Tunable laser operation mode stability test system and method

Abstract

The invention provides a tunable laser operation mode stability test system and method, and the system consists of a tunable laser, a wavelength recognition module, a photoelectric conversion module, and an acquisition and display module. The stability of the operation mode of the tunable laser is tested by calculating whether the preset discrete electric pulse number is equal to the collected discrete electric pulse number and calculating the proportion of the wavelength trigger difference in the preset interval, the measurement difficulty is remarkably reduced, the problem that instrument performance evaluation is complex is solved, and compared with a conventional standard deviation method, the method has the advantage that the accuracy is high. The measurement precision is improved, the data acquisition amount and the data processing amount in the test process are greatly reduced, and the mode hopping and triggering precision characteristics of the instrument can be reflected more visually and accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of tunable laser testing, and provides a tunable laser operation mode stability testing system and method. Background Art

[0002] With the ever-expanding commercial trend of silicon photonic chips and silicon photonic modules in the 800G and 1.6T era, low-cost and high-efficiency production and testing methods are the goals pursued by the industry. This requires the determination of whether the wafer is qualified or not in the front-end process as much as possible, and then accurate testing to improve the product yield and reduce costs. This requires rapid testing of parameters such as the stability of the tunable laser operation mode and the scanning accuracy.

[0003] In response to the need to test the wavelength-dependent optical insertion loss parameters of the entire micro-optical structure on the wafer, including the waveguide, the existing test methods, such as the point test method, the broadband light source + spectrum analyzer test method, and the tunable laser + wavelength meter test method, all have limitations. They can only produce "several points" of wavelength-dependent optical insertion loss spectrum characteristics, or the dynamic range is insufficient, or the introduction of auxiliary test equipment such as wavelength meters increases the test cost. Although the wavelength fast scanning system composed of a tunable laser + a multi-channel high-speed optical power meter can solve the above problems, there is no effective method to quickly characterize the operating stability of its core test instrument, the tunable laser.

[0004] Operation mode stability is an important indicator to measure the mode hopping characteristics and scanning accuracy of tunable lasers. This indicator may even affect the power repeatability and stability of tunable lasers. Operation mode stability is related to factors such as the degree of synchronization between the internal and external cavity modes of the tunable laser, the diffraction efficiency of the frequency-selective element, the ability to resist environmental disturbances, and assembly and precision machining errors. Considering that the above-mentioned many influencing factors are difficult to quantitatively test in actual processes, this has brought great obstacles to the acceptance, comparison, and testing of tunable lasers.

[0005] Existing evaluation methods are mostly based on the calibration of characteristic peaks of absorption spectra combined with multiple measurements of gas absorption cells and calculation of standard deviations of multiple measurement results. In this case, the calculated value of the operating mode stability is directly related to the number of measurements of the gas absorption cell and the gas composition. It requires a large amount of data and multiple gas absorption cells to obtain an approximate value. The test efficiency is low and the cost is high. The impact of the data processing solution on the evaluation of the tunable laser mode stability is not considered, nor is the coverage of the characteristic peaks of the gas absorption cell on the tunable laser output spectrum considered, which leads to limitations in the use of the operating mode stability test method. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the first object of the present invention is to provide a tunable laser operation mode stability test system, comprising:

[0007] A tunable laser, wherein the test parameters of the tunable laser can be set, and the tunable laser generates a tunable laser beam to be tested according to the set test parameters;

[0008] A wavelength recognition module, which recognizes and locks the resonant output wavelength of the tunable laser and outputs an optical wavelength signal;

[0009] A photoelectric conversion module, which converts the optical wavelength signal output by the wavelength recognition module into an electrical pulse signal;

[0010] The acquisition and display module obtains the test parameters set by the tunable laser, collects, counts and analyzes the number and interval of the electrical pulse signals output by the photoelectric conversion module, and analyzes the stability of the tunable laser operation model.

[0011] The second object of the present invention is to provide a method for testing the stability of a tunable laser operation mode:

[0012] The acquisition and display module obtains the scanning speed, starting wavelength, ending wavelength and trigger interval of the laser setting of the tunable laser, and acquires the electrical pulse signal converted by the wavelength recognition module and the photoelectric conversion module, and converts the electrical pulse signal into discrete data;

[0013] Based on the set data and the discrete data, it is determined whether the preset discrete electrical pulse number of the tunable laser is equal to the collected discrete electrical pulse number;

[0014] The trigger wavelength discrete data is calculated based on the time difference between adjacent data points of discrete data, and the wavelength trigger difference between the trigger wavelength discrete data and the trigger interval is calculated. A statistical histogram is constructed according to the number of wavelength trigger differences in multiple divided preset intervals to determine whether the proportion of wavelength trigger differences in the preset interval reaches the stability assessment threshold.

[0015] Specifically, the calculation formula for the preset discrete electrical pulse number is:

[0016] ,

[0017] Where WST is the starting wavelength, WEN is the ending wavelength, TRI is the trigger interval, and J' is the preset number of discrete electrical pulses.

[0018] Specifically, the time difference between the wavelength triggering in adjacent discrete data is calculated to obtain N time-related data distribution values, where N=J-1;

[0019] The calculation formula for trigger wavelength discrete data is:

[0020] ,

[0021] Where TIM[1~N] is the time-related data distribution value, SPE is the scanning speed, and TRW[1~N] is the trigger wavelength discrete data.

[0022] Specifically, the calculation formula of the wavelength trigger difference is:

[0023] ,

[0024] Where TRI is the trigger interval and ABS_Wav1[1~N] is the wavelength trigger difference.

[0025] The preset interval includes a first preset interval, a second preset interval and a third preset interval. The numbers of wavelength trigger differences in the first preset interval, the second preset interval and the third preset interval are counted as D1, D2 and D3 respectively, a statistical histogram H1 is constructed, and it is calculated whether the proportion of D1 in the statistical histogram H1 can reach the stability evaluation threshold, and the stability of the tunable laser operation mode is evaluated. The stability evaluation formula is:

[0026] ,

[0027] Where α and β are the stability assessment weights, and THR is the stability assessment threshold.

[0028] Specifically, the first preset interval is 0-1, the second preset interval is 1-2, and the third preset interval is data greater than 2.

[0029] Specifically, the stability assessment threshold is 85%.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention provides a tunable laser operation mode stability test system. The wavelength recognition module has the ability to quickly lock and identify the output wavelength of the tunable laser. The acquisition and display module analyzes the operation status information carried by the collected electrical signal, which is displayed and output through the acquisition and display module. It can be flexibly configured to achieve ultra-large range coverage of the spectral range to be tested, and provide full-band stability test of the tunable laser to be tested.

[0032] 2. The tunable laser operating mode stability test method provided by the present invention does not need to obtain difficult-to-measure instrument parameters such as the degree of synchronous matching between internal and external cavity modes, thereby reducing the measurement difficulty and solving the problem of complex instrument performance evaluation. Compared with the conventional standard deviation method, it not only improves the measurement accuracy, but also greatly reduces the amount of data acquisition and data processing during the test. It can more intuitively and accurately reflect the mode hopping and triggering accuracy characteristics of the instrument, and is suitable for rapid performance evaluation and inspection of tunable laser sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the test system of the present invention;

[0034] Figure 2 The figure is a flow chart of the testing method of the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below 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. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0036] The present invention provides a tunable laser operation mode stability testing system, which realizes automatic evaluation of the stability of the tunable laser operation mode by sampling the continuously output optical signal of the tunable laser at equal intervals and automatically calculating and analyzing the sampled electrical pulses. The system comprises a tunable laser, a wavelength recognition module, a photoelectric conversion module and a collection and display module.

[0037] The tunable laser can set test parameters and generate a tunable laser beam to be tested according to the set parameters. The typical structure of the tunable laser includes Littman-Metcalf tunable laser, Littrow tunable laser and related improved types.

[0038] The wavelength recognition module is used to identify and lock the resonant output wavelength of the tunable laser and output an optical wavelength signal. The typical structure of the wavelength recognition module is a multi-path phase-shifted FP standard tool group based on multi-beam interference.

[0039] The photoelectric conversion module converts the optical wavelength signal output by the wavelength recognition module into an electrical pulse signal.

[0040] The acquisition and display module obtains the test parameters set by the tunable laser, and collects, counts and analyzes the number and interval of the electrical pulse signals output by the photoelectric conversion module to determine the stability of the tunable laser operation model. The typical structure of the acquisition and display module is a digital oscilloscope.

[0041] The wavelength recognition module has the ability to quickly lock and identify the output wavelength of the tunable laser. The acquisition and display module analyzes the operating status information carried by the collected electrical signal, which is displayed and output by the acquisition and display module. It can be flexibly configured to achieve ultra-wide coverage of the spectral range to be tested, provide full-band stability testing of the tunable laser to be tested, and provide a suitable test source for the wavelength-related optical insertion loss parameter testing of the wafer.

[0042] The present invention uses the above equipment to provide a method for testing the stability of a tunable laser operation mode, and the steps are as follows.

[0043] Step 101: Turn on the tunable laser and wait for the tunable laser to operate stably.

[0044] Step 102: Setting test parameters of the tunable laser, the test parameters include a scanning speed SPE, a start wavelength WST, an end wavelength WEN, a trigger interval TRI, and an output power POW (typically 8 dBm).

[0045] Step 103: The collection and display module collects the intermittent electrical pulse signal carrying the stability of the tunable laser operation mode converted by the wavelength recognition module and the photoelectric conversion module.

[0046] Step 104: The collection and display module converts the intermittent electrical pulse signal into discrete data DAT[1~J], where J represents the Jth discrete electrical pulse data collected, and processes the discrete data DAT[1~J].

[0047] Step 105: The acquisition and display module obtains the test parameters of the tunable laser, calculates the initial and final wavelength difference ABS_Wav between the starting wavelength WST and the final wavelength WEN,

[0048] .

[0049] Step 106: Calculate the preset discrete electrical pulse number based on the set initial and final wavelength difference ABS_Wav and the trigger interval TRI , and its calculation formula is,

[0050] ,

[0051] It is determined whether the preset discrete electrical pulse number J' is equal to the collected discrete electrical pulse number J. If J'=J, go to step 107; if J'≠J, go to step 112.

[0052] Step 107: Calculate the time difference between two adjacent wavelengths in the discrete data DAT[1~J] when they are triggered, and obtain N time-related data distribution values ​​TIM[1~N]. Calculate the trigger wavelength discrete data TRW[1~N] based on the time-related data distribution value TIM[1~N] and the scanning speed SPE. The calculation formula of the trigger wavelength discrete data TRW[1~N] is:

[0053] .

[0054] Step 108: Calculate the wavelength trigger difference ABS_Wav1[1~N] between the trigger wavelength discrete data TRW[1~N] and the trigger interval TRI.

[0055] .

[0056] Step 109: Construct a statistical histogram H1 according to the number of wavelength trigger differences ABS_Wav1[1~N] in multiple preset intervals, the preset intervals include a first preset interval, a second preset interval and a third preset interval, the number of statistical wavelength trigger differences ABS_Wav1[1~N] in the first preset interval is D1, the number in the second preset interval is D2, the number in the third preset interval is D3, the first preset interval is 0-1, the second preset interval is 1-2, and the third preset interval is data greater than 2.

[0057] Step 110: Calculate whether the proportion of D1 in the statistical histogram can reach the stability evaluation threshold THR, and evaluate the stability of the tunable laser operation mode. The formula is:

[0058] ,

[0059] In the formula, α and β are the stability assessment weights;

[0060] In some embodiments, the stability evaluation threshold is 85%. If the calculation result reaches the stability evaluation threshold THR, go to step 111. If the calculation result cannot reach the stability evaluation threshold THR, go to step 112.

[0061] Step 111: End the test and output that the operating mode stability of the tunable laser to be tested is good.

[0062] Step 112: End the test and output that the operating mode stability of the tunable laser to be tested is insufficient.

[0063] The tunable laser operation mode stability test method provided by the present invention does not need to obtain difficult-to-measure instrument parameters such as the degree of synchronous matching between internal and external cavity modes, thereby reducing the measurement difficulty and solving the problem of complex instrument performance evaluation. Compared with the conventional standard deviation method, it not only improves the measurement accuracy, but also greatly reduces the amount of data acquisition and data processing in the test process, and can more intuitively and accurately reflect the mode hopping and triggering accuracy characteristics of the instrument, and is suitable for rapid performance evaluation and inspection of tunable laser sources.

[0064] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A tunable laser operation mode stability test system, characterized in that: include: A tunable laser, wherein the tunable laser can set test parameters and generate a tunable laser beam to be tested according to the set test parameters; A wavelength recognition module, which recognizes and locks the resonant output wavelength of the tunable laser and outputs an optical wavelength signal; A photoelectric conversion module, which converts the optical wavelength signal output by the wavelength recognition module into an electrical pulse signal; The acquisition and display module obtains the test parameters set by the tunable laser, collects, counts and analyzes the number and interval of the electrical pulse signals output by the photoelectric conversion module, and analyzes the stability of the tunable laser operation model.

2. A method for testing the stability of a tunable laser operation mode, characterized in that: Using the tunable laser operation mode stability testing system as claimed in claim 1, The acquisition and display module obtains the scanning speed, starting wavelength, ending wavelength and trigger interval of the laser setting of the tunable laser, and acquires the electrical pulse signal converted by the wavelength recognition module and the photoelectric conversion module, and converts the electrical pulse signal into discrete data; Based on the set data and the discrete data, it is determined whether the preset discrete electrical pulse number of the tunable laser is equal to the collected discrete electrical pulse number; The trigger wavelength discrete data is calculated based on the time difference between adjacent data points of discrete data, and the wavelength trigger difference between the trigger wavelength discrete data and the trigger interval is calculated. A statistical histogram is constructed according to the number of wavelength trigger differences in multiple divided preset intervals to determine whether the proportion of wavelength trigger differences in the preset interval reaches the stability assessment threshold.

3. The method for testing the stability of the tunable laser operation mode according to claim 2, characterized in that: The calculation formula for the preset discrete electrical pulse number is: ， Where WST is the starting wavelength, WEN is the ending wavelength, TRI is the trigger interval, and J' is the preset number of discrete electrical pulses.

4. The method for testing the stability of the tunable laser operation mode according to claim 2, characterized in that: Calculate the time difference when the wavelengths in adjacent discrete data are triggered to obtain N time-related data distribution values, N = J-1; The calculation formula for trigger wavelength discrete data is: ， Where TIM[1~N] is the time-related data distribution value, SPE is the scanning speed, and TRW[1~N] is the trigger wavelength discrete data.

5. The method for testing the stability of the tunable laser operation mode according to claim 2, characterized in that: The calculation formula of wavelength trigger difference is: ， Where TRI is the trigger interval and ABS_Wav1[1~N] is the wavelength trigger difference.

6. The method for testing the stability of the tunable laser operation mode according to claim 2, characterized in that: The preset interval includes a first preset interval, a second preset interval and a third preset interval. The numbers of wavelength trigger differences in the first preset interval, the second preset interval and the third preset interval are counted as D1, D2 and D3 respectively, a statistical histogram H1 is constructed, and it is calculated whether the proportion of D1 in the statistical histogram H1 can reach the stability evaluation threshold, and the stability of the tunable laser operation mode is evaluated. The stability evaluation formula is: ， Where α and β are the stability assessment weights, and THR is the stability assessment threshold.

7. The method for testing the stability of the tunable laser operation mode according to claim 6, characterized in that: The first preset interval is 0-1, the second preset interval is 1-2, and the third preset interval is data greater than 2.

8. The method for testing the stability of the tunable laser operation mode according to claim 6, characterized in that: The stability assessment threshold is 85%.

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