Optical device, optical transmitter, and optical receiver

Abstract

To provide an optical device or the like for improving positioning accuracy when mounting a second substrate on a first substrate while reducing power consumption.SOLUTION: The optical device includes a first substrate and a second substrate mounted on the first substrate and made of a material different from that of the first substrate. The first substrate includes a first waveguide, a second waveguide, a first edge coupler disposed on an end face of the first substrate and configured to input and output light to and from the first waveguide, and a second edge coupler disposed on the end face and configured to input and output light to and from the second waveguide. The second substrate includes a third waveguide, an optical circuit optically connected to the third waveguide, and a loopback waveguide that loops back and outputs input light. In the optical device, the first waveguide and the third waveguide are optically coupled to each other, and the loopback waveguide and the second waveguide are optically coupled to each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical device, an optical transmitter, and an optical receiver. [Background technology]

[0002] 6 is an explanatory diagram showing an example of a conventional test system 100. The test system 100 includes a wafer made of, for example, silicon, on which a plurality of optical chips 110 are formed, a test device 140, and optical fibers F1 and F2.

[0003] A plurality of optical chips 110 are formed on the wafer in a grid-like arrangement. The optical chip 110 has a first region 110A, a second region 110B, and a dicing line DL along which the optical chip 110 can be cut between the first region 110A and the second region 110B. The first region 110A has an optical circuit 113 and first ECs (Edge Couplers) 121A and 121B. The first EC 121A is disposed near the end face of the first region 110A on the dicing line DL side.

[0004] The optical circuit 113 is, for example, a circuit such as a DP-IQ modulator in a digital coherent optical transceiver. The DP-IQ modulator has an input waveguide 111, a branching section 112, a Y-polarized IQ modulator 113B, an X-polarized IQ modulator 113A, a variable optical attenuator (VOA) 114, and a polarization rotator (PR) 117. The DP-IQ modulator also has a polarization beam combiner (PBC) 118, an output waveguide 119, and a monitor PD 120. Each waveguide in the DP-IQ modulator is, for example, a Si waveguide.

[0005] Input waveguide 111 is, for example, a Si waveguide that receives input light from optical fiber F1 connected to a light source. Branching unit 112 is, for example, an XY-branching MMI (Multi-Mode Interferometer) that branches the input light from input waveguide 111 into input light of an X-polarized component and input light of a Y-polarized component.

[0006] The X-polarized IQ modulator 113A modulates the X-polarized IQ component input light and outputs the modulated X-polarized IQ component signal light to the PBC 118. The Y-polarized IQ modulator 113B modulates the Y-polarized IQ component input light and outputs the modulated Y-polarized IQ component signal light to the PR 117. The PR 117 rotates the polarization of the Y-polarized IQ component signal light and outputs the Y-polarized IQ component signal light after the polarization rotation to the PBC 118. The PBC 118 multiplexes the X-polarized IQ component signal light and the Y-polarized IQ component signal light after the polarization rotation and outputs the multiplexed signal light to the output waveguide 119. The VOA 116 is a variable attenuator that adjusts the intensity of the signal light from the X-polarized IQ modulator 113A or the Y-polarized IQ modulator 113B. The monitor PD 120 monitors the level of the signal light after adjustment by the VOA 116 .

[0007] The X-polarized IQ modulator 113A includes an MZI 113A1 for the X-polarized I component, an MZI 113A2 for the X-polarized Q component, a first adjustment unit 114A, a second adjustment unit 114B, and a first multiplexing unit 115. The X-polarized I component MZI 113A1 modulates the X-polarized I component input light in accordance with an RF signal and outputs the modulated X-polarized I component signal light. The X-polarized Q component MZI 113A2 modulates the X-polarized Q component input light in accordance with an RF signal and outputs the modulated X-polarized Q component signal light. The first adjustment unit 114A is a DC phase shifter that shifts the phase of the input light guided through the optical waveguide from the X-polarized I component MZI 113A1 or the Q component MZI 113A2 in accordance with a DC signal. The second adjusting unit 114B is a DC phase shifter that shifts the phase of the input light guided through the optical waveguide of each IQ modulator in response to a DC signal. The first multiplexing unit 115 multiplexes the modulated X-polarized I-component signal light with the modulated X-polarized Q-component signal light, and outputs the multiplexed X-polarized IQ-component signal light to the PBC 118 via the VOA 116.

[0008] Y-polarized IQ modulator 113B includes MZI 113B1 for the I component of Y-polarized wave, MZI 113B2 for the Q component of Y-polarized wave, first adjustment unit 114A, second adjustment unit 114B, and first multiplexing unit 115. MZI 113B1 for the I component of Y-polarized wave modulates the I component of Y-polarized wave input light in accordance with an RF signal and outputs the modulated I component of Y-polarized wave signal light. MZI 113B2 for the Q component of Y-polarized wave modulates the Q component of Y-polarized wave input light in accordance with an RF signal and outputs the modulated Q component of Y-polarized wave signal light. First adjustment unit 114A shifts the phase of the input light guided through the optical waveguide from each MZI 113B1 or 113B2 in accordance with a DC signal. The second adjustment unit 114B shifts the phase of the input light guided through the optical waveguide of each IQ modulator in response to the DC signal. The first multiplexing unit 115 multiplexes the modulated Y-polarized I-component signal light with the modulated Y-polarized Q-component signal light, and outputs the multiplexed Y-polarized IQ-component signal light to the PR 117 via the VOA 116.

[0009] In MZI 113A1 for the I component of X polarization, MZI 113A2 for the Q component of X polarization, MZI 113B1 for the I component of Y polarization, and MZI 113B2 for the Q component of Y polarization, the refractive index of the Si waveguide through which the signal light is guided changes in response to the RF signal. Then, MZI 113A1 for the I component of X polarization, MZI 113A2 for the Q component of X polarization, MZI 113B1 for the I component of Y polarization, and MZI 113B2 for the Q component of Y polarization modulate and output the signal light in response to the change in refractive index.

[0010] The second region 110B has GCs (Grating Couplers) 131A and 131B, connecting waveguides 132A and 132B, and second ECs 133A and 133B. The GC 131A is disposed on the surface of the second region 110B and is detachably connected to an optical fiber F1 that connects to a polarization controller 142 (described later), and is also connected to the connecting waveguide 132A. The connecting waveguide 132A is a Si waveguide that guides light between the GC 131A and the second EC 133A. The second EC 133A is disposed near an end face on the dicing line DL side of the second region 110B. The second EC 133A is optically coupled to the first EC 121A in the first region 110A, thereby optically connecting the connection waveguide 132A in the second region 110B and the input waveguide 111 in the first region 110A.

[0011] The GC 131B is disposed on the surface of the second region 110B and is detachably connected to an optical fiber F2, which is connected to a power meter 143 (described later), and is also connected to a connection waveguide 132B. The connection waveguide 132B is a Si waveguide that guides light between the GC 131B and the second EC 133B. The second EC 133B is disposed near the end face of the second region 110B on the dicing line DL side. The second EC 133B is optically coupled to the first EC 121B in the first region 110A, thereby optically connecting the connection waveguide 132B in the second region 110B to the output waveguide 119 in the first region 110A.

[0012] The test equipment 140 includes a light source 141, a polarization controller 142, and a power meter 143. The light source 141 is, for example, a light source that emits test light corresponding to the transmitted light. The polarization controller 142 polarizes the test light from the light source 141 and outputs the polarized test light to an optical fiber F1. The polarization controller 142 controls the polarization of the test light to generate TM light or TM test light. The power meter 143 receives reflected return light from the optical circuit 113 relative to the test light via an optical fiber F2 and measures the power of the reflected return light.

[0013] Next, the operation of the test system 100 will be described. The polarization controller 142 in the test device 140 polarizes the test light from the light source 141 and outputs the polarized test light to the optical fiber F1. The GC 131A in the second area 110B inputs the test light from the optical fiber F1 to the connecting waveguide 132A. The second EC 133A in the second area 110B outputs the test light from the connecting waveguide 132A to the first EC 121A in the first area 110A. Furthermore, the first area 110A inputs the test light from the first EC 121A and inputs the input test light to the input waveguide 111.

[0014] The input waveguide 111 inputs the test light to a branching section 112 in the optical circuit 113. The optical circuit 113 outputs reflected returning light of the test light to the output waveguide 119. The output waveguide 119 outputs the reflected returning light to the connection waveguide 132B through the first EC 121B. The connection waveguide 132B outputs the reflected returning light from the output waveguide 119 to the optical fiber F2 via the GC 131B. Furthermore, the power meter 143 measures the power of the reflected returning light of the test light from the optical fiber F2.

[0015] In the test system 100, optical fibers F1 and F2 are connected to GCs 131A and 131B from the wafer surface direction to input light, and test light can be input to the optical circuit 113, making it possible to perform testing in the wafer state. The test equipment 140 can evaluate the optical circuit 113 in the first region 110A based on the measurement results of the reflected light from the optical circuit 113. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] US Patent Application Publication No. 2020 / 0158959 [Patent Document 2] JP 2019-207305 A [Patent Document 3] Patent Publication No. 2021-136411 Summary of the Invention [Problem to be solved by the invention]

[0017] However, the optical circuit 113 in the conventional optical chip 110 is composed of a Si waveguide, and therefore the change in refractive index of the Si waveguide when an RF signal is applied is small, and increasing the change in refractive index requires a higher driving voltage, which increases power consumption.

[0018] In one aspect, an object is to provide an optical device or the like that can reduce power consumption. [Means for solving the problem]

[0019] An optical device according to one embodiment includes a first substrate and a second substrate mounted on the first substrate and made of a different material from the first substrate. The first substrate includes a first waveguide, a second waveguide, a first edge coupler disposed on an end surface of the first substrate for inputting and outputting light to and from the first waveguide, and a second edge coupler disposed on the end surface for inputting and outputting light to and from the second waveguide. The second substrate includes a third waveguide, an optical circuit optically connected to the third waveguide, and a loopback waveguide for returning input light to and outputting it. In the optical device, the first waveguide and the third waveguide are optically coupled, and the loopback waveguide and the second waveguide are optically coupled. [Effects of the Invention]

[0020] According to one aspect, power consumption can be reduced. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of a test system according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram illustrating an example of a test system according to a second embodiment. [Figure 3] FIG. 3 is an explanatory diagram illustrating an example of a test system according to a third embodiment. [Figure 4]FIG. 4 is an explanatory diagram illustrating an example of an optical transceiver according to this embodiment. [Figure 5] FIG. 5 is an explanatory diagram showing an example of a test system of a comparative example. [Figure 6] FIG. 6 is an explanatory diagram showing an example of a conventional test system. DETAILED DESCRIPTION OF THE INVENTION

[0022] <Comparative Example> Therefore, the present applicant has proposed a comparative example of a test system 200 for evaluating an optical chip in which an LN chip including an optical circuit with a built-in LN waveguide is mounted on a Si photonics substrate. Fig. 5 is an explanatory diagram showing an example of the comparative example of the test system 200. The test system 200 shown in Fig. 5 includes a wafer, such as silicon, on which a plurality of optical chips 210 are formed, a test device 240, and optical fibers F1 and F2.

[0023] A plurality of optical chips 210 are formed on the wafer in a grid-like arrangement. The optical chip 210 has a first region 210A, a second region 210B, and a dicing line DL along which the optical chip 210 can be cut between the first region 210A and the second region 210B. The first region 210A has an optical circuit 213 and first ECs (Edge Couplers) 221A and 221B.

[0024] The optical circuit 213 is, for example, a circuit such as a DP-IQ modulator in a digital coherent optical transceiver. The DP-IQ modulator is a modulator in which a thin-film LN chip 250 having a modulator body of an X-polarized IQ modulator 213A and a modulator body of a Y-polarized IQ modulator 213B is mounted on a first region 210A of SiPh (silicon photonics). The thin-film LN chip 250 has a support substrate 251 and an LN waveguide 253 on the support substrate 251 that serves as the modulator body.

[0025] The DP-IQ modulator includes an input waveguide 111 , a branching section 112 , an X-polarized IQ modulator 213 A, a Y-polarized IQ modulator 213 B, a VOA 216 , a PR 217 , a PBC 218 , an output waveguide 219 , and a monitor PD 220 .

[0026] The input waveguide 211 is, for example, a Si waveguide, which receives input light from an optical fiber F1 connected to a polarization controller 242 (described later). The branching unit 212 is, for example, an XY branching MMI (Multi-Mode Interferometer) which branches the input light from the input waveguide 211 into input light of an X polarization component and input light of a Y polarization component.

[0027] The X-polarized IQ modulator 213A modulates the X-polarized IQ component input light and outputs the modulated X-polarized IQ component signal light to the PBC 218. The Y-polarized IQ modulator 213B modulates the Y-polarized IQ component input light and outputs the modulated Y-polarized IQ component signal light to the PR 217. The PR 217 rotates the polarization of the Y-polarized IQ component signal light and outputs the Y-polarized IQ component signal light after the polarization rotation to the PBC 218. The PBC 218 multiplexes the X-polarized IQ component signal light and the Y-polarized IQ component signal light after the polarization rotation and outputs the multiplexed signal light to the output waveguide 219. The VOA 216 is a variable attenuator that adjusts the intensity of the signal light from the X-polarized IQ modulator 213A or the Y-polarized IQ modulator 213B. The monitor PD 220 monitors the level of the signal light after adjustment by the VOA 216 .

[0028] X-polarized IQ modulator 213A has input waveguide 212A, MZI 213A1 for the I component of X-polarized wave and MZI 213A2 for the Q component of X-polarized wave, output waveguide 215A, first adjustment unit 214A, second adjustment unit 214B, and first multiplexing unit 215. Input waveguide 212A is, for example, a Si waveguide, and connects input waveguide 211 and MZI 213A1 for the I component of X-polarized wave, and also connects input waveguide 211 and MZI 213A2 for the Q component of X-polarized wave.

[0029] MZI 213A1 for the I component of X polarization incorporates LN waveguide 253, which serves as an arm waveguide of the modulator body, and modulates the signal light guided through LN waveguide 253 in accordance with an RF signal. MZI 213B1 for the Q component of X polarization incorporates LN waveguide 253, and modulates the signal light guided through LN waveguide 253 in accordance with an RF signal.

[0030] Output waveguide 215A connects MZI 213A1 of the I component of the X polarization and first multiplexing unit 215, and also connects MZI 213A2 of the Q component of the X polarization and first multiplexing unit 215, and is, for example, a Si waveguide.

[0031] The first end face D10 of the thin-film LN chip 250 has a coupling portion 253A1 that optically couples the input end 253A of the LN waveguide 253 in the MZI 213A1 for the I component of the X polarization to the input waveguide 212A. The first end face D10 has a coupling portion 253A1 that optically couples the input end 253A of the LN waveguide 253 in the MZI 213A2 for the Q component of the X polarization to the input waveguide 212A.

[0032] The second end face D11 of the thin-film LN chip 250 has a coupling portion 253B1 that optically couples the output end 253B of the LN waveguide 253 in the MZI 213A1 for the I component of the X polarization to the output waveguide 215A. The second end face has a coupling portion 253B1 that optically couples the output end 253B of the LN waveguide 253 in the MZI 213A2 for the Q component of the X polarization to the output waveguide 215A.

[0033] The first adjustment unit 214A is a DC phase shifter that shifts the phase of input light guided through the optical waveguide from MZI 213A1 or 213A2 in response to a DC signal. The second adjustment unit 214B is a DC phase shifter that shifts the phase of input light guided through the optical waveguide of X-polarized IQ modulator 213A in response to a DC signal. The first multiplexing unit 215 multiplexes the modulated X-polarized I-component signal light and the modulated X-polarized Q-component signal light, and outputs the multiplexed X-polarized I-Q component signal light to PBC 218 via VOA 216.

[0034] Y-polarized IQ modulator 213B has input waveguide 212A, MZI 213B1 for the I component of Y-polarized wave and MZI 213B2 for the Q component of Y-polarized wave, output waveguide 215A, first adjustment unit 214A, second adjustment unit 214B, and first multiplexing unit 215. Input waveguide 212A is, for example, a Si waveguide, and connects input waveguide 211 and MZI 213B1 for the I component of Y-polarized wave, and also connects input waveguide 211 and MZI 213B2 for the Q component of Y-polarized wave.

[0035] The MZI 213B1 for the I component of the Y polarization incorporates an LN waveguide 253 and modulates, in accordance with an RF signal, the signal light guided through the LN waveguide 253. The MZI 213B2 for the Q component of the Y polarization incorporates an LN waveguide 253 and modulates, in accordance with an RF signal, the signal light guided through the LN waveguide 253.

[0036] Output waveguide 215A connects MZI 213B1 of the I component of the Y polarization and first multiplexing unit 215, and also connects MZI 213B2 of the Q component of the Y polarization and first multiplexing unit 215, and is, for example, a Si waveguide.

[0037] The first end face D10 of the thin-film LN chip 250 has a coupling portion 253A1 that optically couples the input end 253A of the LN waveguide 253 in the MZI 213B1 for the I component of the Y polarization to the input waveguide 212A. The first end face D10 has a coupling portion 253A1 that optically couples the input end 253A of the LN waveguide 253 in the MZI 213B2 for the Q component of the Y polarization to the input waveguide 212A.

[0038] The second end face D11 of the thin-film LN chip 250 has a coupling portion 253B1 that optically couples the output end 253B of the LN waveguide 253 in the MZI 213B1 for the I component of the Y polarization to the output waveguide 215A. The second end face D11 has a coupling portion 253B1 that optically couples the output end 253B of the LN waveguide 253 in the MZI 213B2 for the Q component of the Y polarization to the output waveguide 215A.

[0039] The first adjustment unit 214A shifts the phase of input light guided through the optical waveguide from the MZI 213B1 for the I component of Y polarization or the MZI 213B2 for the Q component of Y polarization in response to a DC signal. The second adjustment unit 214B shifts the phase of input light guided through the optical waveguide of the Y polarized IQ modulator 213B in response to a DC signal. The first multiplexing unit 215 multiplexes the modulated Y polarized I component signal light and the modulated Y polarized Q component signal light, and outputs the combined Y polarized IQ component signal light to the PR 217 via the VOA 216.

[0040] The second region 210B has GCs (Grating Couplers) 231A and 231B, connecting waveguides 232A and 232B, and second ECs 233A and 233B. The GC 231A is disposed on the surface of the second region 210B and is detachably connected to an optical fiber F1 that connects to the polarization controller 242, and is also connected to the connecting waveguide 232A. The connecting waveguide 232A is a Si waveguide that guides light between the GC 231A and the second EC 233A. The second EC 233A is disposed near the end face on the dicing line DL side of the second region 210B. The second EC 233A is optically coupled to the first EC 221A in the first region 210A, thereby optically connecting the connection waveguide 232A in the second region 210B and the input waveguide 211 in the first region 210A.

[0041] The GC231B is disposed on the surface of the second region 210B and is detachably connected to an optical fiber F2 that connects to a power meter 243 (described later), and is also connected to a connection waveguide 232B. The connection waveguide 232B is a Si waveguide that guides light between the GC231B and the second EC233B. The second EC233B is disposed near the end face of the second region 210B on the dicing line DL side. The second EC233B is optically coupled to the first EC221B in the first region 210A, thereby optically connecting the connection waveguide 232B in the second region 210B to the output waveguide 219 in the first region 210A.

[0042] The test equipment 240 includes a light source 241, a polarization controller 242, and a power meter 243. The light source 241 is, for example, a light source that emits test light corresponding to the transmitted light. The polarization controller 242 polarizes the test light from the light source 241 and outputs the polarized test light to an optical fiber F1. The polarization controller 242 controls the polarization of the test light to generate TM light or TM test light. The power meter 243 inputs reflected return light of the test light from the optical circuit 213 via an optical fiber F2 and measures the power of the reflected return light.

[0043] Next, the operation of the test system 200 will be described. The polarization controller 242 in the test device 240 polarizes the test light from the light source 241 and outputs the polarized test light to the optical fiber F1. The GC 231A in the second area 210B inputs the test light from the optical fiber F1 to the connecting waveguide 232A. The second EC 233A in the second area 210B outputs the test light from the connecting waveguide 232A to the first EC 221A in the first area 210A. Furthermore, the first area 210A inputs the test light from the first EC 221A and inputs the input test light to the input waveguide 211.

[0044] The input waveguide 211 inputs the test light to a branching section 212 in the optical circuit 213. The optical circuit 213 outputs reflected returning light of the test light to the output waveguide 219. The output waveguide 219 outputs the reflected returning light to the connection waveguide 232B through the first EC 221B. The connection waveguide 232B outputs the reflected returning light from the output waveguide 219 to the optical fiber F2 via the GC 231B. Furthermore, the power meter 243 measures the power of the reflected returning light of the test light from the optical fiber F2.

[0045] In the test system 200, optical fibers F1 and F2 are connected to GCs 231A and 231B from the wafer surface direction on which an optical circuit 213 such as a DP-IQ modulator of a thin-film LN chip 250 is mounted, and light is input, so that test light can be input to the optical circuit 213. As a result, testing in the wafer state becomes possible. In the test equipment 240, the optical circuit 213 in the first region 210A can be evaluated based on the measurement results of the reflected light from the optical circuit 213.

[0046] Moreover, the DP-IQ modulator of the thin-film LN chip 250 uses the LN waveguide 253 as the modulator body, which increases the change in refractive index when an RF signal electric field is applied, thereby reducing the drive voltage of the modulator, thereby reducing power consumption.

[0047] However, in the DP-IQ modulator using the thin-film LN chip 250, the Si input waveguide 212A and output waveguide 215A are coupled to the LN waveguide 253. The coupling efficiency is highly dependent on the alignment accuracy when the thin-film LN chip 250 is mounted on the first region 210A. Therefore, alignment errors during the manufacturing process can increase the loss of the modulator, and the cause of the increased loss in the modulator will also affect other elements such as the VOA 216, PR 217, and PBC 218. Furthermore, if a defect occurs due to increased loss in the modulator, it will be difficult to identify the cause, making quality control difficult.

[0048] Therefore, an embodiment of a test system employing an optical device that improves the accuracy of alignment when mounting the thin-film LN chip 250 on the first region 210A will be described below as Example 1.

[0049] Hereinafter, examples of optical devices and the like disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to each example. Furthermore, the examples shown below may be combined as appropriate within the scope of not causing any contradiction. [Example]

[0050] Fig. 1 is an explanatory diagram showing an example of a test system 1 according to Example 1. The test system 1 shown in Fig. 1 includes a wafer made of, for example, silicon, on which a plurality of optical chips 2 are formed, a test device 6, and four optical fibers F1 to F4.

[0051] A plurality of optical chips 2 are formed on the wafer in a lattice arrangement. The optical chip 2 has a first region 2A, which is a first substrate, a second region 2B, and a dicing line DL along which the first region 2A and the second region 2B can be cut. The first region 2A has an optical circuit 13, first ECs (Edge Couplers) 31A and 31B, and third ECs 32A and 32B.

[0052] The optical circuit 13 is, for example, a circuit such as a DP-IQ modulator in a digital coherent optical transceiver. The DP-IQ modulator is a modulator in which a thin-film LN chip 5 having a modulator body of an X-polarized IQ modulator 13A and a modulator body of a Y-polarized IQ modulator 13B is mounted in a first region 2A of a SiPh (silicon photonics). The thin-film LN chip 5 has a support substrate 51 and an LN waveguide 52 on the support substrate 51. The LN waveguide 52 is an arm waveguide that forms the modulator body of the X-polarized IQ modulator 13A and the modulator body of the Y-polarized IQ modulator 13B. The thin-film LN chip 5 is mounted in the first region 2A on a second substrate made of a different material from that of the first region 2A.

[0053] The DP-IQ modulator includes a first input waveguide 11, a branching section 12, an X-polarized IQ modulator 13A, a Y-polarized IQ modulator 13B, a VOA 14, and a PR (Polarization Rotator) 15. The DP-IQ modulator further includes a PBC (Polarization Beam Combiner) 16, a first output waveguide 17, and a monitor PD 18.

[0054] The first input waveguide 11 is, for example, a Si waveguide, which receives input light from an optical fiber F1 that connects to an optical switch 63 (described later). The branching unit 12 is, for example, an XY branching MMI (Multi-Mode Interferometer) that branches the input light from the first input waveguide 11 into input light of an X polarization component and input light of a Y polarization component.

[0055] X-polarized IQ modulator 13A modulates the X-polarized IQ component input light in accordance with the RF signal, and outputs the modulated X-polarized IQ component signal light to PBC 16 via VOA 14. Y-polarized IQ modulator 13B modulates the Y-polarized IQ component input light in accordance with the RF signal, and outputs the modulated Y-polarized IQ component signal light to PR 15 via VOA 14. PR 15 rotates the polarization of the Y-polarized IQ component signal light, and outputs the Y-polarized IQ component signal light after the polarization rotation to PBC 16. PBC 16 multiplexes the X-polarized IQ component signal light and the Y-polarized IQ component signal light after the polarization rotation, and outputs the multiplexed signal light to first output waveguide 17. The VOA is a variable attenuator that adjusts the intensity of the signal light from the X-polarized IQ modulator 13A or the Y-polarized IQ modulator 13B. The monitor PD monitors the level of the signal light after adjustment by the VOA .

[0056] The X-polarized IQ modulator 13A has an input waveguide 22A, a first branching unit 21, a second branching unit 22, an MZI 13A1 for the I component of the X-polarized wave and an MZI 13A2 for the Q component of the X-polarized wave, and an output waveguide 25A. The X-polarized IQ modulator 13A has a first adjusting unit 24A, a second adjusting unit 24B, and a first multiplexing unit 25. The input waveguide 22A is, for example, a Si waveguide, and connects the first input waveguide 11 and the MZI 13A1 for the I component of the X-polarized wave, and also connects the first input waveguide 11 and the MZI 13A2 for the Q component of the X-polarized wave. The first branching unit 21 is disposed on the input waveguide 22A between the branching unit 12 and the second branching unit 22, and branches and outputs the signal light from the branching unit 12 to each of the second branching units 22. The second branching unit 22 is disposed on the input waveguide 22A between the first branching unit 21 and the MZI 13A1 for the I component of the X polarization, and branches and outputs the signal light from the first branching unit 21 to the MZI 13A1 for the I component of the X polarization and the MZI 13A2 for the Q component of the X polarization.

[0057] MZI 13A1 for the I component of X polarization incorporates, for example, two LN waveguides 52, which are arm waveguides of the modulator body, and modulates the signal light guided through the LN waveguides 52 in accordance with an RF signal. MZI 13A2 for the Q component of X polarization incorporates, for example, two LN waveguides 52, and modulates the signal light guided through the LN waveguides 52 in accordance with an RF signal.

[0058] Output waveguide 25A connects MZI 13A1 of the I component of the X polarization to first multiplexing unit 25, and also connects MZI 13A2 of the Q component of the X polarization to first multiplexing unit 25, and is, for example, a Si waveguide.

[0059] The first end face D1 of the thin-film LN chip 5 has a coupling portion 53A that optically couples, for example, indirectly connects, between the input end 52A of the LN waveguide 52 in the MZI 13A1 for the I component of the X polarization and the input waveguide 22A. The first end face D1 has a coupling portion 53A that optically couples, for example, indirectly connects, between the input end 52A of the LN waveguide 52 in the MZI 13A2 for the Q component of the X polarization and the input waveguide 22A. Note that although the coupling portion 53A is shown as being configured by an adiabatic converter or directional coupler that provides an indirect connection, it may also be configured by butt coupling that provides a direct connection, and can be modified as appropriate.

[0060] The second end face D2 of the thin-film LN chip 5 has a coupling portion 53B that optically couples, for example, indirectly connects, between output end 52B of LN waveguide 52 in MZI 13A1 for the I component of the X polarization and output waveguide 25A. The second end face D2 has a coupling portion 53B that optically couples, for example, indirectly connects, between output end 52B of LN waveguide 52 in MZI 13A2 for the Q component of the X polarization and output waveguide 25A. Note that although the coupling portion 53B is illustrated as being configured by an adiabatic converter or directional coupler that provides an indirect connection, it may also be configured by butt coupling that provides a direct connection, and can be modified as appropriate.

[0061] The first adjustment unit 24A in the X-polarized IQ modulator 13A is a DC phase shifter that shifts the phase of input light guided through the optical waveguide from the MZI 13A1 for the X-polarized I component or the MZI 13A2 for the X-polarized Q component in response to a DC signal. The second adjustment unit 24B in the X-polarized IQ modulator 13A is a DC phase shifter that shifts the phase of the X-polarized I component signal light and the Q component signal light adjusted by the first adjustment unit 24A in response to a DC signal. The first multiplexing unit 25 multiplexes the modulated X-polarized I component signal light and the modulated X-polarized Q component signal light, and outputs the multiplexed X-polarized IQ component signal light to the PBC 16 via the VOA 14.

[0062] The Y-polarized IQ modulator 13B has an input waveguide 22A, a first branching unit 21, a second branching unit 22, an MZI 13B1 for the I component of the Y-polarized wave and an MZI 13B2 for the Q component of the Y-polarized wave, and an output waveguide 25A. The Y-polarized IQ modulator 13B has a first adjusting unit 24A, a second adjusting unit 24B, and a first multiplexing unit 25. The input waveguide 22A is, for example, a Si waveguide, and connects the first input waveguide 11 and the MZI 13B1 for the I component of the Y-polarized wave, and also connects the first input waveguide 11 and the MZI 13B2 for the Q component of the Y-polarized wave. The first branching unit 21 is disposed on the input waveguide 22A between the branching unit 12 and the second branching unit 22, and branches and outputs the signal light from the branching unit 12 to each of the second branching units 22. The second branching unit 22 is disposed on the input waveguide 22A between the first branching unit 21 and the MZI 13B1 for the I component of the Y polarization, and branches and outputs the signal light from the first branching unit 21 to the MZI 13B1 for the I component of the Y polarization and the MZI 13B2 for the Q component of the Y polarization.

[0063] MZI 13B1 for the I component of the Y polarization incorporates, for example, two LN waveguides 52, which are arm waveguides of the modulator body, and modulates the signal light guided through the LN waveguides 52 in accordance with an RF signal. MZI 13B2 for the Q component of the Y polarization incorporates, for example, two LN waveguides 52, and modulates the signal light guided through the LN waveguides 52 in accordance with an RF signal.

[0064] Output waveguide 25A connects MZI 13B1 of the I component of the Y polarization to first multiplexing unit 25, and also connects MZI 13B2 of the Q component of the Y polarization to first multiplexing unit 25, and is, for example, a Si waveguide.

[0065] The first end face D1 of the thin-film LN chip 5 has a coupling portion 53A that optically couples, for example, indirectly connects, between the input end 52A of the LN waveguide 52 in the MZI 13B1 for the I component of the Y polarization and the input waveguide 22A. The first end face D1 has a coupling portion 53A that optically couples, for example, indirectly connects, between the input end 52A of the LN waveguide 52 in the MZI 13A2 for the Q component of the Y polarization and the input waveguide 22A.

[0066] The second end face D2 of the thin-film LN chip 5 has a coupling portion 53B that optically couples, for example, indirectly connects, between output end 52B of LN waveguide 52 in MZI 13A1 for the I component of the Y polarization and output waveguide 25A. The second end face D2 has a coupling portion 53B that optically couples, for example, indirectly connects, between output end 52B of LN waveguide 52 in MZI 13A2 for the Q component of the Y polarization and output waveguide 25A.

[0067] A first adjustment unit 24A in Y-polarized IQ modulator 13B shifts the phase of input light guided through the optical waveguide from MZI 13B1 for the I component of Y-polarized wave or MZI 13B2 for the Q component of Y-polarized wave in response to a DC signal. A second adjustment unit 24B in Y-polarized IQ modulator 13B shifts the phases of the I component and Q component signal lights of Y-polarized wave adjusted by first adjustment unit 24A in response to a DC signal. A first multiplexing unit 25 multiplexes the modulated I component signal light of Y-polarized wave and the modulated Q component signal light of Y-polarized wave, and outputs the combined I and Q component signal lights of Y-polarized wave to PR 15 via VOA 14.

[0068] The thin-film LN chip 5 also has a loopback waveguide 54 that folds back the test light. The first region 2A has a second input waveguide 33A of the second waveguide 33, a second output waveguide 33B of the second waveguide 33, and third ECs 32A and 32B. The loopback waveguide 54 is, for example, an LN waveguide that optically couples its input end to the second input waveguide 33A and its output end to the second output waveguide 33B. The second input waveguide 33A is, for example, a Si waveguide that is optically coupled to the input end of the loopback waveguide 54. The second output waveguide 33B is, for example, a Si waveguide that is optically coupled to the output end of the loopback waveguide 54. The loopback waveguide 54 receives the test light from the second input waveguide 33A, and outputs the received test light as reflected back light to the second output waveguide 33B.

[0069] The second end face D2 of the thin-film LN chip 5 has a coupling portion 53B that optically couples, for example, indirectly connects, between the input end of the loopback waveguide 54 and the second input waveguide 33A. The second end face D2 has a coupling portion 53B that optically couples, for example, indirectly connects, between the output end of the loopback waveguide 54 and the second output waveguide 33B. Note that, although the coupling portion 53B is exemplified as being configured by an adiabatic converter or directional coupler that provides an indirect connection, it may also be configured by a butt coupling that provides a direct connection, and can be modified as appropriate.

[0070] The third EC 32A is an EC that is arranged on the end face of the first region 2A near the dicing line DL and is connected to the second input waveguide 33A. The third EC 32B is an EC that is arranged on the end face of the first region 2A near the dicing line DL and is connected to the second output waveguide 33B.

[0071] The second region 2B includes first GCs (Grating Couplers) 41A and 41B, first connecting waveguides 44A and 44B, second ECs 45A and 45B, second GCs 43A and 43B, second connecting waveguides 50A and 50B, and fourth ECs 49A and 49B. The first GC 41A is a GC disposed on the surface of the second region 2B, detachably connected to an optical fiber F1 connected to the optical switch 63, and connected to the first connecting waveguide 44A. The optical fiber F1 is an optical fiber that inputs test light to the optical circuit 13 in the thin-film LN chip 5. The first connecting waveguide 44A is a Si waveguide that guides light between the first GC 41A and the second EC 45A. The second EC 45A is an EC disposed near the end face of the second region 2B on the dicing line DL side. The second EC 45A is optically coupled to the first EC 31A in the first region 2A, thereby optically connecting the first connecting waveguide 44A in the second region 2B and the first input waveguide 11 in the first region 2A.

[0072] The first GC 41B is a GC disposed on the surface of the second region 2B, detachably connected to an optical fiber F2 connected to the power meter 64, and connected to the first connection waveguide 44B. The optical fiber F2 is an optical fiber that outputs reflected return light from the optical circuit 13 in the thin-film LN chip 5. The first connection waveguide 44B is a Si waveguide that guides light between the first GC 41B and the second EC 45B. The second EC 45B is an EC disposed near the end face of the second region 2B on the dicing line DL side. The second EC 45B is optically coupled to the first EC 31B in the first region 2A, thereby optically connecting the first connection waveguide 44B in the second region 2B to the first output waveguide 17 in the first region 2A.

[0073] The second GC 43A is a GC disposed on the surface of the second region 2B, detachably connected to an optical fiber F3 connected to the optical switch 63, and connected to the second connection waveguide 50A. The optical fiber F3 is an optical fiber that inputs test light to the loopback waveguide 54 in the thin-film LN chip 5. The second connection waveguide 50A is a Si waveguide that guides light between the second GC 43A and the fourth EC 49A. The fourth EC 49A is an EC disposed near the end face on the dicing line DL side of the second region 2B. The fourth EC 49A is optically coupled to the third EC 32A in the first region 2A, thereby optically connecting the second connection waveguide 50A in the second region 2B to the second input waveguide 33A in the first region 2A.

[0074] The second GC 43B is a GC disposed on the surface of the second region 2B, detachably connected to the optical fiber F4, and connected to the second connection waveguide 50B. The optical fiber F4 is an optical fiber that outputs reflected return light from the loopback waveguide 54 in the thin-film LN chip 5. The second connection waveguide 50B is a Si waveguide that guides light between the second GC 43B and the fourth EC 49B. The fourth EC 49B is an EC disposed near the end face of the second region 2B on the dicing line DL side. The fourth EC 49B is optically coupled to the third EC 32B in the first region 2A, thereby optically connecting the second connection waveguide 50B in the second region 2B and the second output waveguide 33B in the first region 2A.

[0075] The test equipment 6 includes a light source 61, a polarization controller 62, an optical switch 63, and a power meter 64. The light source 61 is, for example, a light source that emits test light corresponding to the transmitted light. The polarization controller 62 polarizes the test light from the light source 61 and outputs the polarized test light to either the optical fiber F1 or the optical fiber F3. The polarization controller 62 controls the polarization of the test light to generate either the TM light or the TM light test light. The optical switch 63 switches the polarization-controlled test light from the polarization controller 62 to either the optical fiber F1 or the optical fiber F3. The power meter 64 receives reflected return light from the optical circuit 13 relative to the test light via the optical fiber F2 and measures the power of the reflected return light, and also receives reflected return light from the loopback waveguide 54 relative to the test light via the optical fiber F4 and measures the power of the reflected return light.

[0076] Next, the operation of the test system 1 will be described. First, the test device 6 starts a first evaluation test to evaluate whether the thin-film LN chip 5 is correctly positioned and mounted in the first area 2A. The optical switch 63 switches between the polarization controller 62 and the optical fiber F3. The polarization controller 62 polarizes the test light from the light source 61 and outputs the polarized test light to the optical fiber F3 via the optical switch 63. The second GC 43A inputs the test light from the optical fiber F3 to the second connecting waveguide 50A. The fourth EC 49A outputs the test light from the second connecting waveguide 50A to the third EC 32A in the first area 2A. Furthermore, the first area 2A inputs the test light from the third EC 32A and inputs the input test light to the second input waveguide 33A. The loopback waveguide 54 of the thin-film LN chip 5 outputs the test light from the second input waveguide 33A to the second output waveguide 33B as reflected return light.

[0077] The third EC 32B outputs the reflected returning light from the second output waveguide 33B to the fourth EC 49B. The fourth EC 49B outputs the reflected returning light to the second connecting waveguide 50B. The second connecting waveguide 50B outputs the reflected returning light from the loopback waveguide 54 to the optical fiber F4 via the second GC 43B. Furthermore, the power meter 64 measures the power of the reflected returning light from the optical fiber F4. As a result, the test device 6 calculates the amount of loss from the measurement result of the power of the reflected returning light from the optical fiber F4, and if the calculated amount of loss is within a first level, it determines that the thin-film LN chip 5 is correctly positioned and mounted in the first area 2A. The state in which the thin-film LN chip 5 is properly positioned and mounted means that the input end 52A of each LN waveguide 52 for each MZI of the thin-film LN chip 5 is optically coupled to the input waveguide 22A, and the output end 52B of each LN waveguide 52 for each MZI is optically coupled to the output waveguide 25A.

[0078] Next, the test equipment 6 starts a second evaluation test to evaluate the optical circuit 13 of the thin-film LN chip 5. The optical switch 63 switches between the polarization controller 62 and the optical fiber F1. The polarization controller 62 polarizes the test light from the light source 61 and outputs the polarized test light to the optical fiber F1 via the optical switch 63. The first GC 41A inputs the test light from the optical fiber F1 to the first connecting waveguide 44A. The second EC 45A outputs the test light from the first connecting waveguide 44A to the first EC 31A in the first region 2A. Furthermore, the first region 2A inputs the test light from the first EC 31A and inputs the input test light to the first input waveguide 11.

[0079] The first input waveguide 11 inputs the test light to the branching section 12 in the optical circuit 13. The optical circuit 13 outputs reflected return light of the test light to the first output waveguide 17. The first output waveguide 17 outputs the reflected return light to the first connecting waveguide 44B through the first EC 31B. The first connecting waveguide 44B outputs the reflected return light from the first output waveguide 17 to the optical fiber F2 via the first GC 41B. Furthermore, the power meter 64 measures the power of the reflected return light from the optical fiber F2. As a result, if the measurement result of the reflected return light from the optical circuit 13 is equal to or higher than the second level, the test equipment 6 determines that the optical circuit 13 is normal.

[0080] The test device 6 executes a first evaluation test to measure and evaluate the power of reflected return light from the loopback waveguide 54 for each first region 2A in the optical chips 2 arranged in rows on the wafer. Then, the test device 6 executes a second evaluation test to measure and evaluate the power of reflected return light from the optical circuit 13 in the first region 2A1. Then, when the test device 6 has completed the first and second evaluation tests for all the optical chips 2 arranged in rows on the wafer, it dices all the optical chips 2 arranged in rows along the dicing lines DL.

[0081] The test device 6 then starts the first evaluation test and the second evaluation test for each optical chip 2 in the next row, and continues until the first evaluation test and the second evaluation test for all optical chips 2 on the wafer are completed. Then, by dicing the wafer along the dicing lines DL for each optical chip 2, the first region 2A in the optical chip 2 is divided, and the first region 2A in which the first ECs 31A and 31B are exposed can be obtained. As a result, the optical circuit 13 in the first region 2A can be connected to other optical devices such as optical fibers used for operation through the first ECs 31A and 31B.

[0082] The test equipment 6 of Example 1 calculates the loss amount from the measurement results of the power of the reflected light from the optical fiber F4. If the calculated loss amount is within a first level, it is determined that the thin-film LN chip 5 is correctly positioned and mounted in the first area 2A. In the DP-IQ modulator using the thin-film LN chip 5, the thin-film LN chip 5 is correctly mounted on the first area 2A with the Si input waveguide 22A and output waveguide 25A properly coupled to the LN waveguide 52. As a result, the loss of the modulator due to alignment errors during the manufacturing process, as pointed out in the comparative example, is suppressed. Therefore, there is no impact on other elements such as the VOA 14, PR 15, and PBC 16. Furthermore, stable quality control of the modulator can be achieved.

[0083] In the test system 1, optical fibers F1 and F2 are connected to the first GCs 41A and 41B from the wafer surface direction on which an optical circuit 13 such as a DP-IQ modulator of a thin-film LN chip 5 is mounted, and light is input to input test light into the optical circuit 13, making it possible to perform testing in the wafer state. In the test equipment 6, the optical circuit 13 in the first region 2A can be evaluated based on the measurement results of the reflected light from the optical circuit 13.

[0084] For ease of explanation, an example is shown in which four optical fibers F1 to F4 are used, but the number of optical fibers can be reduced to two by using an optical circulator to share the same optical fiber that inputs the test light and outputs the reflected return light from the test light.

[0085] In the thin-film LN chip 5 of Example 1, the input / output ends of the loop-back waveguide 54 are exposed from the second end face D2. However, the present invention is not limited to this, and the input / output ends of the loop-back waveguide 54 may be exposed from another end face such as the first end face D1, without being limited to the second end face D2 of the thin-film LN chip 5, and can be modified as appropriate.

[0086] The thin-film LN chip 5 has been exemplified as having a single loop-back waveguide 54, but the present invention is not limited to this, and an embodiment thereof will be described below as Example 2. [Example]

[0087] 2 is an explanatory diagram showing an example of a test system 1A of Example 2. Note that the same components as those in the test system 1 of Example 1 are given the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The test system 1 of Example 1 differs from the test system 1A of Example 2 in that the latter has multiple loopback waveguides 54 in the thin-film LN chip 5.

[0088] The thin-film LN chip 5 has a first loopback waveguide 54A exposed at the second end face D2 and a second loopback waveguide 54B exposed at the first end face D1. The first region 2A has, in addition to the second input waveguide 33A and the second output waveguide 33B which are second waveguides, the third input waveguide 33C and the third output waveguide 33D which are third waveguides, and fifth ECs 32C and 32D.

[0089] The first loopback waveguide 54A is, for example, an LN waveguide, which optically couples its input end to the second input waveguide 33A and its output end to the second output waveguide 33B. The second input waveguide 33A is, for example, a Si waveguide, which is optically coupled to the input end of the first loopback waveguide 54A. The second output waveguide 33B is, for example, a Si waveguide, which is optically coupled to the output end of the first loopback waveguide 54A. The first loopback waveguide 54A receives test light from the second input waveguide 33A and outputs the received test light as reflected back light to the second output waveguide 33B.

[0090] The second end face D2 of the thin-film LN chip 5 has a coupling portion 53B that optically couples, for example, indirectly connects, between the input end of the first loopback waveguide 54A and the second input waveguide 33A. The second end face D2 has a coupling portion 53B that optically couples, for example, indirectly connects, between the output end of the first loopback waveguide 54A and the second output waveguide 33B. Note that, although the coupling portion 53B is exemplified as being configured by an adiabatic converter or directional coupler that provides an indirect connection, it may also be configured by a butt coupling that provides a direct connection, and can be modified as appropriate.

[0091] The second loopback waveguide 54B is, for example, an LN waveguide, and optically couples its input end to the third input waveguide 33C and its output end to the third output waveguide 33D. The third input waveguide 33C is, for example, a Si waveguide, and optically couples it to the input end of the second loopback waveguide 54B. The third output waveguide 33D is, for example, a Si waveguide, and optically couples it to the output end of the second loopback waveguide 54B. The second loopback waveguide 54B receives test light from the third input waveguide 33C and outputs the received test light as reflected back light to the third output waveguide 33D.

[0092] The first end face D1 of the thin-film LN chip 5 has a coupling portion 53A that optically couples, for example, indirectly connects, between the input end of the second loopback waveguide 54B and the third input waveguide 33C. The first end face D1 has a coupling portion 53A that optically couples, for example, indirectly connects, between the output end of the second loopback waveguide 54B and the third output waveguide 33D. Note that, although the coupling portion 53A is exemplified as being configured by an adiabatic converter or directional coupler that provides an indirect connection, it may also be configured by a butt coupling that provides a direct connection, and can be modified as appropriate.

[0093] The fifth EC 32C is an EC that is arranged on the end face near the dicing line DL in the first region 2A and is connected to the third input waveguide 33C. The fifth EC 32C is an EC that is arranged on the end face near the dicing line DL in the first region 2A and is connected to the third output waveguide 33D.

[0094] The second region 2B includes third GCs 43C and 43D, third connection waveguides 50C and 50D, and sixth ECs 49C and 49D. The third GC 43C is a GC disposed on the surface of the second region 2B and detachably connected to an optical fiber F5 connected to the optical switch 63A, and connected to the third connection waveguide 50C. The third connection waveguide 50C is a Si waveguide through which light is guided between the third GC 43C and the sixth EC 49C. The sixth EC 49C is an EC disposed near the end face of the second region 2B on the dicing line DL side. The sixth EC 49C is optically coupled to the fifth EC 32C in the first region 2A1, thereby optically connecting the third connection waveguide 50C in the second region 2B to the third input waveguide 33C in the first region 2A1.

[0095] The third GC 43D is a GC disposed on the surface of the second region 2B, detachably connected to an optical fiber F6 connected to the first power meter 64A, and connected to the third connection waveguide 50D. The third connection waveguide 50D is a Si waveguide through which light is guided between the third GC 43D and the sixth EC 49D. The sixth EC 49D is an EC disposed near the end face of the second region 2B on the dicing line DL side. The sixth EC 49D optically couples with the fifth EC 32D in the first region 2A1, thereby optically connecting the third connection waveguide 50D in the second region 2B to the third output waveguide 33D in the first region 2A1.

[0096] The test equipment 6 has a first power meter 64A and a second power meter 64B instead of the power meter 64. The optical switch 63A is a switch that selectively outputs the polarization-controlled test light from the polarization controller 62 to the optical fiber F1, the optical fiber F3, or the optical fiber F5. The optical fiber F1 is an optical fiber for inputting the test light to the optical circuit 13. The optical fiber F3 is an optical fiber for inputting the test light to the first loopback waveguide 54A. The optical fiber F5 is an optical fiber for inputting the test light to the second loopback waveguide 54B.

[0097] The first power meter 64A receives the reflected return light of the test light from the second loopback waveguide 54B via optical fiber F6 and measures the power of the reflected return light. The second power meter 64B receives the reflected return light of the test light from the optical circuit 13 via optical fiber F2 and measures the power of the reflected return light. The second power meter 64B also receives the reflected return light of the test light from the first loopback waveguide 54A via optical fiber F4 and measures the power of the reflected return light.

[0098] Next, the operation of the test system 1A will be described. First, the test device 6 starts a first evaluation test to evaluate whether the thin-film LN chip 5 is correctly positioned and mounted in the first area 2A1. First, the optical switch 63A switches between the polarization controller 62 and the optical fiber F3. The polarization controller 62 polarizes the test light from the light source 61 and outputs the polarized test light to the optical fiber F3 via the optical switch 63A. The second GC 43A inputs the test light from the optical fiber F3 to the second connecting waveguide 50A. The fourth EC 49A outputs the test light from the second connecting waveguide 50A to the third EC 32A in the first area 2A. Furthermore, the first area 2A1 inputs the test light from the third EC 32A and inputs the input test light to the second input waveguide 33A. The second input waveguide 33A outputs the test light as reflected return light via the first loopback waveguide 54A of the thin-film LN chip 5 to the second output waveguide 33B.

[0099] The third EC 32B outputs the reflected returning light from the second output waveguide 33B to the fourth EC 49B. The fourth EC 49B outputs the reflected returning light to the second connecting waveguide 50B. The second connecting waveguide 50B outputs the reflected returning light from the first loopback waveguide 54A to the optical fiber F4 via the second GC 43B. Furthermore, the second power meter 64B measures the power of the reflected returning light with respect to the test light from the optical fiber F4. As a result, the test device 6 obtains a measurement result of the reflected returning light from the first loopback waveguide 54A of the thin-film LN chip 5.

[0100] The optical switch 63A switches between the polarization controller 62 and the optical fiber F5. The polarization controller 62 polarizes the test light from the light source 61 and outputs the polarized test light to the optical fiber F5 via the optical switch 63A. The third GC 43C inputs the test light from the optical fiber F5 to the third connecting waveguide 50C. The sixth EC 49C outputs the test light from the third connecting waveguide 50C to the fifth EC 32C in the first area 2A. Furthermore, the first area 2A inputs the test light from the fifth EC 32C and inputs the input test light to the third input waveguide 33C. The third input waveguide 33C outputs the test light as reflected back light to the third output waveguide 33D via the second loopback waveguide 54B of the thin-film LN chip 5.

[0101] The fifth EC 32D outputs the reflected returning light from the third output waveguide 33D to the sixth EC 49D. The sixth EC 49D outputs the reflected returning light to the third connecting waveguide 50D. The third connecting waveguide 50D outputs the reflected returning light from the second loopback waveguide 54B to the optical fiber F6 via the third GC 43D. Furthermore, the first power meter 64A measures the power of the reflected returning light relative to the test light from the optical fiber F6. As a result, the test device 6 obtains a measurement result of the reflected returning light from the second loopback waveguide 54B of the thin-film LN chip 5.

[0102] The test device 6 calculates the amount of loss from the measurement results of the power of the reflected return light from the optical fibers F4 and F6, and if the calculated amount of loss is within a first level, determines that the thin-film LN chip 5 is correctly positioned and mounted in the first area 2A1. The correctly positioned and mounted state means that the input end 52A of each LN waveguide 52 for each MZI of the thin-film LN chip 5 is optically coupled to the input waveguide 22A, and that the output end 52B of each LN waveguide 52 for each MZI is optically coupled to the output waveguide 25A. After executing the first evaluation test, the test device 6 then starts a second evaluation test to evaluate the optical circuit 13 of the thin-film LN chip 5.

[0103] The test equipment 6 of Example 2 calculates the loss amount from the measurement results of the power of the reflected light from the optical fibers F4 and F6. If the calculated loss amount is within a first level, it is determined with high accuracy that the thin-film LN chip 5 is correctly positioned and mounted in the first area 2A. In the DP-IQ modulator using the thin-film LN chip 5, the thin-film LN chip 5 is correctly mounted on the first area 2A1 with the Si input waveguide 22A and output waveguide 25A properly coupled to the LN waveguide 52. As a result, the loss of the modulator due to alignment errors during the manufacturing process, as pointed out in the comparative example, is suppressed. Therefore, there is no impact on other elements such as the VOA 14, PR 15, and PBC 16. Furthermore, stable quality control of the modulator can be achieved.

[0104] In the test system 1A, optical fibers F1 and F2 are connected to the first GCs 41A and 41B from the wafer surface direction on which an optical circuit 13 such as a DP-IQ modulator of a thin-film LN chip 5 is mounted, and light is input to input test light into the optical circuit 13, making it possible to perform testing in the wafer state. In the test equipment 6, the optical circuit 13 in the first area 2A1 can be evaluated based on the measurement results of the reflected light from the optical circuit 13.

[0105] In Example 2, the second region 2B is illustrated as including the second ECs 45A and 45B, the fourth ECs 49A and 49B, the sixth ECs 49C and 49D, the first GCs 41A and 41B, the second GCs 43A and 43B, and the third GCs 43C and 43D. However, this is not limiting. For example, the first GCs 41A and 41B, the second GCs 43A and 43B, and the third GCs 43C and 43D may be arranged in a first region 2A1 adjacent to the first region 2A1 across the dicing line DL. This embodiment will be described below as Example 3. [Example]

[0106] 3 is an explanatory diagram showing an example of a test system 1B of Example 3. Note that the same components as those in the test system 1A of Example 2 are given the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The test system 1A of Example 2 differs from the test system 1B of Example 3 in that the first GCs 41A and 41B, the second GCs 43A and 43B, and the third GCs 43C and 43D are arranged in adjacent first areas 2A2.

[0107] The first ECs 31A and 31B, the third ECs 32A and 32B, and the fifth ECs 32C and 32D are arranged on one end surface of the first region 2A2. Furthermore, the second ECs 45A and 45B, the fourth ECs 49A and 49B, and the sixth ECs 49C and 49D are arranged on the other end surface of the first region 2A2. The other end surface of the first region 2A2 is the end surface opposite to the one end surface of the first region 2A2.

[0108] The first region 2A2 has first GCs 41A and 41B, second GCs 43A and 43B, third GCs 43C and 43D, first connecting waveguides 44A and 44B, second connecting waveguides 50A and 50B, and third connecting waveguides 50C and 50D.

[0109] Each first region 2A2 in Example 3 includes first GCs 41A and 41B, second GCs 43A and 43B, and third GCs 43C and 43D. The first region 2A2 includes first connecting waveguides 44A and 44B, second connecting waveguides 50A and 50B, and third connecting waveguides 50C and 50D. First ECs 31A and 31B, third ECs 32A and 32B, and fifth ECs 32C and 32D are arranged on one end surface of the first region 2A2. Furthermore, second ECs 45A and 45B, fourth ECs 49A and 49B, and sixth ECs 49C and 49D are arranged on the other end surface of the first region 2A2. As a result, the second region 2B is unnecessary, allowing for an increased number of first regions 2A to be obtained from a wafer.

[0110] FIG. 4 is an explanatory diagram illustrating an example of an optical transceiver 70 according to the present embodiment. The optical transceiver 70 shown in FIG. 4 includes a DSP (Digital Signal Processor) 71 and an optical transmitter / receiver 72. The optical transmitter / receiver 72 includes an optical transmitter 72A that transmits an optical signal and an optical receiver 72B that receives the optical signal. The optical transmitter 72A includes an optical modulator element 72A1 that modulates light in response to an electrical signal from the DSP 71. For example, the optical transmitter 72A is the first area 2A after the second area 2B of a digital coherent transmitter or the like is disconnected. The optical receiver 72B includes an optical receiver element 72B1 that converts the optical signal into an electrical signal. For example, the optical receiver 72B is the first area 2A after the second area 2B of a digital coherent receiver or the like is disconnected. The DSP 71 digitally converts each electrical signal input from the optical receiver 72B.

[0111] For convenience of explanation, the optical fibers F1 and F2 are fixed on a wafer prober, and the wafer mounted on the wafer prober moves up, down, left, and right relative to the optical fibers F1 and F2. However, the optical fibers F1 and F2 may also move up, down, left, and right on the wafer, and this can be modified as appropriate.

[0112] Furthermore, the first area 2A is exemplified by a digital coherent transceiver, but is not limited to a digital coherent system, and may be an optical receiver or optical transmitter of another system, and can be changed as appropriate.

[0113] Furthermore, the components of each unit shown in the figure do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0114] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit), MCU (Micro Controller Unit), or DSP). Needless to say, the various processing functions may be executed in whole or in part on a program analyzed and executed by a CPU (or a microcomputer such as an MPU or MCU), or on hardware using wired logic. [Explanation of symbols]

[0115] 2 Optical chip 2A First Area 2B Second Area 5 Thin-film LN chip 11 first input waveguide 17 First output waveguide 13 Optical circuit 13A X-polarized IQ modulator 13B Y-polarized IQ modulator 31A, 31B First EC 32A, 32B Third EC 33A Second input waveguide 33B second output waveguide 33C Third input waveguide 33D Third output waveguide 52 LN waveguide 52A input terminal 52B output terminal 54 Loopback Waveguide 54A First Loopback Waveguide 54B Second Loopback Waveguide

Claims

1. 1. An optical device having a first substrate and a second substrate mounted on the first substrate and made of a different material than the first substrate, The first substrate comprises: a first waveguide; and a second waveguide; and a first edge coupler disposed on an end face of the first substrate and configured to input and output light to and from the first waveguide; a second edge coupler disposed on the end face for inputting and outputting light to and from the second waveguide; The second substrate comprises: a third waveguide; and an optical circuit optically connected to the third waveguide; a loopback waveguide that returns and outputs input light, The optical device is an optical device, wherein the first waveguide and the third waveguide are optically coupled, and the loopback waveguide and the second waveguide are optically coupled;

2. 2. The optical device according to claim 1, wherein the first waveguide, the second waveguide, the third waveguide, and the loopback waveguide are made of different materials.

3. The first waveguide comprises: a first input waveguide and a first output waveguide; The second waveguide comprises: a second input waveguide and a second output waveguide; The third waveguide comprises: an input end disposed on a first end face of the second substrate, connecting the first input waveguide and the optical circuit; and an output end disposed on a second end face of the second substrate, connecting the first output waveguide and the optical circuit; 2. The optical device according to claim 1, wherein:

4. The first waveguide comprises: a first input waveguide and a first output waveguide; The second waveguide comprises: a second input waveguide, a second output waveguide, a third input waveguide, and a third output waveguide; The loopback waveguide is a first loopback waveguide having a first input end and a first output end disposed on a second end face of the second substrate, the first input end connecting to the second input waveguide and the first output end connecting to the second output waveguide; a second input end and a second output end are arranged on a first end face of the second substrate, and a second loopback waveguide connects the second input end to the third input waveguide and the second output end to the third output waveguide; The optical device is 2. The optical device according to claim 1, wherein the first input waveguide and the third waveguide are optically coupled, the first output waveguide and the third waveguide are optically coupled, an input end of the first loopback waveguide and the second input waveguide are optically coupled, an output end of the first loopback waveguide and the second output waveguide are optically coupled, an input end of the second loopback waveguide and the third input waveguide are optically coupled, and an output end of the second loopback waveguide and the third output waveguide are optically coupled.

5. The first substrate comprises: a first grating coupler that is optically connected to a first edge coupler provided on a first substrate in another adjacent optical device and that is connected to a first optical fiber; a second grating coupler that is optically connected to a second edge coupler provided on a first substrate in another adjacent optical device and that is connected to a second optical fiber; 2. The optical device according to claim 1, wherein:

6. An optical transmitter incorporating an optical device having an optical circuit including an optical modulation unit that optically modulates light using a transmission signal and transmits transmission light, The optical device is a first substrate and a second substrate mounted on the first substrate and made of a different material from the first substrate; The first substrate comprises: a first waveguide; and a second waveguide; and a first edge coupler disposed on an end face of the first substrate and configured to input and output light to and from the first waveguide; a second edge coupler disposed on the end face for inputting and outputting light to and from the second waveguide; The second substrate comprises: a third waveguide; and an optical circuit optically connected to the third waveguide; a loopback waveguide that returns and outputs input light, The optical device is a loopback circuit that optically couples the first waveguide and the third waveguide and optically couples the loopback waveguide and the second waveguide; An optical transmitter comprising:

7. An optical receiver incorporating an optical device having an optical circuit including an optical receiving unit that receives a reception signal from received light using light, The optical device is a first substrate and a second substrate mounted on the first substrate and made of a different material from the first substrate; The first substrate comprises: a first waveguide; and a second waveguide; and a first edge coupler disposed on an end face of the first substrate and configured to input and output light to and from the first waveguide; a second edge coupler disposed on the end face for inputting and outputting light to and from the second waveguide; The second substrate comprises: a third waveguide; and an optical circuit optically connected to the third waveguide; a loopback waveguide that returns and outputs input light, The optical device is an optical receiver comprising: a loopback circuit that optically couples the first waveguide and the third waveguide, and optically couples the loopback waveguide and the second waveguide;

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