JP5903074B2 - Optical signal processor - Google Patents

Description

  The present invention relates to an optical signal processing device, and more particularly to an optical signal processing device in an optical communication network node.

  Quartz-based planar lightwave circuit (PLC) technology is used everywhere in optical networks today because of its functionality, stability, and mass productivity. In recent years, even in an optical signal processing device such as a wavelength selective switch (WSS) based on spatial optics, research and development using a PLC as a part thereof has been performed.

  FIG. 1 shows an outline of a wavelength selective switch (hereinafter also simply referred to as a switch or WSS) disclosed in Non-Patent Document 1. The wavelength selective switch in FIG. 1 includes a PLC 101, a lens 102, a diffraction grating 103, a lens 104, and a beam deflection element 105. In Non-Patent Document 1, a liquid crystal cell using LCOS (Liquid Crystal On Silicon) technology arranged in a matrix is used as the beam deflection element 105. In this configuration, the beam incident on the LCOS 105 is preferably about several hundred μm in the switch axis direction (Y-axis direction in the figure), and the PLC 101 is manufactured so as to realize the beam diameter.

  The operation of the switch shown in FIG. 1 is as follows. That is, the optical signal input from the input waveguide 106 is coupled to the arrayed waveguide 108 via the slab waveguide 107 and emitted from the output end of the PLC 101. Since all the arrayed waveguides 108 are of equal length, the angle of the emitted light beam does not depend on the wavelength. A circuit including the input waveguide 106, the slab waveguide 107, and the arrayed waveguide is referred to as an SBT (Spatial Beam Transformer). The optical signal output from the PLC 101 is input to the LCOS 105 via the lens 102, the diffraction grating 103, and the lens 104. Each wavelength component dispersed by the diffraction grating 103 is spatially developed in a direction perpendicular to the paper surface (X-axis direction in the figure). The LCOS (105) deflects and reflects the beam within the plane (YZ plane) formed by the PLC substrate so that each wavelength is output to a desired output port. The reflected light propagates to the PLC 101 via the lens 104, the diffraction grating 103, and the lens 102. Here, the principal ray of the returned optical signal intersects with the principal ray of the forward optical signal at point A. This point A corresponds to the front focal position of the lens 102. The optical signal returned to the PLC 101 returns to the PLC at an angle different from that at the time of emission. Therefore, since it returns with a wavefront having an angle different from that of the input light in the slab waveguide 107, it is coupled to the output port 109, for example. The selection of the output port can be realized by changing the phase distribution given by the LCOS pixel, thereby realizing the wavelength selective switch function.

  In the optical system disclosed in Non-Patent Document 1, the part of the spatial optical system is called a 4f optical system. In such an optical system, since the light beams intersect at the point A, the PLC 101 is connected to different positions of the same slab waveguide 107 for both the input port 106 and the output port 109 as shown in FIG. The

  FIG. 2 schematically shows a wavelength selective switch disclosed in Patent Document 1. (A) is a side view, (b) is a top view. The switch shown in FIG. 2 includes a PLC 101, a cylindrical lens 202, a main lens 203, and a liquid crystal type phase modulator (LCOS: Liquid Crystal on Silicon) 204. The PLC 101 has a configuration in which an arrayed waveguide grating (AWG) including an input / output waveguide 106, a slab waveguide 107, and an arrayed waveguide 108 is arranged in an array, and one AWG is input. And other AWGs are used for output. The light emitted from the input AWG is emitted into the space at different angles for each wavelength, and reaches the LCOS 204 through the main lens 203. The LCOS 204 controls the reflection angle of the beam in the direction of the PLC plane (in the YZ plane) so that each wavelength is output from a desired output port of the PLC 101. The reflected light passes through the main lens 203 and the cylindrical lens 204 and returns to the PLC 101. In each output AWG, a plurality of signals having different wavelengths incident at different angles are multiplexed and emitted from the respective output ports. Thereby, it works as a wavelength selective switch. The optical system disclosed in Patent Document 1 is different from Non-Patent Document 1, and in particular, the part of the spatial optical system is called a 2f optical system.

JP 2009-168840 A

K. Seno, K. Suzuki, N. Ooba, T. Watanabe, M. Itoh, T. Sakamoto, and T. Takahashi, "Spatial beam transformer for wavelength selective switch consisting of silica-based planar lightwave circuit," in Proc. OFC2012, paper JTh2A.5.

  However, the wavelength selective switch (FIG. 1) disclosed in Non-Patent Document 1 has the following problems. That is, when the light whose optical path has been changed by the LCOS 105 recombines with the SBT, the loss is greater when the light is incident obliquely than when the light is incident vertically. Therefore, the loss of this WSS differs depending on the output port, leading to deterioration of communication quality.

  Further, the wavelength selective switch (FIG. 2) disclosed in Patent Document 1 has a problem that the center wavelengths of the AWGs do not match. This is because there is a manufacturing error, and the waveguide length difference ΔL of the AWG is slightly different depending on the AWG. If the center wavelengths do not match, the insertion loss varies due to the AWG even if they are incident at the same angle. That is, the insertion loss differs depending on the output port.

  In both conventional examples, it is necessary to design a wide waveguide interval at the emission end face so that the beam shape is not disturbed by the directional coupling between the waveguides. Directional coupling between waveguides corresponds to crosstalk between adjacent waveguides. Then, the high-order diffracted light of the emitted beam is emitted at a narrow angle with respect to the zero-order light. Therefore, since the optical path of the higher-order diffracted light is also included in the effective diameter of the lens, it returns to the end face of the SBT (AWG) on the output side in the same way as the 0th-order light. This will be described with reference to FIG.

  FIG. 3 shows a state in which light emitted from an input AWG out of an arrayed waveguide grating (AWG) arranged in an array on the PLC 101 and reflected by the LCOS 204 enters the output AWG. ing. In FIG. 3, 302 indicates the desired order of light, 303 indicates the diffracted light of the order adjacent to the desired order, and 306 indicates the profile of the emitted beam. Since lights having different orders pass through different positions of the lens 203, a phase shift caused by aberration occurs between them. As a result, when returning to the end face of the PLC 101, the beam shape is disturbed by the interference between the main signal (0th order light) and the higher order light (becomes a beam profile indicated by 307 in FIG. 3), and crosstalk to adjacent ports In this case, phase disturbance of the optical signal occurs, leading to deterioration of communication quality.

  The present invention has been made in view of such problems, and an object of the present invention is to suppress deterioration in communication quality due to higher-order light. It is another object of the present invention to provide a wavelength selective switch whose insertion loss does not vary depending on the switch state. It is another object of the present invention to provide a wavelength selective switch with less loss non-uniformity for each output port due to manufacturing errors.

In order to achieve such an object, the present invention provides an arrayed waveguide comprising at least one input waveguide, a slab waveguide connected to the input waveguide, and an arrayed waveguide connected to the slab waveguide. An optical signal processing apparatus comprising: an optical waveguide substrate including a grating; and a spatial optical system including a condensing unit that condenses a light beam output from an end surface of the optical waveguide substrate, wherein the arrayed waveguide is A portion of a plurality of waveguides having a structure in which the interval between the plurality of waveguides in the vicinity of the end surface of the optical waveguide substrate is narrow, and the portion in which the interval between the waveguides in the vicinity of the end surface of the optical waveguide substrate is narrow The high-order light beam output from the end face of the optical waveguide substrate has a waveguide interval that passes outside the outer periphery of the light condensing means .

  In one embodiment, a structure of the arrayed waveguide having a plurality of waveguide rows is formed in a vicinity of an end face of the optical waveguide substrate, a portion having a wide waveguide interval, a portion for converting the waveguide interval to be narrow, and a waveguide. A structure in which portions having a narrow waveguide interval are connected in this order may be employed, and the intervals between the plurality of waveguides may be gradually reduced toward the end face of the optical waveguide substrate. In the light beam output from the optical waveguide substrate, the angle formed by the principal ray of the light beam with respect to the end face of the optical waveguide substrate does not vary depending on the wavelength. In one embodiment, the length L (k) of the kth waveguide out of N (an integer greater than or equal to 2) waveguides is L (k) = L (N + 1−k) for any k. The arrayed waveguide may be configured such that In one embodiment, the lengths of the plurality of waveguides included in the arrayed waveguide are all equal. In one embodiment, a correction region for correcting a difference in waveguide length caused by narrowing the interval between the plurality of waveguides is between a portion where the interval between the slab waveguide and the waveguide is converted to be narrow. You may prepare for. In one embodiment, the correction region has a first region and a second region, and the plurality of waveguides sequentially increase in waveguide length in the first region, and in the second region, You may comprise so that waveguide length may become short sequentially.

  In one embodiment, the optical waveguide substrate may include a plurality of the arrayed waveguide gratings. In one embodiment, the distance from the end surface of the optical waveguide substrate of the slab waveguide constituting the arrayed waveguide grating may be different for each arrayed waveguide grating.

  As described above, according to the present invention, it is possible to provide an optical signal processing device that suppresses deterioration of communication quality due to higher-order light.

1 is a schematic configuration diagram of a wavelength selective switch of Non-Patent Document 1. FIG. 2 is a schematic configuration diagram of a wavelength selective switch disclosed in Patent Document 1. FIG. It is a figure explaining the profile of the beam in the end surface of AWG of the wavelength selective switch of patent document 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the optical signal processing apparatus of one Embodiment of this invention, (a) is a side view, (b) is a top view. It is a figure which shows the circuit structure of SBT in the optical signal processing apparatus of one Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the method to implement | achieve the optical system which avoids that a high order light returns to a SBT end surface in the optical signal processing apparatus of one Embodiment of this invention, (a) is a figure which shows from PLC to a main lens. (B) is an enlarged view of the beam exit end of the PLC. FIG. 6 is a diagram for explaining a method of realizing a part 505 (part A) of the circuit configuration of the SBT of FIG. 5. FIG. 6 is a diagram for explaining a method of realizing a part 505 (part A) of the circuit configuration of the SBT of FIG. 5. FIG. 6 is a diagram for explaining a method of realizing a part 505 (part A) of the circuit configuration of the SBT of FIG. 5. It is a figure which shows the circuit structure of SBT in the optical signal processing apparatus of one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

  In all the embodiments, the illustration and description are made assuming that the PLC, the lens, the diffraction grating, the lens, and the LCOS are arranged in this order. However, the present invention is not limited to this. For example, it is a simple optical design matter to change the number, shape, and arrangement position of lenses from the viewpoint of aberration correction, and these do not limit the present invention. In the description, parameters such as the center wavelength, the number of waveguide arrays, and the waveguide array pitch are exemplarily set. Needless to say, the present invention is not limited to this.

(Embodiment 1)
FIG. 4 is a diagram illustrating the optical signal processing device according to the first embodiment. 4A shows a side view, and FIG. 4B shows a top view. This optical system includes a PLC 401, a dispersion direction lens A 402, a dispersion direction lens B 403, a main lens 404, a diffraction grating 405, and a liquid crystal phase modulator (LCOS) 406. The PLC 401 has a configuration in which a plurality of SBTs are arranged in the y-axis direction. Of the plurality of SBT, one is used for input and the other is used for output. In the present embodiment, the case where the lengths of the arrayed waveguides of each SBT are all the same length will be described. However, it is not always necessary if the beams propagate in the same direction regardless of the wavelength. As an example, it is conceivable to add an initial curvature to the output beam by making the length distribution of the waveguide an arc-shaped distribution. That is, the length of the arrayed waveguide of the SBT is such that the number of waveguides is N (an integer greater than or equal to 2), and the length of the kth waveguide from any one end of the waveguide row is L (k). Then, it may be configured such that L (k) = L (N + 1−k) holds for any k.

  The light input from the input waveguide of the input SBT spreads and propagates through the slab waveguide and is distributed to the arrayed waveguide. The arrayed waveguides are terminated in the state of being close to each other at the chip end (the end on the LCOS 406 side of the PLC 401), and the beam is emitted out of the chip. The angle formed between the principal ray of the emitted beam and the end face of the chip does not vary depending on the wavelength. The width of the emitted light beam is a narrow width determined by the thickness of the waveguide in the chip thickness direction (x-axis direction), and the number of arrayed waveguides and the arrangement interval in the chip side direction (y-axis direction). Since the width is determined, a beam with a large aspect ratio can be obtained.

The operation when the signal processing apparatus according to the present embodiment is implemented as a wavelength selective switch will be described below.
First, in the dispersion direction (x-axis direction), the light propagated through the input SBT of the PLC 401 is emitted as a beam spreading in space. Therefore, the beam emitted from the PLC is collimated by the dispersion direction lens A 402 and is incident on the diffraction grating 405, so that a propagation angle change different for each wavelength is given. Next, the light passes through the dispersion direction lens B 403 and reaches the LCOS 406. Angular dispersion given by the diffraction grating becomes position dispersion on the LCOS, and is condensed on different x coordinates for each wavelength. In the wavelength axis direction (x-axis direction), LCOS functions as a simple mirror, so the reflected light follows the same trajectory as the forward path and re-enters the PLC. FIG. 4B shows a state in which the three lights given different angular dispersions by the dispersion direction lens B 403 are condensed on different x-axes of the LCOS 406, respectively.

  In the switch axis direction (y-axis direction), the SBT circuit formed in the PLC 401 emits the beam from the PLC to the space with the output beam diameter adjusted to a desired size. As shown in FIG. 4A, the beam emitted from the PLC is collimated by the main lens 404, and the light emitted from any SBT is condensed at the same y coordinate position on the LCOS 406. In LCOS, the reflection angle is controlled so that each wavelength is emitted from a desired output port. The optical path of the reflected light passes through the main lens 404 again and is incident again so as to be condensed at the end of the PLC 401. At this time, the light of each wavelength enters the SBT connected to the desired output port. As described above, a wavelength switch is realized.

  Unlike the configuration shown in Patent Document 1, SBT has a difference in adjacent array waveguide length, that is, ΔL is 0, and therefore wavelength dependency does not occur in principle. Therefore, there is no problem of transmittance reduction caused by the center wavelength shift caused by the manufacturing error, which is in the conventional example of Patent Document 1. Further, unlike the configuration shown in Non-Patent Document 1, the spatial optical system is configured with a 2f system, so that the re-incident to the PLC by the output port is set regardless of the deflection angle in the LCOS. Since the angles are not different and all are incident perpendicularly to the PLC, there is an advantage that non-uniform insertion loss for each output port can be avoided.

  FIG. 5 is a diagram illustrating a circuit configuration of the SBT of the PLC 401 according to the present embodiment. In FIG. 5, the arrayed waveguide is divided into a portion A 501, a portion B 502, and a portion C 503. Waveguide numbers are # 1 to #N from the bottom in the figure.

Part B is a waveguide interval conversion structure that converts the waveguide interval from d ₁ to d ₂ , and is constituted by an S-shaped waveguide. In the portion B, the width in the z direction is s. Here, d ₁ is a waveguide interval on the slab waveguide side of the structure, and is designed to be a large value such that directional coupling can be virtually ignored. Therefore, no optical coupling occurs in the portion A on the left side. d ₂ is the waveguide spacing conversion structure, a waveguide spacing of the exit end. To broaden the propagation angle of the high-order diffracted light of the output beam is designed to a value smaller than d _1. In part C, waveguides are juxtaposed at intervals d _2. d ₂ is an interval at which directional coupling occurs when propagating for a long distance, but the length of the portion C is designed to be sufficiently short, so that directional coupling does not occur.

  The length of the portion B 502 is shorter as the waveguide number is closer to N / 2, and the length is longer as the waveguide number is farther away. This length shift is offset by the portion A 501.

  Further, according to the present embodiment, it is possible to realize an optical system that avoids the return of the high-order light to the SBT end surface by propagating the high-order light to the outside of the lens. Hereinafter, this will be shown by rough estimation with reference to FIG.

  FIG. 6A is a view showing the PLC 401 to the main lens 404, and FIG. 6B is an enlarged view of the beam output end of the PLC. FIG. 6B also shows the profile of the outgoing beam. Assume that the distance from the PLC 401 to the lens 404 is F, the wavelength of the beam is λ, the distance between the arrayed waveguides at the chip end is d, the distance between the SBTs is D, and the number of SBTs is N. In addition, it is assumed that the beam emitted from the SBT is a Gaussian beam, and the beam waist radius is represented by k × D using a constant k. In the case of a Gaussian beam, the distance from the center of the beam until the electric field amplitude becomes so small that it can be regarded as 0 is assumed to be 1.5 times the beam waist diameter. In FIG. 6A, reference numeral 302 denotes a beam of light of a desired order (0th order light) emitted from two SBTs arranged at positions farthest from the center among N SBTs, and 303 denotes The beam of the light of the order (± primary light) adjacent to the light of the desired order emitted from the two SBTs is shown. From FIG. 6A, it is understood that N number of zero order light beams are arranged between N number of + 1st order light beams and N number of −1st order light beams in the y-axis direction.

  The beam diameter of the 0th-order light emitted from the SBT can be approximated to λF / (kDπ) at the main lens position according to the theory of Gaussian beam optics. Since the zero-order light emitted from any SBT must be within the effective diameter of the main lens 404, the minimum diameter (half value) of the main lens can be found with reference to FIG.

It is. As can be seen from the above equation, in the present embodiment, the minimum diameter of the main lens is the distance from the center of the N SBTs to the SBT arranged at a position furthest away from the center, 1. The amount is added 5 times.

  On the other hand, ± 1st order light is located away from 0th order light by λF / d. This can be easily derived in consideration of diffraction through a plurality of slits having a distance d. Therefore, the maximum diameter (half value) of the lens for not including this inside the lens is

It is. As can be seen from the above equation, in this embodiment, the maximum diameter of the main lens is the + 1st order light (or −1) from the SBT arranged at the center of the N SBT and the position farthest from the center. The amount obtained by subtracting 1.5 times the beam waist diameter from the distance to the position of the next light. The condition that such an optical system can be realized is G> 0 if G = Wmax−Wmin.

  Assume that λ = 1.55 μm, F = 150 mm, D = 250 μm, N = 40, and k = 0.2.

  In the conventional SBT, d is designed to a value in which directional coupling can be ignored. If this is 25 μm, G = −5140.4 μm, which is a negative value, indicating that the above-described optical system cannot be realized. On the other hand, in the present invention, the presence of the portion B makes it possible to narrow the waveguide interval while avoiding directional coupling. If d = 12 μm, G = 4934.6 μm, which is a positive value, the above-described optical system can be realized.

  As described above, by narrowing the waveguide interval in the very vicinity of the chip end, it is possible to prevent the high-order diffracted light from returning to the chip end surface, and to realize WSS with less crosstalk to the adjacent port derived from the high-order diffracted light. .

  As described above, the optical path length in the portion B is not equal. A method for correcting this shift at the portion A will be described. Note that the correction method is not limited to this, and any method may be used as long as all of the waveguides are equal in length for the portion A and the portion B.

  When the waveguide number is k, the length Lb (k) of the waveguide of the portion B is the amount of displacement in the y direction between the ends of the portion B (y coordinate on the slab waveguide side and y on the exit end side). When the difference (with respect to the coordinates) is Δy (k) and the length in the z direction is s, it can be written as shown in Equation (1).

Where the parameter γ is

It is.

Next, a method for laying out the portion A will be described. FIG. 7 is a diagram in which the part A is divided into two parts A-1 and A-2. In FIG. 5, the portion A does not include the slab waveguide, but here, it is necessary to include the slab waveguide in order to determine the arrangement of the arrayed waveguide. The straight line M divides the portions A-1 and A-2 and is a boundary line. The straight line P is a straight line parallel to the chip end. An angle formed by the straight line M and the straight line P is β. δ is an angle formed by the arrayed waveguide with respect to the straight line M, and is the same for all waveguides. Point A is a point where the input waveguide is connected to the slab waveguide, and the starting point of the arrayed waveguide is arranged on an arc centered at point A and having a slab length _Lf as a radius. A perpendicular line from the point A to the straight line M is defined as a straight line Q.

First, a method for determining the portion A-1 will be described. FIG. 8 is a diagram showing the configuration of the portion A-1. A straight waveguide 801, a bending waveguide 802, and a straight waveguide 803 are connected. When the length of the straight waveguide 801 is f _k and the length of the straight waveguide 803 is g _k , the following simultaneous equations (2) can be established. Β and δ are determined in advance.

The first expression of the expression (2) is a condition that the terminal is on the straight line M, and the second expression of the expression (2) is a condition that the length becomes a desired value. Here, u is the radius of the bending waveguide, and w _k is the distance from the intersection of the straight line P and the straight line M to the intersection of the straight line P and the waveguide. l _k is the length of each waveguide.

w _k and l _k are set so as to be an equidistant sequence shown in the following equation (3).

d ₁ is the waveguide pitch on the straight line P, and ΔL is the optical path length difference. As can be seen from the second expression of the expression (3), the portion A-1 becomes longer as the waveguide number is smaller. w ₁ and l ₁ are obtained by giving f ₁ and g ₁ as initial values in the equation (2).

In summary, f _k and g _k can be determined by the following procedures (1) to (5).
Procedure (1) β, δ, f ₁ , g ₁ , u are determined to appropriate values.
Procedure (2) Obtain w ₁ and l ₁ from equation (2).
Step (3) w _k and l _k (k: 2 to N) are obtained from w ₁ and l ₁ obtained in step (2) and equation (3).
Procedure (4) _fk , _gk (k: 2-N) is calculated | required from Formula (2).
Step (5) If there are inconveniences such as waveguides overlapping or having a negative length, return to step (1) and set a different value. Repeat steps (2) to (4). Repeat the process until the inconvenience is resolved.

Further, ξ _{k in} FIG. 8 is the distance from the intersection of the straight line P and the straight line M to the intersection of the straight line M and the waveguide, and is given by the following equation (4). This is necessary for the design of part A-2.

Next, a design method for the portion A-2 will be described. FIG. 9 is a diagram showing the configuration of the part A-2. It consists of a straight waveguide 901, a bending waveguide 902, and a straight waveguide 903. The length of the straight waveguide 901 is p _k , the bending radius of the bending waveguide 902 is q _k , and the length of the straight waveguide 903 is r _k . W is the length of the perpendicular drawn from the point A to the straight line M. φ _k is an angle formed by the k-th arrayed waveguide with respect to the straight line Q. The simultaneous equations to be satisfied here are as shown in Equation (5). φ _k is automatically determined for all k if the inclination φ _{1 of the first} arrayed waveguide is determined.

  The first expression of the expression (5) is an expression for the desired length, the second expression of the expression (5) is an expression for the end to ride on the straight line M, and the third expression of the expression (5) is This is an equation for determining the position on the straight line M so that the connection point matches the arrayed waveguide designed in the part A-1.

l _k and h _k are determined by the following equation (6). According to the first expression of the expression (6), the positional deviation is prevented from occurring at the connection point between the portions A-1 and A-2. According to the second equation of the equation (6), the portion A-2 collectively compensates for the waveguide length difference between the portion A-1 and the portion B, and the sum of the three portions of the portion A-1, the portion A-2, and the portion B Is made equal in all waveguides.

l ₁ , W, and h ₁ can be obtained by determining p ₁ , q ₁ , and r ₁ in Equation (5).
In summary, the part A-2 is designed as in the following procedures (6) to (10).
Procedure (6) p ₁ , q ₁ , r ₁ , and φ ₁ are set to appropriate values.
Step (7) from (5) _W, seek l _{1, h} 1.
Step (8) h _k and l _k (k: 2 to N) are _obtained from l ₁ and h ₁ obtained in step (7) and equation (6).
Step (9) p _k , q _k , and r _k (k: 2 to N) are obtained from the equation (5). φk (k: 2 to N) has already been obtained at the time of step (6).
Step (10) If inconveniences such as waveguides overlapping or having a negative length occur, return to step (6), set a different value, and again steps (7) to (9) Repeat until the inconvenience is resolved.

  The part A-2 designed as described above can be connected to the part A-2 without angular deviation or positional deviation if the part A-2 is rotated in the counterclockwise direction by 3π / 2−β and then translated. Since the length of the portion A thus designed is adapted to correct the waveguide length difference generated in the portion B, the portion A and the portion B together form an equal-length arrayed waveguide.

  According to the above design method, all the arrayed waveguides have the same length. As already described, a non-equal distribution may be given to the arrayed waveguide, but in that case, it can be realized by a method similar to the above method by changing the second equation of equation (6).

(Embodiment 2)
By the way, the number of ports as WSS is determined by the maximum deflection angle of the optical deflection element. Therefore, when the ports can be densely arranged, the number of ports that can be realized increases as compared with the case where the arrangement is sparse. In the second embodiment, a measure for realizing a multi-port configuration with a close beam interval is shown.

  FIG. 10 is a diagram showing a circuit configuration of a PLC SBT used in the optical signal processing apparatus of the present embodiment. The distance between the portion on the left side of the SBT portion A 501 (including the portion A and the slab waveguide) and the PLC end face is slightly different, and a plurality of SBTs are arranged stepwise. In this way, it is possible to avoid interference between SBT even if the widths of the output beams are made dense.

  This stepped arrangement is made possible by providing a long straight waveguide 1001 between part B 502 and part A 501.

  In the conventional SBT shown in Non-Patent Document 1 that does not have the portion B 502, when providing such straight waveguides to arrange them closely, the waveguide interval must be increased to avoid directional coupling. In other words, the problem that the above-described high-order diffracted light propagates at a narrow angle is inevitable.

  As described above, in the embodiment of the present invention, since the SBT has the portion B 502, it is possible to achieve both the wide diffraction angle of the high-order diffracted light and the stepwise arrangement using the long linear waveguide 1001. .

  As described above, according to the present embodiment, it is possible to provide an SBT that can be arranged at a smaller interval than the conventional type without adverse effects due to high-order light, and by using this, it is possible to increase the number of WSS ports. it can.

  In the above embodiment, the example in which the optical signal processing apparatus is operated as WSS has been described. However, the optical signal processing apparatus according to the present invention operates as a wavelength blocker so as not to couple light of a specific wavelength to the output port. You can also.

  As described above, according to the present invention, the spatial optical system between the PLC having the SBT and the LCOS is constituted by the 2f system of the main lens having the focal length f, and the angle of the light re-entering the PLC is Since it becomes vertical, it is possible to provide an optical signal processing device having the same insertion loss between output ports. In addition, by reducing the interval between the waveguides constituting the SBT in the vicinity of the end of the PLC on the LCOS side, optical signal processing that prevents re-incidence of high-order light to the SBT and suppresses crosstalk between the SBT caused by the high-order light An apparatus can be provided.

101 Silica-based planar lightwave circuit (PLC)
102, 104 Lens 103 Diffraction grating 105 Beam deflection element, LCOS
106 Input waveguide 107 Slab waveguide 108 Array waveguide 202 Cylindrical lens 203 Main lens 204 LCOS
302,303 Beam 401 PLC
402, 403 Dispersion direction lens 404 Main lens 405 Diffraction grating 406 Liquid crystal phase modulator, LCOS
1001 Straight waveguide

Claims (8)

An optical waveguide substrate comprising at least one input waveguide, a slab waveguide connected to the input waveguide, and an arrayed waveguide grating comprising an arrayed waveguide connected to the slab waveguide;
An optical signal processing device including a spatial optical system including a condensing unit that condenses the light beam output from the end face of the optical waveguide substrate,
The arrayed waveguide is a row of a plurality of waveguides, and in the vicinity of the end face of the optical waveguide substrate, a portion where the waveguide interval is wide, a portion where the waveguide interval is narrowed, and a portion where the waveguide interval is narrow There are have a connection structure in this order, the waveguide spacing is narrower portion, a waveguide light beam of higher light output from the end face of the optical waveguide substrate is passing outside than the outer periphery of the focusing means An optical signal processing device configured to have an interval .   The optical signal processing apparatus according to claim 1, wherein an angle formed by a principal ray of the light beam with respect to an end surface of the optical waveguide substrate does not vary depending on a wavelength.   N is an integer greater than or equal to 2, k is an integer greater than or equal to 1 and less than or equal to N, the row of the plurality of waveguides is a row of N waveguides, and from any one end of the row of the plurality of waveguides 3. The length of the kth waveguide is defined as L (k), and L (k) = L (N + 1−k) holds for any k. The optical signal processing device described.   4. The optical signal processing apparatus according to claim 1, wherein the plurality of waveguides are all equal in length.   A correction region for correcting a difference in waveguide length generated in a portion that converts the waveguide interval narrowly is provided between the slab waveguide and a portion that converts the waveguide interval narrowly. The optical signal processing device according to claim 1.   The correction region has a first region and a second region, and the plurality of waveguides sequentially increase in waveguide length in the first region, and sequentially increase in waveguide length in the second region. The optical signal processing device according to claim 5, wherein the optical signal processing device is configured to be shorter.   The optical signal processing apparatus according to claim 1, wherein the optical waveguide substrate includes a plurality of the arrayed waveguide gratings.   The optical signal processing apparatus according to claim 7, wherein a distance from an end face of the optical waveguide substrate of the slab waveguide constituting the arrayed waveguide grating is different for each of the arrayed waveguide gratings.

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