JP2004004949A - Optical multiplexer/demultiplexer and light input/output part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical multiplexer/demultiplexer whose constitution is simple, which has the high arraying accuracy of an optical fiber and which is equipped with a light input/output part having high consistency with a coupling system including a refractive index. <P>SOLUTION: The optical multiplexer/demultiplexer is equipped with a diffraction grating, a lens and the light input/output part 3 for inputting and outputting light through the diffraction grating and the lens, and the light input/output part 3 is equipped with a transparent base 73, a first optical waveguide 53 and a second optical waveguide 63 and the optical fiber 4. The first and the second optical waveguides 53 and 63 are formed on either surface of the base 73 and the optical fiber 4 is arranged on a surface opposed to the either surface of the base 73. The light emitted from the optical fiber 4 is dispersed in terms of wavelength by the lens and the diffraction grating, and made incident on the first and the second optical waveguides 53 and 63. Then, the first or the second optical waveguide 53 or 63 corresponding to the light having specified wavelength out of the light dispersed in terms of wavelength is selectively optically coupled with the optical fiber 4. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an optical multiplexer / demultiplexer used for wavelength division multiplexing communication and bidirectional transmission.

In recent years, with the advancement and diversification of information, a large capacity of an optical transmission system is required, and request-type transmission is being realized. A method of increasing the transmission capacity using wavelength division multiplexing transmission for transmitting and receiving bidirectional video and data is effective in expanding an existing optical transmission system using optical fibers. In order to multiplex light of many wavelengths in a limited wavelength band, for example, as shown in Patent Document 1, an input / output optical fiber is two-dimensionally arranged, and an optical fiber for inputting / outputting multiplexed light is used. A configuration has been proposed in which optical fibers for inputting and outputting wavelength-separated light are spatially separated so as not to leak into each other. Further, in order to improve the alignment accuracy of optical fibers, a configuration in which a silicon substrate on which optical fibers are arrayed and an LN (LiNO3) waveguide substrate as an input / output portion of light has been proposed (for example, "J. Lipson, W. J. Minford, E. J. Murphy, T. C. Rice, R. A. Linke and G. T. Harvey: AS-Channel Wavelength Multiplexer and Demultiplexer for Single Mode Systems. EEE Journal of Lightwave Technology Vol.3, N.O. IEEE Journal of L ightwave Technology. Vol.LT-3.No.5.P.1159 (1985)]).
JP-A-3-239207

However, in the former case, Patent Literature 1 does not mention a specific configuration of a highly accurate arrangement of the optical fiber array. On the other hand, in the case of the latter, since bonding between different kinds of substrates such as a silicon substrate and an LN substrate is used, it is impossible to match the refractive indexes. In addition, the material of the array substrate is expensive, and the processing requires selective etching and diffusion / injection steps in accordance with the crystal orientation and high-precision cutting, resulting in low mass productivity and poor yield due to variations in processing accuracy. There was a problem that.

The present invention has been made in order to solve the above problems, and has a simple configuration, a high alignment accuracy of an optical fiber, and an optical input / output unit having high matching with a coupling system including a refractive index. It is an object to provide an optical multiplexer / demultiplexer having the same.

In order to achieve the above object, an optical multiplexer / demultiplexer according to the present invention includes a diffraction grating, a lens, and an optical input / output unit for inputting and outputting light via the diffraction grating and the lens. Comprises a transparent base, a first optical waveguide, a second optical waveguide, and an optical fiber, wherein the first and second optical waveguides are formed on one surface of the transparent base, and the optical fiber Is disposed on the surface of the transparent base opposite to the one surface, and the light emitted from the optical fiber is wavelength-dispersed by the lens and the diffraction grating, and is respectively transmitted to the first and second optical waveguides. The first or second optical waveguide corresponding to light of a specific wavelength among the wavelength-dispersed light and the optical fiber are selectively optically coupled.

Further, another optical multiplexer / demultiplexer of the present invention includes a diffraction grating, a lens, and an optical input / output unit for inputting / outputting light via the diffraction grating and the lens, wherein the optical input / output unit is transparent. A base, a first optical waveguide, a second optical waveguide, and a third optical waveguide, wherein the first and second optical waveguides are formed on one surface of the transparent base; An optical waveguide is formed on the other surface of the transparent base, and light emitted from the third optical waveguide is wavelength-dispersed by the lens and the diffraction grating, and is respectively transmitted to the first and second optical waveguides. The first or second optical waveguide and the third optical waveguide corresponding to light of a specific wavelength among the wavelength-dispersed light are selectively optically coupled to each other. .

In the above configuration, it is preferable that the waveguide interval at one end face of the transparent base is different from the waveguide interval at the other end face.

In addition, in the above configuration, it is preferable that the waveguide interval at the lens-side end surface of the transparent base is smaller than the waveguide interval at the non-lens-side end surface.

In addition, in the above configuration, it is preferable that a light-shielding portion having a depth equal to or greater than the depth of the waveguide groove is provided along a portion where the waveguide interval on the transparent base is reduced.

Further, in the above configuration, the transparent base has a groove for forming a plurality of optical waveguides formed on one plane and an optical fiber for holding an optical fiber provided on a surface opposed to the one plane. It is preferable to use a mold having a V-shaped groove and having a reversed phase shape and formed of a glass material or a resin material.

Alternatively, in the above configuration, the transparent base is provided with a groove for forming a plurality of optical waveguides formed on one plane, and for forming an optical waveguide provided on a surface opposed to the one plane. It is preferable to use a mold having a groove and having a reversed phase shape and molded from a glass material or a resin material.

In addition, in the above configuration, it is preferable that the transparent base is formed of a glass material or a resin material having a refractive index smaller than that of a material forming the optical waveguide.

In addition, in the above configuration, it is preferable that the optical waveguide is disposed so as to intersect at one point on an extension of the lens side end surface.

Further, in the above configuration, the input / output end face on the lens side of the optical waveguide and the separately provided light input / output means is inclined with respect to a plane perpendicular to the light waveguide direction, and the surface is mirror-finished. Is preferred.

In addition, in the above configuration, it is preferable that an antireflection film is provided on the input / output end face on the lens side of the optical waveguide and the optical input / output means provided separately.

The light input / output unit of the present invention includes a transparent base and first, second, and third optical waveguides, and the first and second optical waveguides are formed on one surface of the transparent base. Wherein the third optical waveguide is formed on the other surface of the transparent base, the waveguide interval between the first and second optical waveguides at one end surface of the transparent base, and the waveguide at the other end surface. The intervals are different.

As described above, according to the optical multiplexer / demultiplexer of the present invention, since the optical waveguide and the transparent base are formed integrally, the processing steps can be simplified. In addition, since the input / output unit is provided with the optical fiber, the surface on which the optical waveguide is formed on the transparent base is only one surface, and the processing steps of the transparent base can be simplified.

According to another optical multiplexer of the present invention, it is not necessary to adjust the position of each optical waveguide.

By making the waveguide spacing at one end face of the transparent base different from the waveguide spacing at the other end face, an arbitrary light receiving element or optical transmission device can be used.

In addition, by making the waveguide spacing at the lens-side end face of the transparent base smaller than the waveguide spacing at the non-lens-side end face, the wavelength bandwidth separated by the diffraction grating can be narrowed, and the light coupling A coupling space for an optical fiber or the like coupled to the wave device can be secured.

Further, by providing a light shielding portion having a depth equal to or greater than the depth of the waveguide groove along the portion where the waveguide interval on the transparent base is narrowed, it is possible to suppress leakage of guided light.

Further, the transparent base is provided with a groove for forming a plurality of optical waveguides formed on one plane and a V-shaped groove for holding an optical fiber provided on a surface facing the one plane. Having, using a mold having the opposite phase shape, it shall be molded with a glass material or a resin material, or a groove for forming a plurality of optical waveguides formed on one plane, By having a groove for forming an optical waveguide provided on a surface opposite to the one plane, using a mold having an inverted phase shape, by molding with a glass material or a resin material, Since the optical waveguide and the transparent base are integrally formed, the processing steps can be simplified.

Further, by forming the transparent base with a glass material or a resin material having a smaller refractive index than the material forming the optical waveguide, the formation of the optical waveguide can be facilitated.

変 動 Furthermore, by arranging the optical waveguide on the lens-side end face so as to intersect at one point on an extension of the optical waveguide, it is possible to suppress a change in coupling efficiency due to a shift in the incident angle.

In addition, the input / output end face on the lens side of the optical waveguide and the optical input / output means provided separately is inclined with respect to a plane perpendicular to the light guiding direction, and the surface is mirror-finished, so that reflected return light or optical Multiple reflected light in the system can be suppressed, and distortion and noise in the optical multiplexer / demultiplexer can be reduced.

Further, by providing an antireflection film on the input / output end face on the lens side of the optical waveguide and the separately provided optical input / output means, it is possible to further suppress reflected return light and multiple reflected light in the optical system. Distortion and noise in the duplexer can be reduced.

(First embodiment)
A first preferred embodiment of the optical multiplexer / demultiplexer according to the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a configuration of an optical multiplexer / demultiplexer according to a first embodiment of the present invention. FIG. 2 is a front view showing the configuration of an optical input / output unit 3 in the optical multiplexer / demultiplexer according to the first embodiment. FIG. 3 is a perspective view thereof.

As shown in FIG. 1, for example, three input / output optical fibers 4, 5 and 6 are held in close contact with an array base 7 and a holding plate 8 having a V-shaped groove 7 a having a vertical angle of 60 degrees, for example. The input / output unit 3 is configured. The lens 2 and the diffraction grating 1 are arranged in front of the light input / output unit 3. As shown in FIG. 2, the apex angle of the V-shaped groove 7a of the array base 7 is 60 degrees. Further, since the input / output optical fibers 4, 5 and 6 have the same outer diameter, the lower input / output optical fiber 4 and the upper input / output optical fibers 5 and 6 are arranged in close contact with each other. As shown in FIG. 3, the input / output end face portion 12, which is located on the lens side of the optical input / output section 3 and includes the input / output end faces of the input / output optical fibers 4, 5, and 6, It is inclined at least 7 degrees or more with respect to a plane perpendicular to the arrangement direction of 5 and 6, and the surface is mirror-finished.

波長 Wavelength multiplexed light emitted from the input / output optical fiber 4 of the optical input / output unit 3 passes through the lens 2 and is incident on the diffraction grating 1, and is wavelength-dispersed in a direction perpendicular to the grating groove 1a. The wavelength-dispersed light passes through the lens 2 again, and the light of a specific wavelength out of the wavelength-dispersed light enters the input / output optical fibers 5 and 6 arranged in the wavelength dispersion direction. As a result, the input / output optical fibers 4 and 5 and the input / output optical fibers 4 and 6 corresponding to the light of the specific wavelength among the wavelength-dispersed lights are selectively coupled. The outputs of the input and output optical fibers 5 and 6 are wavelength-separated. The positions of the input and output optical fibers 5 and 6 with respect to the diffraction grating 1 coincide with the wavelength dispersion direction of the light having the specific wavelength among the wavelength-dispersed light. The direction of inclination of the input / output end face 12 of the optical input / output unit 3 is perpendicular to the direction in which the input / output optical fibers 5 and 6 are arranged. Therefore, the optical path length including the lens 2 and the diffraction grating 1 from the input / output optical fiber 4 to each of the input / output optical fibers 5 and 6 is the same.

According to the first embodiment, the three input / output optical fibers 4, 5, and 6 are superimposed and arranged on the V-shaped groove 7a provided on the arrangement base 7, and the V-shaped groove 7a And the side surfaces of the input / output optical fibers 4, 5 and 6 are in close contact with each other, thereby forming an input / output optical fiber array with high alignment accuracy. Further, since the optical path length from the input / output optical fiber 4 to each of the input / output optical fibers 5 and 6 is the same, the variation in the coupling efficiency between the optical fibers is reduced. In addition, since the input / output end face 12 of the optical input / output section 3 is inclined and the surface of the input / output end face 12 is mirror-finished, reflected return light and multiple reflected light in the optical system are suppressed. Distortion and noise are reduced.

In the first embodiment, the apex angle of the V-shaped groove 7a of the array base 7 is set to 60 degrees. However, the present invention is not limited to this. For example, as shown in FIG. A certain range is removed over a part or the entire circumference of the cladding portions of the output optical fibers 51 and 61, and the arrangement base 71 having a V-shaped groove 71a having an apex angle smaller than the apex angle of 60 degrees is used. The input / output optical fibers 4, 51 and 61 may be arranged and held. Alternatively, as shown in FIG. 5, the outer diameter of the cladding of the input / output optical fibers 42, 52 and 62 is reduced by polishing or etching, and thin film layers 4a, 5a and 6a for strength reinforcement are provided on the outer peripheral surface of the cladding. The arrangement may be such that the array base 72 is closely attached to a (small) array base 72 having a V-shaped groove 72a having a vertex angle of 60 degrees similar to that of the first reference example. In any case, the distance between the input and output optical fibers 51 and 61 or 52 and 62 through which the wavelength-separated light is input and output can be narrowed, and the coupling between the input and output optical fibers 51 and 61 or 52 and 62 can be achieved. There is an advantage that the interval at which wavelength separation can be performed as an optical multiplexing / demultiplexing function can be reduced without changing the wavelength bandwidth to be performed. In addition, by providing the thin film layers 4a, 5a and 6a of metal or the like while keeping the clad diameter as it is, it is possible to prevent the leakage between the optical fibers as well as to strengthen the strength, thereby improving the crosstalk.

Further, the processing method of the arrangement base 7, 71 or 72 in the first embodiment is not particularly limited, but a mold having a reversed phase of the base is used, and a glass material cast and molded is used. You may. In this case, the processing accuracy of the array base 7, 71 or 72 is good, the mass productivity is excellent, and the compatibility with the optical fiber material is good, so that there is an advantage that mechanical and physicochemical post-processing can be easily performed. . A specific processing method will be described later.

Further, as shown in FIG. 6A, by providing an antireflection film 10 directly on the input / output end face 12 of the optical input / output section 3 by vapor deposition or the like, the reflected return light and the multiple reflection on the input / output end face 12 are obtained. Light can be further reduced. Further, as shown in FIG. 6B, a flat plate 9 having an anti-reflection film 10 may be arranged on the input / output end face 12 with an adhesive layer 11 interposed therebetween. In the latter case, together with the effects of reducing the reflected return light and the multiple reflected light, the optical fiber array portion is not exposed to the high temperature in the vapor deposition process, and the antireflection film 10 can be stably provided. The thickness of the flat plate 9 and the formation of the wedge between the opposing surfaces of the flat plate 9 need to prevent the multiple reflection light generated on the opposing surface from being recombined into the optical fiber. For example, when a wedge flat plate having a thickness of 0.5 mm and an angle of 1 degree is used, the degree of recombination in a single mode optical fiber can be reduced to -55 dB or less. If the refractive index difference between the adhesive layer 11 and the refractive index of the optical fiber and the refractive index of the flat plate is within 0.03, the Fresnel reflectance between them is -40 dB or less. Can be suppressed.

(Second embodiment)
Next, a second preferred embodiment of the optical multiplexer / demultiplexer according to the present invention will be described with reference to FIGS. The second embodiment differs from the first embodiment only in the configuration of the optical input / output unit 3, and the operation related to wavelength separation (optical demultiplexer) performed by the diffraction grating 1 and the lens 2 is the same as that of the first embodiment. This is the same as the embodiment. Therefore, only the light input / output unit 3 will be described with reference to the drawings.

FIG. 7 is a perspective view showing the configuration of the optical input / output unit 3 of the optical multiplexer / demultiplexer according to the second embodiment. In FIG. 7, the optical waveguides 53 and 63 are integrally formed on an array base 73 by glass or a resin material. The array base 73 is formed of glass or a resin material having a smaller refractive index than the material of the optical waveguides 53 and 63, and has a V-shaped groove 73a. The portions of the optical waveguides 53 and 63 correspond to the core, and the portion of the array base 73 corresponds to the clad, which enables optical transmission. The input / output optical fiber 4 is disposed in the V-shaped groove 73a. The buffer layer 14 is provided on the upper surface of the arrangement base 73 and the optical waveguides 53 and 63. The input / output end face 12 of the array base 73 is inclined from a plane perpendicular to the top or bottom surface of the array base 73, and the surface is mirror-finished. The interval between the input / output end faces 15 and 16 of the optical waveguides 53 and 63 on the input / output end face 12 is set to be smaller than 125 μm, which is the interval in which ordinary optical fibers are closely arranged. The interval between the optical waveguide 53 and the optical waveguide 63 on the other end surface 13 of the array base 73 is set so as to match any light receiving element or the like to be subsequently coupled. That is, the interval between the optical waveguides 53 and 63 can be arbitrarily set when the array base 73 is manufactured according to the light receiving element or the like to be used. The wavelength multiplexed light emitted from the input / output optical fiber 4 disposed in the V-shaped groove 73a of the array base 73 is wavelength-dispersed by the lens 2 and the diffraction grating 1 shown in FIG. The light passes through and enters the optical waveguide end faces 15 and 16, respectively. As a result, the input / output optical fiber 4 and the optical waveguide 53 or 63 corresponding to the light of the specific wavelength out of the wavelength-dispersed light are selectively coupled and wavelength-separated.

Next, a method of manufacturing the optical input / output unit 3 in which the optical waveguides 53 and 63 are formed integrally with the array base 73 will be described with reference to FIGS. In the first method shown in FIG. 8, the array base 73 is molded together with the optical waveguide portion 73b and the V-shaped groove portion 73a by using a mold (not shown) (procedure a). Next, the high refractive material 22 is embedded in the optical waveguide portion 73b side of the array base 73 (procedure b), and the high refractive material is removed to the surface portion of the array base 73 by polishing or the like (procedure c). The buffer layer 14 is bonded on the table 73 (procedure d). The input / output optical fiber 4 is arranged in the V-shaped groove 73a of the array base 73 including the optical waveguides 53 and 63 obtained in this way, and is fixed by the holding plate 8 (procedure e). As a result, the optical input / output unit 3 is completed. On the other hand, in the second method shown in FIG. 9, the array base 73 is collectively formed together with the optical waveguide portion 73b and the V-shaped groove portion 73a by using a mold as in the first method (procedure a), and then heat-treated. Then, the buffer layer 14 is joined (procedure b), and the core equivalent portion 73b is filled with the high refractive index material 22 (procedure c). The input / output optical fiber 4 is arranged in the V-shaped groove 73a of the array base 73 including the optical waveguides 53 and 63 obtained in this way, and is fixed by the holding plate 8 (procedure d).

(4) If the distance between the optical waveguides 53 and 63 is reduced in the vicinity of the input / output end face 12, there is a possibility that guided light leaks between the optical waveguides 53 and 63. However, in the case of a single mode optical waveguide, if the waveguide interval is set to 30 μm or more, the leakage of the guided light can be reduced to −50 dB or less. Further, as shown in FIG. 10, by selectively providing the light shielding layer 20 between the optical waveguides 53 and 63 of the array base 73, it is possible to further suppress the leakage of the guided light. In this case, the step of forming the light-shielding layer 20 can be added to the step of manufacturing the array base 73 and the optical waveguides 53 and 63, and can be formed collectively.

In the second embodiment, the optical waveguides 53 and 63 are formed on one side of the array base 73. However, as shown in FIG. 11, the optical waveguides 53 and 63 of the array base 73 are provided. The optical waveguide 43 may be formed on a surface opposite to the surface on which the light is input, and an optical input / output unit provided with the buffer layer 23 may be configured. As a result, the light input / output unit itself can be an integrated part that can be formed collectively.

As described above, in the second embodiment, by integrating the array base 73 and the optical waveguides 35 and 63, the mass productivity and processing accuracy of the optical input / output unit 3 can be improved, and As a result, the characteristics can be made uniform. Further, there is an advantage that the end faces 12 of the array base 73 and the end faces 15 and 16 of the optical waveguides 35 and 63 can be mirror-finished at the same time. Further, it is possible to reduce the distance between the optical waveguides 53 and 63, and realize an optical multiplexer / demultiplexer having high matching efficiency such as mode field diameter at the time of coupling of the optical waveguides and high coupling efficiency.

(First Reference Example)
Next, a first preferred embodiment of the optical multiplexer / demultiplexer of the present invention will be described with reference to FIG. FIG. 12 is a perspective view showing the configuration of the optical input / output unit 3 of the optical multiplexer / demultiplexer according to the first reference example. The members having the same reference numerals as those in the first and second embodiments are substantially the same, and the description thereof will be omitted. Further, for convenience of explanation, the optical input / output unit 3 is drawn such that the input / output end face 12 side is located in the depth of the paper.

In FIG. 12, optical waveguides 53 and 63 are provided on the upper surface of the first half of the array base 74, and V-shaped grooves 17 and 18 are provided on the upper surface of the second half. Also, a V-shaped groove 74a is provided at the bottom of the array base 74. The input / output optical fibers 44, 54 and 64 are mounted on the V-shaped grooves 74a, 17 and 18, respectively. The input / output optical fibers 54 and 64 are coupled to the end faces 24 and 25 of the optical waveguides 53 and 63 at the end face 19 of the array base 74 on the side of the input / output optical fiber, respectively.

The first reference example is different from the first example in that the end faces 24 and 25 of the waveguides 53 and 63 and the input / output optical fibers 54 and 64 are further coupled to each other. Are provided with V-shaped grooves 17 and 18. The input / output optical fiber 54 mounted and fixed on the V-shaped groove 17 is coupled so that the optical waveguide 53 and the core part are aligned. Similarly, the input / output optical fiber 64 placed and fixed on the V-shaped groove 18 is also coupled so that the optical waveguide 63 and the core portion are aligned.

According to the first embodiment, in addition to the effects of the first embodiment, an optical input / output unit in which an optical fiber and an optical waveguide are coupled with low loss can be configured. In addition, since the array base 74 including the optical waveguides 53 and 63 can be molded at a time, the mass productivity is excellent while maintaining the consistency with the input / output optical fibers 54 and 64.

As for the coupling portion between the optical waveguide and the optical fiber, as shown in FIG. 13 (only the end face portion is specially described), the end face 21 on the optical fiber side of the array base 74 is made into an oblique mirror surface, and as shown in FIG. Alternatively, the optical fiber 56 whose end face is obliquely polished may be arranged so as to abut the end face 21. In this case, the reflected return light at the joint does not re-enter the optical fiber 56 and the optical waveguide 53. By forming the end surface 21 into an oblique mirror surface, it becomes easier to remove a glass material or the like than to form a vertical end surface in the molding process, and stable production is possible. Furthermore, by forming the light input / output end face 12 on the lens side into an oblique mirror surface at the time of fabrication, it is possible to suppress reflected return light in the optical system. Further, by providing an anti-reflection film on the lens-side input / output end face 12 as necessary, it is possible to reduce reflected return light.

(Second reference example)
Next, a second preferred embodiment of the optical multiplexer / demultiplexer according to the present invention will be described with reference to FIGS. FIG. 15 is a perspective view showing the configuration of the light input / output unit 3 of the second reference example, and FIG. 16 is an exploded perspective view thereof. In the second reference example, substantially the same optical input / output unit 3 as shown in FIG. 11 is mounted on a second array base 79 having a V-shaped groove 79a, and the input / output optical fibers 44 and 54 are provided. And 64 are closely arranged in the V-shaped groove 79a. The input / output optical fiber 44 is coupled to the optical waveguide 43, the input / output optical fiber 54 is coupled to the optical waveguide 53, and the input / output optical fiber 64 is coupled to the optical waveguide 63 with good positional accuracy.

As shown in FIG. 16, the second array base 79 has a flat portion 79b on which the optical input / output unit 3 formed separately is placed, and the input / output optical fibers 44, 54 and 64 in close contact with each other. And a V-shaped groove 79a. The end faces of the waveguides 43, 53, and 63 formed integrally with the optical input / output unit 3 are provided at positions matching the cores of the input / output optical fibers 44, 54, and 64 that are closely arranged in the V-shaped groove 79a. ing. In this manner, the V-shaped groove 79a defines the second arrangement base 79 on which the three input / output optical fibers 44, 54, and 64 are accurately arranged, and defines the spacing between the waveguides 43, 53, and 63 during molding. By combining the array base 73 thus manufactured, the total number of manufacturing steps can be reduced, and a highly versatile configuration can be achieved. The optical input / output section can be shared even in optical multiplexer / demultiplexers having various specifications. A configuration having many parts can be adopted.

Although the operation of the optical demultiplexer has been described in each of the above embodiments, the operation of the optical multiplexer may be performed by reversing the traveling direction of the light during the operation of the optical demultiplexer, and the description thereof will be omitted. I do. In addition, it is desirable that the arrangement of the optical waveguides on the lens side intersects one point on an extension of the light emitting direction at the end of the optical waveguide. The reason for this is that, when the wavelength-separated light from the diffraction grating is incident on the optical waveguide with light having a desired wavelength, the incident angle differs due to the deviation of the diffraction angle when the light is coupled. As a specific example, FIG. 17 shows a change in coupling efficiency with respect to a shift in the incident angle in a single mode waveguide (mode field diameter: 10 μm). As described above, the coupling efficiency fluctuates due to the shift of the incident angle, and this may appear as a variation in the insertion loss of each wavelength-separated light. In order to reduce the variation in insertion loss, each of the above optical waveguide arrangement configurations is effective. For example, when a lens having an effective focal length of 5 mm is used and the distance between the optical waveguides is 60 μm, if adjacent optical waveguides intersect at an intersection angle of about 0.7 degrees on an extension from the output end face, the coupling loss variation Can be minimized.

Regarding the arrangement of the diffraction grating, the tilt angle may be set near the Littrow angle or the blaze angle. In particular, Fourier diffraction gratings that preferably have high diffraction efficiency and low polarization dependence (eg, Iida, Hagiwara, Asakura: Holographic Fourier diffraction grating with high diffraction efficiency optimized for optical communication systems, Applied Optics, Vol. 31, No. 15, No. 15) , P. 3015, 1992 [M.Iida, K. Hagiwara, and H. Asakura: Holographic Fourier diffraction gratings with a high diffraction efficiency optimized for optical communication systems, Applied Optics, Vol. 31, No. 15, P. 3015 ( 1992)]). In this case, since the diffraction efficiency is 90% or more for non-polarized light and the polarization dependence is as small as 5% or less, a configuration with low loss and small polarization noise can be obtained.

By using a single aspheric lens or a refractive index distribution (GRIN) lens as the lens, the size of the optical system can be reduced and the number of multiple reflection points can be reduced as compared with a conventional spherical lens. Further, by using a concave grating or a curved plane grating as the diffraction grating, an optical system that does not require a lens can be configured.

Also, in each of the above embodiments, the multiplexer / demultiplexer for two wavelengths has been described, but the present invention is not limited to this, and a configuration of three or more waves may be used. In this case, the number of output fibers is required to be multiplexed, but by arranging them in a V-shaped groove, any number of output fibers can be arranged linearly in principle. Further, the optical waveguides may be formed at desired intervals by increasing the number of optical waveguides of a required wavelength.

1 is a perspective view showing the configuration of a first embodiment of an optical multiplexer / demultiplexer according to the present invention. FIG. 2 is a front view showing the configuration of an optical input / output unit according to the first embodiment. FIG. 2 is a perspective view showing a configuration of an optical input / output unit according to the first embodiment. Front view showing another configuration of the light input / output unit in the first embodiment. Front view showing another configuration of the light input / output unit in the first embodiment. (A) and (b) are side views each showing another configuration of the light input / output unit having the antireflection film in the first embodiment. FIG. 7 is a perspective view showing a configuration of an optical input / output unit in a second embodiment of the optical multiplexer / demultiplexer of the present invention. FIG. 7 is a diagram illustrating an example of a manufacturing process of an optical input / output unit according to a second embodiment of the present invention. FIG. 14 is a diagram showing another example of the manufacturing process of the optical input / output unit according to the second embodiment of the present invention. FIG. 9 is a perspective view showing another configuration of the optical input / output unit in the second embodiment of the optical multiplexer / demultiplexer of the present invention. FIG. 2 is a perspective view showing a configuration of an optical input / output unit in a first reference example of the optical multiplexer / demultiplexer of the present invention. Perspective view showing another configuration of the optical input / output unit in the first reference example of the optical multiplexer / demultiplexer of the present invention. The perspective view which shows the detail of the shape of the arrangement base in the 1st reference example. Sectional side view showing the coupling state between the optical fiber and the optical waveguide in the first reference example. A perspective view showing a configuration of an optical input / output unit in a second reference example of the optical multiplexer / demultiplexer of the present invention. The perspective view which shows the detail of the shape of the arrangement base in the 2nd reference example. Graph showing coupling efficiency variation with incident angle deviation

Explanation of reference numerals

Reference Signs List 1: diffraction grating 1a: grating groove 2: lens 3: light input / output unit 4: input / output optical fiber 4a: intensity compensation thin film layer 5: input / output optical fiber 5a: intensity compensation thin film layer 6: input / output optical fiber 6a : Thin film layer for strength compensation 7: Arrangement base 7 a: V-shaped groove 8: Holding plate 9: Flat plate 10: Antireflection film 11: Adhesive layer 12: Lens side end surface 13: Non-lens side end surface 14: Buffer layer 15: On Output end face 16: Input / output end face 17: V-shaped groove 18: V-shaped groove 19: End face 20: Light shielding layer 21: End face 22: High refractive index material 23: Buffer layer 24: End face 25: End face 42: Input / output optical fiber 43 : Input / output optical fiber 51: input / output optical fiber 52: input / output optical fiber 53: optical waveguide 54: input / output optical fiber 56: input / output optical fiber 61: input / output optical fiber 62: input / output Optical fiber 63: Optical waveguide 64: Input / output optical fiber 71: Array base 71a: V-shaped groove 72: Array base 72a: V-shaped groove 73: Array base 73a: V-shaped groove 73b: Core equivalent portion 74: Array Base 79: Array base 79a: V-shaped groove 79b: Flat portion

Claims (14)

A diffraction grating, a lens, and a light input / output unit for inputting and outputting light via the diffraction grating and the lens,
The optical input / output unit includes a transparent base, a first optical waveguide, a second optical waveguide, and an optical fiber,
The first and second optical waveguides are formed on one surface of the transparent base, and the optical fiber is disposed on a surface of the transparent base opposite to the one surface, and emitted from the optical fiber. Light is wavelength-dispersed by the lens and the diffraction grating, and is made to enter the first and second optical waveguides, respectively, and the first light corresponding to light of a specific wavelength among the wavelength-dispersed light is emitted. Alternatively, an optical multiplexer / demultiplexer, wherein a second optical waveguide and the optical fiber are selectively optically coupled. A diffraction grating, a lens, and a light input / output unit for inputting and outputting light via the diffraction grating and the lens,
The optical input / output unit includes a transparent base, a first optical waveguide, a second optical waveguide, and a third optical waveguide,
The first and second optical waveguides are formed on one surface of the transparent base, and the third optical waveguide is formed on the other surface of the transparent base.
The light emitted from the third optical waveguide is wavelength-dispersed by the lens and the diffraction grating, and is made to enter the first and second optical waveguides respectively. An optical multiplexer / demultiplexer, wherein the first or second optical waveguide corresponding to light having the wavelength of (a) and the third optical waveguide are selectively optically coupled. 3. The optical multiplexer / demultiplexer according to claim 1, wherein a waveguide interval at one end face of the transparent base is different from a waveguide interval at the other end face. 3. The optical multiplexer / demultiplexer according to claim 1, wherein a waveguide interval at the lens-side end surface of the transparent base is smaller than a waveguide interval at the non-lens-side end surface. (3) The optical multiplexer / demultiplexer according to (1) or (2), wherein a light-shielding portion having a depth equal to or greater than the depth of the waveguide groove is provided along a portion of the transparent base on which the waveguide interval is reduced. The transparent base has a groove formed on one plane for forming first and second optical waveguides, and a V-shape for holding an optical fiber provided on a surface facing the one plane. The optical multiplexer / demultiplexer according to claim 1, wherein the optical multiplexer / demultiplexer is formed by using a mold having a groove and having a reversed phase shape, using a glass material or a resin material. The transparent base is used to form first and second optical waveguides formed on one plane and a third optical waveguide provided on a surface facing the one plane. 3. The optical multiplexer / demultiplexer according to claim 2, wherein the optical multiplexer / demultiplexer is formed of a glass material or a resin material by using a mold having the opposite phase shape. 3. The optical multiplexer / demultiplexer according to claim 1, wherein the transparent base is formed of a glass material or a resin material having a refractive index smaller than a refractive index of a material forming the optical waveguide. The optical multiplexer / demultiplexer according to any one of claims 1 to 8, wherein the optical waveguide is disposed so as to intersect at a point on an extension of the lens-side end surface. 3. The optical waveguide and the input / output end face on the lens side of the separately provided optical input / output means are inclined with respect to a plane perpendicular to the light guiding direction, and the surface is mirror-finished. Optical multiplexer / demultiplexer. (3) The optical multiplexer / demultiplexer according to (1) or (2), wherein an antireflection film is provided on the input / output end face on the lens side of the optical waveguide and the separately provided optical input / output means. A transparent base, a first optical waveguide, a second optical waveguide, and a third optical waveguide,
The first and second optical waveguides are formed on one surface of the transparent base, and the third optical waveguide is formed on the other surface of the transparent base.
An optical input / output unit wherein a waveguide interval between the first and second optical waveguides at one end face of the transparent base is different from a waveguide interval at the other end face. 13. The optical input / output unit according to claim 12, wherein a light-shielding portion having a depth equal to or greater than the depth of the waveguide groove is provided along a portion of the transparent base on which the waveguide interval is reduced. 13. The optical input / output unit according to claim 12, wherein the transparent base is formed of a glass material or a resin material having a refractive index smaller than a refractive index of a material forming the optical waveguide.

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