JP2004133114A - Optical multiplexer/demultiplexer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost small-sized optical multiplexer/demultiplexer whose cost is low and which is small and its manufacturing method. <P>SOLUTION: An integrted optical multiplexer/demultiplexer whose spacial integration degree of optical multiplexers/demultiplexers is raised by piling up two or more multiplxer/demultiplxers in three-dimensions is provided. Cost reduction and miniaturization of housing per one optical multiplexer/demutiplxer can be attained by sharing optical elements of a wavelength selecting filter, a diffraction grating and the like with a plurality of optical multiplxers/demultiplexers and by performing the aligning of optical paths en block and, at the same time, by reducing the number of components. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a WDM (wavelength division multiplexer) (wavelength division multiplexing) optical multiplexer / demultiplexer, and particularly to an optical multiplexer / demultiplexer that uses a wavelength filter or a diffraction grating and is low in cost and highly integrated.
[0002]
[Prior art]
With the spread of the Internet, communication technology has remarkably developed. One of them is wavelength division multiplexing optical communication. This wavelength division multiplexing communication is expected as a transmission system supporting a large-capacity optical communication system in the future, and its realization is strongly desired.
[0003]
The wavelength multiplexing communication increases the transmission capacity per optical fiber, and enables a large transmission capacity. In addition, optical wiring is attracting attention as a technique for realizing high-speed and high-density wiring. In order to realize wavelength division multiplexing communication, an optical multiplexer / demultiplexer that bundles transmitters of respective channels into one fiber and separates wavelengths to guide optical signals to respective receivers is indispensable.
Among optical multiplexers / demultiplexers, demand for CWDM, which enables transmission of a plurality of signals over one optical fiber, is expected to increase. This is to split a wavelength division multiplexed signal of about 1.3 μm or 1.5 μm passing through an optical fiber at intervals of several tens of nm. In general, it is desired that CWDM have a demultiplexing characteristic such that crosstalk is small and propagation loss is small. Also, in order to always obtain good demultiplexing characteristics, it is important that the characteristics do not change much with changes in temperature and polarization of incident light.
AWG (arrayed waveguide grating) (arrayed optical waveguide grating type optical multiplexer / demultiplexer) is widely used as a WDM demultiplexer, but the demultiplexing characteristics are easily changed with a change in the wavelength of the light source. Cost is high because precision is required. Therefore, there is a demand for a low-cost CWDM with a small number of demultiplexing but little change in characteristics due to wavelength. However, since alignment is performed at the submicron level of the optical path of the optical fiber with the optical waveguide or microlens at the time of assembly, it takes time, and the processing cost increases accordingly.
A conventional optical multiplexer / demultiplexer (wavelength router) having a plurality of input ports and a plurality of output ports requires M × N wavelength selection elements when M inputs and N outputs (for example, for example). And Patent Document 1.). In such a case, it is necessary to perform alignment by the number of wavelength selection elements.
[0004]
[Patent Document 1]
JP-A-11-174253 (page 1-29, FIG. 1)
[0005]
[Problems to be solved by the invention]
As described in detail above, in the conventional optical multiplexer / demultiplexer, since the alignment of the optical path of the optical fiber or the microlens with the optical path of the optical fiber is performed for each individual demultiplexer, the cost is high. In addition, each duplexer was bulky in order to create a housing to prevent outside light and dust from entering.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a small-sized optical multiplexer / demultiplexer with low cost and good demultiplexing characteristics.
[0006]
[Means for Solving the Problems]
In order to split light in a duplexer, a wavelength selection filter and a diffraction grating are used. These spectroscopic optical elements are shared by multiple demultiplexers, and the optical path alignment is performed collectively and the number of components is reduced, reducing the cost per demultiplexer and reducing the size of the case. Can be achieved.
[0007]
The present invention provides the following integrated optical multiplexer / demultiplexer.
(1) An integrated optical multiplexer / demultiplexer in which two or more optical multiplexers / demultiplexers are three-dimensionally stacked to increase the degree of spatial integration of the optical multiplexer / demultiplexer.
(2) The integrated optical multiplexer / demultiplexer according to (1), wherein integration is realized by stacking PLCs to form a multilayer structure.
(3) The integrated optical multiplexer / demultiplexer according to the above (2), wherein a planar diffraction grating is used for the optical multiplexer / demultiplexer.
(4) The integrated optical multiplexer / demultiplexer according to the above (2) or (3), wherein the period of the plane diffraction grating is different.
(5) The integrated optical multiplexer / demultiplexer according to any one of (2) to (4) above, wherein the plane diffraction grating is a reflection type.
(6) The integrated optical multiplexer / demultiplexer according to any one of (2) to (5) above, wherein a polymer optical waveguide is used for the optical multiplexer / demultiplexer.
(7) The integrated optical multiplexer / demultiplexer according to (6), wherein the wavelength and the polarization are simultaneously separated.
(8) The integrated optical multiplexer / demultiplexer according to any one of (1) to (6) above, wherein a corresponding polarization is determined in each optical multiplexer / demultiplexer.
(9) The integrated optical multiplexer / demultiplexer according to the above (1), wherein a wavelength selection filter is used for the optical multiplexer / demultiplexer.
(10) The integrated optical multiplexer / demultiplexer as described in (9) above, wherein integration is realized by using a microlens array or a Fresnel lens array arranged two-dimensionally at an input or output portion of light to the optical multiplexer / demultiplexer. .
(11) The integrated optical multiplexer / demultiplexer according to the above (10), wherein a mirror is used for the optical multiplexer / demultiplexer.
(12) The integrated optical multiplexer / demultiplexer according to any one of (1) to (11), wherein integration is realized by using an array of optical fibers and optical waveguides corresponding to a two-dimensional MT connector.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The integrated optical multiplexer / demultiplexer of the present invention aims at the same integration effect as that of the optical multiplexer / demultiplexer arranged in multiple layers, thereby increasing the density of electrical wiring by increasing the number of electrical wirings. At this time, optical wiring may be provided between the optical multiplexer / demultiplexers of each layer.
As a method of forming a multilayer, besides a method of stacking a planar optical multiplexer / demultiplexer in layers, a method of stacking in a cylindrical shape like a roll, a method of folding in a W-shape, and the like may be used.
[0009]
By using a PLC (Planar Lightwave Circuit) as described in claim 2, it becomes easier to produce a multilayer structure as compared with a spatial wiring.
[0010]
The number of components can be reduced by using a plane diffraction grating as described in claim 3 and performing all the spectroscopy with one diffraction grating as described in FIGS. The incident light 10 is split into each of λ1 to λ4 and becomes outgoing light 18 for each wavelength. The incident light 10 enters the incident-side channel optical waveguide 14, diffuses in the slab optical waveguide 24, and is separated and condensed by the reflection type diffraction grating 26 and the slab optical waveguide 24. The outgoing light 18 exits from the channel optical waveguide 16 determined from λ1 to λ4.
In addition, when applied to a wavelength router, it is necessary to associate the output port of the light of wavelength λ1 that has entered the input port with the output port, but the separated light is transmitted through an optical waveguide or an optical fiber using an optical fiber. It becomes possible by leading to the output port.
[0011]
As described in the fourth aspect, by setting the period of the plane diffraction grating to a different period, a plurality of functions such as focusing and splitting can be provided. As a result, the number of parts can be reduced.
[0012]
As described in claim 5, by using the reflection type diffraction grating, the entrance surface and the exit surface can be on the same side, so that the size of the optical multiplexer / demultiplexer can be reduced. This makes it possible to reduce the volume per optical multiplexer / demultiplexer to 0.6 cm ² or less.
[0013]
By using the polymer optical waveguide as described in claim 6, the cost can be reduced as compared with the case where the quartz optical waveguide is used. As the polymer, an aromatic heterocyclic polymer such as polyimide, which has heat resistance, is preferable.
[0014]
However, since the aromatic heterocyclic polymer generally has a birefringence, the position of the converging point after the polarization is separated in the TE mode or the TM mode is different. For example, light in which 1.3 μm light in the TE mode is demultiplexed is detected as the same as light in which 1.31 μm light is demultiplexed in the TM mode.
[0015]
Utilizing this, as described in claim 7, it is possible to split the polarization at the same wavelength depending on whether the polarization is the TE mode or the TM mode.
[0016]
However, on the other hand, there are cases where the TE mode and the TM mode cannot be separated from each other due to the design of the optical waveguide. This results in a decrease in wavelength resolution as a spectroscope. In such a case, the corresponding polarization may be changed in each optical multiplexer / demultiplexer as described in claim 8. In other words, if the TE wave and the TM wave are separated in advance, and the light is separated by the layers for which the optical waveguides are designed correspondingly, it is possible to prevent a decrease in the wavelength resolution.
[0017]
As shown in FIG. 3, a plurality of input lights can be collectively wavelength-separated by the wavelength selection filter and the mirror according to the ninth and eleventh aspects. A dielectric multilayer film can be used as the wavelength selection filter. In FIG. 3, three wavelength selective filters 38 and mirrors 34 that selectively reflect only λ1, λ2, and λ3, respectively, are used. The incident light 40 exiting the optical fiber is split by each wavelength selection filter 38 and separated so that the reflected light becomes a different outgoing light 42.
Although the wavelength selection filters 38 are used in an overlapping manner in FIG. 3, they may be used apart from each other, and the angle of incidence on the filters may be changed according to the direction of the outgoing light 42. The same applies to the mirror 34. For example, when the outgoing light 42 is extracted from the right side perpendicular to the incident light 40, the incident angle to the wavelength selection filter 38 and the mirror 34 is 45 °. In that case, a groove for fixing the wavelength selection filter 38 and the mirror 34 is cut on the substrate, and the groove is arranged thereon.
[0018]
The light emitted from the optical fiber is not a parallel light but a diffuse light as it is. In general, the wavelength selection filter has poor wavelength selection efficiency unless it is parallel light. Therefore, it is necessary to collimate the light emitted from the optical fiber into parallel light using a lens. At this time, by using the two-dimensionally arrayed lens array according to the tenth aspect, incident light from the optical fiber can be collectively converted into parallel light. In FIG. 3, three rows and five columns of microlenses are used, of which one column is used for incidence and four columns are used for emission.
Although the microlens array is arranged on the same plane in FIG. 3, it is not always necessary to be on the same plane. For example, the microlens 44 for incident light and the microlens 46 for outgoing light are placed on different substrates. Alternatively, the respective substrates may be arranged opposite to each other.
[0019]
The use of the MT (Mechanical Transfer) connector described in claim 12 facilitates optical connection between the optical fiber and the optical multiplexer / demultiplexer. The connector uses a two-dimensional connector corresponding to the multilayer structure of the incident and exit portions. In FIG. 3, since the microlenses of 5 rows and 3 columns are used, the same MT connector having a two-dimensional array of 5 rows and 3 columns is used. Note that the arrangement of the MT connectors may be divided according to the application. For example, the connector for incidence and the connector for emission may be separated, and MT connectors in three rows and one column and three rows and four columns may be used.
[0020]
【Example】
The present invention will be described in more detail by way of examples.
[0021]
In this embodiment, a polymer optical waveguide is used for a reflective planar diffraction grating. The reflection type planar diffraction grating is made by evaporating Al on the surface of the diffraction grating. For the core and cladding of the optical waveguide, OPI (part number N3265: fluorinated polyimide) manufactured by Hitachi Chemical Co., Ltd. was used. In addition, a copolymer of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,5-diaminopyridine was used for the optical waveguide substrate. The design of the reflective polymer optical waveguide is as shown in FIG. From the distance required for diffusing the incident light 10 and the distance required for condensing, the lengths of l _i and l _o are determined, respectively. The fabrication of the optical waveguide was performed by exposure and RIE (Reactive Ion Etching). The alignment of the diffraction grating 26 was performed by shifting the position of the diffraction grating 26 while monitoring the exit light 18 entering the exit-side channel optical waveguide 16. Each splitter was cut out with a dicer with high precision and the end faces were aligned. The left and right alignment of the three-layer duplexer was optically inspected by passing the light of an optical fiber through the alignment optical waveguide 12. The wavelengths of the incident light are 1300, 1320, 1340, and 1360 nm, and the respective wavelengths include the polarization of the TE mode and the TM mode of the optical waveguide. The TE mode and the TM mode are separated by a polarizing beam splitter and a mirror in advance. The TE mode is input to the top layer, and the TM mode is input to the second layer. The incident light 10 diffuses in the slab light guide 24 as it exits the channel light guide 14. After passing through the diffraction grating 26, it is focused in the slab optical waveguide 24 and enters one of the four channels. These four channels correspond to the wavelengths λ1 to λ4. The signal is a total of eight waves.
The average crosstalk between adjacent channels was 13 dB, and the average propagation loss of outgoing light with respect to the incident light of each channel was 9 dB. The size of this integrated duplexer was 3 duplexers, 2 cm × 1 cm in length and width, and 0.7 cm in height.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an optical multiplexer / demultiplexer using a diffraction grating as viewed from above. This corresponds to a cross-sectional view taken along line B in FIG.
FIG. 2 is a cross-sectional view of an optical multiplexer / demultiplexer using a diffraction grating as viewed from the side. This corresponds to a cross-sectional view taken along line A in FIG.
FIG. 3 is a schematic diagram of an optical multiplexer / demultiplexer using a wavelength selection filter.
[Explanation of symbols]
l _i and l _o are the length of the incident side slab optical waveguide and the length of the output side slab optical waveguide, respectively.
10: Incident light 12: Positioning optical waveguide 14: Incident side channel optical waveguide 16: Exit side channel optical waveguide 18: Outgoing light 20: Incident side slab optical waveguide middle optical path 22: Exit side slab optical waveguide middle optical path 24: Slab optical waveguide 26: Reflective diffraction grating 28: Substrate 30: Core 32: Cladding 34: Mirror 36: Transparent substrate 38: Wavelength selection filter 40: Incident light 42: Outgoing light 44: Incident light microlens 46: Outgoing light Micro lens for

Claims (12)

An integrated optical multiplexer / demultiplexer in which two or more optical multiplexers / demultiplexers are three-dimensionally stacked to increase the degree of spatial integration of the optical multiplexer / demultiplexer. The integrated optical multiplexer / demultiplexer according to claim 1, wherein integration is realized by stacking PLCs to form a multilayer structure. 3. The integrated optical multiplexer / demultiplexer according to claim 2, wherein a plane diffraction grating is used as the optical multiplexer / demultiplexer. 4. The integrated optical multiplexer / demultiplexer according to claim 2, wherein the period of the plane diffraction grating is different. The integrated optical multiplexer / demultiplexer according to any one of claims 2 to 4, wherein the plane diffraction grating is a reflection type. The integrated optical multiplexer / demultiplexer according to any one of claims 2 to 5, wherein a polymer optical waveguide is used as the optical multiplexer / demultiplexer. 7. The integrated optical multiplexer / demultiplexer according to claim 6, wherein the wavelength and the polarization are simultaneously separated. The integrated optical multiplexer / demultiplexer according to any one of claims 1 to 6, wherein a corresponding polarization is determined in each optical multiplexer / demultiplexer. 2. The integrated optical multiplexer / demultiplexer according to claim 1, wherein a wavelength selection filter is used for the optical multiplexer / demultiplexer. 10. The integrated optical multiplexer / demultiplexer according to claim 9, wherein integration is realized by using a microlens array or a Fresnel lens array arranged two-dimensionally for an input or output portion of light to the optical multiplexer / demultiplexer. 11. The integrated optical multiplexer / demultiplexer according to claim 10, wherein a mirror is used for the optical multiplexer / demultiplexer. The integrated optical multiplexer / demultiplexer according to any one of claims 1 to 11, wherein integration is realized by using an array of optical fibers and optical waveguides corresponding to the two-dimensional MT connector.

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