An optimization method for quasi-continuous wavelength tuning of tunable semiconductor lasers

Abstract

This invention discloses an optimization method for quasi-continuous wavelength tuning of tunable semiconductor lasers, applicable to the field of tunable semiconductor laser technology. Unlike traditional tuning methods that obtain initial control parameters through current traversal scanning, this invention designs an optimized wavelength testing framework. Current scanning along the grid lines of the testing framework yields a wavelength-current mapping diagram. By analyzing the data in the mapping diagram, the location and number of channels in the tunable laser can be determined. Linearly connecting the median wavelengths of the same channel yields the centerline of that channel. The wavelength control current of the tunable laser is then set along the centerline with a certain step size to achieve quasi-continuous wavelength tuning, ultimately constructing a simplified wavelength-current lookup table. The optimization method involved in this invention is highly efficient and fast, avoiding the scanning of large amounts of useless data while ensuring data accuracy and validity, making it practical.

Description

Technical Field

[0001] This invention relates to the field of tunable semiconductor laser technology, and more specifically to an optimization method for quasi-continuous wavelength tuning of tunable semiconductor lasers. Background Technology

[0002] Tunable semiconductor lasers, with their advantages of small size, light weight, long lifespan, and low cost, are widely used in distributed sensing, optical communication, and other fields. Modulated grating Y-branch lasers (MG-Y lasers), as a type of tunable semiconductor laser, offer a wide wavelength tuning range, high wavelength accuracy, fast wavelength switching speed, and high side-mode rejection ratio, meeting the requirements of related applications. However, MG-Y lasers are simultaneously controlled by five currents, making the implementation of the tuning function relatively complex. This requires establishing a wavelength-current lookup table (LUT), but the traditional method of table creation uses a current traversal scanning approach. This method is inefficient, time-consuming, difficult to perform regular data calibration, and contains a large amount of useless data (poor wavelength stability, low side-mode rejection ratio, bimodal output spectrum, etc.), resulting in data waste.

[0003] Therefore, an optimization method for quasi-continuous wavelength tuning of tunable semiconductor lasers is proposed to address the difficulties in existing technologies, which is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides an optimized method for quasi-continuous wavelength tuning of tunable semiconductor lasers. An optimized wavelength test framework is designed, which replaces the traditional method of scanning the current through the left and right grating reflection areas. The laser's channel and centerline can be quickly determined by scanning the current according to the grid lines of the test framework. While ensuring the accuracy and stability of wavelength data, it significantly reduces useless data, shortens the table building time, improves the table building efficiency, and is beneficial for subsequent periodic data calibration.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser includes the following steps:

[0007] S1. Perform current scanning along the grid lines of the optimized test frame, and record the corresponding wavelength and side-mode rejection ratio for this current combination to generate a wavelength-current mapping diagram.

[0008] S2. Analyze the wavelength-current mapping diagram to determine the location and number of channels for the tunable semiconductor laser;

[0009] S3. For the same pipe, find the median wavelength corresponding to each grid line and connect them linearly to generate the center line of each pipe;

[0010] S4. Set the current in the left and right grating reflection areas along the centerline of each pipe;

[0011] S5. Linearly fit the phase region current and adjust the phase region current;

[0012] S6. Record the wavelength and the corresponding current, and construct a wavelength-current lookup table.

[0013] Optionally, the specific method for generating the wavelength-current mapping diagram in S1 is as follows:

[0014] Scan the currents of the left and right grating reflection regions of the laser at equal intervals along the grid lines of the optimized test framework. While scanning, fix the phase region current, gain region current, and semiconductor optical amplifier current of the laser. Use an optical wavelength meter to collect the wavelength and side-mode rejection ratio. Discard wavelength-current combinations that do not meet the requirements to obtain a wavelength-current mapping diagram composed of the left and right grating reflection regions and wavelengths.

[0015] The above method, optionally, involves analyzing the wavelength-current mapping diagram in S2 as follows:

[0016] Analyzing the generated wavelength-current mapping, when the current in one of the laser's left and right grating reflection areas remains constant while the current in the other grating reflection area scans along the grid lines of the test frame, the wavelength exhibits a step-like change. Based on the generated wavelength-current mapping, the number and location of the laser channels can be determined.

[0017] Optionally, when determining the current in the left and right grating reflection regions of the laser, it is necessary to screen along the center line of each pipe. The center line of the pipe can be obtained by linearly connecting the center wavelength values ​​of the same pipe in the wavelength-current mapping diagram corresponding to each grid line.

[0018] Optionally, the method described above involves determining the current in the left and right grating reflection regions of the laser along the centerline of each pipe, and achieving quasi-continuous wavelength tuning by changing the current in the phase region of the laser.

[0019] Optionally, when the laser phase region current no longer meets the tuning conditions, the laser output wavelength can be changed by altering the currents in the left and right reflection regions.

[0020] Optionally, when achieving quasi-continuous wavelength tuning by changing the phase current of the laser, a phase current region with a linearity better than 0.99 and a coverage range greater than 0.2 nm is selected. It is required that for every 0.01 mA increase in the phase current within this region, the wavelength blue shifts by 1 to 2 pm, and the phase current data within this region is linearly fitted.

[0021] The currents in the left and right reflection zones of the selected laser, the current in the phase zone, and the output wavelength of the laser are recorded to generate the final wavelength-current lookup table. The lookup table is sorted in ascending order of wavelength and the laser is output sequentially. At the same time, wavelength data is collected by a wavelength meter with a specified tuning step size of 5 pm. When the wavelength collected by the wavelength meter differs from the theoretical value in the table by less than ±3 pm, the data is considered qualified. Otherwise, the phase zone current is readjusted until all wavelengths in the table meet the requirements.

[0022] As can be seen from the above technical solution, compared with the prior art, the present invention discloses an optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser, which has the following beneficial effects:

[0023] (1) The present invention provides an optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser. By scanning the current along the grid lines of the wavelength testing framework, the "pipeline" and its centerline of the tunable semiconductor laser can be quickly determined. Setting the current in the left and right grating reflection regions along the centerline of each "pipeline" can ensure the stability and accuracy of the wavelength. At the same time, the quasi-continuous wavelength tuning function of the laser is achieved by changing the phase region current as much as possible, which further increases the output stability of the laser. The tuning step size of the wavelength in the final wavelength-current lookup table is 5 pm. The deviation between the actual measured wavelength and the theoretical wavelength is within ±2.9 pm, and the repeatability of the wavelength is better than 1.9 pm when continuously tuned 30 times.

[0024] (2) The present invention provides an optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser. By designing an optimized wavelength test framework, the amount of data in the wavelength-current mapping diagram is greatly reduced. Only 3147 sets of current and wavelength data need to be tested to determine the center line of 11 "pipes". This greatly reduces the difficulty and workload of testing, while also ensuring the stability of wavelength data.

[0025] (3) The optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser provided by the present invention is a universal optimization method that is not only applicable to MG-Y lasers, but also applicable to tunable semiconductor lasers based on the same working mechanism, such as SG-DBR lasers. Attached Figure Description

[0026] 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. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 A flowchart illustrating an optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser, provided by the present invention.

[0028] Figure 2 The wavelength testing framework designed for this invention;

[0029] Figure 3 This is the wavelength-current mapping diagram of the MG-Y laser used in this invention;

[0030] Figure 4 These are the center lines of each "pipeline" of the MG-Y laser used in this invention;

[0031] Figure 5 This is a diagram showing the phase region current tuning characteristics of the MG-Y laser used in this invention. Detailed Implementation

[0032] 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, and 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.

[0033] Reference Figure 1 As shown, this invention discloses an optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser, comprising the following steps:

[0034] S1. Perform current scanning along the grid lines of the optimized test frame, and record the corresponding wavelength and side-mode rejection ratio for this current combination to generate a wavelength-current mapping diagram.

[0035] S2. Analyze the wavelength-current mapping diagram to determine the location and number of "pipes" in the tunable semiconductor laser;

[0036] S3. For the same pipe, find the median wavelength corresponding to each grid line and connect them linearly to generate the center line of each pipe;

[0037] S4. Set the current in the left and right grating reflection areas along the centerline of each pipe;

[0038] S5. Linearly fit the phase region current and adjust the phase region current;

[0039] S6. Record the wavelength and the corresponding current, and construct a wavelength-current lookup table.

[0040] Furthermore, the specific method for generating the wavelength-current mapping in S1 is as follows:

[0041] Scan the current in the left and right grating reflection regions at equal intervals along the grid lines of the optimized test framework. While scanning, fix the phase region current, gain region current, and semiconductor optical amplifier current of the laser. Use an optical wavelength meter to collect the wavelength and side-mode rejection ratio. Discard wavelength-current combinations that do not meet the requirements to obtain the wavelength-current mapping diagram composed of the left and right grating reflection regions and wavelengths.

[0042] Furthermore, the wavelength-current mapping diagram analyzed in S2 is as follows:

[0043] Analyzing the generated wavelength-current mapping, when the current in one grating reflection region remains constant while the current in the other grating reflection region scans along the grid lines of the test frame, the wavelength exhibits a step-like change. Based on the generated wavelength-current mapping, the number and location of the laser channels can be determined.

[0044] Specifically, each step corresponds to a laser channel, which refers to several combinations of currents and their corresponding wavelengths that continuously change with the laser's output wavelength.

[0045] Furthermore, when determining the current in the left and right grating reflection regions of the laser, it is necessary to screen along the center line of each "pipe". The center line of the pipe can be obtained by linearly connecting the wavelength center values ​​of the same "pipe" in the wavelength-current mapping diagram corresponding to each grid line.

[0046] Specifically, there is a wavelength jump of 3-6nm between each pipe, so the wavelength stability corresponding to the current combination located at the center line of the pipe is better.

[0047] Furthermore, the currents in the left and right grating reflection zones are determined along the centerline of each pipe, and quasi-continuous wavelength tuning is achieved by changing the current in the phase zone.

[0048] Furthermore, quasi-continuous wavelength tuning is achieved by changing the phase region current as much as possible. When the phase region current no longer meets the tuning conditions, the output wavelength of the laser is changed by changing the currents in the left and right reflection regions.

[0049] Further, when quasi-continuous wavelength tuning is implemented by changing the current of the phase region of the laser, a phase region current region with a linearity better than 0.99 and a coverage range greater than 0.2 nm is selected, wherein for every 0.01 mA increase in the phase region current within the region, the wavelength blue-shifts by 1 to 2 pm, and linear fitting is performed on the phase current data within the region.

[0050] Further, the selected left and right reflection region currents, phase region current and the output wavelength of the laser are recorded to generate a final wavelength-current lookup table, which is sorted in ascending order of wavelength to enable the laser to output sequentially, meanwhile wavelength data is collected by a wavelength meter, and the tuning step is specified as 5 pm. When the difference between the wavelength collected by the wavelength meter and the theoretical value in the table is less than ±3 pm, the data is specified as qualified, otherwise the phase region current is readjusted until all wavelengths in the table meet the requirements.

[0051] With reference to Figure 2 , the framework is composed of 7 grid lines, each grid line is right-angled and represents the scanning path of the current of the left and right grating reflection regions. The scanning range of the current is 2.5 to 30 mA, and the scanning step is 0.1 mA. The first grid line represents the scanning path when one of the currents of the left and right grating reflection regions is 2.5 mA, and the second grid line represents the scanning path when one of the currents of the left and right grating reflection regions is 5 mA. Starting from the third grid line, the current of the reflection region increases sequentially by 5 mA up to 30 mA, and a total of 7 grid lines are scanned.

[0052] In order to realize the quasi-continuous wavelength tuning function of the tunable semiconductor laser, a wavelength-current lookup table needs to be established. In order to reduce the amount of data in the lookup table and improve the efficiency of table construction, an optimized test framework is designed. The phase region of the MG-Y laser is set to 0 mA, the gain current is fixed at 98 mA, and the current of the semiconductor optical amplifier is fixed at 48 mA. The currents of the left and right grating reflection regions are both scanned along the 7 grid lines of the test framework with a step of 0.1 mA, wavelength data with a side-mode suppression ratio greater than 40 dB and a single-peak spectrum is specified as qualified data, and a wavelength-current mapping diagram is obtained by using the wavelength data measured by an optical wavelength meter.

[0053] With reference to Figure 3As shown, when the current in one grating reflector region of the laser is fixed, while the current in the other grating reflector region is scanned along the grid lines of the test frame, the wavelength exhibits a stepped distribution, and these steps constitute the laser's channels. To ensure the stability of the laser's output wavelength, the corresponding left and right grating reflector regions' currents need to be selected along the centerline of these channels. This is because there is a 3-6 nm wavelength jump at the boundary of each channel, resulting in poor wavelength data stability and the possibility of wavelength jumps at the channel boundaries, as well as poor side-mode suppression. By comparing the wavelength-current mapping maps obtained from scanning multiple grid lines, the same channel can be identified, and the centerline of the channel can be obtained by linearly connecting the median wavelengths of each channel within that channel.

[0054] Reference Figure 4 As shown, the left and right grating reflection zone currents and phase zone currents are set along the center line of each pipe to realize the quasi-continuous wavelength tuning function of the laser. The tuning step size of the MG-Y laser used in this invention is set to 5pm. It is stipulated that the quasi-continuous wavelength tuning is achieved by changing the phase zone current as much as possible. When the phase zone current no longer meets the tuning conditions, the left and right reflection zone currents are changed to change the output wavelength of the laser.

[0055] Reference Figure 5 As shown in the figure, there are multiple linear tuning regions with different slopes. This is because when the resonance condition is not met, the wavelength will jump. The region with the wavelength coverage greater than or equal to 0.2nm and the smoothest wavelength change is selected and defined as the tuning data segment. The phase current data in this region is linearly fitted, and the fitted data is used to achieve fine tuning of the laser wavelength.

[0056] The currents in the left and right grating reflection areas and the phase area of ​​the laser are recorded in an Excel spreadsheet to form a wavelength-current lookup table. The data in the table are scanned and wavelength data is collected using a wavelength meter. Data with a difference of ±3 pm between the actual collected wavelength and the theoretical wavelength is considered qualified. Otherwise, the phase area current is readjusted until the requirements are met, thus forming the final wavelength-current lookup table.

[0057] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0058] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser, characterized in that, Includes the following steps: S1. Perform current scanning along the grid lines of the optimized test frame, and simultaneously record the corresponding wavelength and side-mode suppression ratio under the current combination of the left and right grating reflection areas to generate a wavelength-current mapping map. S2. Analyze the wavelength-current mapping diagram to determine the location and number of channels in the tunable semiconductor laser; where a channel refers to several combinations of currents and their corresponding wavelengths that continuously change with the current in the left and right grating reflection regions of the laser output wavelength. S3. For the same pipe, find the wavelength center value corresponding to each grid line and connect them linearly to generate the center line of each pipe; S4. Set the current in the left and right grating reflection areas along the centerline of each pipe; S5. Linearly fit the phase region current, and tune the laser wavelength based on the fitted phase region current. Specifically: When quasi-continuous wavelength tuning is achieved by changing the phase current of the laser, a phase current region with linearity better than 0.99 and wavelength coverage greater than 0.2nm is selected. It is required that for every 0.01mA increase in phase current in this region, the wavelength blue shifts by 1~2pm. The phase current data in this region are then linearly fitted. S6. Record the wavelength and the corresponding current, and construct a wavelength-current lookup table; The specific method for generating the wavelength-current mapping in S1 is as follows: The laser's left and right grating reflection zone currents are scanned at equal intervals along the grid lines of the optimized test framework. Simultaneously, the laser's phase zone current, gain zone current, and semiconductor optical amplifier current are fixed. Wavelength and side-mode suppression ratio (SMSR) are collected using an optical wavelength meter. Unacceptable wavelength-current combinations are discarded, resulting in a wavelength-current mapping diagram composed of the left and right grating reflection zone current combinations and wavelengths. Wavelength data with an SMSR greater than 40dB and a single-peak spectrum are considered acceptable. Specifically, the optimized test framework consists of 7 grid lines, each at a right angle, representing the scanning path of the left and right grating reflection zone currents. The current scanning range is 2.5–30mA, with a scanning step size of 0.1mA. The first grid line represents the scanning path when one of the left and right grating reflection zone currents is 2.5mA; the second grid line represents the scanning path when one of the left and right grating reflection zone currents is 5mA; starting from the third grid line, the reflection zone current increases by 5mA sequentially up to 30mA, scanning a total of 7 grid lines. The wavelength-current mapping diagram analyzed in S2 is as follows: Analyzing the generated wavelength-current mapping, when the current in one of the left and right grating reflection regions of the laser remains constant while the current in the other grating reflection region is scanned according to the grid lines of the test frame, the wavelength exhibits a step-like change; based on the generated wavelength-current mapping, the number and location of the laser channels can be determined. When determining the current in the left and right grating reflection regions of the laser, it is necessary to screen along the center line of each channel. The center line of the channel can be obtained by linearly connecting the wavelength center values ​​of the same channel in the wavelength-current mapping diagram corresponding to each grid line. Determine the currents of the left and right grating reflection regions of the laser along the centerline of each pipe, and achieve quasi-continuous tuning of the wavelength by adjusting the current of the phase region of the laser.

2. The optimization method for quasi-continuous wavelength tuning of a tunable semiconductor laser according to claim 1, characterized in that, Record the selected currents of the left and right reflection regions, the current of the phase region and the output wavelength of the laser, generate a final wavelength-current lookup table, sort the wavelengths in ascending order and enable the laser to output sequentially, collect wavelength data through a wavelength meter, set the tuning step size as 5 pm, when the difference between the wavelength collected by the wavelength meter and the theoretical value in the table is less than ±3 pm, the data is determined to be qualified; otherwise, the current of the phase region is readjusted until all wavelengths in the table meet the requirements.

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