A polarization crosstalk test system for polarizer straight waveguide pigtail

Abstract

The present invention discloses a polarization crosstalk test system for a polarizer straight waveguide pigtail, comprising: a light source, a beam splitter, a polarizer, and a collection device, wherein the light source is connected to the input end of the beam splitter through a polarization-maintaining optical fiber, the beam splitter is provided with a monitoring port and one or more test ports, the monitoring port is connected to the monitoring input end of the collection device through a polarization-maintaining optical fiber, each of the test ports is connected to an optical path input end of the polarizer through a polarization-maintaining optical fiber, each optical path output end of the polarizer is connected to the input end of a device to be tested through a polarization-maintaining optical fiber, and each output end of the device to be tested is respectively connected to the test input end of the collection device. The present invention adopts a lithium niobate array straight waveguide working in a single polarization as a polarizer, thus breaking through the problems of low test accuracy, low efficiency and high cost, and adopts a multi-channel collection instrument, which can realize the requirement of simultaneously collecting polarization crosstalk and insertion loss of multi-channel pigtails.

Description

Technical Field

[0001] The invention relates to the technical field related to optical fibers, in particular to a polarization crosstalk test system for a polarizer straight waveguide pigtail. Background Art

[0002] In the fiber-optic current transformer, the photoelectric performance of the key component, lithium niobate straight waveguide phase modulator, has a great influence on the performance of the entire sensor. Titanium-diffused lithium niobate straight waveguide phase modulator has dual polarization characteristics, can simultaneously transmit transverse electric wave (TE) and transverse magnetic wave (TM) mode, and can simultaneously modulate the phase of these two modes. This feature makes it very popular in the field of fiber-optic sensing, especially in the development of fiber-optic current sensors. Figure 1 As shown, a superluminescent diode (SLD) light source 1', a light receiving component 2', a preamplifier 3', an A / D converter 4', a signal processor 5', a D / A converter 6', a circulator 7', a polarizer 8', a straight waveguide phase modulator 9', a polarization-maintaining fiber delay 10', a λ / 4 wave plate 11', an optical fiber coil 12', a reflector 13', and a current-cutting conductor 14' form a fiber-optic current transformer system. In this system, the fiber-optic current sensor optical path formed by the straight waveguide phase modulator 8' has smaller temperature error and vibration error, and better time reciprocity.

[0003] With the application of current transformers, the temperature drift of measurement accuracy is still a technical bottleneck restricting high-performance current transformers. Titanium-diffused lithium niobate straight waveguide is one of the key components of the system, such as Figure 2 The figure shows a schematic diagram of a straight waveguide structure, including a titanium diffused lithium niobate substrate 21', a waveguide 22', and an electrode 23'. Studies have found that under full temperature conditions, changes in pigtail polarization crosstalk are the main cause of system polarization errors. The low-temperature pigtail polarization crosstalk degradation of the straight waveguide directly leads to low-temperature degradation of the ratio difference. In addition, system temperature noise is also an important factor affecting the high performance of the current transformer. Studies have found that the change in the insertion loss of the straight waveguide is directly related to the noise fluctuation. Therefore, the full-temperature pigtail polarization crosstalk and insertion loss changes are two very critical indicators for evaluating system polarization errors and temperature noise.

[0004] The existing testing methods have the following defects:

[0005] Since the titanium diffused straight waveguide is a dual-polarization working mode, the light of the input waveguide needs to be polarized before the polarization crosstalk of the TE / TM pigtail can be tested respectively. At present, the polarization part uses a fiber-optic polarizer, and the polarization crosstalk is about -20dB, while the polarization crosstalk of the straight waveguide pigtail is better than -27dB, and the highest is even -34dB. Obviously, the fiber-optic polarizer cannot meet the test accuracy requirements. In addition, there are polarization control components that are used for polarization. Although the accuracy can meet the requirements, due to the spatial optical path, the stability is poor, and the direction of the polarizer needs to be calibrated frequently. The operation is cumbersome and the changes in the polarization crosstalk of the pigtail cannot be monitored all the time. In addition, the polarization control component has large loss, high cost, and low test efficiency, which is not conducive to achieving the requirements of batch high-efficiency testing. Summary of the invention

[0006] Based on this, it is necessary to provide a polarization crosstalk test system for a polarizer straight waveguide pigtail to address the technical problems that the existing waveguide testing method has poor stability, cumbersome operation, large loss and high cost of polarization control components, low testing efficiency, and is not conducive to achieving the requirements of batch high-efficiency testing.

[0007] The invention provides a polarization crosstalk test system for a polarizer straight waveguide pigtail, comprising: a light source, a beam splitter, a polarizer, and a collection device, wherein the light source is connected to an input end of the beam splitter through a polarization-maintaining optical fiber, the beam splitter is provided with a monitoring port and one or more test ports, the monitoring port is connected to the monitoring input end of the collection device through the polarization-maintaining optical fiber, each of the test ports is connected to an optical path input end of the polarizer through the polarization-maintaining optical fiber, each optical path output end of the polarizer is connected to an input end of a device to be tested through the polarization-maintaining optical fiber, and each output end of the device to be tested is respectively connected to the test input end of the collection device.

[0008] Furthermore, the polarizer is an array waveguide chip.

[0009] Furthermore, the polarizer includes: an X-cut Y-transmitting lithium niobate material chip substrate, on which one or more groups of polarizer straight waveguides are arranged, an isolation groove is cut between each group of polarizer straight waveguides, the input end of each group of polarizer straight waveguides is the optical path input end, and the output end of each group of polarizer straight waveguides is the optical path output end.

[0010] Furthermore, the isolation groove is coated with a light absorbing material.

[0011] Furthermore, the input end and the output end of the polarizer straight waveguide are coupled by polarization-maintaining optical fiber, and the polarizer straight waveguide is an annealed proton exchange polarizer straight waveguide.

[0012] Furthermore, it also includes a temperature-variable box for accommodating the device under test, and each optical path output end of the polarizer is inserted into the temperature-variable box through a polarization-maintaining optical fiber and connected to an input end of the device under test, and each output end of the device under test passes through the temperature-variable box and is connected to the test input end of the acquisition device.

[0013] Furthermore, it also includes a temperature sensor for measuring the temperature inside the temperature change box, and the output end of the temperature sensor is communicatively connected with the temperature input end of the acquisition device.

[0014] Furthermore, the acquisition device is also provided with a power monitoring port for monitoring the optical power of the test input end and the monitoring input end.

[0015] Furthermore, it also includes a flange, and each of the test ports of the optical splitter is connected to an optical path input end of the polarizer through a polarization-maintaining optical fiber via the flange.

[0016] Furthermore, each optical path output end of the polarizer is fused to an input end of a device under test in an axis-maintaining polarization manner, and the fusion angle is 0° or 90°.

[0017] The present invention adopts a lithium niobate array straight waveguide working in single polarization as a polarizer, which breaks through the problems of low test accuracy, low efficiency and high cost. In addition, a multi-channel collector is adopted to achieve the requirement of simultaneously collecting polarization crosstalk and insertion loss of multi-channel pigtails. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the system block diagram of the optical fiber current transformer;

[0019] Figure 2 It is a schematic diagram of the straight waveguide structure;

[0020] Figure 3 A system schematic diagram of a polarization crosstalk test system for a polarizer straight waveguide pigtail of the present invention;

[0021] Figure 4 Schematic diagram of the polarizer structure. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 3The system schematic diagram of a polarization crosstalk test system of a polarizer straight waveguide pigtail of the present invention is shown, comprising: a light source 1, a beam splitter 2, a polarizer 3, and a collection device 4, wherein the light source 1 is connected to the input end of the beam splitter 2 through a polarization-maintaining optical fiber, the beam splitter 2 is provided with a monitoring port and one or more test ports, the monitoring port is connected to the monitoring input end of the collection device 4 through a polarization-maintaining optical fiber, each of the test ports is connected to an optical path input end of the polarizer 3 through a polarization-maintaining optical fiber, each optical path output end of the polarizer 3 is connected to the input end of a device to be tested through a polarization-maintaining optical fiber, and each output end of the device to be tested is respectively connected to the test input end of the collection device.

[0024] Specifically, the depolarized light emitted by the light source 1 is divided into multiple paths by the optical splitter, wherein, preferably, there are 16 paths in total, 01-15 paths are used as test input light, 16 paths are used as monitoring light source stability and calculation reference, and the light output from the optical splitter 2 of paths 01-15 enters the polarizer 3, and the depolarized light enters the polarizer 3 and becomes single polarization linear polarized light, and is output through the polarization-maintaining optical fiber of the polarizer 3, preferably using a polarization-maintaining pigtail output, and connected to the device to be tested 801-815. During the test period, 801-815 is preferably a straight waveguide to be tested, and more preferably a titanium diffused straight waveguide. The output pigtail of the straight waveguide to be tested is connected to the automatic acquisition system through an adapter, and the pigtail polarization crosstalk and insertion loss change are collected in real time.

[0025] The present invention adopts a lithium niobate array straight waveguide working in single polarization as a polarizer, which breaks through the problems of low test accuracy, low efficiency and high cost. In addition, a multi-channel collector is adopted to achieve the requirement of simultaneously collecting polarization crosstalk and insertion loss of multi-channel pigtails.

[0026] In one embodiment, the polarizer 3 is an array waveguide chip.

[0027] like Figure 4 As shown, in one embodiment, the polarizer 3 includes: an X-cut Y-conducting lithium niobate material chip substrate 31, on which one or more groups of polarizer straight waveguides 32 are arranged, an isolation groove 33 is cut between each group of polarizer straight waveguides 32, the input end of each group of the polarizer straight waveguides 32 is the input end of the optical path, and the output end of each group of the polarizer straight waveguides 32 is the output end of the optical path.

[0028] In this embodiment, the depolarized light of the light source 1 is adjusted to single polarization line polarized light by the polarizer 3 .

[0029] In one embodiment, the isolation groove 33 is coated with a light absorbing material.

[0030] In this embodiment, light absorbing material is coated to prevent crosstalk between waveguides.

[0031] In one embodiment, the input end and the output end of the polarizer straight waveguide 32 are coupled by polarization-maintaining optical fiber, and the polarizer straight waveguide 32 is an annealed proton exchange polarizer straight waveguide.

[0032] The chip of this embodiment adopts annealed proton exchange straight waveguide, supports TE mode transmission only, and uses polarization-maintaining fiber coupling for input and output. Finally, it can be packaged into a polarizer module in a shell and tube. The polarization crosstalk of the pigtail of this module can be as high as 38dB, which is much higher than the crosstalk value of the test straight waveguide and meets the test requirements. The loss of a single fiber is only about 1.2dB, which is convenient for batch testing.

[0033] In one of the embodiments, it also includes a temperature-variable box 5 for accommodating the device under test, and each optical path output end of the polarizer 3 is inserted into the temperature-variable box 5 through a polarization-maintaining optical fiber and connected to an input end of the device under test, and each output end of the device under test passes through the temperature-variable box 5 and is connected to the test input end of the acquisition device.

[0034] This embodiment adds a temperature change box, which has a high and low temperature cycle function and can achieve constant speed temperature change.

[0035] In one of the embodiments, a temperature sensor 6 for measuring the temperature inside the temperature change box 5 is further included, and an output end of the temperature sensor 6 is communicatively connected to a temperature input end of the acquisition device 4 .

[0036] This embodiment uses a temperature sensor to record the temperature change of the temperature change box in real time.

[0037] In one embodiment, the acquisition device 4 is further provided with a power monitoring port 41 for monitoring the optical power of the test input end and the monitoring input end.

[0038] In this embodiment, the optical power output by the multi-channel optical splitter is monitored through the power monitoring port for reference.

[0039] In one of the embodiments, a flange 7 is further included, and each of the test ports of the optical splitter 2 is connected to an optical path input end of the polarizer 3 via the flange 7 through a polarization-maintaining optical fiber.

[0040] In this embodiment, a flange is provided, and the light output from the test port of the spectrometer enters the polarizer through the flange connection point.

[0041] In one embodiment, each optical path output end of the polarizer 3 is fused to an input end of a device under test in an axis-maintaining manner, and the fusion angle is 0° or 90°.

[0042] In this embodiment, the light output from the test port of the optical splitter enters the polarizer, is output through the polarization-maintaining pigtail of the polarizer, and is polarization-maintainingly fused with the device to be tested. The polarizer and the straight waveguide pigtail are both fast-axis fixed-axis, so when the fusion angle is selected to be 0° (90°), the TE (TM) mode is transmitted in the straight waveguide.

[0043] As the best embodiment of the present invention, a polarization crosstalk test system of a polarizer straight waveguide pigtail is provided. Figure 3 As shown, it includes: a light source 1, a beam splitter 2, a polarizer 3, a collection device 4, a temperature change box 5 for accommodating a device to be tested, a temperature sensor 6, and a flange 7. The light source 1 is connected to the input end of the beam splitter 2 through a polarization-maintaining optical fiber. The beam splitter 2 is provided with a monitoring port and one or more test ports. The monitoring port is connected to the monitoring input end of the collection device 4 through a polarization-maintaining optical fiber. Each of the test ports is connected to an optical path input end of the polarizer 3 through the flange 7 through a polarization-maintaining optical fiber. Each optical path output end of the polarizer 3 is connected to a monitoring port through a polarization-maintaining optical fiber. The polarization optical fiber is inserted into the temperature change box 5 and connected to the input end of a device under test. Each optical path output end of the polarizer 3 is fused to the input end of a device under test in an axis-maintaining manner, and the fusion angle is 0° or 90°. The output end of each device under test passes through the temperature change box 5 and is connected to the test input end of the acquisition device. The output end of the temperature sensor 6 is communicatively connected to the temperature input end of the acquisition device 4. The acquisition device 4 is also provided with a power monitoring port 41 for monitoring the optical power of the test input end and the monitoring input end.

[0044] The polarizer 3 is an array waveguide chip, and the polarizer 3 includes: an X-cut Y-transmitting lithium niobate material chip substrate 31, one or more groups of polarizer straight waveguides 32 are arranged on the chip substrate 31, an isolation groove 33 is cut between each group of polarizer straight waveguides 32, and a light-absorbing material is coated on the isolation groove 33. The input end of each group of polarizer straight waveguides 32 is the input end of the optical path, and the output end of each group of polarizer straight waveguides 32 is the output end of the optical path. The input end and the output end of the polarizer straight waveguide 32 are coupled by a polarization-maintaining optical fiber 34. The polarizer straight waveguide 32 is an annealed proton exchange polarizer straight waveguide, and an external packaging tube shell 35.

[0045] The principle of the optical path is as follows: the depolarized light emitted by the light source is divided into 16 paths by the optical splitter, paths 01-15 are used as test input light, path 16 is used as monitoring light source stability and calculation reference, and the light output by the optical splitter paths 1-15 enters the polarizer through the flange connection point. The depolarized light enters the polarizer and becomes single polarization linear polarized light, which is output through the polarizer polarization-maintaining pigtail and polarization-maintainingly spliced ​​with the device to be tested. The polarizer and the straight waveguide pigtail are both fast-axis fixed-axis, so when the splicing angle is selected to be 0° (90°), the TE (TM) mode is transmitted in the straight waveguide, and the straight waveguide output pigtail is connected to the automatic acquisition system through an adapter to collect the polarization crosstalk and insertion loss change of the pigtail in the TE (TM) mode in real time.

[0046] Introduction of components:

[0047] Light source 1: SLD high-power depolarization light source, power 10±1mW.

[0048] Beam splitter 2: 1×16 fiber type beam splitter to achieve beam splitting.

[0049] Polarizer 3: array waveguide chip, such as Figure 4 As shown in the figure, 17 straight waveguides are designed on the X-cut Y-transmitting lithium niobate material, 15 groups are used for testing, and 2 groups are used as spares. An isolation groove is cut between each group of waveguides, and they are coated with light-absorbing materials for isolation to prevent crosstalk between waveguides. The chip uses annealed proton exchange straight waveguides, only supports TE mode transmission, and the input and output are coupled with polarization-maintaining fiber, and finally packaged into a polarizer module using a tube shell.

[0050] Since the polarizer is made of annealed proton exchange waveguide, the waveguide made by this process has the function of polarization (single polarization working state), so the pigtail polarization crosstalk is relatively high. Among them, the insertion loss of a single straight waveguide is 1.2dB, including coupling loss 0.3dB / end, transmission loss 0.3dB / cm, and a total length of 2cm, so the total loss is 0.3dB×2end+0.3dB×2cm=1.2dB. Since the polarization crosstalk of the pigtail of this module can be as high as 38dB, which is much higher than the crosstalk value of the tested straight waveguide, it meets the test requirements, and the loss of a single waveguide is only about 1.2dB, which is convenient for batch testing.

[0051] Device under test: Titanium diffused straight waveguide, capable of transmitting two modes TE / TM simultaneously.

[0052] Temperature change box 5: It has high and low temperature cycle function and can achieve constant speed temperature change.

[0053] Temperature sensor 6: used to record the temperature change of the temperature change box in real time.

[0054] Power monitoring port 41: monitors the optical power output by the 16-way optical splitter for reference.

[0055] Automatic acquisition system 4: implements the acquisition of the polarization crosstalk and insertion loss variation of the pigtail of the device under test.

[0056] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A polarizer straight waveguide pigtail polarization crosstalk test system, characterized in that: include: A light source (1), a beam splitter (2), a polarizer (3), and a collection device (4), wherein the light source (1) is connected to the input end of the beam splitter (2) via a polarization-maintaining optical fiber, the beam splitter (2) is provided with a monitoring port and one or more test ports, the monitoring port is connected to the monitoring input end of the collection device (4) via a polarization-maintaining optical fiber, each of the test ports is connected to an optical path input end of the polarizer (3) via a polarization-maintaining optical fiber, each optical path output end of the polarizer (3) is connected to the input end of a device to be tested via a polarization-maintaining optical fiber, and each output end of the device to be tested is respectively connected to the test input end of the collection device; The polarizer (3) is an array waveguide chip, and comprises: an X-cut Y-conducting lithium niobate material chip substrate (31), one or more groups of polarizer straight waveguides (32) are arranged on the chip substrate (31), an isolation groove (33) is cut between each group of polarizer straight waveguides (32), the input end of each group of polarizer straight waveguides (32) is the optical path input end, and the output end of each group of polarizer straight waveguides (32) is the optical path output end.

2. The polarization crosstalk test system for polarizer straight waveguide pigtail according to claim 1, characterized in that: The isolation groove (33) is coated with a light absorbing substance.

3. The polarization crosstalk test system for polarizer straight waveguide pigtail according to claim 1, characterized in that: The input end and the output end of the polarizer straight waveguide (32) are coupled by polarization-maintaining optical fiber, and the polarizer straight waveguide (32) is an annealed proton exchange polarizer straight waveguide.

4. The polarization crosstalk test system for a polarizer straight waveguide pigtail according to claim 1, characterized in that: It also includes a temperature-variable box (5) for accommodating the device under test, wherein each optical path output end of the polarizer (3) is inserted into the temperature-variable box (5) through a polarization-maintaining optical fiber and connected to an input end of the device under test, and each output end of the device under test passes through the temperature-variable box (5) and is connected to a test input end of the acquisition device.

5. The polarization crosstalk test system for polarizer straight waveguide pigtail according to claim 4, characterized in that: It also includes a temperature sensor (6) for measuring the temperature inside the temperature change box (5), and the output end of the temperature sensor (6) is communicatively connected to the temperature input end of the acquisition device (4).

6. The polarization crosstalk test system for polarizer straight waveguide pigtail according to claim 1, characterized in that: The acquisition device (4) is also provided with a power monitoring port (41) for monitoring the optical power of the test input end and the monitoring input end.

7. The polarization crosstalk test system for polarizer straight waveguide pigtail according to claim 1, characterized in that: It also comprises a flange (7), and each test port of the optical splitter (2) is connected to an optical path input end of the polarizer (3) via a polarization-maintaining optical fiber through the flange (7).

8. The polarization crosstalk test system for polarizer straight waveguide pigtail according to claim 1, characterized in that: Each optical path output end of the polarizer (3) is fused to the input end of a device to be tested in an axially polarization-maintaining manner, and the fusion angle is 0° or 90°.

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