HK1038072A - Integrated bi-directional axial gradient refractive index/diffraction grating wavelength division multiplexer - Google Patents

Description

Integrated bidirectional axial gradient refractive index/diffraction grating wavelength division multiplexer

Cross reference to related applications

The present application relates to two additional patent applications, the first named "integrated bi-directional biaxial gradient index/diffraction grating wavelength division multiplexer" [ D-97031], the second named "integrated bi-directional gradient index wavelength division multiplexer" [ D-97032], both filed on the same day as the present application and assigned to the same assignee, with the difference being the presence or absence of a diffraction grating and the number of gradient index elements.

Technical Field

The present invention relates generally to axial gradient index lenses, and more particularly to axial gradient index lenses for use in wavelength division multiplexing applications.

Background

Wavelength Division Multiplexing (WDM) is a rapidly evolving technology that enables a very significant increase in the amount of data transmitted over an optical fiber. Traditionally, most optical fibers have been used to transmit only one data channel unidirectionally at one wavelength. The basic concept of WDM is to separately guide and retrieve multiple data channels from one fiber. Each data channel is transmitted at a uniform wavelength and the wavelength is chosen such that the channels do not interfere with each other and the optical transmission loss of the fiber is low. Today, there are commercially available WDM systems that allow 2 to 32 channels to be transmitted simultaneously.

WDM is a cost effective way to increase the amount of data (commonly referred to as bandwidth) that is transferred over an optical fiber. Other competing techniques for increasing bandwidth include burying additional fiber optic cables or increasing the transmission speed over the optical fiber. The cost of burying additional cables ranges from $ 15,00 to $ 40,000 per kilometer. Increasing the optical transmission rate is increasingly limited by the speed and economy of the electronics surrounding the fiber optic system. One of the major strategies for increasing bandwidth with electronic technology has been to use Time Division Multiplexing (TDM), which combines or multiplexes multiple lower rate electronic data channels together into a single very high rate channel. Increasing bandwidth with this technology has been very effective over the last 20 years; however, it is nowadays more and more difficult to increase the transmission speed both from a technical and an economic point of view. WDM offers the potential to economically and technically address increased bandwidth by using many parallel channels. WDM is a complement to TDM, i.e., WDM can allow many simultaneous high transmission rate TDM channels to pass through a single fiber.

The use of WDM to increase bandwidth requires two conceptually symmetric basic devices. The first device is a wavelength division multiplexer. This device uses a plurality of beams (each having a separate wavelength, which are initially spaced apart in space) and provides a means for combining all of the beams of different wavelengths into a single polychromatic beam suitable for introduction into an optical fiber. The multiplexer may be an entirely passive optical device or may include electronics to control or monitor the performance of the multiplexer. The input of the multiplexer is typically made of a plurality of optical fibers; however, laser diodes or other light sources may be used. The output of the multiplexer is typically an optical fiber.

Similarly, the second device for WDM is a wavelength division demultiplexer. The function of this device is the reverse of that of the multiplexer; it receives a polychromatic light beam input from an optical fibre and provides a means for spatially separating the wavelengths. The output of the demultiplexer is typically connected to a plurality of optical fibers or to a plurality of photodetectors.

During the past 20 years, various types of WDM have been proposed and demonstrated; see, for example, the following documents: (1) tomlinson, applied optics, vol 16, No. 8, pp 2180-2194 (1997, 8 months); (2) livanos et al, applied physical communication, Vol.30, No. 10, pp.519-521 (1997, 5/15); (3) ishio et al, J.lightwave technology, Vol.2, No. 4, pages 448-463, (8 months 1984); (4) obara et al, electronic communications, Vol.28, No. 13, page 1268-1270 (1992, 6/18); (5) willner et al, IEEE Photonic technology communications, Vol.5, No. 7, p.838-841 (7 months 1993); and (6) Y.T. Huang et al, optical communications, Vol.17, No. 22, page 1629-1631 (11/15/1992).

However, despite all of the above methods, designs and techniques, there remains a real need for a WDM apparatus that has all of the features of low cost, integratable components, good environmental and thermal stability, low channel crosstalk, low channel signal loss, easy connection, large number of channels, and narrow channel spacing.

Disclosure of the invention

In accordance with the present invention, a wavelength division multiplexer or demultiplexer combines an axially graded index element and a diffraction grating to provide an integrated bidirectional wavelength division multiplexer or demultiplexer device. For simplicity, the function of the multiplexer will be thoroughly discussed; however, due to the symmetry of the multiplexer and demultiplexer functions, the discussion of the present invention may also be applied directly to the demultiplexer. The multiplexer of the present invention comprises:

(a) means for receiving a plurality of input beams of light (which contain at least one wavelength) from optical fibres or other light sources (such as lasers or laser diodes), the means comprising a flat front surface on which the input light is incident and being adapted for connection to input optical fibres or integration with other means;

(b) a coupler subsystem, comprising: (1) an axial gradient index collimating lens associated with the planar front surface, and (2) a homogeneous index boot (boot) lens affixed to the axial gradient index collimating lens and having a flat but sloped rear surface;

(c) a near Littrow diffraction grating operatively associated with the homogeneous refractive index shield lens, formed or affixed at the planar exit surface of the coupler subsystem, that combines the plurality of spatially separated wavelengths into at least one polychromatic light beam and reflects the combined light beam back to the coupler subsystem at substantially the same angle as the incident light beam;

(d) an array of optional electro-optical elements for refracting multiple wavelengths to provide channel routing or switching capability; and

(e) means for outputting at least one multiplexed, polychromatic output beam for at least one optical fiber, said means being located at the same input face in (a).

The apparatus of the present invention can operate in either the forward direction to provide a multiplexer function or the reverse direction to provide a demultiplexer function.

Furthermore, the apparatus of the present invention is inherently bidirectional and can be used as both a multiplexer and a demultiplexer in applications such as hubs (hubs) and intersections (intersections) that assign channels to various areas of the network. The axial gradient index and diffraction grating-based WDM devices of the present invention are unique in that they contain one or more uniform index boot lenses, allowing all optical elements to be integrated into a single integrated device. This greatly increases robustness, environmental and thermal stability while at the same time avoiding the introduction of air spaces that contribute to increased alignment sensitivity, device packaging complexity and cost.

In addition, the homogeneous index cap lens provides a large, flat surface for device assembly, alignment, and incorporation of additional device functions. The use of axial gradient index lenses allows very high performance imaging from lenses having conventional spherical surfaces, thereby providing diffraction limited optical imaging required for WDM applications. Furthermore, axial gradient index lenses can be made with high quality and low cost. Alternatively, an axial gradient index lens can be replaced with an aspherical lens; however, the collimation performance is the same, but it is extremely difficult to make a monolithic device with an aspherical surface. In addition, aspheric lenses are generally expensive and have objectionable reflections of the parasitic type (ghost-type).

The integration of WDM equipment allows for small, rugged, and environmentally and thermally stable systems. In particular, integrating the components into a solid block maintains component alignment, which provides long term performance, and conversely, over time, the alignment characteristics and therefore performance of non-integrated air-isolated devices deteriorates.

In summary, the present invention features a novel approach to WDM. The use of an optical lens in conjunction with a diffraction grating allows all wavelengths to be multiplexed and processed identically at the same time. This is in contrast to the less desirable serial WDM approach, which uses interference filter-based or fiber Bragg gratings. These serial WDM approaches have significant optical loss, cross-talk, alignment and temperature problems. Furthermore, in contrast to other parallel multiplexing methods, such as arrayed waveguide grating devices, fused fiber couplers, or tree waveguide couplers, the present invention is free to perform wavelength separation within the glass, as opposed to wavelength separation in lossy waveguide structures. Thus, the present invention has the distinct advantages of lower optical signal loss through the device and easier assembly and alignment compared to the prior art.

Other objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters refer to like features throughout. It will be apparent to those skilled in the art that additional objects, features and advantages not expressly discussed herein are inherent to and follow the spirit of the invention.

Brief Description of Drawings

It should be understood that the drawings referred to in this specification are not drawn to scale unless specifically indicated.

FIG. 1 is a schematic side elevation view (FIG. 1a) and a schematic top plan view (FIG. 1b) of a wavelength division multiplexer device of the present invention comprising an axial gradient index lens, a near Littrow diffraction grating, and a plurality of fiber inputs multiplexed to one fiber output;

FIG. 2a is a perspective view of a portion of the device of FIG. 1, showing in detail the input and output optical connections to the device;

FIG. 2b is a perspective view of the input portion of the device of FIG. 1, showing an alternative input terminal configuration, wherein the input terminal is an array of laser diodes;

FIG. 2c is a perspective view of a portion of the apparatus of FIG. 1 showing an alternative output configuration for a demultiplexer in which the output is an array of photodetectors;

FIG. 3 is a schematic side elevational view (FIG. 3a) and a schematic top plan view (FIG. 3b) of an apparatus similar to FIG. 1, but with the homogeneous index shield lens element removed between the input end and the axial gradient index collimating lens;

FIG. 4 is a perspective view of a portion of the apparatus of FIG. 1, but including an array of beam deflecting elements (parallel to the grating direction) to deflect a respective beam of each input channel to an output fiber port;

FIGS. 5a-5c are graphs of intensity versus wavelength coordinates illustrating different intensity profiles for different configurations or multiplexers of the present invention;

FIG. 6 is a perspective view of a portion of the apparatus of FIG. 1, similar to that of FIG. 2a, but including an array of electro-beam deflecting elements (perpendicular to the grating direction) to deflect each input channel's respective beam to an output fiber port;

FIG. 7 is a perspective view of a portion of the apparatus of FIG. 1, similar to that of FIG. 2a, but including an electro-beam deflecting element to deflect each input channel's respective beam to an output fiber port; and

fig. 8 is a perspective view of a portion of the device of fig. 1, but using two multiplexers, the channel blocking function is accomplished by introducing an electro-optical blocking array on the input face of one multiplexer.

Best mode for carrying out the invention

Reference will now be made in detail to specific embodiments of the invention, which illustrate the best mode presently contemplated by the inventors for carrying out the invention. Still other embodiments are briefly described as applicable.

Figure 1 depicts two views of a preferred embodiment of the present invention which implements an axially graded index/diffraction grating wavelength division multiplexer device. Specifically, FIG. 1a depicts a side elevational view of the device, while FIG. 1b depicts a top plan view.

The apparatus 10 of the first embodiment takes an input fiber array 12 having N discrete optical wavelengths 14 and spatially combines them into a single beam 16 and outputs the single beam to a single fiber output 18. Each wavelength transmits information superimposed thereon by other means, not shown here and not forming part of the invention, but which are well known in the art.

The apparatus 10 further comprises a coupler element 20; a near Littrow diffraction grating 22 is formed or placed on the exit surface 20b of the coupler element. The near Littrow diffraction grating 22 provides angular dispersion of the light beam at different wavelengths and reflects the light beam back at an angle very close to equal to the angle of incidence.

In the present invention, a diffraction grating 22 is used to provide angular dispersion, the magnitude of which depends on the wavelength of each incident beam. Furthermore, in order to obtain Littrow diffraction conditions for a wavelength within or near the range of wavelengths of the emerging light beams, the diffraction grating 22 is oriented at a particular angle relative to the optical axis of the device 10. The Littrow diffraction condition requires that the beam be incident on and reflected from the grating at the same precise angle. Thus, one skilled in the art will readily appreciate that a near Littrow diffraction grating is used to obtain near Littrow diffraction for each of the multiple wavelengths that occur.

The Littrow diffraction angle is determined by the following well-known formula:

mλ=dsin(α_i)

where m is the diffraction order, λ is the wavelength, d is the diffraction grating groove spacing, and α_iAre the same angles of incidence and diffraction. Those skilled in the art will readily appreciate that the diffraction grating angle depends on a number of variables that can be varied as desired to optimize the performance of the device. Variables that affect the diffraction angle of a grating include, for example, the desired diffraction order of the grating, the blaze angle (blaze angle) of the grating, the number of channels, the spatial separation of the channels, and the wavelength range of the device.

The coupler element 20 includes a first homogeneous index shield lens 24 that is connected or affixed to an axial gradient index collimating lens 26. And the axial gradient index collimating lens is connected or affixed to a second homogeneous index shield lens 28. The attachment or attachment is accomplished using an optical adhesive or other optically clear bonding technique. In this first embodiment, the array 12 of optical fibers 12' is positioned such that light radiated by the fiber ends is incident on the entrance surface 20a of the coupler element 20. Each fiber 12' provides a beam of light of a discrete wavelength.

Fig. 2a shows a detail of coupling an input fiber array 12 into a coupler 20 and transmitting a plurality of optical beams 14 therein, one for each fiber 12', using a suitable coupler/interconnect 30. Similarly, the combined beam 16 is coupled into a single fiber output 18 using a suitable coupler/interconnect 32. Such couplers/interconnects 30, 32 are well known in the art and do not form part of the present invention.

The plurality of spatially separated light beams 14 enter a first homogeneous refractive index shield lens 24 where their diameters are expanded. The plurality of light beams 14 then enter a first axial gradient index lens 26 where they are collimated and then pass through a second homogeneous index cover lens 28. At the exit surface 20b of the second homogeneous refractive index shield lens 28, the collimated beam is reflected by a near Littrow diffraction grating 22 that removes angular separation within the plurality of beams 14 and produces a single beam 16 that contains multiple wavelengths within itself. The single light beam 16 returns in the opposite direction through the coupling element 20 (first through the second homogeneous index shield lens 28, then through the axial gradient index focusing lens 26, and finally through the first homogeneous index shield lens 24). The single focused beam 16 is then incident on an optical fiber 18 attached to the entrance face 20a of the first homogeneous refractive index cap lens 24 of the coupler element 20.

In the second homogeneous refractive index cover lens 28, the exit surface 20b is formed with a slanted side whose angle is equal to the Littrow diffraction angle given by the above equation. The tilt angle is relative to an axis parallel to the axis of the diffraction grating 28.

A diffraction grating 22 is formed on the distal surface 20b of the coupler element 20. This diffraction grating can be fabricated by various techniques, such as three-dimensional holograms in a polymer medium that can be attached to the exit face 20b with, for example, an optical adhesive. Alternatively, the diffraction grating 22 may be scribed on the exit surface 20b using a mechanical scriber or other technique or techniques known in the art. The scribed diffraction grating 22 can be formed directly on the exit face 20b or in another flat material such as polymer, glass, silicon, etc. which is then secured to the end of the coupler element by an optical adhesive.

To prevent the multiplexed output beam 16 (a polychromatic beam) from being reflected directly back into the array of incident beams, the input array and output fibers are spaced slightly symmetrically from the central axis of the lens. Alternatively, a small tilt (typically less than 3 °) is created in the second homogeneous refractive index cap lens 28. This small tilt is made by rotating the back surface of the second homogeneous refractive index cap lens about an axis perpendicular to the scribing direction of the diffraction grating 22. This tilt is used to spatially separate output fibers 18 from input array 12 for efficient and easy coupling into and out of device 10. In the embodiment depicted in fig. 1, a plurality of optical fibers 12' making up the input array 12 and the fiber outputs 18 are shown in fig. 2 a. The plurality of light input ends 12' and light output ends 18 are in turn slightly spatially separated at the first surface 20a of the first homogeneous refractive index cap lens 24 due to the inclination of the second homogeneous refractive index cap lens 28.

In the embodiment depicted in fig. 1, the plurality of optical fibers 12' may be replaced with a plurality of laser diodes 34 as shown in fig. 2b to provide the beam input 14 for the wavelength division multiplexer 10. The array of laser diodes 34 may be butt-coupled to the WDM apparatus 10, may be longitudinally spaced, or may have suitable focusing lenses placed between the output facet and the laser diode array to provide optimum coupling and a minimum amount of signal loss or cross-talk.

In a second embodiment, the device 10 shown in FIG. 1, as with all devices described herein, can operate in an inverted configuration having a single fiber input end 18 that introduces a single polychromatic optical beam 16 having a plurality of discrete wavelength channels. These channels are spatially separated by the demultiplexing function of the device 10 for output to the plurality of fibers 12'. Each output fiber 12' carries only a single discrete wavelength channel. In this embodiment, the demultiplexer functionally provides the same but opposite functionality as the multiplexer device 10 described in fig. 1. In a demultiplexer embodiment, instead of multiple optical fibers, multiple photodetectors 36 shown in FIG. 2c may be used to provide the beam output for the wavelength division demultiplexer. The array of photodetectors 36 may be butt-coupled to the WDM apparatus 10, may be longitudinally spaced, or may have suitable focusing lenses placed between the output face and the photodetector array to provide a minimum amount of signal loss or cross-talk.

In a third embodiment, depicted in the two views of fig. 3, the first homogeneous index shield lens 24 is eliminated to make the device more compact in size or for use in devices that do not require the use of a first homogeneous index shield lens for their performance. Figure 3a shows a side elevational view of the device and figure 3b shows a top plan view. In this embodiment, axial gradient index lens 26 'has a flat exit face 20a for direct connection to the plurality of input ends 12' and the single output fiber 18. Another way (not shown) to implement this third embodiment is to include an air space between the input fibers 12 'or laser diodes 34 and the axial index lens 26'. The introduction of air space is not a preferred embodiment because it increases the complexity of the assembly and alignment of the multiplexer 10 and may be subject to greater environmental and temperature instability than the integrated block approach of the preferred embodiment of the present invention. All of the components of this third embodiment are joined or affixed using an optical adhesive or other optically clear bonding technique.

In a fourth embodiment, shown in fig. 4, an array 38 of nonlinear electro-optical elements is integrated to provide the ability to selectively direct the multiplexed light 16 into several possible collinear fiber output ends 18a, 18b, 18c, 18d, 18 e. This is of great value for optical networking, while the wavelength division multiplexer device 10 is capable of providing simultaneous integrated multiplexing and routing functions. The array of electro-optic elements 38 is an electrically controllable solid optical material whose refractive index can be varied by varying the current applied to the material. Such electro-optical cells are well known in the art; examples include lithium niobate and certain polymeric materials.

The output array 18 is separated from the surface 20a by an optional spacer or space 40. The spaces 40 simply provide the same spacing as the deflection array 38 to facilitate input and output coupling.

The change in refractive index is used to increase or decrease the angle of light transmission (relative to the direction of the gradient of the electro-optic material). It is desirable to use electro-optical elements to independently shift the position of the optical beam 14 to any of the output fiber ports 18. The direction of movement is parallel to the input 12' and output array 18. As shown in fig. 4, an array 38 of electro-optical elements is used to direct the output to one of a plurality of possible fiber output ends 18a, 18b, 18c, 18d, 18 e. The plurality of output optical fibers 18a-18e are collinear. It will be appreciated that while 5 such output fibers are shown, the invention is not so limited and any reasonable number of output fibers may be employed in the practice of the invention.

Another fifth embodiment would use the device in the same direction as the demultiplexing and routing device, where each fiber 12' inputs multiple wavelengths, which are demultiplexed and beam deflected to the output fiber array 18. The preferred orientation of the electro-optical elements 38 is such that the spatial variation at the output face 20a of the device 10 is in a direction parallel to the input and output arrays 12, 18. In this alternative embodiment, the demultiplexed output 16 may be routed to one of many possible fiber arrays 18, as shown in FIG. 4. Alternatively, the demultiplexed output may be routed to one of many possible photodetector arrays (not shown), as discussed above in connection with fig. 2 c.

In a sixth embodiment, the apparatus of FIG. 1 can be specifically designed and constructed so that the individual wavelength channels in the polychromatic output beam are non-uniformly focused on the output face of the multiplexer. As depicted in fig. 5a, the preferred embodiment of the apparatus of fig. 1 produces a plurality of very uniform focused beams having a uniform intensity distribution. However, to account for the increasing variation of intensity distribution with wavelength, such as shown in fig. 5b and 5c, the current embodiments change the design of the collimating lens assembly (such as lens curvature or axial gradient index profile). These changes need not be linear but can be complex and non-linear to match the non-uniform gain profile of the optical amplifier, laser diode array or other devices in the optical network.

In the seventh embodiment shown in fig. 6, the wavelength division multiplexing device 10 of fig. 1 is used to make 4 × 4 switches and multiplexers. The basic device 10 of fig. 1 is used to combine and/or route multiple wavelengths present at the input face 20a of the device. An array of beam deflecting elements 42 is first integrated into the input face 20a, each beam deflecting element being individually addressable (one element for each wavelength) and capable of directing light in a direction perpendicular to the input array 12. Each element 40 is used to direct light from a single channel 12' to one of the arbitrary output ports 18a, 18b, 18c, 18 d. The spaces 40 simply provide the same spacing as the beam deflection array 42, as in fig. 4, to facilitate input and output coupling.

In the eighth embodiment shown in fig. 7, the wavelength division multiplexing device 10 of fig. 1 is used to make 4 × 4 switches and demultiplexers. The base device 10 of fig. 1 is used to separate and route multiple wavelengths (which appear at the input face 20a of the device) transmitted on the input fiber 18. An electric beam deflection element 44 is first integrated into the input face 20a, which is capable of directing light in a direction parallel to the scribe lines of the grating 22 (not shown in fig. 7). A beam deflecting element 44 is used to direct the light of a single wavelength to one of the two demultiplexed output ports 12a, 12 b. The blank 40 simply provides the same spacing as the beam deflection array 44, as in fig. 4 and 6, to facilitate input and output coupling.

In the ninth embodiment shown in fig. 8, the wavelength division multiplexing device 10 of fig. 1 is used to make a 4-wavelength blocking switch 110 by using two multiplexing devices 10a and 10b and an array 46 of electro-optical blocking elements. The input and output of the blocking switch device 110 are each a single optical fiber 18. This device provides a blocking function for each individual wavelength.

An array 46 of electro-optical blocking elements, which are individually addressable (one element for each wavelength), which selectively block or do not block the passage of light, is first attached to the output face 20a of the first multiplexer device 10 a. The array of barrier elements 46 is made of liquid crystal, electrochromic (solid state) material, or other similar material, wherein the amount of transmission can be varied as a function of the power applied to the individual array elements.

Behind the blocking array, Porro-type reflective prisms (not shown) or fiber loops 48 are placed, having respective output ends and routing these outputs to separate locations on the input face 20a of the adjacent multiplexer 10 b. These inputs are then multiplexed through the second device 10b to be output to a single optical fiber 18 on the output face 20a of the second device. The spaces 40 simply provide the same spacing as the beam deflection array 46, as described above, to facilitate input and output coupling.

Another embodiment of the present device would use blocking element 46 to tailor the amount of optical energy (gain) transmitted at each wavelength. Such a blocking element 110 can then be used, for example, by an optical amplifier, laser diode array, or network to even out uneven gain from other parts of the optical network. Examples of possible changes in the gain profile are shown in fig. 5a, 5b, and 5c discussed above.

Industrial applicability

The integrated axial gradient index/diffractive wavelength division multiplexer/demultiplexer of the present invention is expected to find wide application in WDM-based networks and communication systems.

Thus, an integrated axial gradient index/diffraction grating wavelength division multiplexer and demultiplexer has been disclosed. It will be readily apparent to those skilled in the art that various changes and modifications may be made to the teachings of one particular aspect, and all such changes and modifications are deemed to be within the scope of the invention as defined in the appended claims.

Claims

Modification according to article 19 of the treaty

1. An integrated axial gradient index/diffraction grating wavelength division multiplexer device, comprising:

(a) means for receiving at least one light beam comprising at least one wavelength from a light source, said means comprising a planar front surface upon which said at least one light beam is incident;

(b) a coupler subsystem, comprising: (1) an axial gradient index collimating lens operatively associated with said flat front surface, and (2) a homogeneous index shield lens affixed to said axial gradient index collimating lens and having a flat exit surface out of which said at least one light beam exits;

(c) a diffraction grating formed at said planar exit surface of said first coupler subsystem for combining a plurality of spatially separated wavelengths from said at least one light beam into at least one multiplexed, polychromatic light beam and for reflecting said at least one multiplexed, polychromatic light beam back into said coupler subsystem; and

(d) for outputting said at least one multiplexed, polychromatic output beam to a light receiver, said device comprising said planar front surface.

2. The apparatus of claim 1, wherein the diffraction grating is a Littrow diffraction grating.

3. The apparatus of claim 1, wherein the flat exit plane has a slanted surface at an angle normal to at least one wavelength diffracted by the diffraction grating, the slanted surface being slanted such that an incident wavelength of the coupler sub-system is reflected back into the coupler sub-system.

4. The apparatus of claim 1, further comprising at least one electro-optical element for refracting single or multiple wavelengths to provide channel routing capability.

5. The apparatus of claim 4, further comprising a non-linear electro-optic element between the light source and the flat front surface.

6. The apparatus of claim 4, further comprising individually addressable electro-optical elements between the light source and the flat front surface.

7. The apparatus of claim 1, wherein the light source is selected from the group consisting of an optical fiber, a laser, and a laser diode.

8. The apparatus of claim 7, wherein the light source comprises at least one optical fiber transmitting a plurality of wavelengths.

9. The apparatus of claim 7, wherein the light source comprises a one-dimensional array of optical fibers.

10. The apparatus of claim 7, wherein the light source comprises a two-dimensional array of optical fibers.

11. The apparatus of claim 7, wherein the light source comprises a one-dimensional array of laser diodes.

12. The apparatus of claim 7, wherein the light source comprises a two-dimensional array of laser diodes.

13. The apparatus of claim 1, wherein the optical receiver is selected from the group consisting of an optical fiber and a photodetector.

14. The apparatus of claim 13, wherein the optical receiver comprises a one-dimensional array of optical fibers.

15. The apparatus of claim 13, wherein the optical receiver comprises a two-dimensional array of optical fibers.

16. The apparatus of claim 13, wherein the light receiver comprises a one-dimensional array of photodetectors.

17. The apparatus of claim 13, wherein the light receiver comprises a two-dimensional array of photodetectors.

18. The apparatus of claim 1, wherein the at least one light beam is incident on the coupler subsystem and exits the coupler subsystem, thereby functioning as a multiplexer.

19. The apparatus of claim 18 wherein more than one of said at least one light beam is incident on said coupler subsystem and exits said coupler subsystem as said at least one multiplexed, polychromatic light beam.

20. The apparatus according to claim 1 wherein the at least one multiplexed, polychromatic optical beam is incident on the coupler subsystem and emerges from the coupler subsystem, thereby functioning as a demultiplexer.

21. An apparatus according to claim 20 wherein at least one of said at least one multiplexed, polychromatic optical beam is incident on said coupler subsystem and emerges from said coupler subsystem as more than one of said at least one optical beam.

22. The apparatus of claim 1, further comprising at least one uniform refractive index element between the receiving means and the coupler subsystem.

23. The apparatus of claim 1, further comprising at least one electro-optic element for blocking single or multiple wavelengths to provide channel blocking capability.

24. The apparatus of claim 1 wherein the coupler subsystem provides a function of the specific desired channel output intensity as a function of wavelength.

25. An integrated axial gradient index/diffraction grating wavelength division multiplexer device, comprising:

(a) an axial gradient index collimating/focusing lens for collimating the plurality of monochromatic light beams propagating in a first direction and for focusing the multiplexed, polychromatic light beam propagating in a second direction, the second direction being substantially opposite to the first direction;

(b) a homogeneous refractive index shield lens affixed to the axial gradient refractive index collimatmg/focusmg lens for transmitting the plurality of monochromatic light beams from the axial gradient refractive index collimatmg/focusmg lens in a first direction and for transmitting the multiplexed, polychromatic light beam to the axial gradient refractive index collimatmg/focusmg lens in a second direction, the homogeneous refractive index shield lens having a planar junction surface; and

(c) a diffraction grating formed at the flat junction surface of the homogeneous refractive index mask lens for combining the plurality of monochromatic light beams into a multiplexed, polychromatic light beam and for reflecting the multiplexed, polychromatic light beam back into the homogeneous refractive index mask lens.

26. The apparatus of claim 25, wherein the homogeneous refractive index illumination lens is a first homogeneous refractive index cover lens, the apparatus further comprising:

a second homogeneous refractive index shield lens affixed to the axial gradient refractive index collimatmg/focusmg lens for transmitting the plurality of monochromatic light beams in a first direction to the axial gradient refractive index collimatmg/focusmg lens and for transmitting the multiplexed, polychromatic light beam from the axial gradient refractive index collimatmg/focusmg lens in a second direction.

27. The apparatus of claim 26 wherein the second homogeneous refractive index mask lens has a flat connecting surface for receiving the plurality of monochromatic light beams from the light source and for outputting the multiplexed, polychromatic light beam to the light receiver.

28. An apparatus as recited in claim 25, wherein the axially graded collimating/focusing lens has a flat connecting surface for receiving the plurality of monochromatic light beams from the light source and for outputting the multiplexed, polychromatic light beam to the light receiver.

29. An integrated axial gradient index/diffraction grating wavelength division demultiplexer comprising:

(a) an axial gradient index collimating/focusing lens for collimating the multiplexed, polychromatic optical beam propagating in a first direction and for focusing the plurality of monochromatic optical beams propagating in a second direction, the second direction being substantially opposite to the first direction;

(b) a homogeneous refractive index shield lens affixed to the axial gradient refractive index collimatmg/focusmg lens for transmitting the multiplexed, polychromatic optical beam from the axial gradient refractive index collimatmg/focusmg lens in a first direction and for transmitting the plurality of monochromatic optical beams to the axial gradient refractive index collimatmg/focusmg lens in a second direction, the homogeneous refractive index shield lens having a planar junction surface; and

(c) a diffraction grating formed at the flat junction surface of the homogeneous refractive index mask lens for splitting the multiplexed polychromatic optical beam into a plurality of monochromatic optical beams and for reflecting the plurality of monochromatic optical beams back into the homogeneous refractive index mask lens.

30. The apparatus of claim 29, wherein the homogeneous refractive index illumination lens is a first homogeneous refractive index shield lens, the apparatus further comprising:

a second homogeneous refractive index shield lens affixed to the axial gradient refractive index collimatmg/focusmg lens for transmitting the multiplexed polychromatic optical beam in a first direction to the axial gradient refractive index collimatmg/focusmg lens and for transmitting the plurality of monochromatic optical beams from the axial gradient refractive index collimatmg/focusmg lens in a second direction.

31. The apparatus of claim 30 wherein the second homogeneous refractive index shield lens has a flat connecting surface for receiving the multiplexed, polychromatic optical beam from the optical source and for outputting a plurality of monochromatic optical beams to the optical receiver.

32. The apparatus of claim 29, wherein the axial index collimatmg/focusmg lens has a flat connecting surface for receiving the multiplexed, polychromatic light beam from the light source and for outputting a plurality of monochromatic light beams to the light receiver.

Text to PCT/US98/26368 International application

Statement of modification according to PCT clause 19

In the replacement page, the original claims 1, 3, 5-17 and 19-22 are modified, the original claims 2, 4 and 18 are kept unchanged and new claims 25-32 are added. Claims 1, 3, 5-17 and 19-22 are modified in order to correct some of the imprecise language. Claims 25-32 have been added to relate to further aspects of the invention. No new content is added.

Claims (24)

1. An integrated axial gradient index/diffraction grating wavelength division multiplexer device, comprising:

(a) means for receiving at least one input light beam comprising at least one wavelength from a light source, said means comprising a flat front surface on which said input light beam is incident and being adapted to connect input and output optical means;

(b) a coupler subsystem, comprising: (1) an axial gradient index collimating lens operatively associated with said planar front surface, and (2) a homogeneous index shield lens affixed to said first axial gradient index collimating lens and having a planar exit surface into and out of which said at least one light beam passes;

(c) a diffraction grating formed at said planar exit surface of said first coupler optics subsystem that combines a plurality of spatially separated wavelengths into at least one beam and reflects said at least one combined beam back into said coupler subsystem; and

(d) for generating at least one multiplexed, polychromatic output beam to an optical receiver, said device comprising said planar input/output surface.

2. The apparatus of claim 1, wherein the diffraction grating is a Littrow diffraction grating.

3. The apparatus of claim 1, wherein the flat exit plane has a slanted surface at an angle normal to at least one wavelength diffracted by the diffraction grating, the slanted surface being slanted such that an incident wavelength of the coupler sub-system is reflected back into the coupler sub-system.

4. The apparatus of claim 1, further comprising at least one electro-optical element for refracting single or multiple wavelengths to provide channel routing capability.

5. The apparatus of claim 4, further comprising a non-linear electro-optic element between the input optical device and the planar front surface.

6. The device of claim 4, further comprising individually addressable electro-optical elements between the input optics and the flat front surface.

7. The apparatus of claim 1 wherein said input optical means is selected from the group consisting of an optical fiber, a laser, and a laser diode.

8. The apparatus of claim 7, wherein the input optical device comprises at least one optical fiber transmitting a plurality of wavelengths.

9. The apparatus of claim 7, wherein the input optical device comprises a one-dimensional array of optical fibers.

10. The apparatus of claim 7, wherein the input optical device comprises a two-dimensional array of optical fibers.

11. The apparatus of claim 7, wherein the input optical device comprises a one-dimensional array of laser diodes.

12. The apparatus of claim 7, wherein the input optical device comprises a two-dimensional array of laser diodes.

13. The apparatus of claim 1 wherein said output optical means is selected from the group consisting of an optical fiber and a photodetector.

14. The apparatus of claim 13 wherein said output optical means comprises a one-dimensional array of optical fibers.

15. The apparatus of claim 13, wherein the output optics comprise a two-dimensional array of optical fibers.

16. The apparatus of claim 13, wherein the output optics comprise a one-dimensional array of photodetectors.

17. The apparatus of claim 13, wherein the output optics comprise a two-dimensional array of photodetectors.

18. The apparatus of claim 1, wherein the at least one light beam is incident on the coupler subsystem and exits the coupler subsystem, thereby functioning as a multiplexer.

19. The apparatus of claim 18, wherein more than one of the light beams is incident on the coupler subsystem and exits the coupler subsystem as a single combined light beam.

20. The apparatus of claim 1, wherein the at least one light beam is incident on the coupler subsystem and exits the coupler subsystem, thereby functioning as a demultiplexer.

21. The apparatus of claim 20 wherein at least one of said beams is incident on said coupler subsystem and exits said coupler subsystem as a plurality of spatially separated beams.

22. The apparatus of claim 1, further comprising at least one uniform index element between the input device and the coupler subsystem.

23. The apparatus of claim 1, further comprising at least one electro-optic element for blocking single or multiple wavelengths to provide channel blocking capability.

24. The apparatus of claim 1 wherein the coupler subsystem provides a function of the specific desired channel output intensity as a function of wavelength.