Integrated test system and test method for optical module multipath interference test

Abstract

An integrated test system and test method for an optical module multipath interference (MPI) test. The system comprises: a light source module; a beam splitter OC1 used for splitting an optical signal into a primary path and an MPI path; a beam splitter OC3 used for splitting an optical signal on the primary path into two paths; an adjustable loss link; a beam splitter OC4 used for splitting into two paths an optical signal outputted on the adjustable loss link; a beam splitter OC2 used for combining optical signals; and an attenuator which receives the optical signal outputted by the beam splitter OC2 and adjusts same. Optical fibers of all optical interfaces in the system are spliced. The advantages are: one system can directly test the tolerance of MPI; optical fibers of all necessary optical interfaces are spliced, so that the generation of light reflection is fundamentally eliminated and additional MPI is not introduced; and a visual real-time display interface is designed, an equivalent reflection coefficient value is directly obtained, and frequent connection and disconnection of optical interfaces are avoided.

Description

Integrated test system and test method for optical module multiple path interference test

[0001] The present application claims priority to the Chinese patent application No. 202410981036.6, filed on July 22, 2024, and entitled "Integrated test system and test method for optical module multiple path interference test", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of optical communication, and in particular to an integrated test system and test method for optical module multiple path interference test. BACKGROUND

[0003] In high-speed optical fiber communication network applications, complex optical fiber links contain many optical fiber interfaces, which have different degrees of optical reflection on the transmitted optical signals. When there are two or more strong reflections in the optical fiber link, multiple path interference (MPI) occurs. Multiple path interference can cause the quality of the optical signal in the optical fiber link to decline, affecting the transmission performance of the optical fiber system, especially in high-speed 50G / 200G / 400G and other high-speed optical fiber communication networks based on fourth-order pulse amplitude modulation (PAM4).

[0004] The high-speed optical modules used in high-speed optical fiber communication networks, such as 50G / 200G / 400G and above, generally use digital signal processing (DSP) chips. Although various DSP manufacturers have introduced compensation functions for multiple path interference, the compensation capability for multiple path interference still needs to be tested and evaluated by optical module manufacturers.

[0005] The conventional test system block diagram of the optical module manufacturer is shown in FIG. 1, which includes the following devices: an external light source module Tx (101), a 10%:90% optical splitter OC1 (102), a 2km optical fiber (103), an optical attenuator VOA1 (104), an optical attenuator VOA2 (107), an optical polarization device PC (105), a 50%:50% optical splitter OC2 (106), and a receiving module Rx DUT (108), i.e., the receiving module to be tested. In this test system, all optical interfaces are connected through flanges, so at least 8 flanges (C1-C8) are required.

[0006] The test system shown in Fig. 1, the idea of testing is: in the optical signal received by the to-be-tested receiving module (108), an adjustable multi-path interference (MPI) equivalent reflected light signal is added, different equivalent reflection coefficients (ERI) are adjusted, the receiving bit error rate (BER) of the receiving module (108) is tested, and the tolerance of the to-be-tested receiving module (108) to the multi-path interference (MPI) can be determined by comparing the index requirements of the receiving bit error rate.

[0007] The specific test method of the test system includes the following steps:

[0008] S1. Measure the light emitting power of the light source module (101) at the C1 interface, denoted as P0;

[0009] S2. Measure the output optical power of the optical splitter OCl (102) main arm at the C2 interface, denoted as P1, and the theoretical value of P1 is P0-0.46;

[0010] S3. Measure the output optical power of the optical splitter OCl (102) MPI arm at the C3 interface, denoted as P2, and the theoretical value of P2 is P0-10;

[0011] S4. The equivalent loss link composed of a 2km optical fiber (103), an optical attenuator VOA1 (104) and an optical polarizer PC (105) is denoted as IL, and the value measured at the C6 interface is denoted as P3, and the theoretical value of P3 is P0-10-IL;

[0012] S5. Combine the two optical signals of the main arm and the MPI arm into one at the C7 interface, and the equivalent reflection coefficient (ERI) of the MPI arm relative to the main arm is denoted as P4, P4=P3-P1=-(9.54+IL);

[0013] S6. By adjusting the optical attenuator VOA1 (104), different equivalent reflection coefficients (ERI) can be obtained;

[0014] S7. At different equivalent reflection coefficients (ERI), adjust the optical attenuator VOA2 (107), test the receiving bit error rate (BER) of the receiving module (108), and obtain the tolerance of the to-be-tested receiving module (108) to the multi-path interference (MPI).

[0015] In the above test system, since multiple independent devices are used to build, there are multiple optical interfaces, which are connected with optical fiber jumpers and flanges, and there are many optical reflection points, so additional multi-path interference (MPI) is introduced, which affects the reliability of the test data. In order to reduce the optical reflection on the optical interface as much as possible, although the optical interface can be selected as an APC interface, this increases the selection difficulty and cost of all devices in the test system, and increases the difficulty of building the test system.

[0016] Meanwhile, when the above test method is used, real-time optical power measurement is performed on each optical interface, and the flange plate needs to be frequently removed, which increases the risk of jumper end face contamination and flange plate misalignment, and makes the consistency and stability of the test result poor. SUMMARY

[0017] One of the purposes of the present application is to provide an integrated test system for optical module multipath interference test, to improve the accuracy and convenience of high-speed optical module multipath interference tolerance test for optical module manufacturers.

[0018] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0019] An integrated test system for optical module multipath interference test, comprising:

[0020] A light source module for emitting optical signals;

[0021] An optical splitter OC1 for splitting the optical signals emitted by the optical module into a main arm and an MPI arm;

[0022] An optical splitter OC3 for splitting the optical signals on the main arm into two paths, one of which is used for real-time monitoring;

[0023] An adjustable loss link for adjusting the loss of the optical signals on the MPI arm;

[0024] An optical splitter OC4 for splitting the optical signals output by the adjustable loss link into two paths, one of which is used for real-time monitoring;

[0025] An optical splitter OC2 for merging the other optical signals split by the optical splitter OC3 and the other optical signals split by the optical splitter OC4;

[0026] A variable optical attenuator VOA2 receiving the merged optical signals output by the optical splitter OC2, adjusting the optical power and outputting to the to-be-tested receiving optical module;

[0027] The splitting ratios of the optical splitter OC3 and the optical splitter OC4 are the same;

[0028] The optical fibers of the optical interfaces between the light source module and the optical splitter OC1, the optical interfaces between the optical splitter OC1 and the adjustable loss link, the optical interfaces between the optical splitter OC3 and the optical splitter OC2, the optical interfaces between the optical splitter OC4 and the optical splitter OC2, and the optical interfaces between the optical splitter OC2 and the variable optical attenuator VOA2 are fusion spliced.

[0029] Further, the optical interface of the output end of the variable optical attenuator VOA2 adopts an APC interface.

[0030] Further, the light source module adopts a built-in light source, including a DSP chip, a microprocessor, a semiconductor cooler driving chip and a laser.

[0031] The microprocessor communicates and controls the DSP chip and the semiconductor cooler driving chip according to the signal of the upper computer.

[0032] The DSP chip is used for outputting a modulation signal to the laser.

[0033] The semiconductor cooler driving chip is used for keeping the laser working at a stable temperature.

[0034] The laser is used for emitting an optical signal.

[0035] Further, the adjustable loss link includes a fixed-length optical fiber line, an attenuator VOA1 and a polarizer.

[0036] The optical fiber line is used for causing a time delay of the optical signal on the MPI arm relative to the optical signal on the main arm.

[0037] The attenuator VOA1 is used for adjusting the size of the optical power loss on the MPI arm.

[0038] The polarizer is used for adjusting the optical polarization state of the MPI arm, so that the optical polarization state of the MPI arm is aligned with that of the main arm.

[0039] The optical fibers of the optical interfaces between the optical fiber line and the attenuator VOA1 and between the attenuator VOA1 and the polarizer are fusion spliced.

[0040] Further, a control interface is included, and the attenuator VOA1 is connected with the control interface.

[0041] Further, a control interface is included, and the polarizer is connected with the control interface.

[0042] Further, a control interface is included, and the attenuator VOA2 is connected with the control interface.

[0043] Further, an optical power real-time display interface is included, and one of the optical signals branched from the optical splitter OC3 is connected to the optical power real-time display interface.

[0044] Further, an optical power real-time display interface is included, and one of the optical signals branched from the optical splitter OC4 is connected to the optical power real-time display interface.

[0045] The second object of the present application is to provide a test method for testing the multi-path interference of the optical module, which is based on the integrated test system for testing the multi-path interference of the optical module.

[0046] record the power T1 of the light signal branched from the main arm and the power T2 of the light signal branched from the MPI arm;

[0047] calculate the equivalent reflection coefficient ERI = T2-T1;

[0048] obtain different equivalent reflection coefficients by adjusting the optical attenuator VOA1;

[0049] adjust the optical attenuator VOA2 under different equivalent reflection coefficients, test the receiving error rate of the receiving optical module, and obtain the tolerance of the receiving optical module to multipath interference.

[0050] The advantages of the present application are:

[0051] 1. The integrated test system for testing the multipath interference of the optical module integrates multiple separate devices, and a set of system can directly test the tolerance of the multipath interference MPI; in the design, all necessary optical fibers of optical interfaces are fused, which fundamentally eliminates the generation of optical reflection and does not introduce additional multipath interference (MPI), thereby improving the reliability of test data of the integrated test system; the design adopts a visual real-time display interface to display the optical power of the main arm and the MPI arm in real time, and the equivalent reflection coefficient (ERI) value can be directly obtained, the test data is stable, and the optical interface is avoided from being frequently disassembled;

[0052] 2. The design adopts a built-in light source, the working rate and working mode of the built-in light source can be directly controlled on the control interface of the integrated system, and the tolerance test of the multipath interference (MPI) of different high-speed optical modules can be adapted;

[0053] 3. The design adopts a real-time control interface, including an attenuator VOA and an optical polarizer PC, and the test is convenient. BRIEF DESCRIPTION OF DRAWINGS

[0054] The drawings described herein are used to provide further understanding of the present application, constitute a part of the present application, and the illustrative embodiments of the present application and the description thereof are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0055] Fig. 1 is a schematic diagram of a conventional technical route test framework in the background art;

[0056] Fig. 2 is a schematic diagram of a multipath interference (MPI) integrated test system in the embodiment;

[0057] Fig. 3 is a schematic diagram of a built-in light source function in the embodiment;

[0058] Fig. 4 is a schematic diagram of an MPI arm adjustable loss function block in the embodiment;

[0059] Label explanation: 101, light source module; 102, optical splitter OC1; 103, 2km optical fiber; 104, optical attenuator VOA1; 105, polarizer PC; 106, optical splitter OC2; 107, optical attenuator VOA2; 108, receiving optical module; 109, optical splitter OC3; 110, optical splitter OC4; flanges C1, C2, C3, C4, C5, C6, C7, C8; fusion points S1, S2, S3, S4, S5, S6, S7. DETAILED DESCRIPTION

[0060] The application will be further described below in conjunction with the embodiments. It should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0061] The embodiment proposes an integrated test system for multi-path interference test of optical modules, as shown in FIG. 2, which is composed of the following parts: built-in light source, optical splitter OC1, optical splitter OC2, optical splitter OC3, optical splitter OC4, adjustable loss link (also called equivalent loss link), optical attenuator VOA2, wherein the adjustable loss link is composed of 2km optical fiber, optical attenuator VOA1 and polarizer PC. The integrated system also designs a visual real-time display interface and a real-time control interface, which facilitates the display and real-time control of data in the system.

[0062] As shown in FIG. 3, the built-in light source serves as a light source module, which contains a DSP chip (built-in Driver), a microprocessor (MCU) chip, a Thermo Electric Cooler (TEC) driving chip and a laser. The function of the DSP chip is to output a high-speed PAM4 modulation signal to the laser (Laser), with a maximum speed of 200Gbps. The function of the microprocessor (MCU) chip is to receive the signals of the control interface at the host computer, and to communicate and control the DSP chip and the Thermo Electric Cooler (TEC) driving chip. The working mode of the DSP chip can be controlled and switched by the microprocessor (MCU) chip. The function of the Thermo Electric Cooler (TEC) driving chip is to provide stable TEC current to make the laser (Laser) work at a stable temperature. The specific working temperature of the laser (Laser) can be controlled by the microprocessor (MCU) chip. The design adopts a built-in light source, which can directly control the working speed and mode of the built-in light source on the control interface of the integrated system, and can adapt to the tolerance test of multi-path interference (MPI) of different high-speed optical modules.

[0063] The splitting ratio of the optical splitter OC1 is 10%:90%, which is used to split the optical signal emitted by the laser (Laser) into the main arm and the MPI arm.

[0064] The optical splitter OC3 is used to split the optical signal on the main arm into two paths, one of which is connected to the visual real-time display interface for real-time monitoring of the optical power, which improves the stability of the test data and avoids repeated disassembly of the optical interface.

[0065] The adjustable loss link is used to adjust the loss of the optical signal on the MPI arm. As shown in FIG. 4, the 2km optical fiber selects the G.652D optical fiber, which functions to increase the delay, so that the optical signal on the MPI arm has a delay compared with the optical signal on the main arm, simulating the actual application state; the attenuator VOA1 adjusts the size of the optical power loss on the MPI arm to achieve the target equivalent reflection coefficient (ERI), and the attenuator VOA1 can be connected to the real-time control interface of the integrated test system to support real-time adjustment and improve the convenience of testing; the polarizer PC is used to adjust the polarization state of the light on the MPI arm, so that the polarization state is aligned with the main arm to achieve the maximum damage, and the control knob of the polarizer PC is also connected to the real-time control interface of the integrated test to support real-time adjustment and improve the convenience of testing.

[0066] The optical splitter OC4 is used to split the optical signal output by the adjustable loss link into two paths, one of which is connected to the visual real-time display interface for real-time monitoring of the optical power, which improves the stability of the test data and avoids repeated disassembly of the optical interface.

[0067] The functions of the optical splitter OC3 and the optical splitter OC4 are to lead out the optical power on the main arm and the MPI arm to the optical power real-time display interface of the integrated test system. As shown in FIG. 2, T1 represents the power of one of the optical signals led out by the optical splitter OC3, and T2 represents the power of one of the optical signals led out by the optical splitter OC4, and the value of T2-T1 is the equivalent reflection coefficient (ERI). It should be noted here that the splitting ratios of the optical splitter OC3 and the optical splitter OC4 must be the same. In this application, the splitting ratio of the optical splitter OC3 is 50%:50%, and the splitting ratio of the optical splitter OC4 is 50%:50%.

[0068] The optical splitter OC2 is used to combine the other optical signal split by the optical splitter OC3 and the other optical signal split by the optical splitter OC4. The optical splitter OC1 splits the light emitted by the laser Laser into the main arm and the MPI arm, and the light of the main arm and the MPI arm is combined again in the optical splitter OC2 after the loss of the MPI arm, so that the adjustable equivalent reflection coefficient (ERI) can be added to the optical signal on the main arm for MPI tolerance test.

[0069] The attenuator VOA2 receives the combined optical signal output by the optical splitter OC2, adjusts the optical power, and outputs to the to-be-tested receiving optical module. The attenuator VOA2 controls the optical power entering the to-be-tested receiving optical module, so that the to-be-tested receiving optical module works near the sensitivity. By adjusting the attenuation of the attenuator VOA2, the BER curve of the to-be-tested receiving optical module can be tested within a certain range of optical power, so as to evaluate the tolerance of the to-be-tested receiving optical module to the MPI. The attenuator VOA2 can be connected to the real-time control interface of the integrated test system, and real-time adjustment is supported, thereby improving the convenience of testing.

[0070] As an improvement, in the system of the embodiment, the optical fibers of the optical interfaces between the built-in light source and the optical splitter OC1, between the optical splitter OC1 and the 2km optical fiber, between the 2km optical fiber and the attenuator VOA1, between the attenuator VOA1 and the polarizer, between the optical splitter OC3 and the optical splitter OC2, between the optical splitter OC4 and the optical splitter OC2, and between the optical splitter OC2 and the attenuator VOA2 are fused (see the fusion points S1-S7 in FIG. 2), and all the necessary optical fibers of the optical interfaces are fused, so that the generation of optical reflection is fundamentally eliminated, no additional MPI is introduced, and the reliability of the test data of the integrated test system is improved. Since the to-be-tested receiving optical module needs to be frequently replaced, in order to weaken the reflection of the optical interface at the output end of the attenuator VOA2, the optical interface at the output end of the attenuator VOA2 of the embodiment adopts an APC interface.

[0071] The test method of the test system includes the following steps:

[0072] Record the power T1 of the optical signal branched on the main arm and the power T2 of the optical signal branched on the MPI arm;

[0073] Calculate the equivalent reflection coefficient ERI = T2-T1;

[0074] Obtain different equivalent reflection coefficients by adjusting the optical attenuator VOA1;

[0075] At different equivalent reflection coefficients, adjust the optical attenuator VOA2, test the receiving BER of the receiving optical module, and obtain the tolerance of the receiving optical module to the MPI.

[0076] The above embodiments are only used to explain the concept of the present application, and are not a limitation on the protection of the present application. Any non-essential modification of the present application shall fall within the scope of protection of the present application.

Claims

1. An integrated testing system for multipath interference testing of optical modules, characterized in that, include: The light source module is used to emit light signals; The beam splitter OC1 is used to split the optical signal emitted by the light source module into the main arm and the MPI arm; The beam splitter OC3 is used to split the optical signal on the main arm into two paths, one of which is used for real-time monitoring of optical power. An adjustable loss link is used to adjust the loss of the optical signal on the MPI arm; the adjustable loss link includes a fixed-length optical fiber line, an attenuator VOA1, and a polarizer. The optical fiber line is used to ensure that the optical signal on the MPI arm has a time delay compared to the optical signal on the main arm; the attenuator VOA1 is used to adjust the optical power loss on the MPI arm; The polarizer is used to adjust the optical polarization state of the MPI arm so that the optical polarization state of the MPI arm is aligned with the main arm; the optical fiber of the optical interface between the optical fiber line and the attenuator VOA1, and the optical fiber of the optical interface between the attenuator VOA1 and the polarizer are fused together. Optical splitter OC4 is used to split the optical signal output from the adjustable loss link into two paths, one of which is used for real-time monitoring of optical power. Optical splitter OC2 is used to combine the other optical signal split from optical splitter OC3 and the other optical signal split from optical splitter OC4; Attenuator VOA2 receives the combined optical signal output from the beam splitter OC2, adjusts the optical power, and then outputs it to the receiving optical module under test. The beam splitter OC3 and the beam splitter OC4 have the same beam splitting ratio; The optical fibers of the optical interface between the light source module and the optical splitter OC1, the optical fiber of the optical interface between the optical splitter OC1 and the adjustable loss link, the optical fiber of the optical interface between the optical splitter OC3 and the optical splitter OC2, the optical fiber of the optical interface between the optical splitter OC4 and the optical splitter OC2, and the optical fiber of the optical interface between the optical splitter OC2 and the attenuator VOA2 are all fused together.

2. The integrated test system for multipath interference testing of optical modules of claim 1, wherein, The optical interface at the output of the attenuator VOA2 is an APC interface.

3. The integrated test system for multipath interference testing of optical modules of claim 1, wherein, The light source module adopts a built-in light source, including a DSP chip, a microprocessor, a semiconductor cooler driver chip, and a laser; The microprocessor communicates and controls the DSP chip and the semiconductor cooler driver chip according to the host computer signal; The DSP chip is used to output a modulation signal to the laser; The semiconductor cooler driver chip is used to keep the laser operating at a stable temperature. The laser is used to emit optical signals.

4. The integrated test system for multipath interference testing of optical modules of claim 1, wherein, It includes a control interface, and the attenuator VOA1 is connected to the control interface.

5. The integrated test system for multipath interference testing of optical modules of claim 1, wherein, It includes a control interface, and the polarizer is connected to the control interface.

6. The integrated test system for multipath interference testing of optical modules of claim 1, wherein, Includes a control interface, and the attenuator VOA2 is connected to the control interface.

7. The integrated test system for multipath interference testing of optical modules of claim 1, wherein, It includes a real-time optical power display interface, wherein one optical signal split from the optical splitter OC3 is connected to the real-time optical power display interface.

8. The integrated test system for multipath interference testing of optical modules of claim 1, wherein, It includes a real-time optical power display interface, wherein one optical signal split from the optical splitter OC4 is connected to the real-time optical power display interface.

9. A test method for multipath interference test of an optical module, characterized in that, Based on the integrated test system for multipath interference testing of optical modules according to any one of claims 1 to 8, the test method includes the following steps: Record the power of the light signal T1 split from the main arm and the power of the light signal T2 split from the MPI arm; Calculate the equivalent reflection coefficient ERI=T2-T1; Get different equivalent reflection coefficients by adjusting the optical attenuator VOA1; Under different equivalent reflection coefficients, adjust the optical attenuator VOA2, test the receiving error rate of the receiving optical module, and get the tolerance of the receiving optical module to multipath interference.

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