A test system for a free-space optical isolator

Abstract

The present invention relates to the technical field of the production and manufacturing of online optical passive devices, and in particular to a test system for a free-space optical isolator, which includes a tunable laser, a polarization control module, an optical switch, a collimator, and a three-dimensional adjustment stage. The laser generated by the tunable laser is irradiated onto two collimators after passing through the polarization control module and the optical switch. One of the collimators serves as the input end of the collimated linearly polarized light, and the other collimator serves as the receiving end of the collimated linearly polarized light. The free-space optical isolator to be tested is arranged between the two collimators. By adding a three-dimensional adjustment stage in the present invention, the incident light can be coupled into the collimator at the receiving end with the highest efficiency after passing through the FSI, making the test results more accurate. Since there are pre-polarization control modules in both the forward optical path and the reverse optical path, the polarization state of the incident light can correspond to the polarization directions of the polarizer and the analyzer respectively, making the test results more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of the production and manufacturing of online optical passive devices, and particularly relates to a test system for a free-space optical isolator. Background Art

[0002] The most important indicators of a free-space optical isolator are insertion loss and isolation. Since it is a polarization-dependent device, it does not have indicators such as PDL and PMD. However, at the same time, different requirements are imposed on the polarization states of the forward input light and the reverse input light during its testing. Therefore, the benchmarks for forward insertion loss testing and reverse isolation testing are inconsistent, and separate benchmarks need to be made.

[0003] The prior art, such as a free-space optical isolator performance automatic detection and automatic sorting system with a publication number of CN113042399A and a publication date of June 29, 2021, adjusts the forward and reverse directions of the optical path through a circulator and an optical switch, and uses one light source and two photodetectors. The polarization direction of its light source mainly achieves the effect that the input light is linearly polarized light and is consistent with the polarization direction of the polarizer of the isolator by adding a polarizer and an electrically controlled rotating stage at the In end during insertion loss testing. Then, the optical path direction is reversed through the optical switch. This set of test systems has two main drawbacks:

[0004] 1. After the optical path is reversed by the optical switch in this set of test systems, there is no polarization control module at the incident end of the device under test to ensure that the polarization direction of the incident light is consistent with that of the analyzer, which causes the measured isolation to be larger;

[0005] 2. When measuring the insertion loss, the light passing through the isolator under test is received by a collimator, and certain coupling losses will be generated during the collimator reception. This part of the loss will be added to the insertion loss of the isolator under test, making the measured value larger. When measuring the isolator, it cannot be guaranteed that the reverse insertion loss has been adjusted to the minimum at this time, resulting in a large deviation in the measurement (usually the isolation is larger). For this reason, we propose a test system for a free-space optical isolator. Summary of the Invention

[0006] The present invention proposes a test system for a free-space optical isolator to solve the technical problems existing in the background art.

[0007] The present invention provides the following technical solution: A test system for a free-space optical isolator, comprising a tunable laser, a polarization control module, an optical switch, a collimator, and a three-dimensional adjustment stage;

[0008] The laser generated by the tunable laser irradiates two collimators after passing through the polarization control module and the optical switch;

[0009] One of the collimators serves as the input end of the collimated linearly polarized light, and the other collimator serves as the receiving end of the collimated linearly polarized light. The free space optical isolator to be measured is arranged between the two collimators;

[0010] The polarization control module is used to make the polarization state of the incident light correspond to the polarization directions of the polarizer and the analyzer respectively, and the optical switch is used to switch the optical path direction;

[0011] The three-dimensional adjustment stage is used to minimize the insertion loss of the two collimators and zero the forward insertion loss optical path and the reverse isolation degree optical path.

[0012] Preferably, an optical power meter is further included, and the optical power meter is used to receive the tunable laser as the light source for measuring the insertion loss and the isolation degree.

[0013] Preferably, an upper computer is further included, and the upper computer is used to control the self-switching of the optical path to test the insertion loss and the isolation degree.

[0014] Preferably, the number of the optical switches is 4 groups, namely optical switch one, optical switch two, optical switch three, and optical switch four. The laser enters optical switch two and optical switch three after passing through optical switch one. Optical switch two and optical switch three are respectively connected to a collimator. Optical switch four is arranged at the front end of the optical power meter and is used to receive the light source for measuring the insertion loss and the isolation degree.

[0015] The present invention provides a test system for a free space optical isolator. By adding a three-dimensional adjustment stage, the incident light can be coupled into the collimator at the receiving end with the highest efficiency after passing through the FSI, making the test result more accurate. Since there are pre-polarization control modules in both the forward optical path and the reverse optical path, the polarization state of the incident light can correspond to the polarization directions of the polarizer and the analyzer respectively, making the test result more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the optical path for detecting the insertion loss and isolation degree indexes of the present invention;

[0017] Figure 2 It is a partial view of the detection optical path of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. [[ID=�5]]

[0019] The insertion loss of a free-space optical isolator is defined as the ratio of the output optical power to the input optical power when the optical isolator is connected in the forward direction, and is expressed in dB. Different from in-line isolators, it requires the incident light to be linearly polarized light (theoretical degree of polarization DOP is 100%), and its polarization direction is consistent with the polarization direction of the polarizer of the isolator under test. If the incident light is natural light (theoretical degree of polarization is 0) or circularly polarized light, the measured insertion loss and isolation will be 3 dB larger.

[0020] As Figure 1 shown, a test system for a free-space optical isolator uses a tunable laser, a polarization control module, four 1×2 optical switches, two collimators, a three-dimensional adjustment stage, an optical power meter, and an upper control computer, so that the loss and isolation can be accurately measured simultaneously. A tunable laser is used as the light source for measuring the insertion loss and isolation, and is received by the optical power meter.

[0021] The laser generated by the tunable laser passes through the polarization control module and the optical switch and then irradiates the two collimators; the configured TLS tunable laser can perform band scanning and can perform scanning tests on isolators with wavelength range requirements.

[0022] From the optical path perspective, when measuring the insertion loss, one of the collimators serves as the input end of the collimated linearly polarized light, and the other collimator serves as the receiving end of the collimated linearly polarized light. The free-space optical isolator under test is set between the two collimators;

[0023] The polarization control module is used to make the polarization state of the incident light correspond to the polarization directions of the polarizer and the analyzer respectively. There are pre-polarization control modules in both the forward optical path and the reverse optical path, which can make the polarization state of the incident light correspond to the polarization directions of the polarizer and the analyzer respectively, making the test results more accurate. The optical switch is used to switch the optical path direction; the number of optical switches is 4 groups, namely optical switch one, optical switch two, optical switch three, and optical switch four. The laser enters optical switch two and optical switch three after passing through optical switch one. Optical switch two and optical switch three are respectively connected to a collimator. Optical switch four is set at the front end of the optical power meter and is used to receive the light source for measuring the insertion loss and isolation.

[0024] The three-dimensional adjustment stage is used to minimize the insertion loss of the two collimators and zero the forward insertion loss optical path and the reverse isolation measurement optical path. By adding the three-dimensional adjustment stage, the incident light can be coupled into the receiving collimator with the highest efficiency after passing through the FSI, making the test results more accurate.

[0025] It also includes an optical power meter, which is used to receive the tunable laser as the light source for measuring the insertion loss and isolation.

[0026] It also includes a host controller, which is used to control the automatic switching of the optical path for testing the insertion loss and isolation. There is no need to manually switch the optical path or manually adjust the FSI direction of the isolator, making the test more convenient and efficient.

[0027] During measurement, first adjust the insertion loss of the collimator to the minimum through the three-dimensional adjustment stage, zero the forward insertion loss optical path and the reverse isolation measurement optical path respectively, and then follow Figure 2 As shown, first put the free space type optical isolator (FSI) on the metal tube, then put the metal tube on the right collimator (pay attention to the light passing direction of the FSI), and then adjust the three-dimensional adjustment stage and the polarization control module to minimize the insertion loss. The measured value at this time is the insertion loss of the measured FSI at this wavelength. Then switch the optical path direction through the optical switch, and adjust the three-dimensional adjustment stage and the polarization control module to obtain the measurement result of the isolation.

[0028] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A test system for a free-space optical isolator, characterized in that: It includes a tunable laser, a polarization control module, an optical switch, a collimator, a three-dimensional adjustment stage, an optical power meter, and a host control computer; The laser generated by the tunable laser is irradiated to two collimators after passing through the polarization control module and the optical switch; One of the collimators serves as the input end of the collimated linearly polarized light, and the other collimator serves as the receiving end of the collimated linearly polarized light. The free space optical isolator to be measured is arranged between the two collimators; The polarization control module is used to make the polarization state of the incident light correspond to the polarization directions of the polarizer and the analyzer respectively, and the optical switch is used to switch the optical path direction; The optical power meter is used to receive the tunable laser as a light source for measuring the insertion loss and isolation; The host control computer is used to control the self-switching of the optical path to measure the insertion loss and isolation; The number of the optical switches is 4 groups, namely optical switch one, optical switch two, optical switch three, and optical switch four. The laser enters optical switch two and optical switch three after passing through optical switch one. Optical switch two and optical switch three are respectively connected to a collimator. Optical switch four is arranged at the front end of the optical power meter and is used to receive the light source for measuring the insertion loss and isolation; The three-dimensional adjustment stage is used to minimize the insertion loss of the two collimators and zero the forward insertion loss optical path and the reverse isolation optical path; The free space optical isolator is sleeved on the metal tube, and the metal tube is sleeved on the right collimator. Then, the three-dimensional adjustment stage and the polarization control module are adjusted to minimize the insertion loss. The optical path direction is switched by the optical switch, and the three-dimensional adjustment stage and the polarization control module are adjusted to obtain the measurement result of the isolation.

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