Directly modulated wavelength scanning light source device and implementation method thereof

Abstract

The invention discloses a directly-modulated wavelength scanning light source device which comprises a pulse control unit, a semiconductor laser, a thermoelectric refrigerating unit, a temperature measuring element, a temperature control system, a coupler, a wavelength calibration element, a photoelectric detector and a wavelength correction system. The pulse control unit drives the semiconductor laser, the semiconductor laser is connected with a first input end of the coupler, a first output end of the coupler is connected to the wavelength calibration element, a second input end of the coupler is connected with the photoelectric detector, and the photoelectric detector is connected with the pulse control unit. A second output end of the coupler is a wavelength scanning light source output end, and the photoelectric detector is connected with the wavelength correction system. The device realizes a light source in a wavelength scanning range from several nm to dozens of nm at a wavelength scanning rate as high as MHz and above, realizes wavelength scanning in each wave band range based on a directly modulated laser, and is beneficial for adapting to more optical fiber sensing high-speed measurement application occasions.

Description

Technical Field

[0001] The present invention relates to the technical field of wavelength scanning light sources, and in particular to a directly modulated wavelength scanning light source device and an implementation method thereof. Background Art

[0002] Traditional directly modulated semiconductor lasers have obvious limitations in wavelength tuning range and scanning rate, making it difficult to achieve high-speed and wide-range wavelength scanning. For example, the wavelength variation range of directly current-tuned distributed feedback (DFB) lasers is limited, usually only a few to tens of picometers per milliampere (pm / mA) [1]. Although temperature tuning can be extended to a range of a few nanometers, its scanning speed is slow, usually not exceeding a few hundred hertz (Hz) [2-4], and therefore cannot meet the needs of dynamic and fast-changing scenes.

[0003] Although there are some high-speed scanning technologies, such as the solution based on Fourier domain mode-locked (FDML) laser, which can achieve wavelength scanning close to 105nm near 1310nm and a scanning rate of 290kHz[5], and patent application number 2020103578517 proposes an ultrafast wavelength scanning laser and its implementation method, which can achieve an ultrafast scanning rate of 1MHz, these methods rely on complex architectures and designs such as broadband light sources, optical amplifiers, tunable filters, frequency doubling optical paths and polarization controllers, which makes them expensive and limits their practical applications.

[0004] At present, mainstream commercial fiber sensor systems, such as fiber Bragg grating interrogators, usually achieve wavelength scanning by combining a broadband light source with a tunable filter, where the filter performance directly affects the parameters of the demodulator, such as wavelength accuracy, repeatability, and scanning rate. Commercial demodulators such as LUNA adopt this design, and their stability and reliability are beneficial to practical applications. However, their high price (nearly US$34,550 per unit) and scanning rate limited to kHz[6] have limited their application in civilian fields such as electric vehicle battery testing and ultrafast biochemical sensing. In contrast, directly modulated semiconductor lasers are more suitable for a wide range of fiber sensing applications due to their low cost, low power consumption, and small size. Therefore, it is urgent to further break through the limitations of their wavelength scanning range and scanning rate and improve their performance to meet the needs of a wider range of applications.

[0005] References

[0006] [1] Wang Haixu, Chen Jiandong, Chang Tianying, Lang Jinpeng, Zeng Xiangbao, Gao Wenzhi, et al. Study on modulation characteristics of distributed feedback laser. Laser Technology, 2017, 41(06): 836-840.

[0007] [2]Fuchs P,Seufert J,Koeth J,Semmel J, S,Worschech L,etal.Widely tunable quantum cascade lasers with coupled cavities for gasdetection.Applied Physics Letters 2010,97(18):181111.

[0008] [3]Duraev V, Medvedev S. Single-frequency tunable semiconductor lasers. Semiconductors 2014,48(1):120-122.

[0009] [4] Lü Guohui, Guo Xinyu, Duan Huaxian, Wang Keda, Bi Chunming, Zhang Jinling. Embedded control system for temperature-tuned DFB laser. Journal of Heilongjiang University Engineering, 2019, 10(01): 53-58.

[0010] [5]Huber R,Wojtkowski M,Fujimoto J.Fourier Domain Mode Locking(FDML):A new laser operating regime and applications for optical coherencetomography.Optics express 2006,14(8):3225-3237.

[0011] [6]Lu X,Tarascon JM,Huang J.Perspective on commercializing smartsensing for batteries.eTransportation 2022,14:100207. Summary of the invention

[0012] The purpose of the present invention is to propose a directly modulated wavelength scanning light source device and its implementation method, so as to solve the problem that the directly modulated semiconductor laser in the prior art cannot obtain a wider wavelength scanning range and the wavelength scanning rate is limited in a large tuning range. The semiconductor laser is driven by a large transient current to stimulate the optical frequency chirp phenomenon within the pulse width time, so as to realize a light source with a wavelength scanning range of several to tens of nm at a wavelength scanning rate of up to MHz and above, and a time-wavelength calibration method is proposed. The low-cost design is adopted to realize wavelength scanning in various bands based on the directly modulated laser, which is conducive to adapting to more fiber optic sensing high-speed measurement applications.

[0013] In order to solve the above technical problems, the technical solution of the present invention is:

[0014] A directly modulated wavelength scanning light source device comprises a pulse control unit, a semiconductor laser, a thermoelectric cooler, a temperature measuring element, a temperature control system, a coupler, a wavelength calibration element, a photodetector and a wavelength correction system;

[0015] The pulse control unit drives the semiconductor laser, the thermoelectric cooler is attached to the semiconductor laser chip, the temperature measuring element is attached to the semiconductor laser chip, the temperature control system connects the thermoelectric cooler and the temperature measuring element, the semiconductor laser is connected to the first input end of the coupler, the first output end of the coupler is connected to the wavelength calibration element, the second input end of the coupler is connected to the photodetector, the second output end of the coupler is the output end of the wavelength scanning light source, and the photodetector is connected to the wavelength correction system.

[0016] Preferably, the pulse control unit includes a voltage stabilizing circuit, a logic control circuit, a signal generating circuit, a pulse generating circuit, a waveform shaping circuit and a high-frequency switch driving circuit. The pulse width emitted by the pulse control unit is at least 10ns, the pulse repetition frequency needs to be at least 1kHz, and the pulse current needs to be greater than the threshold current for normal continuous operation of the semiconductor laser.

[0017] Preferably, the semiconductor laser includes but is not limited to DFB, VCSEL, FP and other lasers, and the central wavelength can meet the low-loss transmission range of 0.8 μm-1.8 μm in the communication optical fiber.

[0018] Preferably, the temperature measuring element is a thermistor, which may be an NTC thermistor.

[0019] Preferably, the temperature control system is a temperature controller, including but not limited to hardware processing systems such as voltage drive circuits and resistance detection circuits, which can be controlled by a host computer in combination with other intelligent algorithms such as PID to achieve stable temperature control.

[0020] Preferably, the coupler is a fiber optic coupler.

[0021] Preferably, the wavelength calibration element is a relative wavelength calibration device, wherein the relative wavelength calibration device adopts an optical standard or an auxiliary fiber interferometer or the like.

[0022] Preferably, the wavelength calibration element is a relative wavelength calibration device combined with an absolute wavelength calibration device, and the absolute wavelength calibration device includes a gas absorption standard or a fiber Bragg grating (FBG) calibration device, etc.

[0023] Preferably, the wavelength calibration system comprises a data acquisition card and a signal processing unit.

[0024] Preferably, the semiconductor laser emits pulse light for wavelength scanning, the laser center wavelength can be adjusted by a temperature control system, the wavelength scanning range can be changed by adjusting the pulse width by a pulse control unit, preferably 500ns, and a wavelength scanning range of nm level can be achieved. Time-wavelength calibration is performed by a wavelength calibration element and a wavelength calibration system, and the wavelength value can be determined according to the scanning time during the time domain measurement process.

[0025] The present invention has the following characteristics and beneficial effects:

[0026] 1. By applying a threshold current higher than the normal continuous operation of the semiconductor laser, the laser frequency chirps in the pulsed operation mode to achieve a spectrum scan of at least nm and a scan rate of at least MHz. This can solve the problem of small wavelength tuning range and low scan rate in traditional continuous modulation schemes such as tunable diode laser absorption spectroscopy (TDLAS). By using a temperature control system to stabilize the central wavelength, a stable and reliable scanning light source is achieved, which is conducive to resisting disturbances in the real environment.

[0027] 2. The wavelength scanning light source implemented in the present invention is pulsed light, which is conducive to subsequent multi-point and distributed sensing measurements based on optical fiber time division multiplexing method and optical time domain reflection method, and has great application potential.

[0028] 3. The present invention is not limited to wavelength scanning within the communication band, but can be flexibly scanned within the operating wavelength range of the semiconductor laser according to actual needs, such as 850nm, 1310nm, 1550nm, 1650nm, etc., and obtaining a wavelength scanning light source by directly modulating the semiconductor laser has significant cost-effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 This is a schematic diagram of the device principle of a typical wavelength scanning light source of the present invention.

[0031] Figure 2 It is a logic diagram of the pulse control unit of the present invention.

[0032] Figure 3 This is a diagram showing the spectrum detection result of directly modulating a 1550nm DFB semiconductor laser according to Example 1 of the present invention.

[0033] Figure 4 (Left) is the spectrum characteristic of the homemade Michelson fiber interferometer in Example 1 of the present invention, and (right) is the time domain detection result diagram of the direct modulation 1550nm DFB semiconductor laser.

[0034] Figure 5 This is a diagram showing the spectrum detection result of directly modulating an 850nm VCSEL semiconductor laser according to Example 2 of the present invention. DETAILED DESCRIPTION

[0035] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0038] Example 1

[0039] This embodiment provides a directly modulated wavelength scanning light source device, such as Figure 1 As shown, it includes a pulse control unit 1, a semiconductor laser 2, a thermoelectric cooler 3, a temperature measuring element 4, a temperature control system 5, a coupler 6, a wavelength calibration element 7, a photodetector 8 and a wavelength correction system 9.

[0040] Specifically, the pulse control unit 1 drives the semiconductor laser 2 by emitting pulses. The pulse control unit 1, such as Figure 2 As shown, it includes a voltage stabilizing circuit, a logic control circuit, a signal generating circuit, a pulse generating circuit, a waveform shaping circuit and a high-frequency switch driving circuit. The pulse width emitted by the pulse control unit is at least 10ns, the pulse repetition frequency needs to be at least 1kHz, and the pulse current needs to meet the threshold current greater than the normal continuous operation of the semiconductor laser. The voltage stabilizing circuit 101 adopts the L7805C2T voltage stabilizing chip, the logic control circuit 102 adopts the SN74LVC1G08DCKR logic control chip, the signal generating circuit 103 adopts the NE555 signal generator, the pulse generating circuit 104 adopts the HC123M-1 pulse generator, and the high-frequency switch driving circuit 106 adopts the UCC27517DBVR switch driving chip.

[0041] Furthermore, the thermoelectric cooler 3 is attached to the semiconductor laser 1 chip, the temperature measuring element 4 is attached to the semiconductor laser 1 chip, and the temperature control system 5 connects the thermoelectric cooler 3 and the temperature measuring element 4 .

[0042] Specifically, the temperature measuring element 4 is a thermistor. In this embodiment, an NTC thermistor is used, the resistance value at 25° C. is 10 kΩ, the tolerance of the resistance value at 25° C. is ±5%, and the thermal sensitivity coefficient is 3950 Kelvin. The temperature measuring element 4 is used to detect the temperature of the chip in the semiconductor laser in real time and transmit it to the temperature control system 5.

[0043] The temperature control system 5 is a temperature controller, including a voltage driving circuit and a resistance detection circuit. By combining a PID algorithm, the host computer can control the thermoelectric cooler 3 to achieve stable temperature control.

[0044] It should be noted that the temperature controller and PID algorithm are conventional technical means, so they are not specifically described in this embodiment.

[0045] Further configuration of this embodiment, in this embodiment, the coupler 6 is a fiber coupler, having dual ports 601 and 602 for input, and dual ports 603 and 604 for output. In this embodiment, the splitting ratio is 90:10.

[0046] The semiconductor laser 2 is connected to the first input end 601 of the coupler 6, the first output end 603 of the coupler 6 is connected to the wavelength calibration element 7, the second input end 602 of the coupler 6 is connected to the photodetector 8, the second output end 604 of the coupler 6 is the wavelength scanning light source output end, and the photodetector 8 is connected to the wavelength correction system 9.

[0047] Specifically, the wavelength calibration element 7 can be a relative wavelength calibration device. In this embodiment, the relative wavelength calibration device adopts an optical etalon or an auxiliary fiber interferometer, and the optical etalon or the auxiliary fiber interferometer needs to meet the requirement that the free spectrum range (FSR) needs to be smaller than the wavelength scanning range, for example, when the scanning range is 3nm, the FSR needs to be smaller than 3nm.

[0048] The photodetector 8 is a PIN photodiode.

[0049] The wavelength calibration system 9 includes a data acquisition card and a signal processing unit. The data acquisition card may be hantek 6074D, and the signal processing unit may be processed by a computer running host computer software.

[0050] Further, the semiconductor laser includes but is not limited to DFB, VCSEL, FP and other lasers, and the central wavelength satisfies low-loss transmission in the range of 0.8μm-1.8μm in the communication optical fiber. In this embodiment, the semiconductor laser 2 is a DFB laser with a central wavelength of 1550nm. The pulse control unit 1 drives the semiconductor laser 2 to emit pulsed light. The pulse control unit 1 adjusts the emission pulse width to 500ns, achieving a scanning rate of 2MHz and a pulse peak current of about 1A. The pulse light passes through the first input end 601 of the coupler 6 and is output from the second output end 604 to obtain a wavelength scanning optical signal; after the pulse light passes through the first output end 603 of the coupler 6 and enters the wavelength calibration element 7, it returns to the coupler 6, passes through the second input end 602 of the coupler 6, is received by the photodetector 8, and transmits the signal to the wavelength correction system 9, which performs time-wavelength curve fitting in the time domain.

[0051] Example 2

[0052] The difference between this embodiment and embodiment 1 is that the wavelength calibration element 7 is a relative wavelength calibration device combined with an absolute wavelength calibration device, and the absolute wavelength calibration device includes a gas absorption standard or a fiber Bragg grating (FBG) calibration device. The absolute wavelength calibration device needs to satisfy the requirement that the wavelength is within the scanning range of the light source. In this embodiment, when scanning near 1550nm, an acetylene (C2H2) absorption cell or a FBG with a wavelength of 1550nm can be used for absolute wavelength measurement.

[0053] In this embodiment, other features are the same as those in Embodiment 1 and will not be described repeatedly.

[0054] Example 3

[0055] This embodiment provides a method for implementing a directly modulated wavelength scanning light source device, and the specific method is as follows:

[0056] Step 1: Determination of absolute wavelength:

[0057] The present invention performs time-wavelength curve fitting in the time domain. The absolute wavelength of the semiconductor laser 2 can be provided by the temperature control system 5. Then the temperature-absolute wavelength relationship is obtained by the following formula:

[0058] λ(T)=λ0+α·(T-T0)

[0059] Where: λ(T) is the laser wavelength at temperature T, λ0 is the laser wavelength (absolute wavelength) at reference temperature T0, α is the temperature sensitivity coefficient of the laser wavelength, usually in nm / K, which indicates the rate at which the wavelength changes with temperature.

[0060] Step 2: Establishment of time-wavelength relationship:

[0061] Assuming that the wavelength scanning process is nonlinear, it needs to be calibrated by reference points in the spectrum, where the reference points are the peaks or troughs of the optical standard or auxiliary fiber interferometer. The wavelength interval of each peak or trough position is equal to the fixed FSR. Set the wavelength of these reference points to λ i , which is related to time t i Correspondingly, then:

[0062] λ i =λ(T)+i·Δλ

[0063] Wherein: λ(T) is the initial wavelength, which is accurately obtained from the above temperature-absolute wavelength relationship, i is the serial number of the reference point (eg, the i-th peak or trough), Δλ is the fixed FSR, and in this embodiment, the FSR is 0.8 nm.

[0064] Step 3: Fitting function for time-wavelength calibration:

[0065] By fitting the known reference point t i and the corresponding wavelength λ i A nonlinear time-wavelength function f(t) is obtained, which represents the relationship between wavelength and time:

[0066] λ(t)=f(t)

[0067] It can be understood that f(t) here can be a polynomial fitting, a piecewise linear fitting or other nonlinear fitting methods, and the specific fitting form depends on the complexity of the scanning nonlinearity.

[0068] Step 4: Conversion of time domain signal to wavelength domain signal After obtaining the time-wavelength function f(t), the light intensity signal I(t) in the time domain can be mapped to the wavelength domain. Assuming that the light intensity measured at time t is I(t), time t is converted to wavelength λ(t) through f(t):

[0069] I(λ(t))=I(t) or I(λ)=I(t)

[0070] Step 5: Final wavelength-intensity curve

[0071] Therefore, the final wavelength-intensity curve can be expressed as:

[0072] I(λ)=I(f -1 (λ)

[0073] Here f -1 (λ) is the inverse function of the time-wavelength function f(t), which maps the wavelength value back to the time domain and is used to obtain the light intensity corresponding to the wavelength from the original light intensity I(t).

[0074] Assuming that the λ(t) obtained through fitting is a specific function, such as λ(t) = 0.8·t+1550 (assuming that the scan starts from 1550nm), then at t = 1 second, the wavelength is λ(1) = 0.8·1+1550 = 1550.8 (nm), and the corresponding light intensity is I(1), that is, I(1550.8nm) = I(1s). In this way, all time points t can be converted into wavelengths through λ(t), and finally a complete wavelength-light intensity curve is obtained.

[0075] The effects achieved by this embodiment are as follows: Figure 3 The DFB semiconductor laser with a central wavelength of 1550nm is pulse driven, and when the emission pulse width is 500ns, a wavelength scanning effect is produced. After measurement by a spectrometer, the model of the spectrometer in this embodiment is: OSA, Yokogawa AQ6370D, and the scanning range reaches at least 3nm. The wavelength calibration element 7 is a homemade fiber Michelson interferometer, with a FSR of 0.13nm and a spectral characteristic such as Figure 4 After the photodetector 8 is converted to the time domain measurement, the wavelength calibration system 9 is based on the acquisition card. In this embodiment, the acquisition card used is Hantek6074BD 500MHz, Hantek Electronic, Qingdao, China. The collected signal is as follows Figure 4 (right) As shown in the figure, the dotted line is the pulse light signal in the time domain, and the solid line is the signal after passing through the interferometer. The wavelength range is estimated by the FSR of the interferometer, which is at least 3nm, which is consistent with the measurement of the spectrometer. According to the time-wavelength calibration method, the time-wavelength calibration curve λ can be obtained: -0.761+0.023t-5.144×10 -5 t 2 +2.403×10 -8 t 3 , the wavelength value can be determined according to the time, and the final wavelength-intensity curve can be determined by back calculation through step five.

[0076] Example 4

[0077] The difference between this embodiment and embodiment 3 is that in step 1, in the time-wavelength calibration method of this embodiment, the determination of the absolute wavelength does not consider the use of the temperature control system 5. The absolute wavelength λ can be provided by combining a relative wavelength calibration device with an absolute wavelength calibration device in the wavelength correction element 7. abs to determine, for example, using an etalon with an absolute wavelength λ abs Gas absorption cell. Then in step 1, the adjustment formula is λ i =λ abs +i·Δλ.

[0078] The relative wavelength calibration device uses an optical standard or an auxiliary fiber interferometer, etc. The absolute wavelength calibration device uses a gas absorption standard or a fiber Bragg grating (FBG) calibration device, etc.

[0079] Example 5

[0080] The difference between this embodiment and embodiment 3 is that Figure 5 As shown, when a VCESL semiconductor laser with a central wavelength of 850nm is pulse driven and the emission pulse width is 500ns, a wavelength scanning effect is produced. After measurement by a spectrometer, the scanning range reaches about 10nm.

[0081] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments including components are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A directly modulated wavelength scanning light source device, characterized in that: It includes a pulse control unit, a semiconductor laser, a thermoelectric cooler, a temperature measuring element, a temperature control system, a coupler, a wavelength calibration element, a photodetector and a wavelength correction system; The pulse control unit drives the semiconductor laser, the semiconductor laser is connected to the first input end of the coupler, the first output end of the coupler is connected to the wavelength calibration element, the second input end of the coupler is connected to the photodetector, the second output end of the coupler is the output end of the wavelength scanning light source, and the photodetector is connected to the wavelength correction system; The thermoelectric cooler and the temperature measuring element are both attached to the chip of the semiconductor laser, and the temperature control system connects the thermoelectric cooler and the temperature measuring element.

2. A directly modulated wavelength scanning light source device according to claim 1, characterized in that: The pulse control unit comprises a voltage stabilizing circuit, a logic control circuit, a signal generating circuit, a pulse generating circuit, a waveform shaping circuit and a high-frequency switch driving circuit which are connected in sequence.

3. A directly modulated wavelength scanning light source device according to claim 1, characterized in that: The pulse width of the pulse control unit is at least 10ns, the pulse repetition frequency of the pulse control unit is required to be at least 1kHz, and the pulse current of the pulse control unit is greater than the threshold current of the normal continuous operation of the semiconductor laser.

4. A directly modulated wavelength scanning light source device according to claim 1, characterized in that: The semiconductor laser is any one of DFB, VCSEL and FP, and the central wavelength of the semiconductor laser satisfies low-loss transmission in the range of 0.8 μm-1.8 μm of the communication optical fiber.

5. A directly modulated wavelength scanning light source device according to claim 1, characterized in that: The central wavelength of the semiconductor laser is 850nm-1650nm.

6. A directly modulated wavelength scanning light source device according to claim 1, characterized in that: The temperature measuring element is a thermistor.

7. A directly modulated wavelength scanning light source device according to claim 1, characterized in that: The coupler is a fiber optic coupler, and the splitting ratio of the coupler is 90:

10.

8. A method for implementing the directly modulated wavelength scanning light source device according to any one of claims 1 to 7, characterized in that: Here are the steps: Step 1, determining the absolute wavelength of the semiconductor laser according to the temperature; Step 2: Assuming that the wavelength scanning process is nonlinear, calibrate through reference points in the spectrum. The wavelength interval of each peak or trough position is equal to the fixed FSR. Set the wavelength of these reference points to λ i With time t i Correspondingly, then: l i =λ(T)+i·Δλ Where λ(T) is the initial wavelength, which is accurately obtained from the above temperature-absolute wavelength relationship, i is the serial number of the reference point, and Δλ is the fixed FSR; Step 3: By fitting the known reference point t i and the corresponding wavelength λ i , we get a nonlinear time-wavelength function f(t), which represents the relationship between wavelength and time: λ(t)=f(t) Step 4: After obtaining the time-wavelength function f(t), map the light intensity signal I(t) in the time domain to the wavelength domain. Assuming that the light intensity measured at time t is I(t), convert time t to wavelength λ(t) through f(t): I(λ(t))=I(t) Step 5: The final wavelength-intensity curve can be expressed as: I(λ)=I(f -1 (l)) Among them, f -1 (λ) is the inverse function of the time-wavelength function f(t), which maps the wavelength value back to the time domain and is used to obtain the light intensity corresponding to the wavelength from the original light intensity I(t).

9. The method for realizing a directly modulated wavelength scanning light source device according to claim 8, characterized in that: In step 1, time-wavelength curve fitting is performed in the time domain. The absolute wavelength of the semiconductor laser 2 can be provided by the temperature control system 5. Then the temperature-absolute wavelength relationship is obtained by the following formula: λ(T)=λ0+α·(T-T0) Among them, λ(T) is the laser wavelength at temperature T, λ0 is the laser wavelength at reference temperature T0, that is, the absolute wavelength, and α is the temperature sensitivity coefficient of the laser wavelength, usually in nm / K, which indicates the rate at which the wavelength changes with temperature.

10. The method for implementing a directly modulated wavelength scanning light source device according to claim 8, characterized in that: In step 1, a relative wavelength calibration device combined with an absolute wavelength calibration device is used in the wavelength correction element to provide an absolute wavelength λ abs To determine, the expression is as follows: l i =λ abs +i·Dl.

11. The method for implementing a directly modulated wavelength scanning light source device according to claim 8, characterized in that: The reference point refers to a peak or a trough of an optical etalon or an auxiliary fiber interferometer.

12. The method for implementing a directly modulated wavelength scanning light source device according to claim 8, characterized in that: In step 4, the time t is converted into the wavelength λ(t) by f(t), and the expression is replaced by: I(λ)=I(t).

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