Mode hopping checking and processing method for wavelength scanning laser for current tuning

Abstract

The invention provides a mode hopping checking and processing method for a wavelength scanning laser for current tuning, and belongs to the technical field of semiconductor laser modulation. According to the method, on the basis that a data set of current and output wavelength is obtained according to a current-wavelength nonlinear model established in an earlier stage, the current change trend of each pin of the laser is in a sawtooth peak shape by controlling the current change gradient of a left reflector, a right reflector and a phase pin of the laser; and further checking the output spectrum by using an optical fiber etalon and a dynamic optical fiber grating array, identifying a current combination in a current data set corresponding to a mode hopping region, removing, changing a spectrum interval, and carrying out calibration and checking again until the mode hopping phenomenon of the output spectrum is completely eliminated. The mode hopping phenomenon of the output spectrum of the current-tuned wavelength scanning laser is eliminated, the working stability and reliability of the laser are improved, and the continuity of the output spectrum of the laser and the system stability are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser modulation technology, specifically relating to a method for detecting and handling mode hopping in current-tuned wavelength scanning lasers. The aim is to solve the mode hopping phenomenon caused by current tuning nonlinearity during wavelength scanning, thereby improving the stability and reliability of the laser output spectrum. Background Technology

[0002] Wavelength-scanning lasers are one of the core components of modern optoelectronic technology, widely used in fiber optic sensing, optical communication systems, and high-precision spectral analysis. Their core function is to precisely control the current input to each pin of the laser, enabling the output wavelength to be continuously tunable. This, combined with specific sensors, allows for real-time monitoring and analysis of the target environment or substances. Among various wavelength tuning technologies, current tuning has become the mainstream driving scheme for wavelength scanning of semiconductor lasers (such as distributed Bragg reflector lasers, DBRs) due to its advantages of fast response, high integration, and low cost.

[0003] However, the nonlinear characteristics of current tuning also present significant technical challenges. The output wavelength of a semiconductor laser is not strictly linearly related to the injected current; its variation is influenced by complex factors such as carrier injection efficiency, quantum well band structure, thermal effects, and mode competition. The laser may transition from one transverse or longitudinal mode to another, causing unexpected abrupt changes in the output spectrum, a phenomenon known as "mode hopping." Mode hopping not only disrupts the continuity of spectral scanning but also introduces noise or spurious signals, potentially leading to system misjudgments in severe cases.

[0004] Traditional methods for addressing the hopping pattern problem mainly rely on the following strategies: (1) Increase the current adjustment step size: By avoiding the current from staying in the mode hopping sensitive area, the probability of mode hopping is reduced. However, this method sacrifices scanning resolution and cannot meet the requirements of high-precision application scenarios.

[0005] (2) Reduce scanning speed: Extend the current change time to weaken the nonlinear effect, but this leads to a decrease in system response speed and makes it unable to adapt to dynamic environment monitoring.

[0006] (3) Threshold detection and compensation algorithm: By monitoring the laser power or wavelength shift in real time, the scanning is paused and the current is adjusted when a sudden change is detected. However, this method relies on the accuracy of the threshold setting, is susceptible to noise interference, and cannot predict the exact current combination that will cause mode skipping, resulting in processing delay or misjudgment.

[0007] In summary, existing technologies generally suffer from low efficiency and poor accuracy when eliminating the hopping pattern phenomenon. Summary of the Invention

[0008] The purpose of this invention is to provide a method for detecting and handling mode hopping in current-tuned wavelength scanning lasers. By using a closed-loop technology of current gradient control and multi-sensor collaborative detection, the method accurately locates the current combination at the moment of mode hopping and dynamically optimizes the scanning parameters, thereby completely eliminating the mode hopping phenomenon in the output spectrum and improving the stability and reliability of the laser operation.

[0009] The technical solution of this invention is as follows: This method, based on the dataset of current and output wavelength obtained from the previously established current-wavelength nonlinear model, realizes the detection and processing of laser mode hopping phenomenon. The detection and processing of mode hopping are carried out through the following steps: A method for detecting and handling mode hopping in a current-tuned wavelength scanning laser includes the following steps: S1: By controlling the left and right reflectors and phase pin currents of the input laser, all current combinations are traversed at the same wavelength interval to establish a current-wavelength nonlinear model and generate a current-wavelength dataset. S2: Based on the current-wavelength dataset and with the laser wavelength output at equal intervals as the target, control the gradient of the phase pin current change of the laser and fine-tune the current values ​​of the left and right reflectors so that the current change trend of each pin of the laser is a sawtooth peak. S3: Use a fiber optic grating array or fiber optic etalon to dynamically detect the spectrum of the laser output, plot the reflection spectrum for each scanning cycle, and identify the mode-hopping point and the current combination in the corresponding dataset. S4: Remove the current combinations in the current-wavelength dataset corresponding to the mode skipping point, and recalibrate and check after adjusting the spectral interval; S5: Repeat steps S3 and S4 until the mode hopping phenomenon in the output spectrum is completely eliminated.

[0010] Furthermore, the sawtooth peak shape of the current change trend refers to the current gradually increasing during the rising phase and rapidly falling back to a low current range during the falling phase, forming a periodic sawtooth peak shape.

[0011] Furthermore, in step S3, the process is as follows: The laser output light is split by an optical fiber beam splitter and then fed into an optical fiber etalon or fiber grating array. The reflected laser light enters a photodetector through another optical fiber port of the optical fiber beam splitter and a dynamic spectrum is plotted to check the spectral characteristics and distinguish spectral mode hopping.

[0012] Furthermore, if a non-Gaussian curve appears in the dynamic spectrum, this state may indicate mode hopping; non-Gaussian curve states include spectral chirp, fine peaks, etc.

[0013] Furthermore, the method for identifying the mode-hopping point includes: performing periodic analysis on the detected optical fiber etalon spectral data, locating the abrupt change point of the spectral curve, and the horizontal axis of the spectrum of the abrupt change point corresponds to the nth combination of the current-wavelength dataset arranged in ascending order of wavelength values.

[0014] Furthermore, the method for identifying mode-hopping points includes: applying a dynamic load to the fiber Bragg grating array to shift the grating spectrum and locating the region where the fiber Bragg grating spectral curve shows abrupt changes or jumps.

[0015] Furthermore, the method for processing the jump points includes: (1) Record the current scanning points corresponding to the spectral abrupt change points or jumping regions, and compare them on the corresponding dataset of current and output wavelength, focusing on the high inflection points of the sawtooth peak current values ​​of the left and right mirrors. (2) Remove the current values ​​near the mode-hopping point. Each time the current-wavelength dataset is removed, the laser needs to be driven with a new current-wavelength dataset. Use fiber optic etalon and fiber optic grating to view the output spectrum. (3) Repeat steps (1) and (2) until the mode skipping phenomenon at the removal position is eliminated. For the current-wavelength data, change the set wavelength interval to recalibrate the laser to form a new current value, which must form a sawtooth peak curve with the remaining current value. (4) Reuse the new current-wavelength dataset to drive the laser for inspection until there is no mode skipping.

[0016] Compared with the prior art, the present invention has the following significant advantages: 1. Precisely pinpoints mode-hopping regions across the entire spectrum: By utilizing the periodic spectrum of the fiber optic etalon, the mode-hopping detection range covers the entire spectrum of the laser output, enabling the identification of mode-hopping points with abnormal spectral shapes (such as chirps or fine spikes), which are easy to reproduce.

[0017] 2. Dynamic detection of mode hopping positions: Using fiber optic etalons to check mode hopping positions has certain limitations. Since the spectrum output by the etalon does not shift, individual mode hopping points may be hidden. Dynamic detection using fiber optic grating arrays allows for the inspection of sensors under actual operating conditions, enabling accurate identification of laser mode hopping.

[0018] 3. No performance degradation: The iterative elimination and recalibration mechanism of the current dataset can maintain the spectral scanning resolution and scanning speed.

[0019] 4. Low cost and easy integration: Only existing optical components such as fiber optic etalons and fiber optic grating arrays are required, without additional hardware investment, and the algorithm can be embedded in existing driving circuit systems.

[0020] Advantages of the present invention High compatibility: Applicable to various current-tuned lasers such as DBR and DFB, requiring no hardware modification.

[0021] Comprehensive and powerful detection: Mode skipping point detection covers the entire output spectrum of the laser.

[0022] High robustness: Real-world environmental interference is simulated through dynamic fiber optic gratings to ensure the reliability of detection results. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of a method for checking and handling mode skipping in current-tuned wavelength scanning lasers.

[0025] Figure 2 This is a schematic diagram of the laser calibration structure.

[0026] Figure 3 This is a sawtooth-shaped schematic diagram of the laser pin current dataset.

[0027] Figure 4 This is a schematic diagram of the structure used for mode skipping checks on lasers.

[0028] Figure 5 This is a schematic diagram of mode hopping in the laser output spectrum.

[0029] Figure 6 This is a schematic diagram of the laser output spectrum after mode-hopping processing. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0032] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0034] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0036] The present invention will now be described in detail, see the appendix to the specification. Figures 1-6 .

[0037] Step 1. Construction of the initial current-wavelength dataset By controlling the left and right reflectors and phase pin currents of the input laser, and traversing all current combinations at certain current intervals, a current-wavelength nonlinear model is established, generating a dataset corresponding to the current and the output wavelength.

[0038] Step 2. Optimization of sawtooth peak waveform for current variation in the dataset Based on the previously generated dataset, and with the goal of equal-interval output of laser wavelengths, the gradient of the phase pin current change of the laser is controlled, and the current values ​​of the left and right reflectors are finely adjusted so that the current change trend of each pin of the laser is a sawtooth peak.

[0039] Sawtooth peak characteristics: The current increases gradually during the rising phase, and after reaching a preset threshold (such as 70mA), it quickly drops back to a low current range (such as the initial value of 20mA), forming a periodic sawtooth peak, thereby suppressing mode hopping caused by mode competition.

[0040] Step 3. Mode scrambling detection and positioning The laser output spectrum is dynamically detected using an etalon and a dynamic fiber Bragg grating array. The laser output light is split into two paths by an optical fiber beam splitter. One path is input to an optical fiber etalon or fiber Bragg grating array, and the reflected light is converted into an electrical signal by a photodetector. The reflection spectrum of each scan cycle is plotted, and the current combination in the current dataset corresponding to the mode-hopping point is identified. Accurate identification of the mode-hopping point is achieved through the following methods: First, use an optical fiber etalon for testing: if the spectral curve shows a non-Gaussian shape (such as spectral chirp or fine peaks), locate the abrupt change point in the spectral curve; Then, fiber optic grating array detection is used: the fiber optic grating array is stretched or compressed to shift the output spectrum and locate the regions where the fiber optic grating spectral curve shows abrupt changes or jumps.

[0041] Step 4. Mode skipping and iterative optimization The following steps should be taken to handle the skipped pattern: (1) Record the current scanning points corresponding to the spectral abrupt change points or jumping regions, and compare them on the dataset. Pay special attention to the high inflection points of the sawtooth peak current values ​​of the left and right mirrors, and lock the current combination region corresponding to the jumping mode point. (2) Remove the current values ​​near the mode-hopping point. Each time the current-wavelength dataset is removed, the laser needs to be driven with a new current-wavelength dataset. Use fiber optic etalon and fiber optic grating to view the output spectrum. (3) Repeat steps (1) and (2) until the mode skipping phenomenon at the removal position is eliminated. For the current-wavelength data, change the set wavelength interval to recalibrate the laser to form a new current value, which must form a sawtooth peak curve with the remaining current value. (4) The laser driven by the new current-wavelength dataset is checked using the method in step 3 to confirm that there is no mode skipping phenomenon.

[0042] Example 1 like Figures 1-5 As shown, the method for mode skipping detection and handling of current-tuned wavelength scanning lasers described in this invention employs... Figure 1The procedure shown is for checking and handling laser mode skipping, and the following steps are taken: Step 1. Construction of the initial current-wavelength dataset a) Establish as Figure 2 The calibration module consists of a host computer, an on-board CPU, a laser driver module, a laser, and a wavelength meter. b) The host computer controls the CPU to generate digital signals, which control the laser driver module to output the corresponding current. The current enters the laser through the laser pin to realize laser output. The output laser enters the wavelength meter to identify the center wavelength, power and other information of the spectrum. This information is sent to the host computer for analysis and the laser driver parameters are changed. c) Establish the mapping relationship between current and output wavelength by combining coarse and fine scaling, and generate a reference dataset containing current values ​​and their corresponding wavelengths.

[0043] Step 2. Optimization of sawtooth peak waveform for current variation in the dataset a) By controlling the current gradient of the left and right reflectors and the phase pin of the laser, the current variation trend of each pin of the laser is made to have a sawtooth peak shape, such as... Figure 3 As shown.

[0044] b) Sawtooth peak characteristics: The current increases gradually during the rising phase, and after reaching a preset threshold (e.g., 70mA), it quickly drops back to a low current range (e.g., initial value 20mA), forming a periodic sawtooth peak, thereby suppressing mode hopping caused by mode competition.

[0045] Step 3. Mode skipping detection a) such as Figure 4 As shown, the optimized current-wavelength dataset is loaded into the CPU on the board, and the laser output is controlled by the laser driver module. The laser is split into two paths by the fiber beam splitter. One path is input into the fiber optic etalon or fiber optic grating array, and the reflected light is converted into an electrical signal by the photodetector and enters the host computer. b) Using an optical fiber etalon for testing: If the spectral curve exhibits a non-Gaussian shape (such as spectral chirp or sharp peaks), locate the abrupt change point in the spectral curve, such as... Figure 5 As shown; c) Detection using fiber grating arrays: Stretch or compress the fiber grating array to shift the output spectrum and locate the regions where the fiber grating spectral curve shows abrupt changes or jumps.

[0046] Step 4. Mode skipping and iterative optimization a) Record the current scanning points corresponding to the spectral abrupt change points or jumping regions, and compare them on the dataset. Pay special attention to the high inflection points of the sawtooth peak current values ​​of the left and right mirrors, and lock the current combination region corresponding to the jumping mode point. b) Remove the current values ​​near the mode-hopping point. Each time the current-wavelength dataset is removed, the laser needs to be driven using a new current-wavelength dataset. Use fiber optic etalon and fiber optic grating to view the output spectrum. c) Repeat steps a) and b) until the mode skipping phenomenon at the removal position is eliminated. For the current-wavelength data, change the set wavelength interval to recalibrate the laser to form a new current value, which must form a sawtooth peak curve with the remaining current value. d) Use the method in step c) to check the laser driven by the new current-wavelength dataset to confirm that there is no mode hopping phenomenon, such as Figure 6 As shown.

[0047] The core innovation of this invention lies in its closed-loop method, which combines current gradient control with multi-sensor collaborative detection, along with a nonlinear model dataset, to achieve precise localization of mode-hopping points and dynamic optimization of current parameters. Specifically, the sawtooth peak current design ensures the laser operates in a stable state, while the combined use of the etalon and dynamic fiber grating provides quasi-static and dynamic detection across the entire output spectrum, simulating real-world practical environments. Finally, by iteratively eliminating mode-hopping current combinations and optimizing scanning parameters, the mode-hopping problem is completely resolved. This method maintains the inherent advantages of current tuning (fast response and low cost) while significantly improving the stability and reliability of wavelength scanning, providing crucial technical support for high-precision fiber optic systems.

[0048] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method for detecting and handling mode hopping in a current-tuned wavelength scanning laser, characterized in that, Includes the following steps: S1: By controlling the left and right reflectors and phase pin currents of the input laser, all current combinations are traversed at the same wavelength interval to establish a current-wavelength nonlinear model and generate a current-wavelength dataset. S2: Based on the current-wavelength dataset and with the laser wavelength output at equal intervals as the target, control the gradient of the phase pin current change of the laser and fine-tune the current values ​​of the left and right reflectors so that the current change trend of each pin of the laser is a sawtooth peak. S3: Use a fiber optic grating array or fiber optic etalon to dynamically detect the spectrum of the laser output, plot the reflection spectrum for each scanning cycle, and identify the mode-hopping point and the current combination in the corresponding dataset. S4: Remove the current combinations in the current-wavelength dataset corresponding to the mode skipping point, and recalibrate and check after adjusting the spectral interval; S5: Repeat steps S3 and S4 until the mode hopping phenomenon in the output spectrum is completely eliminated.

2. The method according to claim 1, characterized in that, The sawtooth peak pattern of the current change trend refers to the current gradually increasing during the rising phase and rapidly falling back to a low current range during the falling phase, forming a periodic sawtooth peak shape.

3. The method according to claim 2, characterized in that, In step S3, the process is as follows: The laser output light is split by an optical fiber beam splitter and then fed into an optical fiber etalon or fiber grating array. The reflected laser light enters a photodetector through another optical fiber port of the optical fiber beam splitter and a dynamic spectrum is plotted to check the spectral characteristics and distinguish spectral mode hopping.

4. The method according to claim 3, characterized in that, If a non-Gaussian curve appears in the dynamic spectrum, then mode hopping may be present in that state.

5. The method according to claim 4, characterized in that, Non-Gaussian curve states include: spectral chirp and fine peaks.

6. The method according to claim 4, characterized in that, The method for identifying the mode-hopping point includes: periodically analyzing the detected optical fiber etalon spectral data, locating the abrupt change point of the spectral curve, and the horizontal axis of the spectrum of the abrupt change point corresponds to the nth combination of the current-wavelength dataset arranged in ascending order of wavelength values.

7. The method according to claim 4, characterized in that, The method for identifying mode-hopping points includes: applying a dynamic load to the fiber Bragg grating array to shift the grating spectrum and locating the regions where the fiber Bragg grating spectral curve shows abrupt changes or jumps.

8. The method according to claim 4, characterized in that, The method for handling jump points includes: (1) Record the current scanning points corresponding to the spectral abrupt change points or jumping regions, and compare them on the corresponding dataset of current and output wavelength, focusing on the high inflection points of the sawtooth peak current values ​​of the left and right mirrors. (2) Remove the current values ​​near the mode-hopping point. Each time the current-wavelength dataset is removed, the laser needs to be driven with a new current-wavelength dataset. Use fiber optic etalon and fiber optic grating to view the output spectrum. (3) Repeat steps (1) and (2) until the mode skipping phenomenon at the removal position is eliminated. For the current-wavelength data, change the set wavelength interval to recalibrate the laser to form a new current value, which must form a sawtooth peak curve with the remaining current value. (4) Reuse the new current-wavelength dataset to drive the laser for inspection until there is no mode skipping.

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