JP5839586B2 - Optical signal processor - Google Patents

Description

  The present invention relates to an optical signal processing apparatus that has small polarization dependence and is easy to mount.

  With the construction of a large-capacity optical communication network that shows rapid progress in recent years, wavelength division multiplexing (WDM) communication technology attracts attention, and the spread of facilities is also progressing. In a WDM node, a method of switching a path after converting an optical signal into an electrical signal without directly controlling it is generally used. However, in the method of converting to an electrical signal, there is a concern that the processing capacity load at the node increases, the communication speed is limited, and the power consumption increases. For this reason, development of an optical signal processing device that performs signal processing with an optical signal as it is without going through switching by an electric signal has been advanced. Such devices include, for example, a wavelength selective switch (WSS) and a tunable dispersion compensator (TODC).

  A general configuration and operation principle of an optical signal processing device such as WSS or TODC that performs signal processing as an optical signal will be described. The WDM signal input from the input optical fiber propagates in space as collimated light by the collimator. The propagating light passes through a plurality of lenses and a diffraction grating for wavelength demultiplexing, and is collected again through the lenses. A spatial light modulator (SLM) for giving a desired phase change to the optical signal is disposed at the condensing position of the propagating light. Typical examples of the SLM include a micro mirror array by a micro-electro mechanical system (MEMS) technique, a liquid crystal cell array, a digital mirror device (DMD), and a liquid crystal on silicon (LCOS).

  Each optical signal is given a desired phase change corresponding to a condensing position, that is, a wavelength, and reflected by the SLM. Each of the reflected optical signals travels in the reverse direction in the forward path, enters the diffraction grating via the lens, is wavelength-multiplexed, and then couples to the output fiber via the lens. When an optical signal processing device is configured as a compensation device such as TODC, a technique is often used in which an input fiber and an output fiber are combined and a signal before and after compensation is separated using a circulator. When configuring a switching device such as WSS, a plurality of output fibers are arranged in addition to at least one input fiber, and the signal light is deflected to a desired angle by the SLM. By changing the deflection angle, the output fiber to which the signal light reflected by the SLM is coupled can be selected and switched.

  Various optical elements for configuring each optical signal processing apparatus as described above include devices having polarization dependency. For example, among SLMs, which are key devices for realizing the above-described optical signal processing apparatus, LCOS is compatible with flexible grid technology that is being studied from the viewpoint of effective use of frequency resources, and has an arbitrary phase. It attracts attention as the most promising SLM because of the advantage that changes can be freely set. However, LCOS is also known as a device having polarization dependency.

  The LCOS is a phase modulation cell array based on liquid crystal, which is composed of a group of finely arranged pixels. Therefore, according to the orientation direction of the liquid crystal molecules sealed in the LCOS, it has a characteristic of selectively operating with respect to any one of a TE (Transverse Electric) mode and a TM (Transverse Magnetic) mode. . Therefore, if the phase modulation operation cannot be performed in the same manner for both polarizations of the TE mode and the TM mode, the characteristics of the optical signal processing are deteriorated. As polarization-dependent transmission quality degradation factors, polarization mode dispersion PMD (Polarization Mode Dispersion), polarization dependent loss PDL (Polarization Dependent Loss), and the like are known. Such a polarization-dependent device is not limited to LCOS. For example, it is a well-known fact that a difference in diffraction efficiency occurs in both polarization states in a bulk diffraction grating or the like.

  In order to operate without problems even when the polarization dependent device as described above is used in an optical signal processing apparatus, a polarization diversity configuration is adopted. The polarization diversity configuration is a configuration in which the polarization dependency is reduced by operating with the polarization state incident on the optical element fixed to either the TE mode or the TM mode. Incorporating the polarization diversity configuration into the optical design is a general consideration.

N. Ooba et al., "Compact Wide Wide-Band Wavelength Blocker Utilizing Novel Hybrid AWG-Free Space Focusing Optics," Proc. OFC'08, Sandiego, (2008), OWI 3.

  FIG. 1 is a diagram illustrating a conceptual diagram of an optical signal processing device having a general configuration. Hereinafter, a more detailed description of the polarization diversity operation will be given with reference to FIG. In the following, in the optical signal processing apparatus 100, the direction of wavelength demultiplexing by the diffraction grating 107 is the x axis, and the traveling direction when the optical signal is output from the fiber 101 is the z axis, the direction orthogonal to the x axis and the z axis. Is defined as the y-axis. FIG. 1A is a diagram of the optical signal processing apparatus 100 according to the first example viewed in the yz plane. For simplicity, the number of input / output fibers 101 is one, but the number and configuration of optical fibers that input or output optical signals are not limited thereto. Further, in the optical signal emitted from the input / output fiber 101, the chief ray of the portion where both polarizations of the TE mode and the TM mode are not separated is thick, and the chief ray separated only in the TM mode is thick. Principal rays that are separated only in the TE mode are indicated by thin broken lines, respectively, by thin broken lines.

  In the optical signal processing apparatus 100, an optical signal 111 propagating through the input / output fiber 101 is emitted from the input / output fiber 101 into the space, and has a constant numerical aperture (NA :) corresponding to the beam diameter confined by the input / output fiber 101. Propagate while spreading at Numerical aperture). This optical signal is adjusted in NA by the microlens 102 whose focal length and arrangement position are adjusted so that the optical signal emitted from the input / output fiber 101 propagates through the space as collimated light, and enters the polarization separation unit 103. To do. The optical signal passing through the polarization separation unit 103 is angle-separated for each polarization mode, and the TE polarization is emitted below the y axis and the TM polarization is emitted above the y axis in FIG. . An example of the polarization separation unit 103 is a Wollaston prism using a birefringent crystal.

  Of the two optical signals separated by the polarization separation unit 103, the λ / 2 plate 104 is disposed in the optical path 114 of TE polarization, and the TE polarization is converted into TM polarization by the λ / 2 plate 104. Is done. Thereafter, the converted TM polarized wave is demultiplexed in the x-axis direction by being incident on the diffraction grating 107 through the lens 106. The demultiplexed optical signal is further condensed via the lens 108 at a position corresponding to the wavelength on the spatial light modulator 109.

  On the other hand, an optical path length correction plate 105 is disposed in the optical path 113 of TM polarization separated by the polarization separation unit 103, and the optical path length is corrected by passing through the optical path length correction plate 105. Thereafter, the light is condensed on the spatial light modulator 109 via the lens 106 and the diffraction grating 107 in the same manner as the TE polarized light. In order to perform the same deflection operation for both the TE polarization and TM polarization separated by the polarization separation unit 103, the same mode field is assumed to be present at the same position on the spatial light modulator 109. Condensed to Here, out of the signal light separated by the polarization separation unit 103, the optical path 114 is emitted from the polarization separation unit 103 to the lower side and condensed on the spatial light modulator 109. An optical path 113 that is emitted from the upper side of the unit 103 and converges on the spatial light modulator 109 is defined as an optical path 2.

  In order to realize the polarization diversity operation, it is necessary that the light that has traveled along the optical path 1 is reflected by the spatial phase modulator 109, travels back along the optical path 2, and enters the polarization separation unit 103. At this time, due to the reciprocity of light, the light that has traveled along the optical path 2 is reflected by the spatial phase modulator 109, travels back along the optical path 1, and enters the polarization separation unit 103. In this case, the TE polarization and TM polarization separated by the polarization separation unit 103 are one kind of TM on each optical path closer to the spatial light modulator 109 than the λ / 2 plate 104 and the optical path length correction plate 105. It is in the state of polarization. One of the two types of polarization modes that originally existed is converted, and only one type of the same polarization mode exists. Therefore, there is no difference depending on the polarization mode, and the spatial phase modulator 109 can obtain a loss amount and diffraction efficiency independent of the polarization state. For this reason, polarization dependence does not occur, and polarization independence is possible. As a premise of this operation, in order to reduce PMD and PDL, it is necessary to determine the thickness and refractive index of the optical path length correction plate 105 so that the optical lengths of the respective optical paths are equal.

The function of polarization diversity by the Wollaston prism shown in FIG. 1A is not limited to the angle separation device such as the Wollaston prism, but also by using the position separation device such as the YVO ₄ crystal (yttrium vanadate). Can also be realized. FIG. 1B shows a configuration when a YVO ₄ crystal is used as the polarization separation unit 110. Also in the configuration of (b), the same operation principle as the polarization diversity operation of the configuration shown in (a) except for the difference that the position separation operation is performed instead of the angle separation by the polarization separation unit 110. Thus, polarization independence can be achieved.

  However, in order to realize the polarization diversity configuration as shown in FIGS. 1A and 1B, the polarization separation unit 103, the λ / 2 plate 104, and the optical path correction plate 105 using a birefringent crystal. Need to be prepared, and the cost of the member increases. Further, specific specifications of these series of optical members need to be considered in the optical design. For example, in order to suppress the increase in the cost of the member as much as possible, it is important to downsize the polarization separation unit. In order to allow signal light to pass through a small polarization separation unit, it is necessary to narrow the beam incident on the polarization separation unit as much as possible using a microlens or the like. Such a demand places a heavy burden on the optical design of the entire optical signal processing apparatus and the arrangement of each member. For example, the accuracy required for the alignment of each component of the optical signal processing device increases, and the accuracy of the component, the position adjustment cost, and the manufacturing cost increase. In addition, the difficulty and limiting factors in optical design increase.

  Therefore, there is a strong demand for a polarization diversity method that can be realized at low cost by simplifying alignment by omitting the polarization diversity optical member including the birefringent crystal as much as possible. The present invention has been made in view of such problems, and the object of the present invention is to eliminate the need for an optical member of a polarization separation unit made of a birefringent crystal while reducing polarization dependency. An object of the present invention is to provide an optical signal processing device that can simplify the alignment of each component of the optical signal processing device at low cost.

In order to achieve the above object, according to the present invention, the invention described in claim 1 includes an input port to which a wavelength multiplexed optical signal is input and a polarization state in which the wavelength multiplexed optical signal is orthogonal to each other on a substrate. Polarization separating means for separating the first polarized wave and the second polarized wave, a first outgoing waveguide for outputting the first polarized wave, and a second outgoing guide for outputting the second polarized wave. An optical waveguide circuit configured with a polarization beam splitter including a waveguide, and deflects signal light emitted into the space from either the first output waveguide or the second output waveguide of the optical waveguide circuit Light deflecting means for reflecting the deflected signal light so as to recombine with the other of the first output waveguide and the second output waveguide; and the first output waveguide on the substrate or the first It was placed on top of one of the second output waveguide, Comprising a polarization rotating means for the wave state is rotated 90 °, the wavelength-multiplexed optical signal emitted from the substrate, and a spectral means for wavelength separation perpendicular wavelength dispersion direction in the circuit configuration surface of the substrate, the substrate The upper optical waveguide circuit includes a slab waveguide in which the first output waveguide and the second output waveguide are connected to an input side, and an output side of the slab waveguide, and each waveguide An arrayed waveguide having a plurality of waveguides having the same length, the arrayed waveguide emitting a plane wave whose phase is aligned in a direction perpendicular to the wavelength dispersion axis direction from the substrate end face to the space. Is an optical signal processing device.

Input port corresponds to the input waveguide in FIG. The polarization rotation means corresponds to a λ / 2 plate arranged so that the refractive index main axis is inclined by 45 ° with respect to the refractive index main axis of the waveguide. The first polarization can be a TM polarization and the second polarization can be a TE polarization. Preferably, the optical waveguide circuit is a quartz-based planar lightwave circuit (PLC) configured on a quartz-based substrate.

According to a second aspect of the present invention, an input port to which a wavelength multiplexed optical signal is input is separated on a substrate, and the wavelength multiplexed optical signal is separated into a first polarization and a second polarization having polarization states orthogonal to each other. A polarization beam splitter for input port, and a polarization beam splitter for an input port including a first output waveguide that outputs the first polarization and a second output waveguide that outputs the second polarization, but the output port for outputting the optical signal wavelength separation of the wavelength-multiplexed optical signal, the polarization separation can be separated into a first polarization and a second polarization having a polarization state orthogonal to the wavelength-multiplexed optical signal from each other And a polarization beam splitter for N output ports including a first output waveguide that outputs the first polarization and a second output waveguide that outputs the second polarization. Optical waveguide circuit and polarized beam beam for the input port The signal light emitted from one of the first output waveguide and the second output waveguide of the liter to the space is deflected, and the deflected signal light is N polarized beams for the output port. Recombination with an output waveguide on a side different from the output waveguide from which the signal light is output out of the first output waveguide and the second output waveguide in one polarization beam splitter selected from the splitter And the first output waveguide of each of the input port polarization beam splitter and the N output port polarization beam splitters on the substrate, or each of the first output waveguides. It was placed on top of one of the second output waveguide, and polarization rotation means for rotating 90 ° the polarization state, the WDM optical signal emitted from the substrate, perpendicular to the circuit configuration surface of the substrate Wavelength dispersion axis Spectroscopic means for wavelength-separating in the direction, and the optical waveguide circuit on the substrate includes a slab waveguide in which the first output waveguide and the second output waveguide are connected to the input side, An arrayed waveguide connected to the output side of the slab waveguide and having a plurality of waveguides each having the same waveguide length, the phase being aligned in the direction perpendicular to the wavelength dispersion axis direction from the substrate end surface to the space. The optical signal processing device further includes an arrayed waveguide that emits a plane wave .

Top entry input port, in FIG. 6, the polarization beam splitter 610-0 positioned at the top, corresponding to the input port signal light is incident. Further, the output port for outputting the wavelength-separated optical signal of the wavelength division multiplexed optical signal is selected from any one of the N polarization beam splitters 610-1 to 610-N in FIG. The wave beam splitter corresponds to an output port that emits signal light.

  A third aspect of the present invention is the optical signal processing apparatus according to the second aspect, wherein the first output guide of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports is provided. The waveguides are configured to be adjacent to each other in an array, and the second output waveguides of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports are adjacent to each other in an array. The polarization rotation means includes the output waveguides configured in an array on one side of the first output waveguide or the second output waveguide on the substrate. It is characterized by being crossed and integrated.

  According to a fourth aspect of the present invention, there is provided the optical signal processing device according to the third aspect, wherein each of the first emission of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports. Light for forming a dummy intersection in addition to the intersection between each first output waveguide and each second output waveguide in a non-intersection region of the waveguide and each second output waveguide A plurality of dummy optical waveguides that are not used for signal processing are provided.

The invention described in claim 5 is the one of the optical signal processing apparatus according to claim 1 to 4, the pre-Symbol wavelength separation optical signal, for condensing onto modulation device forming surface of said light modulating means The optical modulation unit gives a phase shift independently to the optical signal collected by the lens, and the phase shift causes the first output waveguide or the second output of the substrate. The signal light emitted from one of the waveguides is re-coupled to the other of the first emission waveguide or the second emission waveguide of the substrate.

  As described above, the present invention makes it possible to simplify the alignment of each component of the optical signal processing device at a low cost by reducing the polarization dependence and eliminating the need for the optical member of the polarization separation unit made of a birefringent crystal. It is possible to provide an optical signal processing device that can be configured.

FIG. 1 is a diagram illustrating a conceptual diagram of an optical signal processing device having a general configuration. FIG. 2 is a diagram showing a configuration of the optical signal processing apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating the configuration of the optical waveguide substrate in the optical signal processing device according to the first embodiment. FIG. 4 is a diagram showing a different configuration of the optical waveguide substrate including the polarization beam splitter. FIG. 5 is a diagram showing a configuration of an optical signal processing apparatus according to a second embodiment of the present invention. FIG. 6 is a diagram illustrating a configuration of an optical waveguide substrate adapted to a wavelength selective switch function in the optical signal processing device according to the second embodiment. FIG. 7 is a diagram for explaining the behavior of the reflected light path in the vicinity of the spatial light modulator. FIG. 8 is a diagram showing a configuration of a third embodiment of the optical signal processing device according to the present invention. FIG. 9 is a diagram illustrating a configuration of an optical waveguide substrate adapted to a wavelength selective switch function in the optical signal processing device according to the third embodiment. FIG. 10 is a diagram illustrating a waveguide arrangement configuration of the optical waveguide substrate in the optical signal processing device according to the third embodiment. FIG. 11 is a diagram showing a configuration of an optical signal processing apparatus according to a fourth embodiment of the present invention. FIG. 12 is a diagram illustrating a configuration of an optical waveguide substrate adapted to a wavelength selective switch function in the optical signal processing device according to the fourth embodiment. FIG. 13 is a diagram illustrating a configuration of an optical waveguide substrate having a slab waveguide and an arrayed waveguide corresponding to the configuration of the first embodiment. FIG. 14 is a diagram illustrating a configuration of an optical waveguide substrate having a slab waveguide and an arrayed waveguide corresponding to the configuration of the third embodiment.

  The optical signal processing device of the present invention employs an input / output optical system in which a polarization beam splitter is integrated in a silica-based lightwave circuit, thereby reducing the polarization dependence and using the birefringent crystal used in the prior art. This eliminates the need for the optical member of the polarization separation section. Provided is an optical signal processing device capable of realizing cost reduction of members and simplification of device alignment adjustment.

  More specifically, the optical signal processing device according to the present invention includes, on a substrate, an input port to which a wavelength division multiplexed optical signal is input, a first polarization having a polarization state in which the wavelength multiplexed optical signal is orthogonal to each other, and A polarization beam splitter comprising a polarization separation means for separating into a second polarization, a first output waveguide for outputting the first polarization, and a second output waveguide for outputting the second polarization is constructed. And further deflecting the signal light emitted into the space from either the first output waveguide or the second output waveguide of the optical waveguide circuit, and the deflected signal light is Light modulation means (spatial phase modulator) is provided that reflects the other of the exit waveguide and the second exit waveguide to recombine.

  Hereinafter, the present invention will be described with reference to various examples, but the present invention is not limited to the following examples. In the description of the drawings, the same reference numerals denote the same or corresponding elements throughout the drawings.

  FIG. 2 is a diagram showing a configuration of the optical signal processing apparatus according to the first embodiment of the present invention. The optical signal processing apparatus 200 of this embodiment includes microlenses 202 and 206 that convert signal light emitted from the optical waveguide substrate 201 into collimated light, a diffraction grating 203, a lens 204, and a spatial phase modulator 205. Arranged in order. The demultiplexing direction 212 of the diffraction grating 203 is taken as the x axis, the direction in which the signal light reciprocates is taken as the z axis, and the x axis and the direction perpendicular to the z axis are taken as the y axis. In the configuration of this embodiment, the microlenses 202 and 206 and the lens 204 are used in this order as lens components of the spatial optical system. However, any number of lenses may be used as long as the configuration has similar optical characteristics. It does not matter if any arrangement is used. That is, light emitted from the optical waveguide substrate 201 may be converted into collimated light in the x-axis direction, and the signal light may be collected at a predetermined position on the y-axis on the spatial phase modulator 205.

  FIG. 3 is a diagram illustrating the configuration of the optical waveguide substrate in the optical signal processing device according to the first embodiment. The optical waveguide substrate 201 is a quartz-based planar lightwave circuit (PLC) configured on a quartz-based substrate. The optical waveguide substrate 201 includes an input waveguide 301, a 3 dB coupler 302 that divides signal light from the input waveguide 301 into equal power, two arm waveguides 303a and 303b, and two arm waveguides. Among them, a λ / 2 plate 304 inserted into one 303b, a 3dB coupler 305 for multiplexing signal light from two arm waveguides, and two output waveguides 307 and 308 connected to the 3dB coupler 305. And a λ / 2 plate 306 inserted into one of them. From the optical waveguide substrate of this configuration, one of the two polarized waves whose amplitude directions are orthogonal is output from the first output waveguide 307, and the other polarized wave is the second output waveguide 308. Is output from.

  The first output waveguide 307 and the second output waveguide 308 are arranged at angles that are parallel to each other so as to be connected perpendicularly to an end face that coincides with the x-axis of the substrate. In the following description, among the polarizations branched by the subsequent 3 dB coupler 305, the polarizations output to the first output waveguide 307 and the second output waveguide are respectively TM polarization and TE polarization. It is described. As long as two polarization states are orthogonal to each other, any polarization may be output to which output waveguide. In FIG. 3, the λ / 2 plate 306 for converting a certain linearly polarized wave into a perpendicularly polarized wave is inserted on the second outgoing waveguide 308 side, but the first outgoing waveguide 307 is inserted. The structure arrange | positioned in the side may be sufficient. Furthermore, the λ / 2 plate 306 is configured to be disposed on the optical waveguide substrate 301 for ease of mounting, but may be configured to be disposed as a spatial optical system component outside the optical waveguide substrate.

  That is, the configuration of the optical waveguide substrate 301 can be variously modified as long as the polarization diversity function is realized. Various polarization states are separated into two orthogonal linearly polarized waves, and one of them is converted into the other linearly polarized wave by the λ / 2 plate 306, and is provided for the spatial light modulator 205. If only one type of linearly polarized light can be incident, the function of polarization diversity can be realized. It should be noted that the components of the optical waveguide substrate 301 may be arranged in any order and at any position.

  Therefore, the optical signal processing apparatus according to the present embodiment includes an input port to which a wavelength division multiplexed optical signal is input, a first polarization and a second polarization having polarization states orthogonal to each other on the substrate. A polarization beam splitter including polarization separation means for separating into polarized waves, a first output waveguide that outputs the first polarization, and a second output waveguide that outputs the second polarization is configured. An optical waveguide circuit. Further, the signal light emitted from one of the first output waveguide and the second output waveguide of the optical waveguide circuit to the space is deflected, and the deflected signal light is transmitted to the first output waveguide and the second output waveguide. A light modulating means (spatial phase modulator) that reflects to recombine with the other of the exit waveguides and either the first exit waveguide or the second exit waveguide on the substrate, or the first And a polarization rotation means (λ / 2 plate) arranged on an optical path that emits from one of the first output waveguide and the second output waveguide to the space and that rotates the polarization state by 90 °.

  The optical signal processing apparatus 100 of the present invention operates as follows. First, the signal light 310 input to the input waveguide 301 is branched into two arm waveguides 303a and 303b with the same power and the same phase in the 3 dB coupler 302. One of the arm waveguides 303b is provided with a λ / 2 plate 304 having a refractive index principal axis that coincides with the refractive index principal axis of the waveguide, and delays the polarization in one direction by 180 °. Thereafter, the signal light branched by the 3 dB coupler 305 disposed in the subsequent stage is multiplexed. When multiplexed, the signal light from the two arm waveguides interfere with each other, and the condensing conditions of two orthogonally polarized waves are reversed. As a result, the two linearly polarized waves are coupled to the first outgoing waveguide 307 and the second outgoing waveguide 308 which are different from each other.

  As described above, the optical waveguide substrate 301 can separate two orthogonally polarized waves using interference, and thus constitutes a polarization beam splitter. In this embodiment, a λ / 2 plate is inserted into the arm waveguide 303b. However, any configuration can be used as long as two orthogonal linearly polarized waves can be divided into different output waveguides for output. good. For example, the polarization beam splitter can also be configured by a method of adjusting the stress in the arm waveguide.

  The polarization beam splitter according to the present invention further includes a λ / 2 plate 306 arranged on the second output waveguide 306 so that the refractive index main axis is inclined by 45 ° with respect to the refractive index main axis of the waveguide. ing. For this reason, the TE polarized light combined by the post-stage 3 dB coupler 305 is converted into TM polarized light and emitted to the space. Finally, the signal light 310 is separated by the polarization beam splitter, and each polarization output to the space from the first output waveguide 307 and the second output waveguide 308 is a TM polarization. Available in one type.

  Referring to FIG. 2 again, the respective polarizations aligned with the TM polarization are emitted from the optical waveguide substrate 201 into the space and then collimated in the x-axis direction by at least one microlens 202 and 206, respectively. Propagate through space. The collimated light is wavelength-demultiplexed with respect to the x-axis by the diffraction grating 203. The demultiplexed light is collected by the lens 204, is subjected to desired phase modulation by the spatial light modulator 205, and is reflected. Here, the light output from the first output waveguide 307 and reaching the spatial light modulator 205 through the optical path 207 is reflected and then output from the second output waveguide 308 and output from the spatial light modulator 205. The light path 208 of the light that reaches the light travels backward. Similarly, the light output from the second output waveguide 308 and reaching the spatial light modulator 205 through the optical path 208 is reflected and then output from the first output waveguide 307 and output from the spatial light modulator 205. The light path 207 of the light that reaches the light beam 207 travels backward. In this way, the light emitted from the first output waveguide 301 is coupled to the second output waveguide 308, and the light output from the second output waveguide 308 is coupled to the first output waveguide 301. It is important that such a loop optical path is constructed.

  Therefore, the optical signal processing apparatus includes a spectroscopic unit for wavelength-separating the wavelength-multiplexed optical signal emitted from the substrate in a wavelength dispersion direction perpendicular to the circuit configuration surface of the substrate, and the wavelength-separated optical signal for the optical modulation unit. A lens for condensing light on the modulation element forming surface is further provided. The light modulation means independently gives a phase shift to the optical signal collected by the lens, and the signal light emitted from either the first emission waveguide or the second emission waveguide of the substrate by this phase shift. Is recombined to the other of the first output waveguide or the second output waveguide of the substrate.

  Since the polarization state in the optical path of the spatial optical system is aligned to one type, any signal light output from the first output waveguide and the second output waveguide has no polarization dependency. In this state, the deflection operation by the spatial light modulator 205 becomes possible. If non-uniform loss or delay occurs in the two signal lights between the first output waveguide 307 and the spatial light modulator 205, it may become a transmission quality degradation factor depending on polarization such as PDL and PMD. . However, when constructing a loop optical path like this configuration, the two polarized waves divided by the polarization beam splitter of the optical waveguide substrate 201 are exactly the same when viewed in the forward path and the return path as a whole due to the reciprocity of light. You are on the path. Specifically, the light emitted from the first output waveguide 307 travels along the optical path 207 as the forward path and travels in the reverse direction along the optical path 208 as the return path. On the other hand, the light emitted from the second output waveguide 308 travels along the optical path 208 as the forward path and travels in the reverse direction along the optical path 207 as the forward path. Therefore, the two polarized waves divided by the polarization beam splitter are subjected to the same loss and delay in exactly the same path while being aligned with the same polarization. As a result, polarization dependence does not occur even in the portion excluding the spatial light modulator 205.

  In the optical signal processing apparatus 200 of the present embodiment, the optical waveguide substrate 201 including the polarization beam splitter includes a polarization separation unit 110 of a type that separates the emission position as shown in FIG. Both of the fibers 101 are integrated and configured. Therefore, these two optical members can be omitted, and a preparation process including optical polishing for these optical members can be omitted. Furthermore, since the alignment of the component parts is completed when the optical waveguide substrate chip 201 is manufactured, the time and cost for adjustment are reduced, and the burden of accuracy of alignment adjustment and complexity of work itself is reduced. Is realized.

  In the present embodiment, the polarization beam splitter in the optical waveguide substrate 201 has been described as a configuration that separates the positions of polarized waves as shown in FIG. Therefore, the two output waveguides 307 and 308 in FIG. 3 are arranged in parallel. However, it is not limited to this configuration.

  FIG. 4 is a diagram showing a different configuration example of the optical waveguide substrate including the polarization beam splitter. The optical waveguide substrate 401 having this configuration example is the same as the optical waveguide substrate 201 shown in FIG. 3 except for the configuration of the first output waveguide 407 and the second output waveguide 408. The first emission waveguide 407 emits one polarized wave in a direction that is not perpendicular to the x-axis at a certain angle. The second output waveguide 408 emits at an angle different from that of the first output waveguide 407. In the configuration shown in FIG. 4, the function of the polarization separation unit is angle separation, and thus the spatial optical system has a configuration as shown in FIG. Therefore, when the optical waveguide substrate 201 is replaced with the optical waveguide substrate 401 in the configuration of the optical signal processing apparatus in FIG. 2, it is desirable to insert one additional lens between the optical waveguide substrate 401 and the diffraction grating 203. In both the optical waveguide substrate 201 and the optical waveguide substrate 401, a series of optical systems related to polarization diversity can be integrated on the PLC, thereby reducing the cost and reducing the mounting load.

  In the first embodiment described above, the light emitted to the spatial optical system has been described as being configured to be aligned with the TM polarization, but it is naturally possible to align with the TE polarization. In addition, the position of the λ / 2 plate on the optical waveguide substrate and the waveguide in which the λ / 2 plate disposed on one of the two outgoing waveguides is placed can be changed. The feature is that the function of the optical member of the polarization splitting unit by the birefringent crystal in the conventional optical signal processing device is integrated on the PLC. In this embodiment, the input / output of the optical signal is performed at one place. However, the optical signal processing apparatus of the present invention can be applied to a configuration in which the input form and the output form of the optical signal are different.

  FIG. 5 is a diagram showing a configuration of an optical signal processing apparatus according to a second embodiment of the present invention. In the optical signal processing apparatus 500 of this embodiment, the microlens group 502, the diffraction grating 503, the lens 504, and the spatial phase modulator 505 that convert the signal light emitted from the optical waveguide substrate 501 into collimated light reciprocate the signal light. The z direction is arranged in this order. A demultiplexing direction 506 of the diffraction grating 503 is defined as an x-axis, and a direction perpendicular to the x-axis and the z-axis is defined as a y-axis.

  The optical signal processing device 501 of the present embodiment is different from the configuration of the first embodiment in that it has a configuration having at least one input port and at least one output port. Further, the spatial light modulator 505 can deflect the signal light in a direction (y-axis direction) orthogonal to the wavelength dispersion axis 506 of the diffraction grating 503 and perform switching to one of the output ports. That is, by reflecting the spatial light modulator 505 with a different deflection angle for each wavelength, it has a function of selecting an output port for each wavelength of the signal light. Such an optical signal processing device is called a wavelength selective switch. In this embodiment, for simplicity, the number of input ports is 1, and the number of output ports is N (N is a natural number). In FIG. 5, only the input port and the Nth output port are shown, and the 1st to (N-1) th ports are omitted and shown in a simplified manner. As will be described later, the optical signal is input from the input port, reflected by the spatial light modulator 505 at a different deflection angle for each wavelength, and emitted from any one of the selected 1st to Nth output ports. Is done.

  FIG. 6 is a diagram illustrating a configuration of an optical waveguide substrate adapted to a wavelength selective switch function in the optical signal processing device according to the second embodiment. As described above, the optical waveguide substrate 501 includes the polarization beam splitter array 601 composed of N + 1 polarization beam splitters 610-0 to 610-N that can separate and output two orthogonal linearly polarized waves. . The polarization beam splitter 610-0 positioned at the uppermost portion receives the signal light 607 at its input port, and is output from any one output port of the other N polarization beam splitters 610-1 to 610-N. The selected signal light 608 is emitted.

  Each polarization beam splitter has the same configuration as the polarization beam splitter described in FIG. In FIG. 6, the description of the λ / 2 plate inserted into one of the two connected output waveguides arranged in one arm waveguide is omitted. Similarly, the polarization beam splitter may be provided by a method of adjusting the stress in the arm waveguide by using a means other than the λ / 2 plate by using a λ / 2 plate. Accordingly, the polarization beam splitter configured on the PLC can have various configurations.

  Each polarization beam splitter includes a first output waveguide 603-0 to 603-N that outputs one of two polarized waves whose amplitude directions are orthogonal, and a second output that outputs the other polarized wave. Waveguides 604-0 to 604-N are provided. Further, a λ / 2 plate 602 is disposed on one of the two output waveguides. In the polarization beam splitter array 901, the first output waveguide and the second output waveguide connected to each polarization beam splitter are arranged so as to be alternately arranged in the y-axis direction. If each output waveguide and λ / 2 plate are viewed, they are arranged in an array. The layout conditions of the individual elements of the N + 1 polarization beam splitters and the layout conditions such as the distance between the first output waveguide and the second output waveguide in each polarization beam splitter are as follows. All are the same between the splitters. The first output waveguide and the second output waveguide are arranged at angles that are parallel to each other so as to be connected perpendicularly to the end face of the optical waveguide substrate chip 501.

  Therefore, the optical signal processing apparatus according to the present embodiment includes an input port to which a wavelength division multiplexed optical signal is input, a first polarization and a second polarization having polarization states orthogonal to each other on the substrate. Polarization beam for input port including polarization separation means for separating into polarized waves, a first output waveguide for outputting the first polarization, and a second output waveguide for outputting the second polarization A splitter, and an output port that outputs an optical signal that is wavelength-separated from the wavelength division multiplexed optical signal, and a first polarization and a second polarization that have polarization states orthogonal to each other. Polarization beam for N output ports including a polarization separating means capable of separating, a first output waveguide that outputs the first polarization, and a second output waveguide that outputs the second polarization Optical waveguide circuit with splitter That. Further, the signal light emitted to the space from either the first output waveguide or the second output waveguide of the polarization beam splitter for the input port is deflected, and the deflected signal light is used for the output port. A side of the first output waveguide and the second output waveguide that are different from the output waveguide from which the signal light exits in the selected one of the N polarization beam splitters. Each of an optical modulation means (spatial optical modulator) that reflects to recombine with the output waveguide, and the polarization beam splitter for the input port and the polarization beam splitter for the N output ports on the substrate. Space on either the first exit waveguide or each of the second exit waveguides, or from either the first exit waveguide or each of the second exit waveguides Go out Disposed on the optical path to, and a polarization rotation means for rotating 90 ° the polarization state.

  Hereinafter, the operation of the optical signal processing apparatus 500 will be described. Referring to FIG. 5 (and FIG. 6), in the polarization beam splitter 513 to which the signal light 511 is input, TM polarization is output from the “first emission waveguide” (603-0 in FIG. 6). The signal light emitted to the space travels along the optical path 507 and enters the spatial light modulator 505 in the same manner as in the operation of the first embodiment. The deflection angle is determined by the spatial light modulator 505 so as to be coupled to the “second output waveguide” of the polarization beam splitter connected to the desired output port. Here, as an example, it is assumed that the Nth polarization beam splitter 514 at the bottom of the optical waveguide substrate 501 is selected and the optical signal 512 is output. Accordingly, when reflected by the spatial light modulator 505, the light path 510 travels as a return path.

  When all the polarization beam splitters that are arrayed have the same layout, the optical signal output from the “second output waveguide” of the polarization beam splitter 513 travels along the optical path 508, and the spatial light When reflected by the modulator 505, it couples to the “first exit waveguide” of the Nth polarization beam splitter 514 that connects to the selected output port. Accordingly, when reflected by the spatial light modulator 505, the light path 509 travels as a return path.

  As described above, an optical path loop is formed between the polarization beam splitter 513 to which the signal light 511 is input and the polarization beam splitter 514 having the selected output port. That is, one separated polarization of the signal light 511 follows the optical path 507 and the optical path 510, and the other separated polarization of the signal light 511 follows the optical path 508 and the optical path 509.

FIG. 7 is a diagram for explaining the behavior of the reflected light path in the vicinity of the spatial light modulator. Incident angle of the signal light 701 when the outgoing light from the first outgoing waveguide of the polarization beam splitter 513 connected to the input port enters the spatial light modulator 505 via the diffraction grating 503 and the lens 504 Is θ ₁ . Let α be the difference between the incident angle of the signal light from the first output waveguide and the signal light 703 from the second output waveguide. Further, an angle change amount when deflected by the spatial light modulator 505 is β. At this time, the output angle of the reflected light 702 after the signal light 701 from the first output waveguide of the polarization beam splitter 513 is reflected by the spatial light modulator 505 is θ ₂ . At this time, the following equation holds.
θ ₂ = θ ₁ + β Formula (1)

Similarly, when the exit angle of the reflected light 704 after the light from the second exit waveguide of the polarization beam splitter 513 is reflected by the spatial light modulator 505, the following equation is established.
(θ ₁ −α) + β = (θ ₁ + β) −α = θ ₂ −α Formula (2)

  Therefore, as a matter of course, the angle difference between the two signal lights 702 and 704 after being reflected by the spatial light modulator 505 is the same as that before the reflection. If all the N + 1 polarization beam splitters and the output waveguides have the same shape in the optical waveguide substrate 501, an optical path loop is formed as in the first embodiment, and polarization diversity can be realized. In the configuration of the optical waveguide substrate of this embodiment, there is no crossing of the waveguide except for the 3 dB coupler portion. For this reason, the loss due to the crossing of the waveguides is very low loss, the optical polarization dependency is small, the optical member of the polarization separation part by the birefringent crystal is unnecessary, and the alignment is low-cost. A simplified wavelength selective switch can be realized.

  FIG. 8 is a diagram showing a configuration of a third embodiment of the optical signal processing device according to the present invention. The optical signal processing apparatus 800 of this embodiment includes an optical waveguide substrate 801, a microlens 802 that converts signal light emitted from the optical waveguide substrate 801 into collimated light, a diffraction grating 803, a lens 804, and a spatial phase modulator 805. Arranged in this order. The demultiplexing direction 816 of the diffraction grating 803 is taken as the x axis, the direction in which the signal light reciprocates is taken as the z axis, and the direction perpendicular to the x axis and the z axis is taken as the y axis.

  As in the second embodiment, the optical signal processing apparatus 801 according to the present embodiment has a configuration having at least one input port and at least one output port. Further, the spatial light modulator 505 can deflect the signal light in a direction (y-axis direction) orthogonal to the wavelength dispersion axis 506 of the diffraction grating 503 and perform switching to one of the output ports. That is, by reflecting the spatial light modulator 505 with a different deflection angle for each wavelength, it has a function of selecting an output port for each wavelength of the signal light. Compared with the configuration of Example 2, the configuration of the optical waveguide substrate 801 is different.

  FIG. 9 is a diagram illustrating a configuration of an optical waveguide substrate adapted to a wavelength selective switch function in the optical signal processing device according to the third embodiment. As described above, the optical waveguide substrate 801 includes the polarization beam splitter array 901 including the N + 1 polarization beam splitters 905-0 to 905-N that can separate and output two orthogonal linearly polarized waves. . The signal light 907 enters the polarization beam splitter 905-0 positioned at the top, and the selected signal light 908 is emitted from the other N polarization beam splitters 905-1 to 905-N. .

  Each polarization beam splitter has the same configuration as the polarization beam splitter described in FIG. In FIG. 9, the description of the λ / 2 plate inserted into one of the two connected output waveguides arranged in one arm waveguide is omitted. Similarly, the polarization beam splitter may be provided by a method of adjusting the stress in the arm waveguide by using a means other than the λ / 2 plate by using a λ / 2 plate. Therefore, as in the second embodiment, the polarization beam splitter configured on the PLC can have various configurations.

  Each polarization beam splitter includes a first output waveguide that outputs one of two polarized waves whose amplitude directions are orthogonal to each other, and a second output waveguide that outputs the other polarized wave. Further, a λ / 2 plate is disposed on one of the two output waveguides. Unlike the configuration of the second embodiment, N + 1 first output waveguides from the respective polarization beam splitters are arranged in an array 805 so as to be adjacent to each other. Similarly, N + 1 second output waveguides from the respective polarization beam splitters are also arranged in an array 804 so as to be adjacent to each other. The λ / 2 plate is not arranged separately in each second output waveguide, but is realized as an integral λ / 2 plate 902.

  The layout conditions of the individual elements of the N + 1 polarization beam splitters and the layout conditions such as the distance between the first output waveguide and the second output waveguide in each polarization beam splitter are as follows. All are the same between the splitters. The first output waveguide and the second output waveguide are respectively arranged at angles that are parallel to each other so as to be connected perpendicularly to the end face of the optical waveguide substrate chip 801.

  Therefore, the optical signal processing apparatus of the present embodiment is different from the configuration of the second embodiment in that the first output waveguide of the polarization beam splitter for input ports and the polarization beam splitter for N output ports is: The second output waveguides of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports are configured to be adjacent to each other in an array. The wave rotation means (λ / 2 plate) is integrally formed across the output waveguide configured in the array on one side of the first output waveguide or the second output waveguide on the substrate. It is configured.

  Hereinafter, the operation of the optical signal processing apparatus 800 will be described. The operation of the polarization diversity function in this embodiment is exactly the same as in the second embodiment. In the present embodiment, the first output waveguide group 903 connected to the polarization beam splitter array 901 is arranged in an array shape, and all of them are collected in one adjacent place and arranged at a constant interval. The second output waveguide group 904 connected to the polarization beam splitter array 901 is also arranged at a fixed interval at a position different from the first output waveguide group 903, all at one adjacent location. Has been. In order to arrange the output waveguides in this way, intersections of the output waveguides occur.

  FIG. 10 is a diagram illustrating a waveguide configuration of an optical waveguide substrate in the optical signal processing device according to the third embodiment. FIG. 10 does not show the shape of the actual waveguide, but the number of waveguide crossings when the number of output ports that can be selected is 9 (N = 9) when the input ports are arranged in the uppermost stage. Is conceptually shown. In FIG. 10, black circles indicate the positions of waveguide intersections that occur on the output waveguide layout. For example, among the branches from the input port 901 of the polarization beam splitter to which the optical signal is input, the output polarization can propagate without passing through the waveguide at all in the first output waveguide 903. . On the other hand, among the branches from the input port 901, the output polarized wave propagates through all waveguide intersections for the second output waveguide 905. That is, there are nine intersections for the second output waveguide 905. Thus, the number of intersections leading to the end of the output waveguide differs depending on the output waveguide.

  It is generally known that the waveguide crossing causes a crossing loss of about 0.1 dB at one place. Therefore, depending on which polarization beam splitter is selected as the output port, the loss varies depending on the two ports that output the signal light separated in each polarization beam splitter. This variation occurs in a place different from the basic optical path loop configuration for performing polarization diversity in the optical circuit of the spatial optical system.

  In order to eliminate this variation, in this embodiment, in the optical waveguide substrate 901, a dummy waveguide that does not actually guide the signal light is installed so that all the output waveguides have the same number of intersections. Is desirable. That is, in the non-intersection region, a plurality of dummy optical waveguides that are not used for the optical signal processing for forming the dummy intersections are provided in addition to the intersections between the first emission waveguides and the second emission waveguides. Prepare. In FIG. 10, dummy waveguides 907 and 908 are shown, and white circles are intersection positions when the number of intersections is intentionally increased by the dummy waveguides. By installing the dummy waveguide along the white circles in FIG. 10, loss of polarization dependence, that is, PDL can be eliminated.

  Therefore, in the optical signal processing device of the present embodiment, the first output waveguide and the second output waveguide of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports are not connected. In the intersection region, a plurality of dummy optical waveguides that are not used for optical signal processing for forming a dummy intersection can be provided in addition to the intersection between each first emission waveguide and each second emission waveguide. .

  In this embodiment, since all the output waveguide ends in the optical waveguide substrate 801 are arranged in one place adjacent to each other according to the polarization state, one λ / 2 plate 902 is provided. The polarization can be easily aligned by inserting. Compared with the configuration of the optical waveguide substrate of Example 2, it is possible to realize a low-cost wavelength selective switch in which the optical members of the polarization separation unit using the birefringent crystal used in the past are reduced and the alignment of the apparatus is simplified. is there.

  In Examples 1 to 3, an optical waveguide substrate having a configuration in which one or more polarization beam splitters are configured on a PLC circuit and input signal light is selected for each wavelength is used. The wavelength selection function can be simplified by using an arrayed waveguide grating, further reducing the use of optical members.

  FIG. 11 is a diagram showing a configuration of an optical signal processing apparatus according to a fourth embodiment of the present invention. 1A is a view of a substrate surface (yz plane) of an optical waveguide substrate 1101 described later, and FIG. 1B is a side surface (xz plane) of the optical waveguide substrate 1101 described later. ). The optical signal processing apparatus 1100 of this embodiment includes an optical waveguide substrate 1101, a cylindrical lens 1102 having power in the substrate thickness direction (x-axis direction) of the optical waveguide substrate 1101, a first lens 1103, a diffraction grating 1104, a second The lens 1105 and the spatial light modulator 1106 are arranged in this order. The optical axis direction of the signal light emitted from the optical waveguide substrate 1101 is taken as the z axis, and the axial direction perpendicular to the z axis and the x axis is taken as the y axis. The first lens 1103 and the second lens 1105 are lenses having power concerning both the x-axis and the y-axis. The diffraction grating 1104 has a demultiplexing axis 114 in the x-axis direction. As will be described later, the spatial light modulator 1106 can be realized by, for example, an LCOS having a phase providing capability in a two-dimensional direction.

  In the configuration of the present embodiment, the cylindrical lens 1102, the first lens 1103, and the second lens 1105 are used in this order as lens system components. Any number of lenses may be used as long as they have optical characteristics. Any arrangement may be used. When the optical path is bent by approximately 90 ° in the diffraction grating 1104 so that the incident light optical path of the forward path and the diffracted optical path of the return path are relatively close to each other, the first lens 1103 and the 21st lens 1105 are It is also possible to share one.

  FIG. 12 is a diagram illustrating a configuration of an optical waveguide substrate adapted to a wavelength selective switch function in the optical signal processing device according to the fourth embodiment. The optical waveguide substrate 1101-1 includes N + 1 polarization beam splitter arrays 1201 that separate and output two orthogonally polarized waves, and each of the polarization beam splitter arrays has two amplitude directions orthogonal to each other. A first output waveguide that outputs one of the polarized waves and a second output waveguide that outputs the other polarized wave are provided. Further, a λ / 2 plate inserted into one of the two output waveguides connected to each polarization beam splitter is provided, and the above-described components are common to the optical waveguide substrate shown in FIG. ing. Of the N + 1 polarization beam splitter arrays 1201, signal light 1209 is input to the uppermost polarization beam splitter, and one of the remaining N polarization beam splitters is selected, and the emitted light 1210 is output. Is output. That is, it operates as a wavelength selective switch.

  The optical waveguide substrate 1101-1 in the present embodiment further includes a slab waveguide 1205 to which each output waveguide is connected, and an arrayed waveguide 1206 connected to the slab waveguide. Signal light is emitted from each of the first output waveguide 1203 and the second output waveguide 1204 and propagates through the slab waveguide 1205 while being confined to the substrate thickness. The installation angle of each output waveguide at the start point of the slab waveguide 1205 is determined so that the principal ray when propagating through the slab waveguide 1205 intersects at a certain point at the end of the slab waveguide 1205. By configuring each output waveguide and slab waveguide 1205 in this way, light from all angles of the output waveguide connected to the slab waveguide is superimposed at the output end of the optical waveguide substrate 1101-1. It becomes composition. The array waveguide 1206 connected to the slab waveguide 125 will be described later.

  The optical signal processing apparatus 1100 of the present invention operates as follows. Referring to FIG. 12, first, the signal light 1209 input to the input port is divided into two linearly polarized waves orthogonal to each other by the polarization beam splitter located at the uppermost stage, similarly to the operation in the second embodiment. The signal is input to the slab waveguide 1205 via the λ / 2 plate array 1202-0 on one output waveguide 1204-0. In the slab waveguide 1205, the signal light propagates through the waveguide so as to spread in the plane of the optical waveguide substrate 1101-1 while being confined in the x-axis direction (substrate thickness direction). Since the wavefront of the spreading signal light has a curvature corresponding to the propagation distance, the end of the slab waveguide 1205 is configured to match the curvature of the wavefront. The end of the slab waveguide 1205 is connected to an arrayed waveguide 1206 composed of waveguides having the same length. Of the end faces of the optical waveguide substrate 1101-1, the end face to which the arrayed waveguide 1206 is connected coincides with the y-axis.

  Referring again to FIG. 11A, the optical signal output to the space from the arrayed waveguide 1206 of the optical waveguide substrate 1101 is output as a plane wave whose phase is aligned in the y-axis direction. Propagating through space as a focused beam. On the other hand, the beam output to the space behaves as divergent light having a large NA in the substrate thickness direction of the optical waveguide substrate 1101, that is, the x-axis direction. Therefore, as shown in FIG. 1B, it is desirable to suppress beam divergence by a cylindrical lens 1102 that collimates in the x-axis direction.

  The optical signal that has passed through the cylindrical lens 1102 passes through the first lens 1103 and is collected on the diffraction grating 1104. As shown in FIG. 12 (b), the diffraction grating 1104 divides the angle for each wavelength in the x-axis direction and further passes through the second lens 1105, so that each wavelength is positioned from the angle. Converted. In other words, the light enters the spatial light modulator 1106 perpendicularly at different positions on the x-axis of the spatial light modulator 1106 according to the wavelength of the signal light. At this time, as shown in FIG. 11A, the second lens 1105 focuses light on the spatial light modulator 1106 at one point on the y-axis regardless of the wavelength.

  The optical signal is reflected at an arbitrary angle by the spatial light modulator 1106 for each wavelength with respect to the y-axis direction, and travels in the reverse direction of the z-axis along the second path 1105, the diffraction grating 1104, the first The optical waveguide substrate 1101 is recombined via the lens 1103 and the cylindrical lens 1102. Here, consider a case where the signal light 1209 is input to the uppermost polarization beam splitter in FIG. 12 and the signal light 1210 having the selected wavelength is output from the lowermost polarization beam splitter.

  More specifically, one polarization of the signal light 1111 input to the optical waveguide substrate 1101 exits the optical waveguide substrate 1101 from the first output waveguide of the polarization beam splitter at the uppermost stage, and the optical path Proceeding 1110, the spatial light modulator 1106 is reached. When the light is reflected at a specific position on the x-axis of the spatial light modulator 1106, it travels along the optical path 1107. The optical signal on the optical path 1107 is reconnected to the optical waveguide substrate 1101 and input to the second output waveguide of the N-th polarization beam splitter at the lowermost stage selected. Similarly, the other polarization of the signal light 1111 input to the optical waveguide substrate 1101 exits the optical waveguide substrate 1101 from the second output waveguide of the polarization beam splitter at the uppermost stage, and proceeds on the optical path 1109. To the spatial light modulator 1106. When the light is reflected at a specific position on the x-axis of the spatial light modulator 1106, it travels along the optical path 1108. The optical signal on the optical path 1108 is reconnected to the optical waveguide substrate 1101 and input to the first output waveguide of the N-th polarization beam splitter at the lowermost stage selected. The two polarized waves are synthesized by the N-th polarization beam splitter at the lowest stage, and output light 1112 having the selected wavelength is output. The signal light in the section optical system is aligned with the TM mode, and the two separated polarized waves follow substantially the same optical path.

Referring now to FIG. 12, the signal light emitted from the input port passes through the first output waveguide and enters the spatial light modulator 1106, and is deflected about the y axis by the spatial light modulator 1106. and the principal ray 1207 when the reflected light is again incident on the optical waveguide substrate 1101-1, the angle between the z axis and theta _1. Further, the pitch of the arrayed waveguide 1206 at the −1 end face of the optical waveguide substrate 1101 is d ₁ , the pitch of the arrayed waveguide 1206 connected to the slab waveguide 1205 is d ₂ , the length of the slab waveguide 1205 is f _slab , and the slab. Let n _{s be} the refractive index of the waveguide 1205. Furthermore, in the slab waveguide 1205, when the reflected light deflected about the y axis by the spatial light modulator 1106 propagates in the slab waveguide 1205, the angle formed by the principal ray 1208 and the z axis is θ ₂ . The following relationship holds.

As is clear from Equation (3), the light recombined with the optical waveguide substrate 1101 at the angle θ ₁ is given an angle change at θ ₂ . That is, the waveguide to be coupled can be selected by appropriately selecting the connection angle between the first output waveguide and the first output waveguide and the parameters of the arrayed waveguide 1206.

  In order to increase the number of output ports in the wavelength selective switches as in the second embodiment, the third embodiment, and the present embodiment, the beam deflection angle by the spatial light modulator 1106 is increased or the spatial light modulator 1106 is increased. It is necessary to increase the beam diameter in the y-axis direction of the beam focused on. Once the characteristics of the spatial light modulator 1106 are determined, there is no other way than increasing the beam diameter to increase the number of output ports. For this reason, designs are often made such that the beam diameter in the y-axis direction of the light condensed on the spatial light modulator 1106 is as large as possible.

  Whereas the spatial light modulator 1106 is a deflection device, a fiber array or the like used in the wavelength selective switch is a so-called position offset device in which the emission angle from each fiber is equal and only the emission position is different. For this reason, it is necessary to perform an odd number of Fourier transforms between the input / output fiber array and the deflection device. This means that an odd number of Fourier transform elements, that is, an odd number of lenses, must be arranged between the input / output fiber array and the deflection device. Assuming a configuration in which an odd number of lenses are arranged, the larger the beam diameter on the spatial light modulator 1106, the smaller the beam diameter on the input / output fiber side, and more output ports can be arranged. This is because it can.

  On the other hand, the beam diameter in the x-axis direction in the wavelength selective switch as in this embodiment needs to be designed as small as possible in order to ensure a wide transmission band characteristic. Therefore, the ratio of the beam diameter in the x-axis direction and the beam diameter in the y-axis direction, that is, the aspect ratio, of the beam condensed on the spatial light modulator 1106 must be designed to be very large.

  In the configuration of the optical signal processing apparatus according to the present embodiment, the slab waveguide 1205 formed on the optical waveguide substrate 1101 can be regarded as a lens in the y-axis direction. Since the beam emitted from the optical waveguide substrate 1101 to the space passes through an even number of condenser lenses 1103 and 1105 before reaching the spatial light modulator 1106, the beam is collected on the spatial light modulator 1106. The aspect ratio of the light beam is determined when the spatial light modulator 1101 is emitted. That is, a device for increasing the aspect ratio of the beam emitted from the spatial light modulator 1101 is required.

In the configuration of the optical signal processing apparatus of the present embodiment, the beam diameter in the x-axis direction is determined by the relative refractive index and thickness of the waveguide layer embedded in the optical waveguide substrate 1101, and therefore the aspect ratio is adjusted. This is realized by adjusting the beam diameter in the y-axis direction. In this case, the beam diameter w _y in the y-axis direction of the beam exiting the optical waveguide substrate 1101 can be expressed by the following equation.

In Equation (4), λ represents the wavelength of the signal light, f _slab represents the length of the slab waveguide, and w _{I / O} represents the beam diameter in the y-axis direction incident on the slab waveguide. According to equation (4) can be slab waveguide in proportion to the length f _slab to enlarge the beam diameter w _y in the y-axis direction.

  In the configuration of the present embodiment, the aspect ratio of the beam emitted from the optical waveguide substrate 1101 needs to be adjusted only for the layout of the components of the optical waveguide substrate 1101, without adding the number of members and alignment adjustment of individual components. It is feasible without.

  In order to adjust the beam diameter, a configuration employing a beam expander, an anamorphic prism pair, or the like is common. However, with such a structure, the cost of a new member and the burden of alignment adjustment will increase. In this regard, the configuration of the present embodiment in which the optical system for anamorphic prism pair and polarization diversity is integrated in the optical waveguide substrate 1101 by one PLC reduces the member cost and the burden of alignment adjustment. It has a very big effect.

  Regarding the method of arranging the polarization beam splitter arranged in the previous stage of the optical waveguide substrate 1101 having the slab waveguide 1205 and the arrayed waveguide 1206, not only the arrangement method according to the above-described second embodiment but also the first and third embodiments. It is also possible to adopt each layout corresponding to the optical signal processing apparatus.

  FIG. 13 is a diagram illustrating a configuration of an optical waveguide substrate having a slab waveguide and an arrayed waveguide corresponding to the configuration of the optical signal processing device according to the first embodiment. This is a case where the optical signal processing apparatus includes a single polarization beam splitter and has a configuration for inputting and outputting signal light at the same port.

  The optical waveguide substrate 1101-2 is a polarization beam splitter 1301 that separates and outputs two orthogonal linearly polarized waves, and a first one that outputs one of the two polarized waves whose amplitude directions are orthogonal. Output waveguide 1303 and a second output waveguide 1304 that outputs the other polarized wave. Further, a λ / 2 plate 1302 inserted into one of the two output waveguides is provided. In the present optical waveguide substrate 1102-2, the first slab waveguide 1305 and the second arrayed waveguide 1306 connected to the first output waveguide 1303, and the second connected to the second output waveguide 1304. Slab waveguide 1307 and a second arrayed waveguide 1308.

  FIG. 14 is a diagram illustrating a configuration of an optical waveguide substrate having a slab waveguide and an arrayed waveguide corresponding to the configuration of the optical signal processing device according to the third embodiment. The optical waveguide substrate 1101-3 has one signal light input port and one or more (N) signal light output ports, and is configured to select one output port.

  The optical waveguide substrate 1101-3 includes N + 1 polarization beam splitter arrays 1401 that separate and output two orthogonally polarized waves, and two polarization beams whose amplitude directions are orthogonal in each polarization beam splitter. Among these, a first output waveguide 1403 that outputs one polarized wave and a second output waveguide 1404 that outputs the other polarized wave are provided. Each of the first output waveguide 1403 and the second output waveguide 1404 has an array configuration in which N + 1 pieces are arranged together. An integral λ / 2 plate 1402 is inserted on one output waveguide. The present optical waveguide substrate 1102-3 includes a slab waveguide 1405 and an arrayed waveguide 1406 connected to the first outgoing waveguide 1403 and the second arrayed waveguide 1406.

  In any of the configurations shown in FIGS. 13 and 14, while having the advantage of the polarization diversity configuration in the first and third embodiments, the beam diameter can be freely changed without adding additional members. An optical signal processing device (for example, a wavelength selective switch) having more output ports can be realized. Even in this case, the function realized by the optical member of the polarization splitting unit using the birefringent crystal and the function of adjusting the beam diameter, which are necessary in the optical signal processing device of the prior art, are integrated on the PLC. It does not have a great effect on reducing the cost related to the member cost and alignment adjustment.

  As described above in detail, the optical signal processing device of the present invention can realize the polarization diversity function and eliminate the need for the optical member of the polarization separation unit using the birefringent crystal used in the prior art. it can. Provided is an optical signal processing apparatus capable of realizing cost reduction of an optical member and simplification of alignment adjustment of the apparatus.

  The present invention is generally applicable to communication systems. In particular, it can be used for an optical signal processing apparatus in an optical communication system.

100, 200, 500, 800, 1100 Signal processing apparatus 101, 201, 401, 501, 801, 1101 Optical waveguide substrate 103 Polarization separator 106, 108, 204, 504, 804, 1103, 1105 Lens 107, 203, 503 , 803, 1104 Spectral element 109, 205, 505, 1106 Spatial light modulator 301 Input port 302, 305 3 dB coupler 306, 602, 902, 1202-0, 1202-N, 1302, 1402 λ / 2 plate 307, 308, 407, 408, 603-0, 603-N, 604-0, 604-N, 903, 904 Outgoing waveguide 513, 514, 610-0, 610-N, 811, 812, 905-0, 905-N1201, 1301 and 1401 Polarization beam splitters 1205 and 1305 1307,1405 slab waveguide 1206,1306,1308,1406 arrayed waveguide

Claims (5)

An input port to which a wavelength multiplexed optical signal is input, a polarization separation means for separating the wavelength multiplexed optical signal into a first polarization and a second polarization having orthogonal polarization states; An optical waveguide circuit configured with a polarization beam splitter including a first output waveguide that outputs one polarization and a second output waveguide that outputs the second polarization;
The signal light emitted from one of the first output waveguide and the second output waveguide of the optical waveguide circuit to the space is deflected, and the deflected signal light is transmitted to the first output waveguide and the first output waveguide. Light modulating means for reflecting to recombine with the other of the second exit waveguides;
Was placed on top of one of the first output waveguide or said second output waveguide on the substrate, a polarization rotation means for rotating 90 ° the polarization state,
Spectral means for wavelength-separating the wavelength multiplexed optical signal emitted from the substrate in a wavelength dispersion axis direction perpendicular to the circuit configuration surface of the substrate;
The optical waveguide circuit on the substrate comprises:
A slab waveguide in which the first output waveguide and the second output waveguide are connected to the input side;
An arrayed waveguide connected to the output side of the slab waveguide and having a plurality of waveguides each having the same waveguide length, and having a phase in a direction perpendicular to the wavelength dispersion axis direction from the substrate end surface to the space An arrayed waveguide that emits a uniform plane wave
An optical signal processing device further comprising: On the board
An input port to which a wavelength-multiplexed optical signal is input, polarization separation means for separating the wavelength-multiplexed optical signal into a first polarization and a second polarization having polarization states orthogonal to each other, and the first polarization A polarization beam splitter for an input port including a first output waveguide for outputting and a second output waveguide for outputting the second polarized wave;
Polarization each, which can separate the output port for outputting the optical signal wavelength separation of the wavelength-multiplexed optical signal, the first polarization and a second polarization having a polarization state orthogonal to the wavelength-multiplexed optical signal from each other And a polarization beam splitter for N output ports including a separating unit, a first output waveguide that outputs the first polarization, and a second output waveguide that outputs the second polarization. An optical waveguide circuit,
The signal light emitted to the space from either the first output waveguide or the second output waveguide of the polarization beam splitter for the input port is deflected, and the deflected signal light is converted to the output port. The first output waveguide and the second output waveguide of the selected one of the N polarization beam splitters for use are different from the output waveguide from which the signal light is output. Light modulating means for reflecting to recombine with the output waveguide on the side;
Either the first output waveguide of each of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports on the substrate, or each of the second output waveguides. It was placed on top of, and polarization rotation means for rotating 90 ° the polarization state,
Spectral means for wavelength-separating the wavelength multiplexed optical signal emitted from the substrate in a wavelength dispersion axis direction perpendicular to the circuit configuration surface of the substrate;
The optical waveguide circuit on the substrate comprises:
A slab waveguide in which the first output waveguide and the second output waveguide are connected to the input side;
An arrayed waveguide connected to the output side of the slab waveguide and having a plurality of waveguides each having the same waveguide length, and having a phase in a direction perpendicular to the wavelength dispersion axis direction from the substrate end surface to the space An arrayed waveguide that emits a uniform plane wave
An optical signal processing device further comprising: The first output waveguides of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports are configured adjacent to each other in an array,
The second output waveguides of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports are configured adjacent to each other in an array,
The polarization rotation means is integrally formed across the output waveguide configured in the array shape on either one of the first output waveguide or the second output waveguide on the substrate. The optical signal processing device according to claim 2, wherein:   Each of the first output waveguides and the second output waveguides of the polarization beam splitter for the input port and the polarization beam splitter for the N output ports are arranged in a non-intersection region of the first output waveguide. 4. A plurality of dummy optical waveguides that are not used for optical signal processing for forming a dummy intersection, in addition to the intersection between the output waveguide and each of the second emission waveguides, 2. An optical signal processing device according to 1. The pre-Symbol wavelength separation optical signal, further comprising a lens for condensing onto modulation device forming surface of said light modulating means,
The optical modulation unit independently gives a phase shift to the optical signal collected by the lens, and the phase shift causes either the first emission waveguide or the second emission waveguide of the substrate. 5. The optical signal processing device according to claim 1, wherein the signal light emitted from the optical fiber is recombined with the other of the first emission waveguide and the second emission waveguide of the substrate. .

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