Optical multiplexer

Abstract

To provide an optical multiplexer that outputs a plurality of interference light beams having had the phase difference between signal light and reference light changed.SOLUTION: The optical multiplexer comprises: a first light branching delay unit for branching signal light and generating a plurality of branch signal light beams, as well as delaying the plurality of branch signal light beams so that the phase difference of the plurality of branch signal light beams to each individual signal light is differentiated; a second light branching delay unit for branching reference light and generating a plurality of branch reference light beams, as well as delaying the plurality of branch reference light beams so that the phase difference of the plurality of branch reference light beams to each individual branch reference light is differentiated; and a matrix type light waveguide array intersection unit in which intersections of each of a plurality of signal light waveguides which the plurality of branch signal light beams propagate and each of a plurality of reference light waveguides which the plurality of branch reference light beams propagate are arranged in a matrix form, and which multiplexes branch signal light entering each intersection with some of branch reference light beams to output interference light.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an optical multiplexer. [Background technology]

[0002] Various optical devices require a technique for estimating the phase state of light propagating through an optical waveguide. For example, in a Mach-Zehnder optical modulator, light propagating through an optical waveguide is branched into two optical waveguides, and different phases are imparted to the light propagating through one or both optical waveguides, thereby estimating the phase state from the difference in the intensity of the combined light. Furthermore, Patent Documents 1 and 2 disclose techniques for estimating the phase state of light propagating through each of multiple optical waveguides in an optical phased array (OPA) having multiple optical waveguides in order to calibrate manufacturing variations in each of the multiple optical waveguides and characteristic variations in phase shifters. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-079493 [Patent Document 2] Special Publication No. 2023-508155 Summary of the Invention [Problem to be solved by the invention]

[0004] In an optical device having a plurality of optical waveguides, in order to estimate the phase state of each of the plurality of optical waveguides with high accuracy, it is desirable to acquire a large amount of data in which the phase difference between the signal light propagating through the optical waveguides and the reference light whose phase state is known or does not fluctuate is changed. This specification provides an optical multiplexer that generates a plurality of interference lights in which the phase difference between the signal light and the reference light is changed. [Means for solving the problem]

[0005] The optical multiplexer disclosed in the present specification may include a first optical branching delay unit that branches signal light to generate a plurality of branched signal lights and delays the plurality of branched signal lights so that a phase difference between each of the plurality of branched signal lights and the signal light is different; a second optical branching delay unit that branches reference light to generate a plurality of branched reference lights and delays the plurality of branched reference lights so that a phase difference between each of the plurality of branched reference lights and the reference light is different; and a matrix-type optical waveguide array intersection unit in which intersections of a plurality of signal light waveguides through which the plurality of branched signal lights output from an output end of the first optical branching delay unit propagate and a plurality of reference light waveguides through which the plurality of branched reference lights output from an output end of the second optical branching delay unit propagate are arranged in a matrix, and which multiplexes the branched signal lights and portions of the branched reference lights branched by an optical distributor that branches a portion of each of the branched signal lights and the branched reference lights input to each intersection, and outputs interference light.

[0006] The optical multiplexer described above can generate a plurality of interference lights for each combination of a plurality of branched signal lights obtained by branching and delaying signal light and a plurality of branched reference lights obtained by branching and delaying reference light, thereby enabling the optical multiplexer described above to generate a plurality of interference lights with different phase differences between the signal light and the reference light. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram schematically illustrating a configuration of a photodetector device. [Figure 2A] FIG. 2 is a diagram illustrating a configuration of an example of an optical branching delay unit. [Figure 2B] FIG. 2 is a diagram illustrating a configuration of an example of an optical branching delay unit. [Figure 2C] FIG. 2 is a diagram illustrating a configuration of an example of an optical branching delay unit. [Figure 3] FIG. 10 is a diagram schematically illustrating a configuration of an example of a matrix-type optical waveguide array intersection portion. [Figure 4A] FIG. 10 is a diagram schematically illustrating a configuration of an example of an intersection of a matrix-type optical waveguide array intersection portion. [Figure 4B] FIG. 10 is a diagram schematically illustrating a configuration of an example of an intersection of a matrix-type optical waveguide array intersection portion. [Figure 4C] FIG. 10 is a diagram schematically illustrating a configuration of an example of an intersection of a matrix-type optical waveguide array intersection portion. [Figure 4D] FIG. 10 is a diagram schematically illustrating a configuration of an example of an intersection of a matrix-type optical waveguide array intersection portion. [Figure 5] 10A and 10B are diagrams illustrating the configuration of a modified example of a matrix-type optical waveguide array intersection portion. [Figure 6] 10A and 10B are diagrams illustrating the branching ratio of an optical multiplexer at an intersection of a matrix-type optical waveguide array. [Figure 7] 10A and 10B are diagrams illustrating an example of an optical multiplexer and an optical detector at an intersection of a matrix-type optical waveguide array. DETAILED DESCRIPTION OF THE INVENTION

[0008] The photodetector disclosed in this specification will be described below with reference to the drawings. Note that in some figures, for the purpose of clarifying the illustration, only some of the components that are repeatedly arranged are labeled with reference numerals. The photodetector disclosed in this specification is not particularly limited, but may be configured to be used, for example, in the final stage of a measuring instrument that uses Mach-Zehnder interferometry, and to detect phase changes with high precision.

[0009] As shown in FIG. 1, the optical detection device 1 includes an optical branching delay unit 10, a matrix-type optical waveguide array intersection unit 20, and an estimation unit 30. The optical branching delay unit 10 and the matrix-type optical waveguide array intersection unit 20 constitute an optical multiplexer 2. The optical branching delay unit 10 and the matrix-type optical waveguide array intersection unit 20 are configured by a cladding layer (e.g., a silicon oxide layer) stacked on a semiconductor substrate, and a core layer (e.g., a silicon layer) covered by the cladding layer and having a refractive index higher than that of the cladding layer. Hereinafter, when the shapes of the optical branching delay unit 10 and the matrix-type optical waveguide array intersection unit 20 are described with reference to several drawings, the shapes of the core layer in a direction perpendicular to the main surface of the semiconductor substrate, i.e., when the semiconductor substrate is viewed in a plan view, are described.

[0010] The optical branching delay unit 10 has a first optical branching delay unit 12 and a second optical branching delay unit 14. A first input port IN1 is connected to the first optical branching delay unit 12, and a second input port IN2 is connected to the second optical branching delay unit 14.

[0011] The first input port IN1 is configured with a single-mode optical waveguide and is an input port into which the signal light S, the phase of which is to be measured, is input. In this example, the initial phase of the signal light S is set to φ s Let's say.

[0012] The second input port IN2 is configured with a single-mode optical waveguide, and is an input port into which reference light R having the same wavelength as the signal light S is input. In this example, the initial phase of the reference light R is set to φ r Let's say.

[0013] The first optical branching and delaying unit 12 is an optical circuit that branches the signal light S to generate a plurality of branched signal lights, and delays the plurality of branched signal lights so that each of the plurality of branched signal lights has a different phase difference with respect to the signal light S. As shown in FIG. 1, each of the plurality of branched signal lights has an initial phase φ s Phase difference Δφ sj The signal is delayed by a phase difference Δφ sj Each output end of the first optical branching delay unit 12 is configured with a single-mode waveguide. A plurality of signal light waveguides 16 are connected to the output end of the first optical branching delay unit 12. A corresponding branch signal light from among the plurality of branch signal lights generated by the first optical branching delay unit 12 is input to each of the plurality of signal light waveguides 16.

[0014] The second optical branching and delaying unit 14 is an optical circuit that branches the reference light R to generate a plurality of branched reference lights, and delays the plurality of branched reference lights so that each of the plurality of branched reference lights has a different phase difference with respect to the reference light R. As shown in FIG. 1, each of the plurality of branched reference lights has an initial phase φ r Phase difference Δφ ri The signal is delayed by a phase difference Δφ riEach of the output ends of the reference light waveguides 18 is configured by a single-mode optical waveguide. A plurality of reference light waveguides 18 are connected to the output end of the second optical branching delay unit 14. A corresponding branched reference light beam from among the plurality of branched reference light beams generated by the second optical branching delay unit 14 is input to each of the plurality of reference light waveguides 18.

[0015] 2A to 2C illustrate circuit configurations applicable to each of the first optical branching delay unit 12 and the second optical branching delay unit 14. As shown in FIG. 2A, each of the first optical branching delay unit 12 and the second optical branching delay unit 14 may be configured with a single-input, multiple-output star coupler and a delay line unit in which multiple optical waveguides connected to the output end of the star coupler have different optical path lengths. As shown in FIG. 2B, each of the first optical branching delay unit 12 and the second optical branching delay unit 14 may be configured with a single-input, multiple-output star coupler and a phase shifter provided in each of multiple optical waveguides connected to the output end of the star coupler. As shown in FIG. 2C, each of the first optical branching delay unit 12 and the second optical branching delay unit 14 may be configured with a single-input, multiple-output star coupler and a delay line unit in which multiple optical waveguides connected to the output end of the star coupler have different waveguide widths.

[0016] Returning to Fig. 1, the number of ports at the output end of the first optical branching delay unit 12 is m (m is a natural number), and the port number (i.e., also corresponds to the number of the signal light waveguide 16) is "j". The number of ports at the output end of the second optical branching delay unit 14 is n (n is a natural number), and the port number (i.e., also corresponds to the number of the reference light waveguide 18) is "i". Although not particularly limited, the phase difference Δφ of the branched signal light with respect to the signal light S is sj and the phase difference Δφ of the branched reference beam with respect to the reference beam R ri may be expressed by the following formula:

number

[0017] Phase difference Δφ of the branched reference light riThe phase difference Δφ of the branched signal light is distributed evenly at regular intervals (2π / n) between 0 and -2π. sj is the phase difference Δφ of the branched reference light ri are distributed evenly within a fixed interval (2π / n).

[0018] The matrix-type optical waveguide array intersection 20 has intersections of each of the plurality of signal light waveguides 16 and each of the plurality of reference light waveguides 18 arranged in a matrix, and is configured to multiplex a portion of the branched signal light and branched reference light input to each intersection and output interference light.

[0019] 3 shows an example of a matrix-type optical waveguide array intersection portion 20. This matrix-type optical waveguide array intersection portion 20 is an example in which intersections 22 of each of two signal optical waveguides 16 and each of three reference optical waveguides 18 are arranged in a matrix.

[0020] 4A and 4B illustrate examples of configurations applicable to the intersection 22 of the matrix-type optical waveguide array intersection portion 20. As shown in FIG. 4A, the signal optical waveguide 16 and the reference optical waveguide 18 may intersect with each other without changing the waveguide width to form the intersection 22. As shown in FIG. 4B, the signal optical waveguide 16 and the reference optical waveguide 18 may intersect with each other so that the waveguide width monotonically increases toward the intersection 22 to form the intersection 22. As shown in FIG. 4C, the signal optical waveguide 16 and the reference optical waveguide 18 may intersect with each other via a multi-mode interference (MMI) to form the intersection 22. As shown in FIG. 4D, the signal optical waveguide 16 and the reference optical waveguide 18 may intersect with each other at a twisted position via a vertical directional coupler 19 to form the intersection 22.

[0021] Returning to FIG. 3, each of the multiple signal light waveguides 16 extending within the matrix-type optical waveguide array intersection section 20 has a first signal light waveguide portion 16a and a second signal light waveguide portion 16c aligned along the propagation direction of the branched signal light. The first signal light waveguide portion 16a is the portion of the signal light waveguide 16 extending from the output end of the first optical branching delay section 12. The second signal light waveguide portion 16c is the portion of the signal light waveguide 16 connected downstream of the first signal light waveguide portion 16a. A bend 16b exists between the first signal light waveguide portion 16a and the second signal light waveguide portion 16c. The first signal light waveguide portion 16a and the second signal light waveguide portion 16c are coupled in an inclined relationship at the bend 16b.

[0022] Each of the multiple reference optical waveguides 18 extending within the matrix-type optical waveguide array intersection section 20 has a first reference optical waveguide portion 18a and a second reference optical waveguide portion 18c aligned along the propagation direction of the branched reference light. The first reference optical waveguide portion 18a is a portion of the reference optical waveguide 18 extending from the output end of the second optical branching delay section 14. The second reference optical waveguide portion 18c is a portion of the reference optical waveguide 18 connected downstream of the first reference optical waveguide portion 18a. A bend 18b exists between the first reference optical waveguide portion 18a and the second reference optical waveguide portion 18c. The first reference optical waveguide portion 18a and the second reference optical waveguide portion 18c are coupled in an inclined relationship at the bend 18b.

[0023] The bent portions 16b of each of the multiple signal light waveguides 16 and the bent portions 18b of each of the multiple reference light waveguides 18 are aligned on a straight line 17. In this example, the bent portions 16b of each of the multiple signal light waveguides 16 and the bent portions 18b of each of the multiple reference light waveguides 18 are aligned on a common straight line 17, but the line on which the bent portions 16b of each of the multiple signal light waveguides 16 are aligned and the line on which the bent portions 18b of each of the multiple reference light waveguides 18 are aligned may be offset from each other in a parallel relationship. The first signal light waveguide portion 16a of each of the multiple signal light waveguides 16 and the first reference light waveguide portion 18a of each of the multiple reference light waveguides 18 extend in parallel. The direction in which the second signal light waveguide portion 16c in each of the plurality of signal light waveguides 16 is inclined with respect to the straight line 17 is opposite to the direction in which the second reference light waveguide portion 18c in each of the plurality of reference light waveguides 18 is inclined with respect to the straight line 17. Furthermore, the angle θ at which the second signal light waveguide portion 16c in each of the plurality of signal light waveguides 16 is inclined with respect to the straight line 17 is s and an angle θ at which the second reference optical waveguide portion 18c in each of the plurality of reference optical waveguides 18 is inclined with respect to the straight line 17. r and are the same. With this configuration, in the matrix-type optical waveguide array intersection 20, the optical path length of the signal optical waveguide 16 from any one of the multiple intersections 22 to the output end of the first optical branching delay unit 12 (which is also the input end of the matrix-type optical waveguide array intersection 20, and the same applies hereinafter) is equal to the optical path length of the reference optical waveguide 18 to the output end of the second optical branching delay unit 14 (which is also the input end of the matrix-type optical waveguide array intersection 20, and the same applies hereinafter). Note that when the line on which the bent portions 16b of the multiple signal optical waveguides 16 are aligned and the line on which the bent portions 18b of the multiple reference optical waveguides 18 are aligned are offset in a parallel relationship, the optical path difference between the optical path length of the signal optical waveguide 16 from any one of the multiple intersections 22 to the output end of the first optical branching delay unit 12 and the optical path length of the reference optical waveguide 18 to the output end of the second optical branching delay unit 14 becomes a constant.

[0024] The matrix-type optical waveguide array intersection 20 has a signal light distributor 23a, a reference light distributor 23b, and an optical multiplexing coupler 24 provided at each intersection 22. The optical multiplexing coupler 24 has two input ends, one of which is coupled to the signal light distributor 23a, and the other of which is coupled to the reference light distributor 23b. The signal light distributor 23a inputs a portion of the branched signal light that has passed through each intersection 22 from the signal light waveguide 16 to the optical multiplexing coupler 24. The reference light distributor 23b inputs a portion of the branched reference light that has passed through each intersection 22 from the reference light waveguide 18 to the optical multiplexing coupler 24. The optical distributors 23a and 23b are not particularly limited, and may be, for example, 2×2 optical directional couplers. The optical multiplexing coupler 24 multiplexes a portion of the branched signal light distributed by the optical distributor 23a and a portion of the branched reference light distributed by the optical distributor 23b, and outputs an interference light. The optical multiplexing coupler 24 is not particularly limited, but may be, for example, a 2×1 MMI coupler. Alternatively, the optical multiplexing coupler 24 may be a two-input, multiple-output MMI coupler. The matrix-type optical waveguide array intersection 20 further has a photodetector 26 provided at each intersection 22. The photodetector 26 photoelectrically converts the interference light output from the optical multiplexing coupler 24 to generate an interference signal I ij It outputs multiple interference signals I ij is converted into a voltage signal by a current-voltage conversion circuit and then input to the estimation unit 30 (see FIG. 1). In the following, the voltage signal converted by the current-voltage conversion circuit will also be referred to as the interference signal I ij There is something to be said.

[0025] The matrix-type optical waveguide array intersection portion 20 intersects each of m signal optical waveguides 16 with each of n reference optical waveguides 18 at n×m intersections 22. The number of signal optical waveguides 16 (i.e., m) and the number of reference optical waveguides 18 (i.e., n) may be the same or different. The number of intersections 22 is preferably 6 or more. The phase difference Δ of the interference light output from the intersection 22 of the j-th signal optical waveguide 16 and the i-th reference optical waveguide 18 is ij is expressed by the following formula:

number

[0026] Phase difference Δφ of branched signal light sj and the phase difference Δφ of the branched reference light ri When the relationship of the above-mentioned formula 1 is satisfied, the phase difference Δ ij can be distributed comprehensively between 0 and 2π without overlapping.

[0027] Table 1 shows the interference signals I output from each intersection 22 when the phase difference of the branched signal light S1 is 0°, the phase difference of the branched signal light S2 is 60°, the phase difference of the branched reference light R1 is 0°, the phase difference of the branched reference light R2 is −120°, and the phase difference of the branched reference light R3 is −240°. ij In this way, the phase difference between the interference signal I output from the matrix-type optical waveguide array crossing portion 20 is ij The phase differences can be distributed comprehensively between 0 and 2π without overlapping. [Table 1]

[0028] In addition, in the example shown in Table 1, the interference signal I 22 and the interference signal I 11 phase difference of the interference signal I 32 and the interference signal I 21 and the phase difference of the interference signal I 31 and the interference signal I 12 The phase difference between these signals is π. Therefore, if the photodetector 26 is configured to detect each combination of these interference signals using a balanced photodetector (BPD), an interference signal from which common mode noise (DC component) has been removed can be obtained.

[0029] The matrix-type optical waveguide array intersection 20 can generate multiple interference lights for each combination of multiple branched signal lights obtained by branching and delaying signal light S and multiple branched reference lights obtained by branching and delaying reference light R. Furthermore, the optical path lengths of the signal light waveguides 16 and the reference light waveguides 18 extending from the input end of the matrix-type optical waveguide array intersection 20 to any one of the multiple intersections 22 are set to be equal or have a constant optical path difference, so that the phase difference of each of the multiple interference lights is determined by the phase difference of the branched signal light and the phase difference of the branched reference light used to generate that interference light. In this way, the phase difference of the interference lights generated at the matrix-type optical waveguide array intersection 20 can be determined based on the design value of the delay amount of the optical branching delay unit 10.

[0030] The estimation unit 30 has an input / output port 32, a CPU 34, a ROM 36, and a RAM 38. The input / output port 32 is connected to the photodetector 26 of the matrix-type optical waveguide array intersection portion 20, and receives a plurality of interference signals I from the photodetector 26. ij The CPU 34 is connected to the input / output port 32, the ROM 36, and the RAM 38, and receives a plurality of interference signals I ij The CPU 34 executes a process for estimating the phase state of the signal light S based on the received signal light S. Various programs for estimating the phase state are stored in the ROM 36. The RAM 38 temporarily stores data required when the CPU 34 executes the various programs.

[0031] The estimation unit 30 estimates the interference signal I ij The data set consisting of the phase difference and its output voltage value is fitted to a sine wave, and the phase difference (φ s -φ r ) and the amplitude of the signal light S can be estimated.

[0032] In this way, the photodetector 1 of this embodiment can obtain a data set of interference light having different phase differences in a single measurement. The number of data sets depends on the number n×m of intersections 22 of the matrix-type optical waveguide array intersection 20. When the number n×m of intersections 22 of the matrix-type optical waveguide array intersection 20 is 6 or more, the interference signal I ij The phase difference can be made to comprehensively fall within the range of 0 to 2π. As a result, the photodetection device 1 of this embodiment can estimate the phase state (i.e., phase and amplitude) of the signal light S with high accuracy and high efficiency.

[0033] 5 shows an example in which an adjustment element 28 is inserted in the optical waveguides 16, 18. The effective refractive index at the intersection 22 is different from the refractive index of the optical waveguides 16, 18 other than the intersection 22. As described above, in the matrix-type optical waveguide array intersection 20, the optical path lengths of the signal optical waveguide 16 and the reference optical waveguide 18 extending to any one of the multiple intersections 22 are formed to be equal or have a constant optical path difference. However, for some of the multiple intersections 22, differences may occur in the effective optical path lengths and transmittances of the signal optical waveguide 16 and the reference optical waveguide 18 depending on the number of intersections 22 through which the propagating light passes before reaching that intersection 22. For example, for the intersections 22 surrounded by dashed lines in FIG. 5 , the branched signal light propagating through the signal light waveguide 16 passes through two intersections 22 before reaching the intersection 22 surrounded by the dashed line, while the branched reference light propagating through the reference light waveguide 18 reaches the intersection 22 surrounded by the dashed line without passing through any of the intersections 22. The adjustment element 28 is an element configured to adjust the change in effective refractive index and the insertion loss caused by one intersection 22. The adjustment element 28 is not particularly limited, and may be, for example, a structure in which the waveguide widths of the optical waveguides 16 and 18 are changed, or may be a dummy intersection having a common shape with the intersection 22. In this way, the total number of intersections 22 and adjustment elements 28 passed by any one of the multiple intersections 22 is the same between the signal light waveguide 16 and the reference light waveguide 18. This suppresses variations in the phase difference of the interference light output at each intersection 22.

[0034] 6 shows an example in which the branching ratio of the optical distributor 23a at each intersection 22 is adjusted. In FIG. 6, a signal optical waveguide 16 is shown intersecting with n reference optical waveguides 18. The branching ratio is calculated by dividing the optical intensity t n and the optical intensity d of the branched signal light that passes through the intersection 22 and then enters the optical multiplexing coupler 24 (see FIG. 3) via the optical distributor 23a. n The branching ratio of the optical distributor 23a at each intersection 22 is expressed by the following formula: The branching ratio of the reference light distributor 23b is adjusted in the same manner as the adjustment example of the signal light distributor 23a.

number

[0035] In the example shown in FIG. 6, the branched signal light input to the optical multiplexing coupler 24 at each intersection 22 is uniform, so that the variation in the interference light output at each intersection 22 is suppressed.

[0036] 7 shows an example in which the optical multiplexing coupler 24 is configured with a 2×2 MMI coupler and the photodetector 26 is configured with a BPD. In this example, an output with a phase difference π required for quadrature detection can be easily obtained. When the configuration shown in FIG. 7 is adopted, the phase difference φ of the multiple branched signal lights generated in the first optical branching delay unit 12 is sj and the phase difference φ of the plurality of branched reference lights generated by the second optical branching delay unit 14. ri By designing the matrix type optical waveguide array crossing portion 20 so that the following formula is satisfied, it is possible to prevent the phase differences of the interference signals output from the matrix type optical waveguide array crossing portion 20 from overlapping.

number

[0037] The photodetector 1 disclosed in this specification is applicable to various optical devices. The photodetector 1 disclosed in this specification is particularly useful when applied to a large-scale system such as a LiDAR system, although it is not particularly limited thereto.

[0038] The features of the technology disclosed in this specification are summarized below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness either alone or in various combinations.

[0039] (First feature) An optical multiplexer, a first optical branching delay unit that branches a signal light to generate a plurality of branched signal lights and delays the plurality of branched signal lights so that a phase difference between each of the plurality of branched signal lights and the signal light is different; a second optical branching delay unit that branches a reference light to generate a plurality of branched reference light beams and delays the plurality of branched reference light beams so that each of the plurality of branched reference light beams has a different phase difference with respect to the reference light beam; an optical multiplexer, comprising: a matrix-type optical waveguide array intersection section in which intersections of a plurality of signal light waveguides through which the plurality of branched signal light beams output from the output end of the first optical branching delay section propagate and a plurality of reference light waveguides through which the plurality of branched reference light beams output from the output end of the second optical branching delay section propagate are arranged in a matrix; and an optical distributor that branches a portion of each of the branched signal light beams and the branched reference light beams input to each intersection section, multiplexes the branched signal light beams and a portion of each of the branched reference light beams, and outputs interference light.

[0040] (Second feature) 2. The optical multiplexer according to Feature 1, wherein an optical path length of the signal optical waveguide from any one of a plurality of intersections of the matrix-type optical waveguide array intersection section to the output end of the first optical branching delay section and an optical path length of the reference optical waveguide to the output end of the second optical branching delay section are equal or have a constant optical path difference.

[0041] (Third feature) each of the plurality of signal light waveguides extending within the matrix-type optical waveguide array intersection portion has a first signal light waveguide portion and a second signal light waveguide portion aligned along a traveling direction of the branched signal light, and the second signal light waveguide portion is inclined with respect to the first signal light waveguide portion at a bend portion between the first signal light waveguide portion and the second signal light waveguide portion; each of the plurality of reference optical waveguides extending within the matrix-type optical waveguide array intersection portion has a first reference optical waveguide portion and a second reference optical waveguide portion aligned along a traveling direction of the branched reference light, and the second reference optical waveguide portion is inclined with respect to the first reference optical waveguide portion at a bending portion between the first reference optical waveguide portion and the second reference optical waveguide portion; the bent portions of the plurality of signal light waveguides are aligned in a straight line, the bent portions of the plurality of reference optical waveguides are aligned in a straight line, the first signal optical waveguide portion of the signal optical waveguide and the first reference optical waveguide portion of the reference optical waveguide are parallel to each other, a direction in which the second signal light waveguide portion of the signal light waveguide is inclined with respect to the straight line and a direction in which the second reference light waveguide portion of the reference light waveguide is inclined with respect to the straight line are opposite to each other; 3. The optical multiplexer according to feature 2, wherein an angle at which the second signal optical waveguide portion of the signal optical waveguide is inclined with respect to the straight line is the same as an angle at which the second reference optical waveguide portion of the reference optical waveguide is inclined with respect to the straight line.

[0042] (Fourth feature) 4. The optical multiplexer according to Feature 3, wherein the bent portion of each of the plurality of signal optical waveguides and the bent portion of each of the plurality of reference optical waveguides are aligned on the same straight line.

[0043] (5th feature) 5. The optical multiplexer according to any one of features 1 to 4, wherein the initial phases of the interference lights output from the plurality of intersections of the matrix-type optical waveguide array intersection portion are different among the plurality of intersections.

[0044] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0045] 1: optical detection device, 2: optical multiplexer, 10: optical branching delay unit, 12: first optical branching delay unit, 14: second optical branching delay unit, 16: signal light waveguide, 18: reference light waveguide, 20: matrix type optical waveguide array intersection unit, 30: estimation unit, IN1: first input port, IN2: second input port, R: reference light, S: signal light

Claims

1. An optical multiplexer, a first optical branching delay unit that branches a signal light to generate a plurality of branched signal lights and delays the plurality of branched signal lights so that a phase difference between each of the plurality of branched signal lights and the signal light is different; a second optical branching delay unit that branches a reference light to generate a plurality of branched reference light beams and delays the plurality of branched reference light beams so that each of the plurality of branched reference light beams has a different phase difference with respect to the reference light beam; an optical multiplexer, comprising: a matrix-type optical waveguide array intersection section in which intersections of a plurality of signal light waveguides through which the plurality of branched signal light beams output from the output end of the first optical branching delay section propagate and a plurality of reference light waveguides through which the plurality of branched reference light beams output from the output end of the second optical branching delay section propagate are arranged in a matrix; and an optical distributor that branches a portion of each of the branched signal light beams and the branched reference light beams input to each intersection section, multiplexes the branched signal light beams and a portion of each of the branched reference light beams, and outputs interference light.

2. 2. The optical multiplexer according to claim 1, wherein an optical path length of the signal optical waveguide from any one of a plurality of intersections of the matrix-type optical waveguide array intersection section to the output end of the first optical branching delay section and an optical path length of the reference optical waveguide to the output end of the second optical branching delay section are equal or have a constant optical path difference.

3. each of the plurality of signal light waveguides extending within the matrix-type optical waveguide array intersection portion has a first signal light waveguide portion and a second signal light waveguide portion aligned along a traveling direction of the branched signal light, and the second signal light waveguide portion is inclined with respect to the first signal light waveguide portion at a bend portion between the first signal light waveguide portion and the second signal light waveguide portion; each of the plurality of reference optical waveguides extending within the matrix-type optical waveguide array intersection portion has a first reference optical waveguide portion and a second reference optical waveguide portion aligned along a traveling direction of the branched reference light, and the second reference optical waveguide portion is inclined with respect to the first reference optical waveguide portion at a bend portion between the first reference optical waveguide portion and the second reference optical waveguide portion; the bent portions of the plurality of signal light waveguides are aligned in a straight line, the bent portions of the plurality of reference optical waveguides are aligned in a straight line, the first signal optical waveguide portion of the signal optical waveguide and the first reference optical waveguide portion of the reference optical waveguide are parallel to each other, a direction in which the second signal light waveguide portion of the signal light waveguide is inclined with respect to the straight line and a direction in which the second reference light waveguide portion of the reference light waveguide is inclined with respect to the straight line are opposite to each other, 3. The optical multiplexer according to claim 2, wherein an angle at which the second signal optical waveguide portion of the signal optical waveguide is inclined with respect to the straight line is the same as an angle at which the second reference optical waveguide portion of the reference optical waveguide is inclined with respect to the straight line.

4. 4. The optical multiplexer according to claim 3, wherein the bent portion of each of the plurality of signal optical waveguides and the bent portion of each of the plurality of reference optical waveguides are aligned on the same straight line.

5. An optical multiplexer according to any one of claims 1 to 4, wherein the initial phase of the interference light output from each of the plurality of intersections of the matrix-type optical waveguide array intersection section is different among the plurality of intersections.

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