carrier surface 29b.
  • the core can be disposed below the first earner surface 29a, such that the core is disposed between the first carrier surface 29a and the second carrier surface 29b. It is recognized that if the core is disposed below the first carrier surface 29a, then the carrier can define a pocket sized to receive the PIC 76, such that the cores can be optically aligned with the waveguides of the PIC 76.
  • the carrier 29 can include a plurality of vias that define electrical paths configured to place the electrical components of the optical engine in electrical communication with the substrate 26,
  • the electrical components can include the PIC, the modulator driver 25 (in the case of a transmitter), the current-to-voltage converter 66 (in the case of a receiver), a microprocessor, an additional other electrical components as desired.
  • the carrier 29 can include a plurality of electrically conductive PIC vias 106 that are configured to electrically connect to the PIC 76, and are further configured to electrically connect to the substrate 26. In one example, one or more up to all of the PIC vias 106 can thus extend from the base 97 of the pocket 96 to the second carrier surface 29b.
  • the carrier 29 can further include electrically conductive auxiliary vias 1 4 that are configured to electrically connect to the modulator driver 25 or the current-to-voltage converter 66 at the first carrier surface 29a, and are configured to electrically connect to the substrate 26 at the second carrier surface 29b.
  • the auxiliary vias 104 can extend from, the first carrier surface 29a to the second carrier surface 29b.
  • the optical engine can further include a plurality of electrical contacts 108 that are exposed on the first carrier surface 29a, the second carrier surface 29b, and the base 97 of the pocket 96.
  • the electrical contacts 108 can include at least one surface trace 99.
  • the electrical contacts 108 can terminate the electrically conductive vias.
  • the electrical contacts 108 are configured to establish electrical connections to mated elements.
  • the mated elements can include electrical components of the optical engine and the substrate 26.
  • the electrical contacts 108 may take many forms and the electrical connections can be made using any desired configuration.
  • the electrical contacts 108 on the different surfaces may be different.
  • the electrical contacts 108 may be solder balls, copper pillars, or some other type of contact.
  • the electrical connection can be established by soldering, thermo-compression bonding, ultrasonic bonding or some other type of connection method.
  • the at least one first alignment indicator 80 can include at least a pair of first alignment indicators 80
  • the at least one second alignment indicator 1 10 can include at least a pair of second alignment indicators 82.
  • the PIC 76 and the earner 29 are aligned with each other in a predetermined relative position with respect to the longitudinal direction L and the lateral direction A.
  • the PIC 76 is aligned with the alignment channels 1 0 such that the optical fibers 85 received in the alignment channels 100 are in optical alignment with the corresponding waveguides of the photonic integrated circuit 76.
  • the PIC 76 can be disposed adjacent the alignment channels 100 such that the cores that extend forward from, the buffer a distance equal to the length of the alignment channels 100 can be butt coupled to the PIC 76.
  • the alignment indicators 80 and 1 10 can be aligned with each other along the transverse direction T.
  • One or both of the first and second alignment indicators 80 and 1 10 can be configured as visual markings. The visual markings can be visible in ambient lighting conditions or visible with infrared light.
  • the first and second alignment indicators 80 and 1 10 can be visible alignment indicator.
  • the first and second alignment indicators 80 and 1 10 can be structures, wherein one of the first and second alignment indicators 80 and 1 10 is configured to mate with or receive the other of the first and second alignment indicators 80 and 1 10.
  • the first and second alignment indicators 80 and 1 10 can be structures each configured to receive or otherwise mate with at least one auxiliary alignment structure so as to align the PIC 76 with the earner 29.
  • the PIC 76 can be sized larger than the pocket 96 with respect to one or both of the longitudinal direction L and the lateral direction A. Thus, when the PIC 76 is attached to the first carrier surface 29a, the PIC 76 can extend over the pocket 96. In one example, the PIC 76 can extend over and past both sides of the pocket 96 with respect to the lateral direction A, and can extend over and past one longitudinal end of the pocket 96 that is opposite a registration face 103 that is disposed between the alignment channels 100 and the pocket 96. In another example, the registration face 103 can be spaced from the pocket 96, such that the PIC 76 can extend over and past both longitudinal ends of the pocket 96 along the longitudinal direction L.
  • the electrical contacts 108 can extend between the PIC vias 106 and the PIC 76.
  • the electrical contacts 108 are configured as solderable elements, surface tension in the solder while it is liquid can tend to pull the PIC 76 substantially flush against the first carrier surface 29a.
  • the electrical contacts 108 can be positioned between the PIC 76 and the earner 29 can be slightly offset along the longitudinal direction. That is, the electrical contacts 108 can be offset toward the registration face 103 such that the liquid solder urges the coupling edge of the PIC 76 to move against the registration face. When the solder solidifies, the PIC 76 is thus registered against both the first carrier surface 29a and the registration face 103.
  • the first carrier surface 29a where the PIC 76 is mounted can be slightly recessed with respect to the first carrier surface 29 at the registration face 103, such that the coupling edge is aligned with the registration face 103 along the longitudinal direction L.
  • the coupling edge of the PIC 76 can extend into the pocket 96 such that the coupling edge is aligned with the registration face 103 along the longitudinal direction.
  • the electrical contacts 108 can extend from electrical contact locations of the substrate 26 to electrical contact locations of the PIC 76 so as to urge the PIC 76 against the first su bstrate surface 26a and the registration face 103 in the manner described above.
  • the alignment channels 100 are designed such that when the optical fibers 85 are registered in the alignment channels 100, and the PIC 76 is aligned with, and attached to, the carrier 29, the cores of the optical fibers 85 are optically aligned with the waveguides of the PIC 76 with respect to the lateral direction A and the transverse direction T.
  • the center of the waveguides is 1 to 10 microns above the first carrier surface 29a when the PIC 76 is substantially flush with the first carrier surface 29a, such that the distance between the core and the first carrier surface 29a is also in the range of 1 to 10 microns.
  • Registration between the cores and the waveguides of the PIC in the in the longitudinal direction L is accomplished by urging the coupling edge of the PIC 76 against the registration face 103 of the carrier 29, using solder surface tension between offset electrical contacts 108 or an alternative alignment mechanism .
  • the first and second alignment indicators 80 and 110 can be mechanical indicators that align the PIC 76 with the carrier 29 along the lateral direction A and the transverse direction ! ' .
  • the first and second alignment indicators 80 and 110 can be can be structures each configured to receive or otherwise mate with at least one auxiliary alignment structure 112 so as to align the PIC 76 with the earner 29.
  • the auxiliary alignment structure 112 can be configured as at least one alignment pin such as a pair of alignment pins 1 14.
  • the alignment pins 114 can be any suitable elongate structure configured to extend along a respective one of the alignment channels 100 of the carrier 29.
  • the alignment channels 100 that receive the alignment pins 114 can be configured the same as the alignment channels 100 that receive the optical fibers 85.
  • the alignment pins 114 can be configured as optical fibers 85.
  • the alignment pms 114 can be sized differently than the optical fibers 85
  • the alignment channels 100 that receive the alignment pins 114 can be sized differently than the alignment channels 100 that receive the optical fibers 85.
  • the alignment pins 1 14 can be configured as metallic or ceramic pins, such as alignment pins of a mechanical transfer fermle.
  • the alignment pins 114 may be optical fibers which are solely used for mechanical purposes and are not past of the optical circuit.
  • alignment pins 1 14 are configured as optical fibers 85
  • optical alignment of the alignment pins 114 with respective waveguides of the PIC 76 can confirm alignment of the PIC 76 with the alignment channels 100.
  • the outermost alignment channels 100 with respect to the lateral direction can receive the alignment pins 114.
  • the alignment pins 114 can overhand the registration face 103, and can extend into
  • the first alignment indicator 80 can be defined by the registration grooves 116.
  • the registration grooves 116 can extend into the bottom surface of the PIC 76 that faces the substrate 26.
  • the optical fibers 85 and the alignment pins 114 configured as optical fibers 85 can be defined by a fiber ribbon cable.
  • the alignment pins 1 14 can extend from the alignment channels 100 and into the registration channels 116 of the PIC 76.
  • the registration grooves 116 can have a width along the lateral direction A that is greater than the alignment channels 100, since the alignment pins 114 is disposed initially in the alignment channel 100 and then aligns with the registration channels 116 for insertion therein. It is appreciated that the registration channels 116 can be open to the bottom of the PIC 76, and the alignment channels 100 can be open to the top of the carrier 29. Thus, the open ends of the registration channels 116 and the open ends of the alignment channels 100 can face each other with respect to the transverse direction T, though they are offset from each other along the longitudinal direction L.
  • the PIC 76 and carrier 29 can be spaced from one another so as to define a gap 78 between exists between the PIC 76 and the carrier 29 so that alignment between the two is provided by line contacts (shown as points 71 in Fig 16).
  • Each alignment pin 1 14 can be supported by four contact lines 71, two on the carrier 29 and two on the PIC 76. If the angle a of the alignment channel 100 is the same as the corresponding angle of the registration channels 1 16, and if the registration channels 1 16 have a width along the lateral direction A that is greater than the alignment channels 100, then the plane defined by the optical fiber cores 79 lies closer to the PIC 76 than the carrier 29. It should be appreciated that any of the alignment systems and methods described relative to the waveguide holder 86 and alignment module 74 in Figs. 7A-7G may be applied to the PIC 76 and carrier 29.
  • the optical fibers 85 of Figs. 10-14 and the optical fibers of Figs. 15-16 can be attached at different stages of the assembly process.
  • the alignment channels 100 of the carrier 29 can be fully populated with the optical fibers 85 and alignment pins 1 14 if used.
  • the optical fibers 85 and alignment pins can be adhesively secured to the carrier 29 by an epoxy, or secured by some other methods.
  • the PIC 76 is then placed on the carrier 29 over the pocket 96, and the alignment indicators 80 of the PIC 76 are registered with the alignment indicators of the carrier 29 as previously described.
  • a solder reflow process may be used to both make electrical connections from the carrier 29 to the PIC 76, and to mechanically secure the PIC 76 to the carrier 29 in the manner described above.
  • An auxiliary electrical structure such as a driver or current-to-voltage converter can be soldered to the carrier 29 during the same reflow operation.
  • a carrier/PIC subassembly or current-to-voltage converter/PIC subassembly can be referred to as a pigtaiied subassembly , since the optical fibers are permanently secured to the subassembly.
  • the optical fibers 85 can be mounted to the carrier 29 in the alignment channels 100 after the PIC 76 has been secured to the carrier 29.
  • the alignment pins 1 14 can be secured to the carrier 29 prior to securing the optical fibers 85 to the carrier 29.
  • the PIC 76 is then aligned with the carrier 29 and secured to the earner, and the optical fibers can be subsequently mounted to the carrier.
  • the optical fibers 85 may be detachable from the carrier 29.
  • the carrier 29 can be mounted to the substrate 26, which can be configured as a printed circuit board, to form the optical transceiver 20.
  • the substrate 26 can provide electrical paths for electrical signals to transfer between the PIC 76 and the driver 25 or current-to-voltage converter 66.
  • the carrier 29 can support one or both of the transmitter 22 and the receiver 24.
  • a first carrier 29 can support the transmitter 22 in the manner described above, and a second carrier 29 can support the receiver 24 in the manner described above.
  • the carrier 29 to define an alignment module as described above with respect to Figs. 10-16 can have additional advantages that the optical fiber 85 and PIC 76 can be independently coupled to the carrier 29, which is relatively large and mechanically robust. Thus mechanical stresses that can be transmitted down the optical fibers 85 are not directly- coupled into the PIC 76.
  • a further advantage is that in some embodiments only a single component, the carrier 29, is used to align the optical fibers 85 adjacent the PIC 76, thereby reducing complexity.
  • the fibers 85 can be detachable from the carrier. Further, the fibers 85 can be installed in the carrier 29 after mounting the carrier 29 to the substrate 26. This facilitates manufacture of the transceiver 20 because the pigtailed
  • subassembly can be fabricated without a solder reflow process step.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

Un émetteur-récepteur optique comprend un circuit intégré photonique qui est configuré pour être placé en alignement avec un module d'alignement qui est configuré pour porter une pluralité de fibres optiques. Lorsque le circuit intégré photonique est aligné avec le module d'alignement, les fibres optiques sont placées en alignement optique avec des guides d'ondes respectifs du circuit intégré photonique.
PCT/US2017/058402 2016-10-26 2017-10-26 Émetteur-récepteur optique ayant un module d'alignement Ceased WO2018081340A1 (fr)

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TWI870793B (zh) * 2022-12-28 2025-01-21 大陸商訊芸電子科技（中山）有限公司 光電收發器件及光模組

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US10852494B2 (en) * 2018-12-11 2020-12-01 The Boeing Company Avionics pluggable active optical connector
US11163128B2 (en) 2019-03-20 2021-11-02 Ppc Broadband, Inc. Enclosure for spliced cables for use in an outdoor environment
US11443998B2 (en) * 2019-06-05 2022-09-13 Te Connectivity Solutions Gmbh Electronic assembly including optical modules
US20240085621A1 (en) * 2022-09-14 2024-03-14 Taiwan Semiconductor Manufacturing Co., Ltd. Signal Communication Through Optical-Engine Based Interconnect Component

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US11009727B2 (en) 2018-11-13 2021-05-18 International Business Machines Corporation Integrated waveguide structure with pockels layer having a selected crystal orientation
TWI771662B (zh) * 2019-03-18 2022-07-21 佑勝光電股份有限公司 光學收發模組及光纖纜線模組
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CN112055485B (zh) * 2019-06-05 2024-06-07 泰连公司 具有光学模块的电子组件
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TWI870793B (zh) * 2022-12-28 2025-01-21 大陸商訊芸電子科技（中山）有限公司 光電收發器件及光模組

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