WO2016016915A1 - Optical module and manufacturing method therefor - Google Patents

Abstract

An optical module according to the present invention includes: an optical signal processing circuit; and a first signal-light incidence-side lens and a first local-transmission-light incidence-side lens which are connected to the incidence-side end surface of the optical signal processing circuit. The optical signal processing circuit allows for input of a signal light from a single-mode fiber as well as input of a local transmission light from a polarization plane holding fiber, and performs signal processing on the signal light and the local transmission light to generate respective output signal lights. The first signal-light incidence-side lens allows the signal light to pass therethrough. The first local-transmission-light incidence-side lens allows the local transmission light to pass therethrough. The image of the signal light is formed on a part where an end surface of a signal-light incident waveguide is positioned, at a connection surface of the first signal-light incidence-side lens with the signal processing circuit. The image of the local transmission light is formed on a part where an end surface of a local-transmission-light incident waveguide is positioned, at a connection surface of the first local-transmission-light incidence-side lens with the signal processing circuit.

Description

Optical module and manufacturing method thereof

The present invention relates to an optical module and a manufacturing method thereof, and more particularly, to a reception front end module compatible with a digital coherent system and a manufacturing method thereof.

In recent years, with the increase in communication capacity, ultra high-speed optical transmission systems of 100 Gbit / sec or more are becoming mainstream. In the ultra-high-speed optical transmission system, the communication technology using the digital coherent transmission method is currently mainstream. In recent years, in the ultra-high-speed optical transmission system, along with further increase in communication traffic, an optical module for demodulation corresponding to the optical phase modulation method, that is, the PQPSK transmission method and the DP-QPSK transmission method has been developed. In particular, in an ultra-high-speed optical transmission system, an integrated coherent receiver (ICR (Integrated Coherent Receiver)), which is a reception front-end module compatible with a digital coherent method, is a key device.

1A and 1B are diagrams showing a configuration of an optical module 100 compatible with a conventional digital coherent method. 1A is a top perspective view of the optical module 100, and FIG. 1B is a side perspective view of the optical module 100. The optical module 100 is an ICR compatible with a digital coherent method (see Patent Document 1). The optical module 100 includes a housing unit 101, a lid 150, a single mode fiber 111 that makes signal light incident on the optical module 100, a polarization-maintaining fiber 112 that makes local light incident on the optical module 100, and a single mode fiber. 111 and a fiber block 113 that holds the polarization-maintaining fiber 112. In addition, the optical module 100 is connected to the fiber block 113 and has an optical signal processing circuit 120 configured by a planar optical waveguide circuit, and a lens 131 that collects the first output signal light emitted from the optical signal processing circuit 120. And a lens 132 that condenses the second output signal light emitted from the optical signal processing circuit 120, and converts the first and second output signal lights collected by the lenses 131 and 132 into electric signals, respectively. And a photoelectric conversion unit 140. The housing unit 101 and the lid 150 package the fiber block 113, the optical signal processing circuit 120, the lenses 131 and 132, and the photoelectric conversion unit 140. The photoelectric conversion unit 140 receives a photodiode 141 that receives the first output signal light from the lens 131, a photodiode 142 that receives the second output signal light from the lens 132, and an output voltage from the photodiode 141. An amplifier 143 for amplifying and an amplifier 144 for amplifying the output voltage from the photodiode 142 are provided.

The optical signal processing circuit 120 performs signal processing on the incident signal light and the local transmission light, converts the phase difference between the signal light and the local transmission light into the light intensity of the output signal light of the optical signal processing circuit 120, and outputs the phase A polarization multiplexing hybrid circuit (DPOH: Dual Polarization Optical Hybrid) that generates a plurality of different output signal lights is used.

In the optical module 100, the signal light propagating through the single mode fiber 111 is incident on the signal light incident waveguide 121 of the optical signal processing circuit 120, and the locally transmitted light propagating through the polarization-maintaining fiber 112 is the optical signal processing circuit 120. Is incident on the locally transmitted light incident waveguide 122. The signal light and the locally transmitted light incident on the optical signal processing circuit 120 are subjected to signal processing in the optical signal processing circuit 120, and the phase difference between the signal light and the locally transmitted light is the output signal light of the optical signal processing circuit 120. It is converted into light intensity and converted into first output signal light and second output signal light having different phases. The first output signal light subjected to signal processing by the optical signal processing circuit 120 is received by the photodiode 141 of the photoelectric conversion unit 140 via the lens 131 and converted into an electric signal. Further, the second output signal light that has been subjected to signal processing by the optical signal processing circuit is received by the photodiode 142 of the photoelectric conversion unit 140 via the lens 132 and converted into an electrical signal.

The single mode fiber 111 and the polarization plane holding fiber 112 are arrayed at a predetermined pitch and are connected to the optical module 100. In the optical module 100, the single mode fiber 111 and the polarization plane holding fiber 112 are held at a predetermined pitch by a fiber block 113 covered with glass, and are connected to the optical signal processing circuit 120 by a UV adhesive or the like. .

In order to stably hold the single mode fiber 111 and the polarization plane holding fiber 112 having a predetermined length, the fiber block 113 needs to have high rigidity. However, the fiber block 113 increases in size when the rigidity is increased. As a result of the increase in size of the fiber block 113, there is a problem that the optical module 100 itself is also increased in size.

Further, when the optical module 100 is manufactured, the optical coupling between the single mode fiber 111 and the signal light incident waveguide 121 of the optical signal processing circuit 120, and the locally transmitted light incident waveguide 122 of the polarization plane holding fiber 112 and the optical signal processing circuit 120 are used. Are respectively coupled by bad coupling. In this case, in order to obtain good optical coupling efficiency between the single mode fiber 111 and the signal light incident waveguide 121, the mode field diameter of the single mode fiber 111 and the signal light incident waveguide 121 of the optical signal processing circuit 120 are It is necessary to match the mode field diameter. In order to obtain good optical coupling efficiency between the polarization-maintaining fiber 112 and the locally transmitted light incident waveguide 122 of the optical signal processing circuit 120, the mode field diameter of the polarization-maintaining fiber 112 and the locally transmitted light incident guide It is necessary to match the mode field diameter of the waveguide 122.

Therefore, the optical module 100 needs to perform spot size conversion on the mode field diameters of the signal light incident waveguide 121 and the locally transmitted light incident waveguide 122 to match the mode field diameters of the single mode fiber 111 and the polarization-maintaining fiber 112, respectively. is there.

However, it is difficult to make the mode field diameters of the signal light incident waveguide 121 and the locally transmitted light incident waveguide 122 exactly match the mode field diameters of the single mode fiber 111 and the polarization-maintaining fiber 112, resulting in an increase in cost. It was also a factor. In addition, manufacturing errors may occur. Therefore, there are subtle differences between the mode field diameters of the signal light incident waveguide 121 and the locally transmitted light incident waveguide 122 and the mode field diameters of the single mode fiber 111 and the polarization-maintaining fiber 112, respectively. There was a problem that the coupling loss increased.

Furthermore, the single mode fiber 111 and the polarization-maintaining fiber 112 are arrayed via the fiber block 113, and an array pitch shift is unavoidable due to manufacturing errors of the fiber block 113. Due to the deviation of the array pitch, a difference occurs between the pitch of the single mode fiber 111 and the polarization-maintaining fiber 112, and the pitch of the signal light incident waveguide 121 and the locally transmitted light incident waveguide 122 of the optical signal processing circuit 120. There has been a problem that variation occurs in the optical coupling efficiency between light and locally transmitted light.

JP 2012-58409 A

One aspect of the present invention is an optical module, wherein a single mode fiber that propagates signal light, a polarization-maintaining fiber that propagates locally transmitted light, the signal light is incident from the single-mode fiber, and the polarization plane The local transmission light is incident from a holding fiber, and is connected to the incident side end face of the optical signal processing circuit, an optical signal processing circuit that generates an output signal light by processing the signal light and the local transmission light, A first signal light incident side lens that transmits the signal light; and a first local light incident side lens that is connected to an incident side end face of the optical signal processing circuit and transmits the local transmitted light. The signal light is imaged on a connection surface of the first signal light incident side lens with the signal processing circuit, and the local portion is formed on the connection surface of the first local light incident side lens with the signal processing circuit. Outgoing light The position where the signal light is imaged and the signal light is imaged is located at the end face of the signal light incident waveguide of the optical signal processing circuit on the connection surface of the first signal light incident side lens with the signal processing circuit. The position at which the locally transmitted light is imaged is determined by the local transmitted light incident guide of the optical signal processing circuit on the connection surface of the first locally transmitted light incident side lens with the signal processing circuit. It is a portion where the end face of the waveguide is located.

It is a top perspective view which shows the structure of the conventional optical module. It is a side perspective view which shows the structure of the conventional optical module. 1 is a top perspective view showing a configuration of an optical module according to an embodiment of the present invention. It is a side perspective view showing the composition of the optical module concerning one embodiment of the present invention. It is a perspective view which shows the 1st signal light incident side lens. It is a figure which shows the optical signal path | route from the single mode fiber or polarization plane holding fiber of the optical module of FIG. 2A and FIG. 2B to an optical signal processing circuit. The distance from the single mode fiber or polarization plane maintaining fiber of the optical module shown in FIGS. 2A and 2B to the second signal light incident side lens or the second local oscillation light incident side lens, and the first signal light incident side It is a graph which shows the relationship with the imaging beam spot radius in the optical signal processing circuit connection surface of a lens, or the optical signal processing circuit connection surface of a 1st local oscillation light incident side lens. 2A and 2B, the imaging beam spot on the optical signal processing circuit connecting surface of the first signal light incident side lens or the optical signal processing circuit connecting surface of the first local light incident side lens in the optical module shown in FIGS. It is a figure which shows light intensity in three dimensions. It is a perspective view which shows the subassembly by which the 1st signal light incident side lens and the 1st local transmission light incident side lens were connected to the optical signal processing circuit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

2A and 2B are diagrams showing a configuration of an optical module 200 according to one embodiment of the present invention. 2A is a top perspective view of the optical module 200, and FIG. 2B is a side perspective view of the optical module 200. The optical module 200 is an ICR that supports a digital coherent method. The optical module 200 includes a casing unit 201, a lid 250, a single mode fiber 211 that makes signal light incident on the optical module 200, a polarization plane holding fiber 212 that makes local light incident on the optical module 200, and a single mode fiber. A fiber holder 213 that connects 211 to the casing 201 and a fiber holder 214 that connects the polarization-maintaining fiber 212 to the casing 201 are provided. The optical module 200 includes a planar optical waveguide circuit, and an optical signal processing circuit 220 that performs signal processing of signal light from the single mode fiber 211 and local transmission light from the polarization plane holding fiber 212, and an optical signal processing circuit 220. An output side lens 231 for condensing the first output signal light emitted from the optical signal processing circuit 220, an output side lens 232 for condensing the second output signal light emitted from the optical signal processing circuit 220, an output side lens 231, and And a photoelectric conversion unit 240 that converts the first and second output signal lights collected by the H.232 into electric signals.

A first signal light incident side lens 251 having a plano-convex shape is connected to a portion of the incident side end surface 223 of the optical signal processing circuit 220 where the signal light incident waveguide 221 is disposed. A plano-convex first local transmission light incident side lens 252 is connected to a portion where the waveguide 222 is disposed. In addition, a second signal light incident side lens 253 is provided on the light exit side of the single mode fiber 211 in the fiber holder 213, and a second light beam on the light exit side of the polarization plane holding fiber 212 in the fiber holder 214. Is provided with a lens 254 of the local transmission light incident side. The first signal light incident side lens 251 and the second signal light incident side lens 253 convert the signal light emitted from the single mode fiber 211 into the first signal light incident side lens 251 and the second signal light incident side. Ideally, an imaging beam spot is formed at one point where the signal light incident waveguide 221 is disposed on the incident side end face 223 via the side lens 253, that is, a confocal system is configured. In addition, the first locally transmitted light incident side lens 252 and the second locally transmitted light incident side lens 254 also convert the locally transmitted light emitted from the polarization plane holding fiber 212 into the first locally transmitted light incident side lens. An imaging beam spot is formed at one point where the local transmission light incident waveguide 222 of the incident side end surface 223 is disposed via the 252 and the second local transmission light incident side lens 254, that is, a confocal system is formed. Ideally. However, there is no problem even if it is a pseudo-confocal system with high coupling efficiency and a low manufacturing tolerance at the time of manufacturing the module. The second signal light incident side lens 253 and the second local transmitted light incident side lens 254 can convert the signal light from the single mode fiber 211 and the local transmitted light from the polarization plane holding fiber 212 into parallel light. If so, the shape is not particularly limited.

The casing unit 201 and the lid 250 include an optical signal processing circuit 220, a first signal light incident side lens 251, a first local transmission light incident side lens 252, output lenses 231 and 232, and photoelectric conversion. The part 240 is packaged. The single mode fiber 211 and the polarization plane holding fiber 212 are not arrayed and are independently connected to the casing unit 201. The single mode fiber 211 is connected to the housing 201 via a fiber holder 213 by spot welding such as YAG laser welding. Further, the polarization-maintaining fiber 212 is connected to the housing 201 via a fiber holder 214 by spot welding such as YAG laser welding.

The photoelectric conversion unit 240 receives the first output signal light emitted from the optical signal processing circuit 220 via the emission side lens 231 and emits from the optical signal processing circuit 220 via the output side lens 232. A photodiode 242 that receives the second output signal light, an amplifier 243 that amplifies the output voltage from the photodiode 241, and an amplifier 244 that amplifies the output voltage from the photodiode 242.

In the present embodiment, the optical signal processing circuit 220 performs signal processing on the incident signal light and the local transmission light, and determines the phase difference between the signal light and the local transmission light as the output signal light of the optical signal processing circuit 220. A polarization multiplexing hybrid circuit (DPOH: Dual Polarization Optical Hybrid) that converts into intensity and generates a plurality of output signal lights having different phases is used.

In the optical module 200, the signal light propagating through the single mode fiber 211 is incident on the signal light incident waveguide 221 of the optical signal processing circuit 220, and the locally transmitted light propagating through the polarization-maintaining fiber 212 is the optical signal processing circuit 220. Is incident on the locally transmitted light incident waveguide 222. The signal light and the locally transmitted light incident on the optical signal processing circuit 220 are subjected to signal processing in the optical signal processing circuit 220, and the phase difference between the signal light and the locally transmitted light is the output signal light of the optical signal processing circuit 220. It is converted into light intensity and converted into first output signal light and second output signal light having different phases. The first output signal light subjected to signal processing by the optical signal processing circuit 220 is received by the photodiode 241 of the photoelectric conversion unit 240 via the emission side lens 231 and converted into an electric signal. In addition, the second output signal light that has been subjected to signal processing by the optical signal processing circuit 220 is received by the photodiode 242 of the photoelectric conversion unit 240 via the emission side lens 232 and converted into an electrical signal.

The optical module 200 has a configuration in which the signal light from the single mode fiber 211 enters the optical signal processing circuit 220 via the second signal light incident side lens 253 and the first signal light incident side lens 251. In addition, the optical module 200 transmits the locally transmitted light from the polarization plane holding fiber 212 to the optical signal processing circuit 220 via the second locally transmitted light incident side lens 254 and the first locally transmitted light incident side lens 252. It is the structure which injects. Therefore, the optical module 200 does not need to be provided with a fiber block for directly connecting an optical fiber to the optical signal processing circuit, the area of the housing 201 can be greatly reduced, and the miniaturization of the optical module can be realized. . Actually, in the conventional optical module 100 shown in FIGS. 1A and 1B, a fiber block having a length of 6 mm is used, but the first optical module 200 according to the present embodiment shown in FIGS. 2A and 2B is used. Since the length of the signal light incident side lens is 1 mm, the module length can be reduced by 5 mm.

The optical signal processing circuit 220 of the optical module 200 is connected to small lenses (the first signal light incident side lens 251 and the first locally transmitted light incident side lens 252) instead of a large fiber block. . Therefore, the load stress at the time of vibration impact in the height direction of the connection portion between the optical signal processing circuit 220 and the first signal light incident side lenses 251 and 252 is when a large fiber block is connected to the optical signal processing circuit 220. And the reliability of the optical module is improved.

Also, the optical module 200 has a configuration in which the single mode fiber 211 and the polarization plane holding fiber 212 are not arrayed but are held independently by the fiber holders 213 and 214 and fixed to the casing 201. Accordingly, the single mode fiber 211 and the polarization plane holding fiber 212 can be optically coupled and aligned independently. In the optical coupling alignment, the image formation of the signal light on the incident side end face 223 of the optical signal processing circuit 220 is performed by adjusting the spatial distance (working distance) between the single mode fiber 211 and the second signal incident side lens 253. The shape of the beam spot can be converted into a shape that matches the mode field diameter of the signal light incident waveguide 221. In addition, by adjusting the spatial distance between the polarization plane holding fiber 212 and the second locally transmitted light incident side lens 254, the shape of the imaging beam spot of the locally transmitted light on the incident side end surface 223 is changed to the locally transmitted light incident guide. It can be converted into a shape that matches the mode field diameter of the waveguide 222. By converting the shape of the imaging beam spot, optical coupling alignment in the x-axis direction can be performed. Further, by adjusting the angles of the second signal incident side lens 253 and the second local oscillation light input side lens 254 with respect to the yz plane, optical coupling alignment in the y-axis and z-axis directions can be performed. By optical coupling alignment in the xyz-axis direction, stable optical coupling is possible, and optical coupling loss due to member tolerance can be easily suppressed.

Further, in the conventional optical module 100 shown in FIGS. 1A and 1B, the fiber block 113 is connected and fixed to the optical signal processing circuit 120 using a polymer material such as a UV adhesive, but the connection strength is maintained. Therefore, the connection area between the optical signal processing circuit 120 and the fiber block 113 has to be widened. Therefore, a large amount of UV adhesive was required. However, in the optical module 200, the fiber block is not connected to the optical signal processing circuit 220, and only small lenses (the first signal light incident side lens 251 and the first local oscillation light incident side lens 252) are connected. Since the first signal light incident side lens 251 and the first locally transmitted light incident side lens 252 are smaller than the fiber block 113 shown in FIGS. 1A and 1B, the connection area with the optical signal processing circuit 220 is as shown in FIG. It is smaller than the connection area between the fiber block 113 and the optical signal processing circuit 120 shown in 1A and 1B. Therefore, the amount of UV adhesive used can be greatly reduced. Therefore, the outgas and the amount of moisture released from the UV adhesive are greatly reduced, and it becomes possible to provide a highly reliable optical module.

Next, the first signal light incident side lens 251 and the first locally transmitted light incident side lens 252 connected to the optical signal processing circuit 220 will be described in detail. FIG. 3 is a perspective view showing the first signal light incident side lens 251. The first signal light incident side lens 251 includes an incident side end surface 310 and an emission side end surface 320. The incident side end surface 310 includes a parallel light incident surface 311 formed in a convex shape. The emission side end surface 320 includes an optical signal processing circuit connection surface 321 connected to the optical signal processing circuit 220. Note that the first local light incident side lens 252 has the same configuration as the first signal light incident side lens 251. The first signal light incident side lens 251 is made of glass or the like.

The parallel light incident surface 311 condenses the signal light converted into the parallel light from the second signal light incident side lens 253 and forms an image on the optical signal processing circuit connection surface 321. In the present embodiment, the size of the parallel light incident surface 311 is set to about three times the parallel light flux of the signal light that is not affected by diffraction.

The optical signal processing circuit connection surface 321 is inclined by a predetermined angle with respect to the light guiding direction. Further, in order to connect the optical signal processing circuit connection surface 321 to the incident side end surface 223 of the optical signal processing circuit 220 without any gap, the incident side end surface 223 of the optical signal processing circuit 220 is also the same as the optical signal processing circuit connection surface 321. It is inclined by the angle of. The connection is fixed with an adhesive or the like. The optical signal processing circuit connection surface 321 and the incident-side end surface 223 are preferably yz planes of FIGS. 2A and 2B from the viewpoint of ease of manufacturing the optical signal processing circuit 220 and the first signal light incident-side lens 251. However, it is preferable that the surface is inclined by about 8 degrees in the light guiding direction. When the inclination angle of the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 and the incident side end surface 223 of the optical signal processing circuit 220 is 8 degrees, the optical return loss (ORL: Optical Return Loss) is 40 dB or more can be secured.

The optical signal processing circuit connection surface 321 and the incident side end surface 223 of the optical signal processing circuit 220 are inclined at the same angle and are connected without a gap. Therefore, the light field angle of the signal light collected by the first signal light incident side lens 251 is the same as the light beam angle of the signal light incident end face of the signal light incident waveguide 221 of the optical signal processing circuit 220. It propagates to the signal light incident waveguide 221 of the optical signal processing circuit 220 without causing any coupling loss. In addition, since the first signal light incident side lens 251 and the incident side end surface 223 of the optical signal processing circuit 220 have a predetermined inclination, light reflection as a noise source is suppressed, and the light reflection resistance of the optical module 200 is improved. .

FIG. 4 is a diagram showing an optical signal path from the single mode fiber 211 or the polarization plane holding fiber 212 to the optical signal processing circuit 220 in the optical module 200 shown in FIGS. 2A and 2B. The signal light emitted from the single mode fiber 211 enters the second signal light incident side lens 253 at a predetermined radiation angle. The signal light incident on the second signal light incident side lens 253 is converted into parallel light and incident on the first signal light incident side lens 251. The signal light incident on the first signal light incident side lens 251 is at a portion where the signal light incident end surface of the signal light incident path waveguide 221 of the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 is located. Form an image. The optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 and the signal light incident end surface of the signal light incident waveguide 221 of the optical signal processing circuit 220 are connected, and the signal light is subjected to optical signal processing. The optical signal is coupled to the signal light incident waveguide 221 of the circuit 220 and propagates through the optical signal processing circuit 220.

In addition, the locally transmitted light emitted from the polarization-maintaining fiber 212 is incident on the second locally transmitted light incident side lens 254 at a predetermined radiation angle. The locally transmitted light that has entered the second locally transmitted light incident side lens 254 is converted into parallel light and is incident on the first locally transmitted light incident side lens 252. The local transmitted light incident on the first local transmitted light incident side lens 252 is the local transmitted light incident end surface of the local transmitted light incident path waveguide 222 of the optical signal processing circuit connection surface 321 of the first local transmitted light incident side lens 252. An image is formed at a portion where is located. The optical signal processing circuit connection surface 321 of the first local transmission light incident side lens 252 and the local transmission light incident end surface of the local transmission light incident waveguide 222 of the optical signal processing circuit 220 are connected, and the signal light is The optical signal processing circuit 220 propagates through the optical signal processing circuit 220 by being optically coupled with the locally transmitted light incident waveguide 222.

The end face of the single mode fiber 211 is inclined with respect to the light guiding direction at a predetermined angle, and light reflection that becomes a noise source is suppressed. Further, the end face of the polarization-maintaining fiber 212 is inclined at a predetermined angle with respect to the light guiding direction, and light reflection that becomes a noise source is suppressed.

In addition, the optical module 200 includes the first signal light incident side lens 251 and the first local light incident side lens 252 and the second signal so that the signal light and the locally transmitted light enter the optical signal processing circuit 220. In this configuration, the light incident side lens 253 and the second locally transmitted light incident side lens 254 are used. In the present embodiment, the imaging beam spot size of the signal light on the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 is adjusted to a desired size by setting the lens coupling magnification. Can do. In addition, the imaging beam spot size of the locally transmitted light on the optical signal processing circuit connection surface 321 of the first locally transmitted light incident side lens 252 can be adjusted to a desired size.

For example, it is assumed that the mode field diameter of the single mode fiber 211 is 10 μm, and the mode field diameter of the signal light incident waveguide 221 of the optical signal processing circuit 220 is 7 μm. At this time, if the imaging magnification of the lens is set to 0.7, the imaging beam spot size on the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 is changed to the mode of the signal light incident waveguide 221. Can match the field diameter. The imaging magnification of the lens can be obtained by the following equation (1).
M = F1 / F2 (1)
Here, M is the imaging magnification, F2 is the focal length of the second signal light incident side lens 253, and F1 is the focal length of the first signal light incident side lens 251. From equation (1), in order to set the imaging magnification M to 0.7, the focal length F1 of the first signal light incident side lens 251 is set to the focal length F2 of the second signal light incident side lens 253. What is necessary is just to set to 0.7 time.

Further, by adjusting the spatial distance (working distance WD) between the fiber end of the single mode fiber 211 and the second signal light incident side lens 253, the imaging beam of the signal light incident on the signal light incident waveguide 221 is adjusted. It is possible to finely adjust the spot size. Further, by adjusting the working distance WD between the fiber end of the polarization-maintaining fiber 212 and the second locally transmitted light incident side lens 254, an imaging beam of the locally transmitted light incident on the locally transmitted light incident waveguide 222 is adjusted. It is possible to finely adjust the spot size.

5 shows the working distance WD and the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 or the optical signal processing circuit connection surface of the first local light incident side lens 252 (321 in FIG. 3). Is a graph showing the relationship with the imaging beam spot radius.

When the working distance WD is changed by ± 20 μm from the design center, the imaging beam spot radius of the signal light or the locally transmitted light irradiated to the signal light incident waveguide 221 or the locally transmitted light incident waveguide 222 of the optical signal processing circuit 220 It can be seen that changes by about 0.3 μm. That is, in this embodiment, by making the working distance WD variable, the optical module 200 allows the subtle difference in mode field diameter in the signal light incident waveguide 221 or the locally transmitted light incident waveguide 222 of the optical signal processing circuit 220. Can be easily adjusted. By simplifying the adjustment of the mode field diameter, an optical module with good optical coupling efficiency can be provided.

In the present embodiment, the working distance WD is optimized by moving the single mode fiber 211 in the optical waveguide direction within the fiber holder 213. Further, the polarization maintaining fiber 212 is also moved in the optical waveguide direction in the fiber holder 214 to optimize the working distance WD. After optimizing the working distance WD, the single mode fiber 211 is fixed to the fiber holder 213 and the polarization plane holding fiber 212 is fixed to the fiber holder 214 by spot welding such as YAG welding.

FIG. 6 shows the connection on the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 or the optical signal processing circuit connection surface (corresponding to 321 in FIG. 3) of the first locally transmitted light incident side lens 252. It is a figure which shows three-dimensionally the distribution of the light intensity of an image beam spot. In FIG. 6, the light intensity of the imaging beam spot is expressed by being converted in the height direction with respect to the beam irradiation surface. The stronger the light intensity, the higher the position. The light intensity is strongest at point C in FIG. 6 (the light intensity reaches a peak). Here, assuming that point C is the center point of the imaging beam spot, in order to realize high optical coupling efficiency, the imaging beam spot on the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 is reduced. It is necessary to match the center point with the center of the signal light incident waveguide 221. In addition, the center point of the imaging beam spot on the optical signal processing circuit connection surface (corresponding to 321 in FIG. 3) of the first locally transmitted light incident side lens 252 and the center of the locally transmitted light incident waveguide 222 are matched. There is a need. Therefore, when connecting the first signal light incident side lens 251 and the first locally transmitted light incident side lens 252 to the signal processing circuit 220, the center point of the imaging beam spot, the center of the signal light incident waveguide 221 and The connection position is adjusted so as to match the center of the locally transmitted light incident waveguide 222.

Next, the manufacturing process of the optical module 200 of this embodiment will be described. In the optical module 200 of this embodiment, first, a subassembly in which the first signal light incident side lens 251 and the first locally transmitted light incident side lens 252 are connected to the optical signal processing circuit 220 is manufactured. FIG. 7 is a perspective view showing a subassembly 700 in which the first signal light incident side lens 251 and the first local oscillation light incident side lens 252 are connected to the optical signal processing circuit 220.

In the first signal light incident side lens 251, the center of the imaging beam spot on the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 is the signal of the signal light incident waveguide 221 of the optical signal processing circuit 220. The optical signal processing circuit 220 is fixed to the incident side end surface 223 so as to coincide with the center of the light incident end surface. In addition, the first locally transmitted light incident side lens 252 has an optical signal processing centered on the imaging beam spot on the optical signal processing circuit connection surface (corresponding to 321 in FIG. 3) of the first locally transmitted light incident side lens 252. The optical signal processing circuit 220 is fixed to the incident side end face 223 so as to coincide with the center of the local outgoing light incident end face of the local outgoing light incident waveguide 222 of the circuit 220. Specifically, the light is incident from the parallel light incident surface of the first signal light incident side lens 251 and the light intensity emitted from the output side waveguide end surface of the optical signal processing circuit 220 is maximized. One signal light incident side lens 251 is fixed to the incident side end face 223 of the optical signal processing circuit 220. Further, the first local transmission light incident side lens 252 receives light from the parallel light incident surface, and the light intensity emitted from the output-side waveguide end surface of the optical signal processing circuit 220 is maximized. The locally transmitted light incident side lens 252 is fixed to the incident side end surface 223 of the optical signal processing circuit 220. When the first signal light incident side lens 251 and the first locally transmitted light incident side lens 252 are fixed, the subassembly 700 is completed. The subassembly 700 is installed and fixed at a predetermined position in the housing 201.

Next, an ideal parallel beam is incident on the first signal light incident side lens 251 from the outside of the housing 201, and the output side lens 231 is light so that the light receiving sensitivity of the photodiode 241 of the photoelectric conversion unit 240 is maximized. Alignment alignment and fixing to the housing 201. In addition, an ideal parallel beam is incident on the first locally transmitted light incident side lens 252 from the outside of the housing 201, and the output side lens 232 is light so that the light receiving sensitivity of the photodiode 242 of the photoelectric conversion unit 240 is maximized. Alignment alignment and fixing to the housing 201. The housing 201 is filled with an inert gas such as nitrogen, and the lid 250 is fixed and sealed by resistance welding such as seam welding.

Next, the xyz axes in FIGS. 2A and 2B are set so that the imaging beam spot on the optical signal processing circuit connection surface 321 of the first signal light incident side lens 251 matches the mode field diameter of the signal light incident waveguide 221. Perform optical coupling alignment in the direction. In the optical coupling alignment, the second signal light incident side lens 253 and the single mode fiber 211 are maximized so that the light intensity emitted from the end face of the emission side waveguide is maximum, that is, the light receiving sensitivity of the photodiode 241 is maximized. Align. After the alignment, the second signal light incident side lens 253 is fixed to the housing 201 by spot welding such as YAG welding. Next, the single mode fiber 211 and the fiber holder 213 are fixed by spot welding such as YAG welding, and the fiber holder 213 and the second signal light incident side lens 253 are fixed by spot welding such as YAG welding.

Further, the imaging beam spot on the optical signal processing circuit connecting surface (corresponding to 321 in FIG. 3) of the first locally transmitted light incident side lens 252 matches the mode field diameter of the locally transmitted light incident waveguide 222. Optical coupling alignment in the xyz-axis direction in FIGS. 2A and 2B is performed. In the optical coupling alignment, the light intensity emitted from the end face of the exit side waveguide is maximized, that is, the light receiving sensitivity of the photodiode 242 is maximized, with respect to the second locally transmitted light incident side lens 254 and the polarization plane holding fiber 212. Align so that. After the alignment, the second locally transmitted light incident side lens 254 is fixed to the casing 201 by spot welding such as YAG welding. Next, the polarization-maintaining fiber 212 and the fiber holder 214 are fixed by spot welding such as YAG welding, and the fiber holder 214 and the second locally transmitted light incident side lens 254 are fixed by spot welding such as YAG welding.

As a result of the manufacturing process described above, it is possible to provide an optical module (ICR) having high light receiving sensitivity, small size, and high reliability.

Claims (6)

A single mode fiber that propagates signal light;
A polarization maintaining fiber that propagates locally transmitted light; and
An optical signal processing circuit in which the signal light is incident from the single mode fiber, the local oscillation light is incident from the polarization-maintaining fiber, and the signal light and the local oscillation light are signal-processed to generate output signal light. When,
A first signal light incident side lens that is connected to an incident side end face of the optical signal processing circuit and transmits the signal light;
A first locally transmitted light incident side lens connected to the incident side end face of the optical signal processing circuit and transmitting the locally transmitted light;
The signal light is imaged on the connection surface of the first signal light incident side lens with the signal processing circuit, and the local transmission is generated on the connection surface of the first local light incident side lens with the signal processing circuit. The light is imaged,
The position where the signal light is imaged is a portion where the end face of the signal light incident waveguide of the optical signal processing circuit is located on the connection surface of the first signal light incident side lens with the signal processing circuit. ,
The position at which the locally transmitted light is imaged is located at the end surface of the locally transmitted light incident waveguide of the optical signal processing circuit of the connection surface with the signal processing circuit of the first locally transmitted light incident side lens. An optical module characterized by being a part. A first fiber holder holding the single mode fiber;
A second fiber holder for holding the polarization maintaining fiber;
A second signal light incident side lens provided on the light exit side of the single mode fiber in the first fiber holder;
A second locally transmitted light incident side lens provided on the light output side of the polarization maintaining fiber in the second fiber holder, and the first signal light incident side lens and the second signal light. The incident side lens constitutes a confocal system, and the first local oscillation light incidence side lens and the second local oscillation light incidence side lens constitute a confocal system. The optical module as described. The connection surface of the first signal light incident side lens and the first local transmission light incident side lens and the optical signal processing circuit is a plane, and is inclined with respect to the optical axes of the optical signal and the local transmission light. The optical module according to claim 2, wherein: 4. The optical module according to claim 3, wherein light incident surfaces of the first signal light incident side lens and the first local signal light incident side lens are convex. The imaging beam spot size of the signal light is adjusted by adjusting the distance between the single-mode fiber and the second signal light incident side lens when the optical module is manufactured, and the local transmission light is coupled. 5. The image beam spot size is adjusted by adjusting a distance between the polarization maintaining fiber and the second locally transmitted light incident side lens when the optical module is manufactured. The optical module as described. It is a manufacturing method of the optical module according to claim 5,
Connecting the first signal light incident side lens and the first local light incident side lens to the optical signal processing circuit to produce a subassembly, wherein the first signal light incident side lens Is incident on the optical signal processing circuit so that the center of the imaging beam spot on the connection surface with the optical signal processing circuit coincides with the center of the signal light incident end surface of the signal light incident waveguide of the optical signal processing circuit. The first locally transmitted light incident side lens fixed to the side end surface is such that the imaging beam spot center at the connection surface with the optical signal processing circuit is a local part of the locally transmitted light incident waveguide of the optical signal processing circuit. Fixed to the incident side end face of the optical signal processing circuit so as to coincide with the center of the outgoing light incident end face; and
Fixing the subassembly in place within the housing;
The step of fixing the second signal light incident side lens and the single mode fiber to the housing, wherein the second signal light incident side lens and the single mode fiber are the first signal Aligning the imaging beam spot on the connection surface of the optical signal processing circuit of the light incident side lens with the mode field diameter of the signal light incident waveguide, and
The step of fixing the second locally transmitted light incident side lens and the polarization plane holding fiber to the housing, wherein the second locally transmitted light incident side lens and the polarization plane holding fiber are: A step of aligning the imaging beam spot on the connection surface of the optical signal processing circuit of the first locally transmitted light incident side lens with the mode field diameter of the locally transmitted light incident waveguide; and A manufacturing method comprising:

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