Optical phased array system

Abstract

To provide technology that makes it possible to estimate the phase characteristic of each of a plurality of optical waveguides highly efficiently with high accuracy.SOLUTION: An optical phased array system comprises: a plurality of optical waveguides where light emitted from a light source enters; a phase shifter for controlling the phase of propagation light propagating through each of the plurality of optical waveguides; an optical antenna provided in a later stage than the phase shifter, for radiating propagation light propagating through each of the plurality of optical waveguides toward a free space; a light mixer for generating a plurality of interference light beams derived by multiplexing monitor light and reference light and having different initial phases, with the monitor light including at least propagation light having propagated through the optical waveguide to be measured among the plurality of optical waveguides; and an estimation unit for estimating the relationship between the control value of the phase shifter in the optical waveguide to be measured and the phase of propagation light on the basis of the plurality of interference light beams.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an optical phased array system equipped with an optical phased array (OPA). [Background technology]

[0002] An optical phased array has multiple optical waveguides into which light emitted from a light source is incident. A phase shifter is provided in front of the multiple optical waveguides to control the phase of the propagating light propagating through each of the multiple optical waveguides. An optical antenna is provided behind the multiple optical waveguides to radiate the propagating light propagating through each of the multiple optical waveguides toward free space. The multiple propagating lights radiated from the optical antenna become optical beams with specific deflection angles. The deflection angle of the optical beam depends on the phase difference between the multiple propagating lights. Therefore, an optical phased array can control the deflection angle of the optical beam by using a phase shifter to generate multiple propagating lights with mutual phase differences. Such an optical phased array can be installed in, for example, a LiDAR (Light Detection and Ranging) device.

[0003] For example, due to manufacturing variations in optical waveguides and variations in the characteristics of phase shifters, the relationship between the control value of a phase shifter in an arbitrary optical waveguide and the phase of propagating light (hereinafter sometimes referred to as the "phase characteristics of an optical waveguide") may vary from the design value. In order to control the deflection angle of an optical beam emitted from an optical antenna with high precision, a phase calibration technique is required that estimates the phase characteristics of each of multiple optical waveguides and appropriately feedback-controls the phase shifter based on the estimated phase characteristics.

[0004] Patent Document 1 discloses a technology for estimating the phase characteristics of an optical waveguide to be measured by rotating the phase of light propagating through the optical waveguide to be measured, combining the phase-rotated propagating light with light propagating through other optical waveguides, and fitting the detection signal of the combined light with an approximation curve based on a mathematical model. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2021-517656 Summary of the Invention [Problem to be solved by the invention]

[0006] To estimate the phase characteristics of each of multiple optical waveguides with high accuracy, it is desirable to change the initial phase of the light resulting from interference between the phase-rotated propagating light and all the propagating light propagating through the optical waveguide under measurement for each phase rotation of the propagating light, and acquire a large amount of data at different initial phases. The initial phase here refers to the phase of the interference light when the phase of the propagating light propagating through the optical waveguide under measurement is not controlled. However, the technology of Patent Document 1 can only acquire data at one initial phase per measurement. Therefore, for example, in an optical phased array requiring hundreds to thousands of optical waveguides, the estimation time required for high-accuracy estimation becomes enormous.

[0007] The present specification provides a technique that can estimate the phase characteristics of each of a plurality of optical waveguides with high accuracy and high efficiency. [Means for solving the problem]

[0008] The optical phased array system disclosed in the present specification may include: a plurality of optical waveguides into which light emitted from a light source is incident; a phase shifter that controls the phase of the propagating light propagating through each of the plurality of optical waveguides; an optical antenna that is provided after the phase shifter and radiates the propagating light propagating through each of the plurality of optical waveguides toward free space; an optical mixer that combines monitor light and reference light to generate a plurality of interference lights having different initial phases, wherein the monitor light includes at least the propagating light that has propagated through an optical waveguide that is a measurement target among the plurality of optical waveguides; and an estimating unit that estimates a relationship between a control value of the phase shifter and the phase of the propagating light in the optical waveguide that is the measurement target, based on the plurality of interference lights.

[0009] The above-mentioned optical phased array system includes an optical mixer that combines monitor light and reference light to generate multiple interference lights with different initial phases. Therefore, the above-mentioned optical phased array system can acquire data with different initial phases in a single measurement, thereby enabling highly accurate and efficient estimation of the phase characteristics of an optical waveguide. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an optical phased array system. [Figure 2A] FIG. 2 is a diagram schematically illustrating a configuration of an example of an optical mixer. [Figure 2B] FIG. 1 is a diagram schematically illustrating a configuration of an example of an optical mixer. [Figure 2C] FIG. 2 is a diagram schematically illustrating a configuration of an example of an optical mixer. [Figure 3] FIG. 10 is a plot of the output signal of the monitor light measured when the control voltage applied to the target CH is swept in the optical phased array system of the comparative example. [Figure 4] FIG. 10 is a diagram plotting a plurality of interference signals of monitor light A measured when sweeping the control voltage applied to a target CH in the optical phased array system of this embodiment, and is a diagram fitting an approximate curve based on a mathematical model. [Figure 5]FIG. 10 is a diagram plotting actual measured values ​​of the control voltage applied to the target CH and the phase shift amount in the optical phased array system of this embodiment, and is a diagram fitting an approximate curve based on a fifth-order polynomial. [Figure 6] FIG. 10 is a diagram schematically illustrating the configuration of a modified example of an optical phased array system. [Figure 7A] FIG. 10 is a diagram showing the relationship between the electric field vectors of the multiplexed light A″, the standard light R, and the reference light B″ of other CHs that is not ideal. [Figure 7B] 10 is a diagram showing the relationship between the electric field vectors of ideal other CH multiplexed light A″, standard light R, and reference light B″. FIG. [Figure 8] FIG. 10 is a diagram schematically illustrating the configuration of a modified example of an optical phased array system. [Figure 9] FIG. 10 is a diagram schematically illustrating the configuration of a modified example of an optical phased array system. [Figure 10] FIG. 1 is a diagram illustrating the configuration of a large-scale optical phased array system. DETAILED DESCRIPTION OF THE INVENTION

[0011] The optical phased array system 1 disclosed in this specification will be described below with reference to the drawings. The optical phased array system 1 disclosed in this specification is not particularly limited, and may be mounted on, for example, a LiDAR device. Note that in the following drawings, for the purpose of clarity of illustration, only some of the repeatedly arranged components are denoted by reference numerals.

[0012] (Configuration of Optical Phased Array System 1) As shown in Fig. 1, the optical phased array system 1 includes a laser light source 2, a two-branch coupler 3, a reference light optical waveguide 4a, an optical antenna optical waveguide 4b, an optical demultiplexer 5, multiple optical waveguides 6, a voltage driver 7, a phase shifter 8, an optical antenna 10, an optical multiplexer 12, an optical mixer 14, a photodetector 16, and an estimation unit 20. The optical demultiplexer 5, the multiple optical waveguides 6, the phase shifter 8, and the optical antenna 10 constitute an optical phased array. Furthermore, these components constituting the optical phased array system 1 are not particularly limited, and may be configured, for example, as an optical integrated circuit on a semiconductor substrate.

[0013] The laser light source 2 is not particularly limited, but may emit laser light in the infrared wavelength band, for example. The laser light emitted from the laser light source 2 enters the two-branch coupler 3.

[0014] The two-branch coupler 3 branches the incident laser light, and directs one of the branched propagation lights into the reference light optical waveguide 4a and the other branched propagation light into the optical antenna optical waveguide 4b. The propagation light that has entered the reference light optical waveguide 4a enters the optical mixer 14 as reference light R. The propagation light that has entered the optical antenna optical waveguide 4b enters the optical demultiplexer 5 as input light.

[0015] The optical demultiplexer 5 is configured with an optical coupler that splits input light into a plurality of propagating lights of the same phase. The split propagating lights are distributed to a plurality of optical waveguides 6.

[0016] The phase shifter 8 is provided in front of the multiple optical waveguides 6 and modulates the phase of the light propagating through each of the multiple optical waveguides 6 based on the control voltage output from the voltage driver 7. The phase shifter 8 is not particularly limited, but may be, for example, a carrier injection type electro-optic (EO) phase shifter that utilizes the carrier-plasma effect. Therefore, the phase shifter 8 can individually modulate the phase of the light propagating through each of the multiple optical waveguides 6 by adjusting the control voltage applied to each of the multiple optical waveguides 6.

[0017] The optical antenna 10 is provided after the multiple optical waveguides 6 and radiates multiple phase-modulated propagating lights toward free space. The optical antenna 10 is not particularly limited, but may include, for example, a diffraction grating provided corresponding to each of the multiple optical waveguides 6, and radiate the multiple phase-modulated propagating lights as a light beam toward free space. The multiple propagating lights radiated from the optical antenna 10 become light beams with a specific deflection angle. The deflection angle of the light beam depends on the phase difference between the multiple propagating lights. Therefore, the deflection angle of the light beam radiated from the optical antenna 10 is controlled by using a phase shifter 8 to generate multiple propagating lights with mutual phase differences. In the optical antenna 10, most of the propagating lights propagating through each of the multiple optical waveguides 6 are radiated, and the remaining propagating lights enter the optical multiplexer 12.

[0018] The optical multiplexer 12 is composed of multiple optical couplers that multiplex multiple propagation lights that have passed through the optical antenna 10. The optical multiplexer 12 has multiple input ports and one output port. Each of the multiple input ports is coupled to a corresponding one of the multiple optical waveguides 6 located downstream of the optical antenna 10. One output port is coupled to one of two input ports of the optical mixer 14. The optical multiplexer 12 multiplexes propagation light (referred to herein as "signal light A'") propagating through the optical waveguide 6 to be measured (referred to herein as "target CH") with multiplexed light A'' obtained by multiplexing all propagation lights propagating through multiple optical waveguides 6 other than the target CH (referred to herein as "other CHs") to generate one monitor light A, and inputs the generated monitor light A to the optical mixer 14. The optical multiplexer 12 is designed so that the optical path length from the input port to the output port is the same regardless of the route taken.

[0019] The optical mixer 14 combines the monitor light A and the reference light R to cause interference between the signal light A′ and the reference light B″, thereby generating a plurality of interference lights B1 to B″ having different initial phases. N(N is a natural number of 2 or more). The reference light B'' here is the sum of the lights other than the signal light A', and in this example, is the sum of the combined light A'' and the reference light R. The optical mixer 14 generates a plurality of interference lights B1 to B N The initial phase of the multiple interference lights B1 to B2 is designed to be uniform between 0 and 2π radians. N are generated for each phase difference Δφ of 2π / N. The optical mixer 14 is not particularly limited, but may generate, for example, four or more interference lights.

[0020] As shown in FIG. 2A, the optical mixer 14 may be configured to adjust the phase difference by the difference between the optical path length from the input port where the monitor light A is input to the optical coupler and the optical path length from the input terminal where the reference light R is input to the optical coupler. Alternatively, as shown in FIG. 2B, the optical mixer 14 may be configured as a two-input, multiple-output star coupler. The optical mixer 14 in this example is configured to adjust the phase difference by the difference between the optical path length from the input port where the monitor light A is input to the output port and the optical path length from the input port where the reference light R is input to the output port. Alternatively, as shown in FIG. 2C, the optical mixer 14 may be configured as a multistage coupler connected in multiple stages. The optical mixer 14 in this example is configured with a one-input, two-output coupler that splits the light into in-phase signals, a one-input, two-output coupler that splits the light into signals with a phase difference of π / 2, and a two-input, two-output coupler that mixes the two input lights with a relative phase difference of π and generates an output, and the optical path lengths between the couplers are equal for all paths. 2C shows relative phases based on 0. Note that FIG. 2C shows an example in which a plurality of interference light beams having phase differences of 0, π / 2, π, and 3π / 2 are generated. The optical mixer 14 illustrated in FIGS. 2A to 2C is just an example, and various types of optical mixers capable of generating a plurality of interference light beams having different initial phases can be used as the optical mixer 14.

[0021] Returning to FIG. 1, the photodetector 16 has a plurality of photodiodes. Each of the plurality of photodiodes detects a plurality of interference light beams B1 to B NThe photodetector 16 is configured to receive the corresponding interference light from the photodiode and generate a current corresponding to the intensity of the interference light. The photodetector 16 further includes a current-to-voltage conversion circuit that converts the current flowing through the photodiode into a voltage signal. The converted voltage signal, the interference signal P out1 (V)~P outN (V) is input to the estimation unit 20. The photodetector 16 may be configured to generate an interference signal for each combination of interference light with a phase difference of π using a balanced photodetector (BPD). In this example, an interference signal is obtained from which common mode noise (DC component) has been removed.

[0022] The estimation unit 20 has an input / output port 22, a CPU 24, a ROM 26, and a RAM 28. The input / output port 22 is connected to the photodetector 16, and receives a plurality of interference signals P out1 (V)~P outN The CPU 24 is connected to the input / output port 22, the ROM 26, and the RAM 28, and executes a process for estimating the phase characteristics of each of the plurality of optical waveguides 6 based on the plurality of interference signals, as will be described later. The ROM 26 stores various programs for estimating the phase characteristics. The RAM 28 temporarily stores data required when the CPU 24 executes the various programs. In this manner, the estimation unit 20 has the function of estimating the phase characteristics of each of the plurality of optical waveguides 6 based on the plurality of interference signals. The estimation unit 20 is further connected to the voltage driver 7. The estimation unit 20 also functions as a control unit that feedback-controls the control voltage that the voltage driver 7 outputs to the phase shifter 8 based on the estimated phase characteristics.

[0023] As explained in the background art, the relationship between the control voltage V of the phase shifter 8 in any optical waveguide 6 and the phase of the propagating light (i.e., the phase characteristics of the optical waveguide 6) may vary from the design value due to manufacturing variations in the optical waveguides 6 and characteristic variations in the phase shifters 8. In order to control the deflection angle of the optical beam radiated from the optical antenna 10 with high precision, it is necessary to estimate the phase characteristics of each of the multiple optical waveguides 6 and to appropriately feedback-control the phase shifters 8 based on the estimated phase characteristics. Below, a phase characteristic estimation procedure for the optical phased array system 1 of this embodiment will be explained by comparing it with a comparative example.

[0024] (Procedure for estimating phase characteristics of an optical phased array system in a comparative example) First, a comparative example will be described in which the two-branch coupler 3 and the optical mixer 14 are not provided. In this comparative example, phase characteristic estimation is performed based on an output signal P obtained by voltage-converting only the monitor light A output from the optical multiplexer 12. The output signal P of the monitor light A when a control voltage V is applied to the signal light A' propagating through the target CH via the phase shifter 8 and the phase of the signal light A' is modulated is expressed by the following mathematical model. Note that the propagating light propagating through the other CHs is all modulated under conditions that result in a fixed phase. For example, the fixed condition for the other CHs may be a condition in which the control voltage V is not applied and the propagating light is not modulated.

number

[0025] θ(V) is the phase of the signal light A' propagating through the target CH, and θ c is the phase difference of the reference light B'' (equal to the combined light A'' in the comparative example), α(V) is the electric field strength of the signal light A', and C is the electric field strength of the reference light B''. C, θ c The two parameters take different values ​​in each of the optical waveguides 6 due to manufacturing variations in the optical waveguides 6, variations in the characteristics of the phase shifters 8, and the control amount of the phase shifters 8 in other CHs.

[0026] Figure 3 shows the plot of the output signal P of monitor light A measured when sweeping the control voltage V applied to the target CH. The parameters (θ(V), α(V)) can be estimated by fitting an approximate curve based on the above mathematical model to the measured output signal P of monitor light A using the least squares method or the like. θ(V) represents the relationship between the control voltage V and the phase of signal light A' propagating through the target CH. α(V) represents the relationship between the control voltage V and the electric field strength of signal light A' propagating through the target CH.

[0027] In the comparative example, in the measurement of the target CH, the control voltages V applied to the other CHs are all fixed, and the phase difference θ c However, only data under one condition can be obtained. As a result, the accuracy of the estimated parameters (θ(V), α(V)) is low. Even if more data is added under the same initial phase condition, as shown in Figure 3, at the peak value of the sine wave (for example, when the control voltage is Va and Vb), ∂P / ∂θ is zero, and almost no phase information can be obtained. For this reason, in the comparative example, it is difficult to improve the accuracy of the estimated parameters (θ(V), α(V)).

[0028] (Procedure for Estimating Phase Characteristics of the Optical Phased Array System 1 of the Present Embodiment) In the optical phased array system 1 of this embodiment, the monitor light A and the reference light R are combined when a control voltage V is applied to the target CH, causing the signal light A′ and the reference light B″ to interfere with each other, generating a plurality of interference lights B1 to B″ having different initial phases. N are generated, and the multiple interference lights B1 to B N A plurality of interference signals P out1 (V)~P outN (V) is obtained. The interference signal P of the arbitrary interference light B is out (V) is expressed by the following mathematical model.

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[0029] A(V) is the electric field strength of monitor light A, R is the electric field strength of reference light R, and θ A(V) is the phase of monitor light A, and θ R is the phase of the reference light R. The relationship between the electric field vectors of the signal light A', the combined light A'', the monitor light A, the reference light R, the reference light B'', and the interference light B is as follows:

number

[0030] Therefore, the electric field vector of any interference light B can be distinguished into signal light A' propagating through the target channel and reference light B'' (=A''+R), which is the sum of all propagating lights propagating through the optical waveguides other than the target channel. As a result, the interference signal P out (V) can be written as follows:

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[0031] Here, A'(V) is the electric field strength of the signal light A' propagating through the target CH, A'' is the electric field strength of the multiplexed light A'', B'' is the electric field strength of the reference light B'', and θ A (V) is the phase of signal light A', and θ A’’+R is the phase difference between the multiplexed light A'' and the reference light R, and θ B’’ is the phase of the reference light B''. By combining the monitor light A and the reference light R via the optical mixer 14, the signal light A' and the reference light B'' are made to interfere with each other, and a plurality of interference lights having different initial phases are generated. The generated interference lights B1 to B N A plurality of interference signals P out1 (V)~P outN (V) is expressed by the following mathematical model.

number

[0032] In this way, the optical phased array system 1 of this embodiment can acquire data of different initial phases in a single measurement. The number of data sets depends on the number N of output terminals of the optical mixer 14. As shown in FIG. 4, the optical phased array system 1 of this embodiment can comprehensively estimate parameters (θ(V), α(V)) by fitting an approximation curve based on a mathematical model for each data set of different initial phases. The optical phased array system 1 of this embodiment can estimate parameters (θ(V), α(V)) that are common to data sets of different initial phases, parameters (C, θ C ) are estimated by fitting an approximate curve based on a mathematical model, and the common parameters (θ(V), α(V)) with the smallest error from the actual measured values ​​are adopted as the optimal parameters. By performing the phase characteristic estimation procedure for each of the multiple optical waveguides 6, the optimal parameters for each of the multiple optical waveguides 6 are obtained. As a result, the accuracy of the estimated parameters (θ(V), α(V)) is improved for each of the multiple optical waveguides 6.

[0033] In the optical phased array system 1 of this embodiment, the estimated parameters, including the phase characteristic θ(V), which represents the relationship between the control voltage V of the phase shifter 8 and the phase of the signal light A′ propagating through the target channel, can be further improved in accuracy by fitting using an approximation curve appropriate for the type of phase shifter 8. For example, in the case of a carrier-injection EO phase shifter utilizing the carrier-plasma effect, a fifth-order polynomial may be used as an approximation curve to represent a mathematical model of θ(V). Figure 5 shows a graph obtained by fitting a fifth-order polynomial to the measured values ​​of the control voltage V of the phase shifter 8 and the phase shift amount. The parameters of this approximation curve are difficult to estimate using data from a single initial phase, but can be estimated with high accuracy using data sets with different initial phases. In this way, the optical phased array system 1 of this embodiment can estimate the phase characteristic θ(V) with high accuracy.

[0034] The optical phased array system 1 of this embodiment feedback-controls the control voltage of the phase shifter 8 based on the phase characteristic θ(V) among the estimated parameters. This allows the phase shifter 8 to be appropriately feedback-controlled based on the phase characteristic of each of the multiple optical waveguides 6, thereby enabling the deflection angle of the optical beam radiated from the optical antenna 10 to be controlled with high precision.

[0035] In order to improve the estimation accuracy of the parameters (θ(V), α(V)), it is effective to increase the number of data sets. For this reason, as shown in FIG. 6, a pre-mixing phase shifter 13 may be provided between the optical multiplexer 12 and the optical mixer 14. In this modification, the phase of the monitor light A can be modulated according to the control voltage of the pre-mixing phase shifter 13. Therefore, it is possible to increase the variation of the interference light output from the optical mixer 14. Note that the pre-mixing phase shifter 13 may be connected to one of the two input ports of the optical mixer 14, which input port receives the reference light R. Alternatively, different pre-mixing phase shifters 13 may be connected to each of the two input ports of the optical mixer 14.

[0036] It is desirable that the relationship between the optical intensities of the combined light A'' and the reference light R satisfies the following relationship:

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[0037] FIG. 7A shows the relationship between the electric field vectors of the combined light A″, the reference light R, and the reference light B″1 to B″4 when the light intensities of the combined light A″ and the reference light R are approximately equal. In this case, the optical mixer 14 generates the reference light B″1 to B″4 with different phase differences, which results in the generation of interference light B1 to B4 with different initial phases. However, the phase difference (Δφ i) is less than π radians, the fluctuation range of the initial phases of the interference beams B1 to B4 is also less than π radians. On the other hand, as shown in FIG. 7(B), when the optical intensity of the reference beam R is sufficiently greater than that of the combined beam A″ or the optical intensity of the combined beam A″ is substantially zero, the fluctuation range of the initial phases of the interference beams B1 to B4 can cover 0 to 2π radians. In the optical phased array system 1 of this embodiment, the laser beam emitted from the laser source 2 is branched by the two-branch coupler 3 to generate the reference beam R. Therefore, the optical intensity of the reference beam R is high, and Equation 6 can be satisfied. When the fluctuation range of the initial phases of the interference beams B1 to B4 is 0 to 2π radians, data bias is suppressed, and improvement in the estimation accuracy of the parameters (θ(V), α(V)) is expected.

[0038] As shown in Fig. 8, a switch 11 may be provided in each of the multiple optical waveguides 6. In this modification, the switch 11 is provided in the optical waveguide 6 between the optical antenna 10 and the optical multiplexer 12. By turning on the switch of the optical waveguide 6 to be measured and turning off the switches of the other optical waveguides 6, it is possible to prevent the multiplexed light A'' of the propagating light propagating through the other optical waveguides 6 from being multiplexed with the signal light monitor light A. In the optical phased array system 1 of this example, the optical intensity of the multiplexed light A'' and the signal light A can be suppressed to 0, and therefore the relationship of Equation 6 can be satisfied.

[0039] In the optical phased array system 1 described so far, the laser light emitted from the laser light source 2 is branched by the two-branch coupler 3 to generate the reference light R. In the modified example shown in FIG. 9 , the outputs of the two optical couplers in the final stage of the optical multiplexer 12 are input to the optical mixer 14. That is, the optical multiplexer 12 of this modified example has multiple input ports and two output ports. Each of the multiple input ports is coupled to a corresponding optical waveguide 6 among the multiple optical waveguides 6 located downstream of the optical antenna 10. One of the two output ports is coupled to one of the two input ports of the optical mixer 14, and the other of the two output ports is coupled to the other of the two input ports of the optical mixer 14. In the optical multiplexer 12 of this modified example, one of the two output ports outputs the monitor light, and the other of the two output ports outputs the reference light. The optical phased array system 1 of this example can be simply configured.

[0040] FIG. 10 shows an example of a large-scale optical phased array system 100. The large-scale optical phased array system 100 is partitioned into multiple blocks 102. In this example, it is partitioned into four blocks 102, and only one of these blocks 102 is labeled with a reference numeral. Each of the multiple blocks 102 includes the optical demultiplexer 5, multiple optical waveguides 6, phase shifter 8, optical antenna 10, optical multiplexer 12, optical mixer 14, and photodetector 16 described above. In the optical phased array system 100, the phase characteristics of the multiple optical waveguides 6 are estimated for each block 102 based on the phase characteristic estimation procedure described above.

[0041] 10, the optical phased array system 100 is configured so that the optical path lengths from the laser light source 2 to the optical mixers 14 of each of the multiple blocks 102 are equal. This makes it possible to estimate the phase difference between the blocks 102 using the reference light R as a reference. Therefore, by using the reference light R, the optical phased array system 100 can simultaneously perform phase calibration within the block 102 and phase calibration between the blocks 102. This configuration is particularly useful when a large-scale system such as LiDAR is required.

[0042] 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.

[0043] (First feature) a plurality of optical waveguides into which light emitted from a light source is incident; a phase shifter that controls the phase of light propagating through each of the plurality of optical waveguides; an optical antenna provided at a stage subsequent to the phase shifter, the optical antenna radiating the propagated light propagating through each of the plurality of optical waveguides toward free space; an optical mixer that multiplexes monitor light and reference light to generate a plurality of interference lights having different initial phases, the monitor light including at least propagation light that has propagated through an optical waveguide to be measured among the plurality of optical waveguides; an estimating unit that estimates a relationship between a control value of the phase shifter in the optical waveguide to be measured and a phase of the propagating light, based on the plurality of interference lights.

[0044] (Second feature) a two-way coupler that branches the light emitted from the light source into input light and the reference light; 2. The optical phased array system according to Feature 1, further comprising: an optical splitter that splits the input light into the plurality of optical waveguides.

[0045] (Third feature) 3. The optical phased array system according to Feature 2, further comprising an optical multiplexer that multiplexes the propagated light beams that have propagated through the plurality of optical waveguides to generate the monitor light.

[0046] (Fourth feature) It is divided into several blocks, each of the plurality of blocks is provided with the optical demultiplexer, the phase shifter, the optical antenna, the optical multiplexer, and the optical mixer; 4. The optical phased array system of Feature 3, wherein an optical path length from the light source to the optical mixer in each of the plurality of blocks is equal.

[0047] (5th feature) 2. The optical phased array system according to Feature 1, further comprising an optical multiplexer that multiplexes the propagating light that has propagated through each of the plurality of optical waveguides to generate the monitor light and the reference light, respectively.

[0048] (6th feature) 6. The optical phased array system according to any one of features 1 to 5, further comprising a pre-mixing phase shifter that controls a phase of at least one of the monitor light and the reference light incident on the optical mixer.

[0049] 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]

[0050] 1: Optical phased array system, 2: Laser light source, 3: Two-way coupler, 5: Optical splitter, 6: Optical waveguide, 7: Voltage driver, 8: Phase shifter, 10: Optical antenna, 12: Optical multiplexer, 14: Optical mixer, 16: Photodetector, 20: Estimation unit

Claims

1. a plurality of optical waveguides into which light emitted from a light source is incident; a phase shifter that controls the phase of light propagating through each of the plurality of optical waveguides; an optical antenna provided at a stage subsequent to the phase shifter, the optical antenna radiating the propagated light propagating through each of the plurality of optical waveguides toward free space; an optical mixer that multiplexes monitor light and reference light to generate a plurality of interference lights having different initial phases, the monitor light including at least a propagation light that has propagated through an optical waveguide to be measured among the plurality of optical waveguides; an estimator configured to estimate a relationship between a control value of the phase shifter in the optical waveguide under measurement and a phase of the propagating light, based on the plurality of interference lights.

2. a two-way coupler that branches the light emitted from the light source into input light and the reference light; 2. The optical phased array system according to claim 1, further comprising: an optical splitter that splits the input light into the plurality of optical waveguides.

3. 3. The optical phased array system according to claim 2, further comprising an optical multiplexer that multiplexes the propagated light beams that have propagated through the plurality of optical waveguides to generate the monitor light beam.

4. It is divided into several blocks, each of the plurality of blocks is provided with the optical demultiplexer, the phase shifter, the optical antenna, the optical multiplexer, and the optical mixer; 4. The optical phased array system of claim 3, wherein an optical path length from the light source to the optical mixer in each of a plurality of blocks is equal.

5. 2. The optical phased array system according to claim 1, further comprising an optical multiplexer that multiplexes the propagated light beams that have propagated through the plurality of optical waveguides to generate the monitor light beam and the reference light beam, respectively.

6. 6. The optical phased array system according to claim 1, further comprising a pre-mixing phase shifter that controls a phase of at least one of the monitor light and the reference light incident on the optical mixer.

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