Rapid absolute wavelength calibration method and system for continuous frequency sweeping laser light source

Abstract

The invention relates to the technical field of laser and optical sensing, in particular to a rapid absolute wavelength calibration method and system for a continuous frequency sweeping laser light source, and the method comprises the steps: carrying out the filtering of broadband frequency sweeping light through an adjustable narrow-band filter, generating transmission light 1, and generating transmission light 2 through an FP etalon; the generated transmission light 1 and transmission light 2 are converted into electric signals by a photoelectric detector 1 and a photoelectric detector 2 respectively, and trigger signals and electric signals are acquired by an oscilloscope; and the upper computer PC end performs waveform fitting and peak searching on the electric signal according to the trigger signal acquired by the oscilloscope, and performs curve smoothing and interpolation processing on a wavelength and time coordinate point set represented by a peak value position of a transmission peak to obtain a change relation of the wavelength of the original nonlinear frequency sweep light along with time. The calibration method provided by the invention is simple and efficient, is not influenced by wavelength tuning step size and frequency sweeping speed, and solves the problem of wavelength overlapping at the switching position of each adjacent DFB laser channel of the laser array.

Description

Technical Field

[0001] This invention relates to the field of laser and optical sensing technology, specifically to a method and system for rapid absolute wavelength calibration of a continuously swept frequency laser source. Background Technology

[0002] Laser and optical sensing technologies, with their rapid response, high stability, and excellent electromagnetic interference resistance, have demonstrated broad application potential and significant technological advantages in important fields such as environmental health monitoring, large-scale infrastructure projects, and aerospace, providing strong support for the intelligent transformation and high-quality development of various industries. The core of optical sensing technology lies in its ability to efficiently and accurately capture optical signals and convert them into information about the physical quantities to be measured that can be analyzed in depth. The swept-frequency laser source, as a key component of this technology, directly determines the overall performance of the sensing system, including core indicators such as detection speed, sensor coverage, measurement accuracy, and resolution. However, the effective utilization of the swept-frequency source and its compatibility with the sensing system depend on the accurate calibration of its wavelength-time relationship. This process is crucial for accurately mapping the sensing signal from the frequency domain to the time domain, and is essential for achieving high-precision measurements.

[0003] Currently, most mainstream frequency sweep light source calibration methods employ a point-by-point calibration strategy, which involves measuring the frequency of the tunable light source at different wavelengths using a high-precision wavelength meter. While this method meets certain application requirements to some extent, its workload increases dramatically and its efficiency decreases as the required calibration wavelength step decreases and the sweep speed increases. More importantly, point-by-point calibration is essentially a discrete measurement method; it does not produce a true continuous sweep effect, but rather an approximate continuous sweep composed of a large number of independently emitted laser points. This limits the performance of some sensing system applications, especially in scenarios requiring high-precision and high-speed measurements. For example, the wavelength calibration of tunable distributed Bragg reflector (DBR) lasers based on the Vernier effect, commonly used in fiber optic grating sensing, faces this problem.

[0004] Furthermore, with advancements in photonic integration technology, such as monolithically integrated distributed feedback (DFB) semiconductor laser arrays, which consist of multiple DFB lasers of different wavelengths connected in series and parallel, a continuous and stable frequency-sweeping optical signal can be emitted by applying a continuously varying current driving signal to each unit laser. However, an effective calibration method for this type of continuous but nonlinear fast frequency-sweeping light source is still lacking. Traditional point-by-point calibration methods are clearly no longer applicable due to their discreteness and time consumption. Summary of the Invention

[0005] This invention addresses the shortcomings of existing sweep frequency light source wavelength calibration techniques by providing a rapid absolute wavelength calibration method and system for continuously sweep frequency laser light sources, thereby resolving the wavelength overlap problem at the switching points of adjacent DFB laser channels in a laser array.

[0006] This invention is achieved through the following technical solution: A method for rapid absolute wavelength calibration of a continuously sweeping laser source is provided, the method comprising the following steps: Step S10: Generate broadband continuous sweep light with wavelength nonlinearly changing over time through a multi-wavelength DFB laser array and corresponding hardware drive control circuit, and generate a trigger signal at the beginning of the sweep cycle of each sweep light to indicate the start of the sweep. The wavelength spacing between adjacent channels can be customized according to requirements, for example, continuously covering a wavelength range of more than 40 nm, and the sweep speed can reach up to 5 kHz. Step S20: The broadband continuous sweep frequency light is split into two optical signals by a 3-dB fiber coupler and connected to the input of an adjustable narrowband filter and an FP standard, respectively. The adjustable narrowband filter converts the optical signal into transmitted light 1, and the FP standard converts the optical signal into transmitted light 2. The resulting transmitted light 1 and transmitted light 2 are converted into electrical signal 1 and electrical signal 2 by photodetector 1 and photodetector 2, respectively. The trigger signal, electrical signal 1 and electrical signal 2 are acquired by an oscilloscope. Step S30: The host PC marks the starting position of the entire frequency sweep cycle according to the trigger signal collected by the oscilloscope. It performs waveform fitting and peak finding on electrical signals 1 and 2 to find the horizontal coordinate corresponding to the peak position of each transmission peak in electrical signals 1 and 2. The horizontal coordinate represents time information. Based on the positions of the two identical wavelength transmission peaks that appear repeatedly in two adjacent laser channels in the laser array, the wavelength overlap part at the channel switching point of the laser array is identified. The wavelength and time represented by the peak position of the transmission peak of electrical signal 2 are smoothed and interpolated to obtain the wavelength change relationship of the original nonlinear frequency sweep light over time.

[0007] Preferably, the tunable narrowband filter in step S20 is an optical filter with adjustable bandwidth and wavelength. The bandwidth of the filter can be tuned in steps of 1 GHz within the range of 10 GHz to 100 GHz. Its center frequency can be programmed in increments of 1 GHz throughout the corresponding frequency band of the entire C-band. The absolute wavelength of each transmission peak position can be obtained based on the center frequency.

[0008] Preferably, in step S20, the FP etalon contains two glass plates and a quartz plate coated with a high-reflectivity film, so that the transmitted light presents multiple transmission peaks with equal frequency spacing. The spacing between two adjacent peaks is equal and constant. The specific value is set according to the cavity length of the etalon and the refractive index of the medium filling the etalon, and can be customized as needed.

[0009] Preferably, in step S30, identifying the wavelength overlap at the channel switching point of the laser array based on the positions of two identical wavelength transmission peaks that repeatedly appear in two adjacent laser channels of the laser array, includes: The filter generates a transmission peak only at the center wavelength set in the program during each frequency sweep cycle. Therefore, electrical signal 1 will only have one transmission peak in the channel range of normal frequency sweep. Transmission peaks appear at the end of the previous channel and the beginning of the next channel at the channel switching point. These two transmission peaks are actually the same transmission peak. The middle part of the two transmission peaks is the wavelength overlap part when the laser array is swept, and the absolute wavelength value of the overlap part is further identified.

[0010] Preferably, in step S30, curve smoothing and interpolation are performed based on the wavelength and time coordinate point set represented by the transmission peak position corresponding to electrical signal 2 to obtain the wavelength variation relationship of the original nonlinear swept light over time, including: The transmission peaks corresponding to electrical signals 1 and 2 are defined as interval peak 1 and interval peak 2, respectively. After the center positions of the collected interval peak 1 and interval peak 2 are completely matched, the absolute frequency and absolute wavelength of interval peak 2 can be obtained. Since the free spectral range of the FP etalon is fixed and the wavelength spacing between each interval peak 2 is equal, after solving the wavelength overlap problem, the absolute wavelength values ​​of all interval peak 2 can be obtained sequentially based on the absolute wavelength of one interval peak 2. Finally, the abscissa of the center position of each interval peak 2 and the absolute wavelength information represented by the peak point are recorded, thereby obtaining the wavelength change relationship of the swept frequency optical signal over time.

[0011] Preferably, in step S30, the host PC can further adjust the sweep frequency light source module while determining the peak position of the trigger signal and electrical signal at the start of the sweep frequency, thereby adjusting the sweep frequency rate and wavelength range of the laser array to optimize the accuracy and efficiency of wavelength calibration.

[0012] Furthermore, to achieve the above objectives, the present invention also proposes a rapid absolute wavelength calibration system for a continuously swept frequency laser source, the system comprising: Frequency sweep light source module: used to generate broadband continuous frequency sweep light with wavelength nonlinearly changing over time through a multi-wavelength DFB laser array and corresponding hardware drive control circuit. The wavelength spacing between adjacent channels can be customized according to requirements, for example, continuously covering a wavelength range of more than 40 nm, and the frequency sweep speed can reach up to 5 kHz. Feedback-adjustable light source module: used to split broadband continuous sweep light into two optical signals through a 3-dB fiber coupler, which are respectively connected to the input terminals of an adjustable narrowband filter and an FP standard. The adjustable narrowband filter converts the optical signal into transmitted light 1, and the FP standard converts the optical signal into transmitted light 2. The resulting transmitted light 1 and transmitted light 2 are converted into electrical signal 1 and electrical signal 2 by photodetector 1 and photodetector 2, respectively, and the trigger signal, electrical signal 1 and electrical signal 2 are acquired by an oscilloscope. The host computer (PC) is used to mark the start and end of the entire frequency sweep cycle based on the trigger signal acquired by the oscilloscope. It performs waveform fitting and peak finding on electrical signals 1 and 2, identifies the horizontal coordinate corresponding to the peak position of each transmission peak in electrical signals 1 and 2, and the horizontal coordinate represents time information. Based on the positions of the two identical wavelength transmission peaks that repeatedly appear in two adjacent laser channels in the laser array, it identifies the wavelength overlap at the channel switching point of the laser array. It performs curve smoothing and interpolation processing on the wavelength and time represented by the peak position of the transmission peak of electrical signal 2 to obtain the wavelength change relationship of the original nonlinear frequency sweep light over time.

[0013] Furthermore, to achieve the above objectives, the present invention also proposes a fast absolute wavelength calibration device for a continuously swept laser source. The device includes: a memory, a processor, and programs such as a fast absolute wavelength calibration algorithm for a continuously swept laser source stored in the memory and executable on the processor. The fast absolute wavelength calibration algorithm for a continuously swept laser source comprises the steps for implementing the fast absolute wavelength calibration method for a continuously swept laser source as described above.

[0014] In addition, to achieve the above objectives, the present invention also provides a computer program product, which includes programs such as a fast absolute wavelength calibration algorithm for a continuously swept laser source. When the program such as the fast absolute wavelength calibration algorithm for a continuously swept laser source is executed by a processor, it implements the fast absolute wavelength calibration method for a continuously swept laser source as described above.

[0015] The advantages and effects of this invention are: 1. This invention effectively identifies and solves the wavelength overlap problem between different laser array channels by recognizing the repeated occurrence of the transmission peak signal of the tunable narrowband filter at the channel switching point, thereby ensuring the continuity and accuracy of wavelength calibration; 2. This invention, by combining the use of an FP etalon and a tunable narrowband filter, enables rapid absolute wavelength calibration of a continuously sweeping light source. The tunable narrowband filter can accurately identify the absolute wavelength, while the FP etalon provides transmission peaks with equal frequency spacing. The combination of the two allows the system to accurately obtain the wavelength information of the sweeping light source, improving the accuracy of wavelength calibration. 3. The adjustable narrowband filter of this invention features adjustable bandwidth and wavelength, enabling the system to adapt to sweep frequency light sources with different wavelength ranges, thus improving the system's flexibility and applicability. The FP etalon is used to directly control the frequency and wavelength calibration accuracy of the sweep frequency light source. The smaller the free spectral range, the denser the transmission peak spacing, thereby achieving higher calibration accuracy and meeting the measurement needs of different fields.

[0016] 4. The host PC of this invention can not only determine the trigger signal and peak position of the electrical signal at the start of the frequency sweep, but also provide feedback adjustment to the frequency sweep light source module. This feedback mechanism enables the system to adjust the frequency sweep rate and wavelength range of the laser array in real time based on the calibration results, and the calibration efficiency and accuracy are not limited by the frequency sweep speed. Attached Figure Description

[0017] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for rapid absolute wavelength calibration of a continuously swept laser source according to the present invention.

[0019] Figure 2 This is a schematic diagram of a rapid absolute wavelength calibration system for a continuously swept laser source according to the present invention.

[0020] Figure 3 This is a schematic diagram of a multi-wavelength tunable DFB laser array sweeping laser source module based on a 4×5 matrix structure used in an embodiment of the present invention.

[0021] Figure 4 The diagram shows the electrical signal 1, which shows only one transmission peak in the channel range of the adjustable narrowband filter used in this embodiment of the invention, and the electrical signal 2, which shows the change of the transmittance of the transmitted light of the original continuously swept frequency optical signal to the FP etalon used as a function of frequency.

[0022] Figure 5The diagram shows the electrical signal data of the adjustable narrowband filter used in this embodiment of the invention, where two identical transmission peaks appear at the channel switching point of adjacent lasers.

[0023] Figure 6 This is a flowchart illustrating the algorithm used in this embodiment of the invention to solve the wavelength overlap problem and perform absolute wavelength calibration based on an adjustable narrowband filter and FP etalon.

[0024] Figure 7 This is a schematic diagram illustrating the process of accurately determining the wavelength overlap region at the channel switching point after processing electrical signal 1 and electrical signal 2 in this embodiment of the invention, and calibrating the equal wavelength interval time based on the FP etalon. Figure 8 This is a schematic block diagram of an electronic device for rapid absolute wavelength calibration of a continuously swept laser source according to the present invention. Detailed Implementation

[0025] 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.

[0026] like Figure 1 As shown, in one embodiment of the present invention, a method for rapid absolute wavelength calibration of a continuously sweeping laser source includes the following steps: Step S10: A broadband continuous sweep light with wavelength nonlinearly changing over time is generated by a multi-wavelength DFB laser array and corresponding hardware drive control circuit. A trigger signal is generated at the beginning of the sweep cycle of each sweep light to indicate the start of the sweep. The wavelength spacing between adjacent channels can be customized according to requirements, for example, continuously covering a wavelength range of more than 40 nm. The sweep speed can reach up to 5 kHz.

[0027] Step S20: The broadband continuous sweep frequency light is split into two optical signals by a 3-dB fiber coupler and connected to the input of an adjustable narrowband filter and an FP etalon, respectively. The adjustable narrowband filter converts the optical signal into transmitted light 1, and the FP etalon converts the optical signal into transmitted light 2. The resulting transmitted light 1 and transmitted light 2 are converted into electrical signal 1 and electrical signal 2 by photodetector 1 and photodetector 2, respectively. The trigger signal, electrical signal 1 and electrical signal 2 are acquired by an oscilloscope.

[0028] Specifically, in step S20, the tunable narrowband filter is an optical filter whose bandwidth and wavelength are both adjustable. The bandwidth of the filter can be tuned in steps of 1 GHz within the range of 10 GHz to 100 GHz. Its center frequency can be programmed in increments of 1 GHz throughout the corresponding frequency band of the entire C-band. The absolute wavelength of each transmission peak position can be obtained based on the center frequency.

[0029] Specifically, in step S20, the FP etalon contains two glass plates and a quartz plate coated with a high-reflectivity film, so that the transmitted light presents multiple transmission peaks with equal frequency spacing. The spacing between two adjacent peaks is equal and constant. The specific value is set according to the cavity length of the etalon and the refractive index of the medium filling the etalon, and can be customized as needed.

[0030] Step S30: The host PC marks the starting position of the entire frequency sweep cycle according to the trigger signal collected by the oscilloscope. It performs waveform fitting and peak finding on electrical signals 1 and 2 to find the horizontal coordinate corresponding to the peak position of each transmission peak in electrical signals 1 and 2. The horizontal coordinate represents time information. Based on the positions of the two identical wavelength transmission peaks that appear repeatedly in two adjacent laser channels in the laser array, the wavelength overlap part at the channel switching point of the laser array is identified. The wavelength and time represented by the peak position of the transmission peak of electrical signal 2 are smoothed and interpolated to obtain the wavelength change relationship of the original nonlinear frequency sweep light over time.

[0031] Specifically, in step S30, based on the positions of the two identical wavelength transmission peaks that repeatedly appear in two adjacent laser channels of the laser array according to the electrical signal 1, the wavelength overlap portion at the channel switching point of the laser array is identified, including: The filter generates a transmission peak only at the center wavelength set in the program during each frequency sweep cycle. Therefore, electrical signal 1 will only have one transmission peak in the channel range of normal frequency sweep. Transmission peaks appear at the end of the previous channel and the beginning of the next channel at the channel switching point. These two transmission peaks are actually the same transmission peak. The middle part of the two transmission peaks is the wavelength overlap part when the laser array is swept, and the absolute wavelength value of the overlap part is further identified.

[0032] Specifically, in step S30, curve smoothing and interpolation are performed based on the wavelength and time coordinate point set represented by the transmission peak position corresponding to electrical signal 2 to obtain the wavelength variation relationship of the original nonlinear swept light over time, including: The transmission peaks corresponding to electrical signals 1 and 2 are defined as interval peak 1 and interval peak 2, respectively. After the center positions of the collected interval peak 1 and interval peak 2 are completely matched, the absolute frequency and absolute wavelength of interval peak 2 can be obtained. Since the free spectral range of the FP etalon is fixed and the wavelength spacing between each interval peak 2 is equal, after solving the wavelength overlap problem, the absolute wavelength values ​​of all interval peak 2 can be obtained sequentially based on the absolute wavelength of one interval peak 2. Finally, the abscissa of the center position of each interval peak 2 and the absolute wavelength information represented by the peak point are recorded, thereby obtaining the wavelength change relationship of the swept frequency optical signal over time.

[0033] Specifically, in step S30, while determining the peak position of the trigger signal and electrical signal at the start of the frequency sweep, the host PC can further adjust the frequency sweep light source module to adjust the frequency sweep rate and wavelength range of the laser array, so as to optimize the accuracy and efficiency of wavelength calibration.

[0034] In addition, such as Figure 2 As shown, in one embodiment of the present invention, a fast absolute wavelength calibration system for a continuously swept frequency laser source is proposed. The system includes: Frequency sweep light source module: used to generate broadband continuous frequency sweep light with wavelength nonlinearly changing over time through a multi-wavelength DFB laser array and corresponding hardware drive control circuit. The wavelength spacing between adjacent channels can be customized according to requirements, for example, continuously covering a wavelength range of more than 40 nm, and the frequency sweep speed can reach up to 5 kHz. Feedback-adjustable light source module: used to split broadband continuous sweep light into two optical signals through a 3-dB fiber coupler, which are respectively connected to the input terminals of an adjustable narrowband filter and an FP standard. The adjustable narrowband filter converts the optical signal into transmitted light 1, and the FP standard converts the optical signal into transmitted light 2. The resulting transmitted light 1 and transmitted light 2 are converted into electrical signal 1 and electrical signal 2 by photodetector 1 and photodetector 2, respectively, and the trigger signal, electrical signal 1 and electrical signal 2 are acquired by an oscilloscope. The host computer (PC) is used to mark the start and end of the entire frequency sweep cycle based on the trigger signal acquired by the oscilloscope. It performs waveform fitting and peak finding on electrical signals 1 and 2, identifies the horizontal coordinate corresponding to the peak position of each transmission peak in electrical signals 1 and 2, and the horizontal coordinate represents time information. Based on the positions of the two identical wavelength transmission peaks that repeatedly appear in two adjacent laser channels in the laser array, it identifies the wavelength overlap at the channel switching point of the laser array. It performs curve smoothing and interpolation processing on the wavelength and time represented by the peak position of the transmission peak of electrical signal 2 to obtain the wavelength change relationship of the original nonlinear frequency sweep light over time.

[0035] This application provides a rapid absolute wavelength calibration system for a continuously swept laser source, employing a rapid absolute wavelength calibration method for a continuously swept laser source as described in the above embodiments. This system effectively solves the technical problem of wavelength overlap at the switching points of adjacent DFB laser channels in a laser array. Compared to the prior art, the beneficial effects of the rapid absolute wavelength calibration system for a continuously swept laser source provided in this application are the same as those of the rapid absolute wavelength calibration method for a continuously swept laser source provided in the above embodiments. Furthermore, other technical features of the rapid absolute wavelength calibration system for a continuously swept laser source are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0036] like Figure 3 As shown, in one embodiment of the present invention, a monolithically integrated 20-channel tunable DFB semiconductor laser array is used in a swept-frequency light source module. It employs a 4×5 series-parallel matrix structure design, where four waveguides are connected in parallel, and five lasers with sequentially increasing wavelengths are connected in series on each waveguide. This design effectively avoids grating crosstalk between lasers in adjacent channels, ensuring the single-mode characteristic of the lasers. Simultaneously, two cascaded active waveguide combiners (Y-combiners) and a semiconductor optical amplifier (SOA) are integrated on the front-end chip of the laser array's output waveguide. The SOA can perform power equalization and amplify the output of the combined optical signal.

[0037] In this embodiment, the wavelength interval between two adjacent lasers is designed to be 2 nm. Starting with the laser with the shortest wavelength, a non-linearly varying sawtooth wave current signal is sequentially applied to each of the 20 unit lasers using a driving circuit. Each DFB laser then covers a swept wavelength range of approximately 2.2 nm. By sequentially stitching together all 20 DFB lasers, a continuous coverage of a wavelength range exceeding 40 nm can be achieved, with a sweep speed of 5 kHz. It is worth noting that to ensure continuous wavelength sweep coverage of the channel wavelength interval during switching between the 20 different DFB laser channels without signal interruption, the sweep range of a single DFB laser must be greater than 2 nm. Therefore, wavelength overlap is unavoidable at the switching points between adjacent laser channels. To ensure wavelength accuracy during demodulation by the subsequent fiber optic sensing system, we need to address the wavelength overlap problem during laser array scanning and accurately calibrate the wavelength information of the continuously swept optical signal.

[0038] By utilizing the tunable narrowband filter and FP etalon proposed in this invention, combined with the characteristics of nonlinear continuous broadband sweep light, the problem of wavelength overlap between adjacent channels of the laser array during scanning is solved, achieving precise wavelength calibration. Specifically: the tunable narrowband filter is a programmable optical processor that provides tunable optical filtering and switching with adjustable bandwidth and wavelength. The filter's bandwidth can be tuned in 1 GHz steps within the range of 10 GHz to 100 GHz, and its center frequency can be programmed in 1 GHz increments across the entire C-band frequency band. Furthermore, the absolute wavelength information of each transmission peak can be determined based on the center frequency. The FP etalon contains two glass / quartz plates coated with high-reflectivity films. When broadband continuous sweep light is incident on it, the incident light undergoes multiple reflections, resulting in interference. This causes the transmission spectrum to consist of multiple transmission peaks with equal frequency spacing, and its free spectral range (FSR), i.e., the spacing between two adjacent peaks, is equal and remains fixed.

[0039] To improve the precision of the wavelength calibration system, in this embodiment, the tunable narrowband filter is set to a fixed bandwidth of 10 GHz and the original continuous sweep light is filtered using the wavelength-tunable center frequency. The transmission peak of the resulting electrical signal 1 is the interval peak 1, which has a large half-width at half-maximum and is defined as a "large peak". A FP etalon with a frequency of 12.5 GHz and a wavelength interval of 0.1 nm between the two transmission peaks is selected for wavelength calibration. The transmission peak of the resulting electrical signal 2 is the interval peak 2, which has a narrow half-width at half-maximum and is defined as a "small peak".

[0040] like Figure 4 As shown, when the adjustable narrowband filter parameters are set to a bandwidth of 10 GHz and a frequency of 195.323 THz (corresponding to a wavelength of 1535.917 nm), the center wavelength is within the normal 2 nm sweep range of a single DFB laser channel. Therefore, the electrical signal 1 of the transmitted light from this filter exhibits only one transmission peak throughout the entire sweep cycle. Since the horizontal axis represents time, in the time domain, at 24.8421... The peak value of the transmission peak represents an optical signal with a center wavelength of 1535.917 nm. From electrical signal 2, we can see the change in the transmitted light signal of the 12.5 GHz FP etalon with frequency. There is the same frequency change between two adjacent transmission peaks, that is, the wavelength interval between the peak values ​​of two adjacent transmission peaks is 0.1 nm. For example, the horizontal coordinate of the peak value of a transmission peak in electrical signal 2 almost coincides with the only large transmission peak in electrical signal 1. Then the wavelength value represented by this peak is also 1535.917 nm. The wavelength value of the adjacent left peak is 1535.907 nm, and the wavelength value of the adjacent right peak is 1535.927 nm. Thus, we can determine the wavelength information represented by each peak position.

[0041] like Figure 5 The image shows the phenomenon when the wavelength of electrical signal 1 overlaps at the channel switching point of two adjacent DFB lasers. At this time, the bandwidth of the adjustable narrowband filter remains unchanged at 10 GHz, but the frequency changes to 195.130 THz (corresponding to a wavelength of 1537.437 nm). Therefore, electrical signal 1 simultaneously exhibits two large transmission peaks in adjacent channels throughout the entire frequency sweep cycle, one at the end of the previous channel (24.063 nm). ) and the start of the next channel (26.683) These two transmission peaks are actually the same transmission peak, representing the same wavelength information of 1537.437 nm. Therefore, the middle part of these two transmission peaks, i.e., from 24.063 nm in the time domain... ~26.683 This refers to the wavelength overlap portion during laser frequency sweep switching. In the calibration procedure, the wavelength information of the continuously sweeping light is determined by the 12.5 GHz FP etalon. Therefore, the transmission peak of electrical signal 2 within the aforementioned wavelength overlap range should be discarded when calibrating the wavelength information. That is, electrical signal 2 contains two small peaks that overlap with the two large peaks in electrical signal 1, denoted as small peak 1 and small peak 2. The remaining small peaks between small peak 1 and small peak 2 represent the wavelength overlap portion, which should be discarded during calibration. The specific algorithm flow for solving the wavelength overlap problem and absolute wavelength calibration based on the adjustable narrowband filter and FP etalon is as follows: Figure 6 As shown.

[0042] like Figure 7 As shown, the oscilloscope displays in real-time the trigger signal marking the start of a sweep cycle, the electrical signal 1 of the transmitted light from the adjustable narrowband filter, and the electrical signal 2 of the transmitted light from the FP etalon. Using this filter, after sequentially resolving the wavelength overlap at the switching points of 20 adjacent DFB laser channels, the time-domain position of the abscissa of each transmission peak of the 12.5 GHz FP etalon is determined via a host computer (PC). After ignoring the transmission peaks in the wavelength overlap portion, precise wavelength calibration of the original broadband sweep light can be achieved, enabling true continuous wavelength coverage. Furthermore, the host computer can feed back the precisely calibrated wavelength information signal to the sweep light source module via a serial port and display it in real-time on the oscilloscope via an RF cable, as shown below. Figure 5 The calibration trigger signal ignores the wavelength overlap of adjacent lasers in the time domain, but each calibration signal represents a fixed wavelength value, and the wavelength interval between any two adjacent calibration signals is 0.1 nm, so as to achieve true continuity and non-overlap in the frequency domain (wavelength).

[0043] This application provides a rapid absolute wavelength calibration device for a continuously swept laser source. The device includes: at least one processor; and a memory communicatively connected to the at least one processor. The memory stores instructions executable by the at least one processor, which are executed by the at least one processor to enable the at least one processor to perform the rapid absolute wavelength calibration method for a continuously swept laser source as described in Embodiment 1 above.

[0044] like Figure 8 As shown in the illustration, in one embodiment of the present invention, a structural schematic diagram of a fast absolute wavelength calibration device for a continuously swept laser source suitable for implementing the embodiments of this application is presented. The fast absolute wavelength calibration device for a continuously swept laser source in this application embodiment may include, but is not limited to, mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions), PMPs (Portable Media Players), etc., as well as fixed terminals such as digital TVs, desktop computers, etc. Figure 8 The illustrated device for rapid absolute wavelength calibration of a continuously swept laser source is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments in this application.

[0045] Figure 8The continuously sweeping laser source rapid absolute wavelength calibration device shown may include a processing system 1001 (e.g., a central processing unit, graphics processor, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage system 1003 into a random access memory (RAM) 1004. The RAM 1004 also stores various programs and data required for the operation of the continuously sweeping laser source rapid absolute wavelength calibration device. The processing system 1001, ROM 1002, and RAM 1004 are interconnected via a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to I / O interface 1006: input systems 1007 including, for example, touchscreens, touchpads, keyboards, mice, image sensors, microphones, accelerometers, gyroscopes, etc.; output systems 1008 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage systems 1003 including, for example, magnetic tapes, hard disks, etc.; and communication systems 1009. Communication system 1009 allows a continuous sweep laser source fast absolute wavelength calibration device to communicate wirelessly or wiredly with other devices to exchange data. Although a continuous sweep laser source fast absolute wavelength calibration device with various systems is shown in the figure, it should be understood that it is not required to implement or possess all the systems shown. More or fewer systems may be implemented alternatively.

[0046] Specifically, according to the embodiments disclosed in this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication system, or installed from storage system 1003, or installed from ROM 1002. When the computer program is executed by processing system 1001, it performs the functions defined in the methods of the embodiments disclosed in this application.

[0047] This application provides a rapid absolute wavelength calibration device for a continuously swept laser source, employing a rapid absolute wavelength calibration method for a continuously swept laser source as described in the above embodiments. This method effectively solves the technical problem of wavelength overlap at the switching points of adjacent DFB laser channels in a laser array. Compared to the prior art, the beneficial effects of the rapid absolute wavelength calibration device for a continuously swept laser source provided in this application are the same as those of the rapid absolute wavelength calibration method for a continuously swept laser source provided in the above embodiments. Furthermore, other technical features of this rapid absolute wavelength calibration device for a continuously swept laser source are the same as those disclosed in the previous embodiment method, and will not be elaborated upon here.

[0048] The various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0049] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described method for fast absolute wavelength calibration of a continuous sweep laser source.

[0050] The computer program product provided in this application can solve the technical problem of wavelength overlap at the switching points of adjacent DFB laser channels in a laser array. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the fast absolute wavelength calibration method for a continuously swept laser source provided in the above embodiments, and will not be repeated here.

[0051] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for rapid absolute wavelength calibration of a continuously sweeping laser source, characterized in that, The method includes the following steps: Step S10: Generate broadband continuous sweep light with wavelength nonlinearly changing over time through a multi-wavelength DFB laser array and corresponding hardware drive control circuit, and generate a trigger signal at the beginning of each sweep light sweep cycle. Step S20: The broadband continuous sweep frequency light is split into two optical signals by a 3-dB fiber coupler and connected to the input of an adjustable narrowband filter and an FP standard, respectively. The adjustable narrowband filter converts the optical signal into transmitted light 1, and the FP standard converts the optical signal into transmitted light 2. The resulting transmitted light 1 and transmitted light 2 are converted into electrical signal 1 and electrical signal 2 by photodetector 1 and photodetector 2, respectively. The trigger signal, electrical signal 1 and electrical signal 2 are acquired by an oscilloscope. Step S30: The host PC marks the starting position of the entire frequency sweep cycle according to the trigger signal collected by the oscilloscope. It performs waveform fitting and peak finding on electrical signals 1 and 2 to find the horizontal coordinate corresponding to the peak position of each transmission peak in electrical signals 1 and 2. The horizontal coordinate represents time information. Based on the positions of the two identical wavelength transmission peaks that appear repeatedly in two adjacent laser channels in the laser array, the wavelength overlap part at the channel switching point of the laser array is identified. The wavelength and time represented by the peak position of the transmission peak of electrical signal 2 are smoothed and interpolated to obtain the wavelength change relationship of the original nonlinear frequency sweep light over time.

2. The method for rapid absolute wavelength calibration of a continuously swept laser source according to claim 1, characterized in that, In step S20, the tunable narrowband filter is an optical filter with adjustable bandwidth and wavelength. The bandwidth of the filter is tuned in steps of 1 GHz within the range of 10 GHz to 100 GHz. The center frequency is programmed in increments of 1 GHz throughout the corresponding frequency band of the entire C-band, and the absolute wavelength of each transmission peak position is obtained based on the center frequency.

3. The method for rapid absolute wavelength calibration of a continuously swept frequency laser source according to claim 1, characterized in that, In step S20, the FP etalon contains two glass plates and a quartz plate coated with reflective films, so that the transmitted light presents multiple transmission peaks with equal frequency spacing. The spacing between two adjacent peaks is equal and constant. The specific value is set according to the cavity length of the etalon and the refractive index of the medium filling the etalon.

4. The method for rapid absolute wavelength calibration of a continuously swept frequency laser source according to claim 1, characterized in that, In step S30, based on the positions of the two identical wavelength transmission peaks that repeatedly appear in two adjacent laser channels of the laser array according to electrical signal 1, the wavelength overlap portion at the channel switching point of the laser array is identified, including: The filter generates a transmission peak only at the center wavelength set in the program during each frequency sweep cycle. Electrical signal 1 only has one transmission peak in the channel range of normal frequency sweep. Transmission peaks appear at the end of the previous channel and the beginning of the next channel at the channel switching point. These two transmission peaks are the same transmission peak. The middle part of the two transmission peaks is the wavelength overlap part when the laser array is swept, and the absolute wavelength value of the overlap part is further identified.

5. The method for rapid absolute wavelength calibration of a continuously swept frequency laser source according to claim 1, characterized in that, In step S30, the wavelength and time represented by the peak position of the transmission peak of electrical signal 2 are smoothed and interpolated to obtain the wavelength variation relationship of the original nonlinear swept light over time, including: The transmission peaks corresponding to electrical signals 1 and 2 are designated as interval peak 1 and interval peak 2, respectively. After the center positions of the collected interval peak 1 and interval peak 2 are completely aligned, the absolute frequency and absolute wavelength of interval peak 2 are obtained. Since the free spectral range of the FP etalon is fixed, the wavelength spacing between each interval peak 2 is equal. Based on the absolute wavelength of one interval peak 2, the absolute wavelength values ​​of all interval peak 2 are obtained sequentially. Finally, the abscissa of the center position of each interval peak 2 and the absolute wavelength information represented by the peak point are recorded to obtain the wavelength change relationship of the swept frequency optical signal over time.

6. The method for rapid absolute wavelength calibration of a continuously swept frequency laser source according to claim 1, characterized in that, In step S30, the host PC determines the peak position of the trigger signal and electrical signal at the start of the frequency sweep, and further adjusts the frequency sweep light source module to adjust the frequency sweep rate and wavelength range of the laser array.

7. A rapid absolute wavelength calibration system for a continuously sweeping laser source, characterized in that, The continuous sweep laser source rapid absolute wavelength calibration system includes: Frequency sweep light source module: used to generate broadband continuous frequency sweep light with wavelength nonlinearly changing over time through a multi-wavelength DFB laser array and corresponding hardware drive control circuit; Feedback-adjustable light source module: used to split broadband continuous sweep light into two optical signals through a 3-dB fiber coupler, which are respectively connected to the input terminals of an adjustable narrowband filter and an FP standard. The adjustable narrowband filter converts the optical signal into transmitted light 1, and the FP standard converts the optical signal into transmitted light 2. The resulting transmitted light 1 and transmitted light 2 are converted into electrical signal 1 and electrical signal 2 by photodetector 1 and photodetector 2, respectively, and the trigger signal, electrical signal 1 and electrical signal 2 are acquired by an oscilloscope. The host computer (PC) is used to mark the start and end of the entire frequency sweep cycle based on the trigger signal acquired by the oscilloscope. It performs waveform fitting and peak finding on electrical signals 1 and 2, identifies the horizontal coordinate corresponding to the peak position of each transmission peak in electrical signals 1 and 2, and the horizontal coordinate represents time information. Based on the positions of the two identical wavelength transmission peaks that repeatedly appear in two adjacent laser channels in the laser array, it identifies the wavelength overlap at the channel switching point of the laser array. It performs curve smoothing and interpolation processing on the wavelength and time represented by the peak position of the transmission peak of electrical signal 2 to obtain the wavelength change relationship of the original nonlinear frequency sweep light over time.

8. A rapid absolute wavelength calibration device for a continuously sweeping laser source, characterized in that, The continuous sweep laser source rapid absolute wavelength calibration device includes: The system includes a memory, a processor, and a fast absolute wavelength calibration program for a continuously swept laser source stored in the memory and executable on the processor. When the processor executes the fast absolute wavelength calibration program for a continuously swept laser source, it implements a fast absolute wavelength calibration method for a continuously swept laser source as described in any one of claims 1 to 6.

9. A computer program product, characterized in that, The computer program product includes a fast absolute wavelength calibration program for a continuously swept laser source, which, when executed by a processor, implements a fast absolute wavelength calibration method for a continuously swept laser source as described in any one of claims 1 to 6.

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