Optical fiber light source based on fiber-optic gyroscope and control method thereof

Abstract

The application discloses a fiber-optic gyroscope-based fiber-optic light source and a control method thereof. The fiber-optic light source comprises a double-pass forward module and a backward module. The double-pass forward module comprises a fiber-optic circulator, a first wavelength division multiplexer, a first pump source, a first erbium-doped fiber, a first isolator and a first fiber-optic grating. The backward module comprises a second erbium-doped fiber, a second wavelength division multiplexer, a second pump source, a second isolator and a second fiber-optic grating. By adopting the combination of the double-pass forward module and the backward module, the high gain of the double-pass forward structure and the high stability performance of the single-pass backward structure are fully utilized, a C+L waveband super-wide spectrum laser beam with a controllable wavelength range can be finally obtained, the scale factor performance requirement of the ultra-high precision fiber-optic gyroscope is met, the zero bias stability of the ultra-high precision fiber-optic gyroscope is improved, and the scale factor performance requirement of the ultra-high precision fiber-optic gyroscope is met.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of fiber laser, in particular to a fiber light source based on a fiber gyroscope and a control method thereof. BACKGROUND

[0002] The fiber gyroscope and the inertial measurement product taking the fiber gyroscope as the core have been widely applied in the fields of navigation, aviation, spaceflight, weapon, energy and the like. The error of the ultra-high precision fiber gyroscope mainly includes the scale factor error and the output noise error. The two errors are greatly related to the light source spectrum and the transmission rule of the spectrum in the fiber light path. The change of the spectrum directly leads to the change of the average wavelength, and further leads to the deviation of the scale factor of the fiber gyroscope. The relationship between the Sagnac phase shift Φ of the fiber gyroscope and the input rotation speed Ω can be expressed as: s

[0003]

[0004] wherein, λ is the average wavelength, L is the length of the fiber ring, D is the diameter of the fiber ring, and C is the speed of light in vacuum. It can be seen that the Sagnac phase difference is directly related to the wavelength of the sensitive rotation speed.

[0005] In the design of the ultra-high precision fiber gyroscope, in order to suppress the drift of the coherent characteristics in the sensitive loop, a wide spectrum light source with low time coherence is generally used. The light emitted by the wide spectrum light source contains a plurality of wavelength components. According to the formula (1), each wavelength of light corresponds to a Sagnac phase difference. Generally, the Sagnac phase difference detected and output finally is the average value of the Sagnac phase differences corresponding to the wavelength components, i.e.

[0006]

[0007] In the formula (2), A SFO is the optical scale factor of the fiber gyroscope. In the research and test of the fiber gyroscope, the average wavelength of the wide spectrum light source is generally considered as the average wavelength in the formula (1), and the average wavelength of the wide spectrum light source is obtained by weighted average with the spectrum P(λ) as the weighted factor, i.e.

[0008]

[0009] It can be known from the combination of (2) that the change of the average wavelength directly affects the scale factor of the ultra-high precision fiber gyroscope.

[0010] ​​Generally, in order to improve the zero bias stability of the ultra-high precision fiber optic gyroscope, a wide spectrum fiber light source is adopted, but with the increase of the spectrum width, the wavelength stability and the spectrum type asymmetry of the wide spectrum fiber light source begin to deteriorate, which has an influence on the zero bias stability and the scale of the ultra-high precision fiber optic gyroscope, and makes the scale factor performance of the ultra-high precision fiber optic gyroscope difficult to meet the use requirements. SUMMARY

[0011] The application provides a fiber light source based on a fiber optic gyroscope and a control method thereof, the wavelength and spectrum type of the fiber light source are real-time controllable, and the performance of the fiber light source for the fiber optic gyroscope is greatly improved.

[0012] In a first aspect, an embodiment of the application provides a fiber light source based on a fiber optic gyroscope, the fiber light source comprising a double-pass forward module and a backward module.

[0013] The double-pass forward module comprises a fiber optic circulator, a first wavelength division multiplexer, a first pump source, a first erbium-doped fiber, a first isolator and a first fiber Bragg grating; and the backward module comprises a second erbium-doped fiber, a second wavelength division multiplexer, a second pump source, a second isolator and a second fiber Bragg grating.

[0014] A first end of the first wavelength division multiplexer is connected with the fiber optic circulator, a second end of the first wavelength division multiplexer is connected with an excitation light output end of the first pump source, a third end of the first wavelength division multiplexer is connected with a first end of the first erbium-doped fiber, a second end of the first erbium-doped fiber is connected with an input end of the first isolator, an output end of the first isolator is connected with a first end of the first fiber Bragg grating, a second end of the first fiber Bragg grating is connected with a first end of the second erbium-doped fiber, a second end of the second erbium-doped fiber is connected with a first end of the second wavelength division multiplexer, a second end of the second wavelength division multiplexer is connected with an excitation light output end of the second pump source, a third end of the second wavelength division multiplexer is connected with an input end of the second isolator, an output end of the second isolator is connected with a first end of the second fiber Bragg grating, and a second end of the second fiber Bragg grating is a laser output end; the laser output end is used for outputting a laser beam for a fiber optic gyroscope.

[0015] Optionally, a wavelength control module is further included; the wavelength control module comprises a coupler, an F-P tunable filter, a first piezoelectric ceramic, a second piezoelectric ceramic, a photodetector, an A / D converter, a control unit, a first D / A converter, a second D / A converter, a piezoelectric ceramic driving unit and an F-P filter driving unit; the first piezoelectric ceramic is wrapped around a side wall of the first fiber Bragg grating, and the second piezoelectric ceramic is wrapped around a side wall of the second fiber Bragg grating.

[0016] The first end of the coupler is connected with the output end of the second isolator, the second end of the coupler is connected with the first end of the second fiber grating, the third end of the coupler is connected with the optical signal input end of the F-P tunable filter, the optical signal output end of the F-P tunable filter is connected with the input end of the photodetector, the output end of the photodetector is connected with the signal input end of the A / D converter, the signal output end of the A / D converter is connected with the signal input end of the control unit, the first piezoelectric signal output end of the control unit is connected with the input end of the first D / A converter, the output end of the first D / A converter is connected with the input end of the F-P filter driving unit, and the driving signal output end of the F-P filter driving unit is connected with the driving signal input end of the F-P tunable filter; the second piezoelectric signal output end of the control unit is connected with the input end of the second D / A converter, the output end of the second D / A converter is connected with the input end of the piezoelectric ceramic driving unit, and the driving signal output end of the piezoelectric ceramic driving unit is connected with the first piezoelectric ceramic and the second piezoelectric ceramic respectively.

[0017] Optionally, the 3dB bandwidth of the transmission spectrum of the F-P tunable filter is less than the 3dB bandwidth of the reflection spectrum of the second fiber grating.

[0018] Optionally, the fiber length of the second erbium-doped fiber is greater than the fiber length of the first erbium-doped fiber; and the doping concentration of the erbium element in the second erbium-doped fiber is greater than the doping concentration of the erbium element in the first erbium-doped fiber.

[0019] Optionally, the optical power of the second pump source is greater than the optical power of the first pump source.

[0020] Optionally, the control unit is further connected with the first pump source and the second pump source respectively.

[0021] In a second aspect, an embodiment of the present application provides a control method of a fiber-optic light source based on a fiber-optic gyroscope, which is used to control the fiber-optic light source provided in the first aspect, and the control method comprises the following steps of:

[0022] determining a laser parameter of a first laser beam for the fiber-optic gyroscope; the laser parameter comprises a center wavelength and a spectral line width;

[0023] controlling a pump light parameter of the first pump source and the second pump source respectively according to the laser parameter, so that the laser output end outputs the first laser beam; wherein the pump light parameter comprises a pump light center wavelength and a pump light power.

[0024] Optionally, according to the laser parameters, the pump light parameters of the first pump source and the second pump source are controlled respectively, so that after the laser output end outputs the first laser beam, the method further comprises:

[0025] receiving an output power of the photodetector;

[0026] controlling an F-P filter driving unit to adjust a cavity length of the F-P tunable filter according to a corresponding relationship between the output power and a center wavelength driving model of a transmission spectrum of the F-P tunable filter;

[0027] determining a first center wavelength of the first laser beam when the center wavelength of the transmission spectrum of the F-P tunable filter coincides with a center wavelength of a reflection spectrum of the second fiber grating.

[0028] Optionally, after the first center wavelength of the first laser beam is determined, the method further comprises:

[0029] controlling the first center wavelength of the first laser beam output by the laser output end to switch to a ring-in center wavelength according to a comparison result of the first center wavelength and the ring-in center wavelength;

[0030] wherein the ring-in center wavelength is a center wavelength of a laser beam inside the fiber-optic gyroscope sensitive ring.

[0031] Optionally, the wavelength control module further comprises a temperature detection unit, which is connected with the control unit.

[0032] after the first center wavelength of the first laser beam output by the laser output end is controlled to switch to the ring-in center wavelength according to the comparison result of the first center wavelength and the ring-in center wavelength, the method further comprises:

[0033] receiving a working temperature of the fiber-optic gyroscope sensitive ring in a current working state output by the temperature detection unit;

[0034] controlling the laser output end to output a compensation beam corresponding to the current working temperature according to a comparison result of the working temperature and a temperature compensation model;

[0035] wherein the input end of the fiber-optic gyroscope sensitive ring is connected with the laser output end; and the temperature compensation model refers to a corresponding relationship between a working temperature of the fiber-optic gyroscope sensitive ring and a center wavelength of a laser beam inside the ring.

[0036] The example provided by the application provides a fiber-optic light source based on a fiber-optic gyroscope, which adopts a combination of a double-pass forward module and a backward module, fully utilizes the high gain of the double-pass forward structure and the high stability performance of the single-pass backward structure, and finally obtains a C+L waveband super wide spectrum laser beam with a controllable wavelength range, meets the scale factor performance requirement of the super high precision fiber-optic gyroscope, is beneficial to improving the zero bias stability of the super high precision fiber-optic gyroscope, and meets the scale factor performance requirement of the super high precision fiber-optic gyroscope. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a structural schematic diagram of a fiber-optic light source based on a fiber-optic gyroscope provided by the application;

[0038] Figure 2 is a module schematic diagram of a fiber-optic light source based on a fiber-optic gyroscope provided by the application;

[0039] Figure 3 is Figure 2 a structural schematic diagram of a fiber-optic light source based on a fiber-optic gyroscope provided by the application;

[0040] Figure 4 is a control method schematic diagram of a fiber-optic light source based on a fiber-optic gyroscope provided by the application;

[0041] Figure 5 is a control method schematic diagram of another fiber-optic light source based on a fiber-optic gyroscope provided by the application;

[0042] Figure 6 is Figure 3 a C+L super wide spectrum fiber-optic light source closed loop circuit diagram based on a fiber-optic gyroscope;

[0043] Figure 7 is a super high precision fiber-optic gyroscope compensation principle diagram adopting a C+L waveband fiber-optic light source. DETAILED DESCRIPTION

[0044] The application will be further described in detail below in combination with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the application, and not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings, not all structures.

[0045] Figure 1 is a light path schematic diagram of a fiber-optic light source based on a fiber-optic gyroscope provided by the application. In combination with Figure 1As shown, the embodiment of the present application provides a fiber-optic gyroscope based fiber-optic light source, which comprises a double-pass forward module 10 and a backward module 20; the double-pass forward module 10 comprises a fiber-optic circulator 11, a first wavelength division multiplexer 12, a first pump source 13, a first erbium-doped fiber 14, a first isolator 15 and a first fiber-optic grating 16; the backward module 20 comprises a second erbium-doped fiber 21, a second wavelength division multiplexer 22, a second pump source 23, a second isolator 24 and a second fiber-optic grating 25.

[0046] The first end 1 of the first wavelength division multiplexer 12 is connected with the fiber-optic circulator 11, the second end 2 of the first wavelength division multiplexer 12 is connected with the excitation light output end of the first pump source 13, the third end 3 of the first wavelength division multiplexer 12 is connected with the first end 1 of the first erbium-doped fiber 14, the second end 2 of the first erbium-doped fiber 14 is connected with the input end of the first isolator 15, the output end of the first isolator 15 is connected with the first end 1 of the first fiber-optic grating 16, the second end 2 of the first fiber-optic grating 16 is connected with the first end 1 of the second erbium-doped fiber 21, the second end 2 of the second erbium-doped fiber 21 is connected with the first end 1 of the second wavelength division multiplexer 22, the second end 2 of the second wavelength division multiplexer 22 is connected with the excitation light output end of the second pump source 23, the third end 3 of the second wavelength division multiplexer 22 is connected with the input end of the second isolator 24, the output end of the second isolator 24 is connected with the first end 2 of the second fiber-optic grating 25, and the second end 3 of the second fiber-optic grating 25 is a laser output end B; the laser output end B is used for outputting a laser beam for a fiber-optic gyroscope.

[0047] For example, the fiber-optic light source outputs a wide-spectrum laser beam of C band + L band, the C band is 1530nm-1565nm, and the L band is 1530nm-1625nm. Among them, Figure 1 In the embodiment of the present application,

[0048] The light path at the left end of point A is a double-pass forward controlled design, the first pump source 13 can adopt a 980nm pump light device to generate a 980nm band laser light source. The first wavelength division multiplexer 12 adopts a 2×1 channel wavelength division multiplexer, and the laser generated by the first pump source 13 is injected into the first erbium-doped fiber 14 (forward) and the fiber-optic circulator 11 (backward) through the first wavelength division multiplexer 12. The laser along the forward direction passes through the first erbium-doped fiber 14 to generate an amplified spontaneous emission signal, and the laser along the backward direction passes through the first erbium-doped fiber 14 again after being reflected by the fiber-optic circulator 11. The fiber-optic circulator 11 has a full reflection mirror function, and can reflect the backward laser to realize bidirectional optical signal transmission in a single fiber. The first isolator 15 can conduct the forward C band light output by the first erbium-doped fiber 14 in one direction, and has the function of isolating reflected light, so that high-gain laser output can be obtained at point A.

[0049] The light path between A and B is a single round back controlled design, the second pump laser 23 can also use a 980 nm pump laser to generate a 980 nm band laser source. The second wave division multiplexer 22 uses a 1x2 channel wave division multiplexer, and the laser generated by the second pump laser 23 is injected into the second erbium-doped fiber 21 through the second wave division multiplexer 22. In the second erbium-doped fiber 21, amplified spontaneous emission signals are generated in the forward direction (from A to B) and the backward direction (from B to A); the forward light is output by the second isolator 24, and the backward light is useless light. Since the output light is opposite to the pump light, additional noise caused by optical feedback can be avoided. The second isolator 24 unidirectionally conducts the forward light output by the second wave division multiplexer 22, which plays a role in isolating reflected light, so that high-stability laser output can be obtained at point A.

[0050] The first pump source 13 and the second pump source 23 include semiconductor lasers or fiber lasers, and can also use 1064 nm, 808 nm, etc. band light sources. The first fiber grating 16 and the second fiber grating 25 can both use Bragg fiber gratings. Under the action of external stress, the center wavelength of the first fiber grating 16 has a linear relationship with the stress, which can control the wavelength and frequency of the C-band light, so that the C-band light signal output at point A meets the requirements; the center wavelength of the second fiber grating 25 has a linear relationship with the stress, which can control the wavelength and frequency of the L-band light, so that the L-band light signal output at point B meets the requirements.

[0051] The fiber grating is a cylindrical waveguide medium. When its refractive index meets the propagation condition, the light wave entering the optical fiber will propagate along a specific direction. In the case of satisfying the resonance condition of the fiber grating, the light wave will mode-couple in the grating area of the optical fiber. The fiber grating will reflect the light meeting the Bragg law back, and the light of other bands will be transmitted. By using this structural characteristic, the wavelength selection of the light wave entering the optical fiber can be realized. Since the center wavelength and frequency of the C-band light signal and the L-band light signal are controlled by the fiber grating, by reasonably setting the grating parameters of the first fiber grating 16 and the second fiber grating 25, such as the grating period, the wavelength selection of the C-band light signal at point A and the wavelength selection of the C-band light signal and the L-band light signal at point B can be realized, and finally a C+L band super-wide spectrum laser beam with controllable wavelength range can be obtained at point B.

[0052] In conclusion, the optical fiber light source based on the fiber-optic gyroscope provided by the embodiment of the application can finally obtain a C+L waveband super-wide spectrum laser beam with a controllable wavelength range by adopting a combination of a double-pass forward module and a backward module, fully utilizing the high gain of the double-pass forward structure and the high stability performance of the single-pass backward structure, and meeting the scale factor performance requirement of the ultra-high precision fiber-optic gyroscope. The optical path setting is conducive to improving the zero bias stability of the ultra-high precision fiber-optic gyroscope and meeting the scale factor performance requirement of the ultra-high precision fiber-optic gyroscope.

[0053] Figure 2 is a module schematic diagram of the optical fiber light source based on the fiber-optic gyroscope provided by the application; Figure 3 is Figure 2 a structural schematic diagram of the optical fiber light source based on the fiber-optic gyroscope provided by the application. As shown in Figures 2-3 the embodiment of the application provides an optical fiber light source based on the fiber-optic gyroscope, which also comprises a wavelength control module 30; the wavelength control module 30 comprises a coupler 31, an F-P tunable filter 32, a first piezoelectric ceramic 33, a second piezoelectric ceramic 34, a photodetector 35, an A / D converter 36, a control unit 37, a first D / A converter 38, a second D / A converter 39, a piezoelectric ceramic driving unit 330, and an F-P filter driving unit 320. The first piezoelectric ceramic 33 is wrapped around the sidewall of the first fiber grating 16, and the second piezoelectric ceramic 34 is wrapped around the sidewall of the second fiber grating 25.

[0054] As shown in Figure 3 the first end 1 of the coupler 31 is connected to the output end of the second isolator 24, the second end 2 of the coupler 31 is connected to the first end 1 of the second fiber grating 25, the third end 3 of the coupler 31 is connected to the optical signal input end of the F-P tunable filter 32, the optical signal output end of the F-P tunable filter 32 is connected to the input end of the photodetector 35, the output end of the photodetector 35 is connected to the signal input end of the A / D converter 36, the signal output end of the A / D converter 36 is connected to the signal input end of the control unit 37, the first piezoelectric signal output end of the control unit 37 is connected to the input end of the first D / A converter 38, the output end of the first D / A converter 38 is connected to the input end of the F-P filter driving unit 320, the driving signal output end of the F-P filter driving unit 320 is connected to the driving signal input end of the F-P tunable filter 32, the second piezoelectric signal output end of the control unit 37 is connected to the input end of the second D / A converter 39, the output end of the second D / A converter 39 is connected to the input end of the piezoelectric ceramic driving unit 330, and the driving signal output end of the piezoelectric ceramic driving unit 330 is connected to the first piezoelectric ceramic 33 and the second piezoelectric ceramic 34 respectively.

[0055] Specifically, the photoelectric detector 35 can monitor the laser power entering the F-P tunable filter 32 in real time, and output an analog signal carrying the laser power to the A / D converter 36. The A / D converter 36, namely an analog-to-digital converter or simply an ADC, can convert the continuous analog signal output by the photoelectric detector 35 into a discrete digital signal and transmit it to the control unit 37. The control unit 37 can adopt a host computer, a controller, a field programmable gate array circuit (FPGA), etc., for realizing the reception and processing of signals and the output of control signals. The first D / A converter 38 and the second D / A converter 39, namely digital-to-analog converters or simply DACs, can convert the digital signal output by the control unit 37 into an analog signal, for driving the piezoelectric ceramic driving unit 330 and the F-P filter driving unit 320. The first piezoelectric signal and the second piezoelectric signal are digital signals.

[0056] The coupler 31 can adopt a 1x2 channel. The L-band optical signal generated by the second erbium-doped optical fiber 2 and the C-band optical signal not excited at point A pass through the second isolator 24 and the coupler 31 to enter the second fiber grating. Part of the C+L-band optical signal is reflected by the second end 2 of the second fiber grating 25, enters the F-P tunable filter 32 through the third end 3 of the coupler 31, and is used for exciting the center wavelength detection of the light. The remaining part of the C+L-band optical signal is output at point B, as the laser light source of the super-high-precision fiber optic gyroscope. The present application can realize the reflection of part of the C+L-band optical signal and the transmission of part of the C+L-band optical signal by reasonably setting the transmission-reflection ratio of the second end 2 of the second fiber grating 25, so as to meet the requirements of signal light detection.

[0057] The F-P tunable filter 32, i.e. a Fabry-Perot filter, is an optical narrowband filter that can detect the center wavelength of the Bragg fiber grating. When the broadband light source is transmitted into the F-P cavity, the light wave with a certain wavelength that meets the coherence requirement has the strongest interference. The cavity length of the F-P cavity is controlled by the piezoelectric ceramic inside. The application drives the F-P filter driving unit 320 by outputting a triangular wave voltage signal from the control unit 37 to the first D / A converter 38, so as to control the cavity length of the F-P tunable filter 32. With the change of the cavity length, the output wavelength of the F-P cavity will also change, which is equivalent to that the F-P tunable filter 32 can scan the input light within a certain wavelength range. The photodetector 35 collects the laser power of the C+L band optical signal entering the F-P tunable filter 32 in real time. When the reflection spectrum center wavelength position of the second fiber grating 25 and the transmission spectrum center wavelength position of the F-P tunable filter 32 completely overlap, the output light intensity of the F-P tunable filter 32 reaches the maximum, and the photodetector 35 collects the maximum laser power. At this time, the transmission spectrum center wavelength of the F-P tunable filter 32 is the reflection spectrum center wavelength of the second fiber grating 25.

[0058] The first fiber grating 15 and the second fiber grating 25 adopt Bragg fiber gratings, which have good sensitivity to strain. The simulation results of a Bragg fiber grating with a center wavelength of 1530 nm show that when the Bragg fiber grating is not subjected to strain, its reflection spectrum is a Bragg center wavelength of 1530 nm. When the fiber grating is subjected to a gradually increasing positive axial stress, its reflection spectrum will gradually shift to the right, i.e. the reflection spectrum center wavelength gradually increases. When the fiber grating is subjected to a gradually increasing negative axial stress, its reflection spectrum will gradually shift to the left, i.e. the reflection spectrum center wavelength gradually decreases.

[0059] Strain acting on the fiber grating will cause the grating period to change. Pulling or pressing the fiber grating will cause the grating area to deform, which will cause the center wavelength of the Bragg fiber grating to shift. The application coats the first piezoelectric ceramic 33 on the side wall of the first fiber grating 16 and the second piezoelectric ceramic 34 on the side wall of the second fiber grating 25. The control unit 37 outputs a triangular wave voltage signal to the second D / A converter 39 to drive the piezoelectric ceramic driving unit 330, so as to control the pressure of the first piezoelectric ceramic 33 acting on the first fiber grating 16 and realize the adjustment of the reflection spectrum center wavelength of the first fiber grating 16. The control unit 37 outputs a triangular wave voltage signal to the second D / A converter 39 to drive the piezoelectric ceramic driving unit 330, so as to control the pressure of the second piezoelectric ceramic 34 acting on the second fiber grating 25 and realize the adjustment of the reflection spectrum center wavelength of the second fiber grating 25.

[0060] The relationship between the triangular wave voltage signal of the driving source of the F-P tunable filter 32 and the wavelength of the transmitted light can be calibrated in advance, and then the center wavelength of the reflection peak of the second end 2 of the second fiber grating 25 at this moment can be calculated by measuring the driving voltage of the F-P filter 32.

[0061] Optionally, in combination with the above Figure 3 As shown, the control unit 37 is also connected with the first pump source 13 and the second pump source 23 respectively. The control unit 37 can also control the laser power of the first pump source 13 and the second pump source 23 according to the center wavelength of the reflection peak of the second end 2 of the second fiber grating 25.

[0062] Optionally, in combination with the above Figure 3 As shown, the 3dB bandwidth of the transmission spectrum of the F-P tunable filter 32 is set to be less than the 3dB bandwidth of the reflection spectrum of the second fiber grating 25. Generally, the 3dB bandwidth of the reflection spectrum of a Bragg fiber grating is about 0.2nm, and thus the 3dB bandwidth of the transmission spectrum of the F-P tunable filter 32 is set to be less than 0.2nm. Through this setting, the demodulation accuracy can be ensured and the photoelectric detector 35 can measure the light intensity in the F-P tunable filter 32.

[0063] In optical communication applications, the commonly used method for specifying the spectral width is the half-width, which is the same conventionally used bandwidth defined as the frequency range over which the power drops by less than half (up to -3dB). The fineness refers to the wavelength resolution capability of the F-P tunable filter, and its value is approximately equal to the value of the free spectral range divided by the value of the 3dB bandwidth of the transmission spectrum. The greater the value of the fineness, the stronger the wavelength resolution capability of the F-P tunable filter. The fineness of the F-P tunable filter is set to be greater than or equal to 100000, and the wavelength tuning range of the F-P tunable filter is about 30nm.

[0064] The erbium-doped fiber refers to an optical fiber doped with a small amount of rare earth element erbium. Since the emission and absorption coefficients of L-band optical signals are less than those of C-band optical signals, the fiber length of the second erbium-doped fiber 21 is set to be greater than that of the first erbium-doped fiber 14, and the doping concentration of the erbium element in the second erbium-doped fiber 21 is set to be greater than that in the first erbium-doped fiber 14.

[0065] In a feasible implementation, in order to improve the excitation efficiency of the L-band optical signal, the fiber length of the second erbium-doped fiber 21 is set to be L2>2L1, the fiber length of the first erbium-doped fiber 14 is L1, L2>2L1; the doping concentration of the erbium element in the second erbium-doped fiber 21 is N2, the doping concentration of the erbium element in the first erbium-doped fiber 14 is N1, N2>2N1.

[0066] In order to further improve the excitation efficiency of the L-band optical signal, optionally, the optical power of the second pump source 23 is greater than that of the first pump source 13. Preferably, the optical power of the first pump source 13 is P1, and the optical power of the second pump source 23 is P2, P2>2P1.

[0067] Based on the same inventive concept, the embodiment of the present application also provides a control method of the optical fiber light source based on the fiber-optic gyroscope, which is used for controlling the optical fiber light source of the fiber-optic gyroscope provided by the above-mentioned embodiment. Figure 4 It is a control method of the optical fiber light source based on the fiber-optic gyroscope provided by the present application. In combination with Figure 1 and Figure 4 It is shown that the control method provided by the embodiment of the present application comprises:

[0068] S101, determining the laser parameter of the first laser beam for the fiber-optic gyroscope.

[0069] The laser parameter comprises a center wavelength and a spectral line width. The spectral line width refers to the frequency width between two upper half maximum intensity points on the radiation spectrum distribution curve, which is called spectral line width or half value width, and is simply called spectral width. The spectral value radiated by the spectral width is the wavelength region of the specified percentage of the maximum value.

[0070] Specifically, in combination with Figure 1 It is shown that according to the use requirement of the fiber-optic gyroscope, the laser parameter of the first laser beam output by the optical fiber light source at B point is determined, such as the first laser beam with a C+L-band super wide spectral range whose wavelength range is 1530nm-1625nm for the ultra-high precision fiber-optic gyroscope.

[0071] S102, according to the laser parameter, respectively controlling the pump light parameter of the first pump source and the second pump source, so as to make the laser output end output the first laser beam.

[0072] The pump light parameter comprises a pump light center wavelength and a pump light power.

[0073] Specifically, in combination with Figure 1 It is shown that the C+L-band light generation process is as follows:

[0074] The 980nm band pump light provided by the first pump source 13 is controlled, the C-band optical signal is generated at A point after the first doped erbium fiber 14 absorbs the 980nm band pump light, the C-band optical signal is isolated by the first isolator 15 and selected by the first fiber grating 16, and then the C-band optical signal enters the second doped erbium fiber 21 as the induced light.

[0075] The 980nm waveband pump light provided by the second pump source 23 is controlled, and after the second doped fiber 21 absorbs the 980nm waveband pump light, C waveband light signals are generated. At this time, part of the C waveband light signals generated at the A point are absorbed together with the C waveband light signals generated by the second doped fiber 21 to generate L waveband light signals. After being isolated by the second isolator 24 and selected by the second fiber grating 25, the remaining part of the C waveband light signals generated at the A point by the double-pass forward module 10 and the L waveband light generated by the backward module 20 are output as C+L waveband super wide spectrum laser beams at the B point (laser output end).

[0076] In the use of the fiber optic gyroscope, by regulating the central wavelength and the pump light power of the first pump source 13 and the second pump source 23 and changing the grating parameters of the first fiber grating 16 and the second fiber grating 25, the laser parameters of the C+L waveband super wide spectrum laser beams output at the B point, such as the power size and the wavelength range, can be regulated to meet the use requirements of the super high precision fiber optic gyroscope.

[0077] On the basis of the above embodiment, combined with Figure 2 and Figure 3 , the fiber optic light source based on the fiber optic gyroscope provided by the embodiment of the present application further comprises a wavelength control module 30. The wavelength control module 30 comprises a coupler 31, an F-P tunable filter 32, a first piezoelectric ceramic 33, a second piezoelectric ceramic 34, a photodetector 35, an A / D converter 36, a control unit 37, a first D / A converter 38, a second D / A converter 39, a piezoelectric ceramic driving unit 330, and an F-P filter driving unit 320. The first piezoelectric ceramic 33 is wrapped around the first fiber grating 16, and the second piezoelectric ceramic 34 is wrapped around the second fiber grating 25.

[0078] Figure 5 is another control method of the fiber optic light source based on the fiber optic gyroscope provided by the present application; Figure 6 is a closed loop circuit diagram of Figure 3 based on the fiber optic gyroscope. Combined with Figure 2 , Figure 3 , Figure 5 and Figure 6 , the embodiment of the present application further provides a control method of the fiber optic light source based on the fiber optic gyroscope, which comprises the following steps:

[0079] S201, determining the laser parameters of the first laser beam for the fiber optic gyroscope.

[0080] Continuing to combine the above-mentioned embodiments of Figure 1 and Figure 4 .

[0081] S202, control the pump light parameters of the first pump source and the second pump source respectively according to the laser parameters, so that the first laser beam is output at the laser output end.

[0082] Continue to combine the above-mentioned embodiments Figure 1 As shown, the C-band optical signal generated at point A enters the second erbium-doped fiber 21 as the inducing light; the second erbium-doped fiber 21 generates a C-band optical signal under the action of the pump laser, and the C-band optical signal generated at point A is absorbed by the second erbium-doped fiber 21 together with the C-band optical signal, to generate an L-band optical signal, the wavelength and frequency of the L-band optical signal are controlled by the second fiber grating 25, and a controlled C+L-band super-wide spectrum fiber light source can be finally obtained at point B.

[0083] S203, receive the output power of the photodetector.

[0084] Specifically, combined with Figure 2 , Figure 3 , Figure 5 As shown, the C+L-band optical control process is as follows:

[0085] The photodetector 35 monitors the optical power signal of the light signal output end of the F-P tunable filter 32 in real time, and transmits the optical power signal to the A / D converter 36; the A / D converter 36 converts the continuous analog signal output by the photodetector 35 into a discrete digital signal, and transmits the digital signal to the control unit 37; the control unit 37 analyzes, stores and processes the received optical power signal, wherein the control unit 37 adopts an FPGA digital processing circuit.

[0086] S204, according to the corresponding relationship of the output power and the center wavelength driving model of the F-P tunable filter transmission spectrum, control the F-P filter driving unit to adjust the cavity length of the F-P tunable filter.

[0087] The center wavelength driving model of the F-P tunable filter transmission spectrum refers to the relationship between the driving source triangular wave voltage of the F-P tunable filter and the transmission wavelength thereof.

[0088] The control unit 37 outputs a triangular wave voltage signal in real time according to the received optical power signal, and drives the F-P filter driving unit 320 after signal conversion by the first D / A converter 38, so as to control the cavity length of the F-P tunable filter 32; with the change of the cavity length, the F-P cavity output wavelength will also change, which is equivalent to that the F-P tunable filter 32 can scan the input light within a certain wavelength range.

[0089] S205, when the transmission spectrum center wavelength of the F-P tunable filter coincides with the reflection spectrum center wavelength of the second fiber grating, the first center wavelength of the first laser beam is determined.

[0090] The photoelectric detector 35 collects the laser power of the C+L band optical signal entering the F-P tunable filter 32 in real time. When the reflection spectrum center wavelength position of the second fiber grating 25 and the transmission spectrum center wavelength position of the F-P tunable filter 32 completely overlap, the output power of the F-P tunable filter 32 detected by the photoelectric detector 35 reaches the maximum, and the induced current of the photodiode in the photoelectric detector 35 is also the maximum. Since the relationship between the driving source triangular wave voltage of the F-P tunable filter and the transmission light wavelength thereof can be set in advance, the center wavelength of the reflection peak of the grating at this moment can be calculated by measuring the driving voltage of the F-P filter, so as to determine the first center wavelength of the first laser beam output by the laser output end (point B). That is, the transmission spectrum center wavelength of the F-P tunable filter 32 at this moment is the reflection spectrum center wavelength of the second fiber grating 25.

[0091] Optionally, before step S204, the driving method further comprises:

[0092] establishing the relationship between the driving source triangular wave voltage of the F-P tunable filter and the transmission light wavelength thereof.

[0093] S206, according to the comparison result of the first center wavelength and the in-ring center wavelength, controlling the first center wavelength of the first laser beam output by the laser output end to switch to the in-ring center wavelength.

[0094] The in-ring center wavelength is the center wavelength of the preset laser beam in the sensitive ring of the fiber optic gyroscope.

[0095] In the working of the sensitive ring of the fiber optic gyroscope, the fiber light source provided by the embodiment of the application can control the wavelength and the spectrum type output in real time in a closed loop, so that the center wavelength of the laser beam in the sensitive ring of the fiber optic gyroscope is controllable. Figure 6 is Figure 3 a closed loop circuit diagram of a C+L super wide spectrum fiber light source based on a fiber optic gyroscope. As shown in Figure 3 and Figure 6 The photoelectric detector 35 converts the output light intensity of the F-P tunable filter 32 in real time, transmits into an AD converter for analog-digital conversion, and the converted signal is processed by the FPGA digital processing circuit. The FPGA digital processing circuit generates the triangular wave signal required for driving the first piezoelectric ceramic 33 and the second piezoelectric ceramic 34. The first piezoelectric ceramic 33 generates stress under the driving of the external triangular wave signal, so as to change the center wavelength and the spectrum type of the first fiber grating 16. The second piezoelectric ceramic 34 generates stress under the driving of the external triangular wave signal, so as to change the center wavelength and the spectrum type of the second fiber grating 25.

[0096] When the reflection spectrum center wavelength of the second fiber grating 25 overlaps with the center wavelength position of the F-P tunable filter 32, the F-P tunable filter 32 outputs the maximum light intensity. The FPGA digital processing circuit can calculate the first center wavelength and spectrum of the first laser beam output by the fiber light source at the current B point, and if the preset value requirement is not met, the piezoelectric ceramic drive of the first piezoelectric ceramic 33 and the second piezoelectric ceramic 34 is adjusted in real time by adjusting the triangular wave signal, so as to change the center wavelength and spectrum of the fiber grating, control the first center wavelength of the first laser beam output by the laser output end (B point) to switch to the in-ring center wavelength, and the F-P tunable filter 32 detects the changed center wavelength and spectrum of the fiber light source; when it is consistent with the preset value, no further adjustment is made.

[0097] The fiber light source provided by the embodiment of the present application controls the center wavelength and spectrum output by the laser output end in real time through closed loop control. Under the stress effect of the piezoelectric ceramic, the center wavelength, reflection spectrum and transmission spectrum of the Bragg fiber grating will shift. The reflection spectrum of the Bragg fiber grating is scanned and detected by the F-P tunable filter, and the piezoelectric ceramic output is controlled in closed loop to control the center wavelength and spectrum of the Bragg fiber grating in the C band and the L band, so that the wavelength and spectrum of the C+L ultra-wide spectrum fiber light source for the ultra-high precision fiber optic gyroscope are controllable in real time, and the performance of the fiber light source is greatly improved.

[0098] In the research and test of the fiber optic gyroscope, it is found that when the ultra-high precision fiber optic gyroscope sensitive ring is subjected to external temperature change, the performance of the sensitive ring will change, such as the change of the average wavelength and the transmission spectrum of the ring caused by temperature. Research shows that the change of the average wavelength of the ring caused by temperature has strong correlation with temperature. According to formula 2, since the angular velocity Φ of the fiber optic gyroscope sensitive and the average wavelength are related, the average wavelength output by the fiber light source can be actively controlled by establishing a temperature-average wavelength model, and the model is compensated, so as to improve the scale factor and zero bias performance of the gyroscope. Figure 7 is a compensation principle diagram of the ultra-high precision fiber optic gyroscope using the C+L band fiber light source. According to Figure 3 and Figure 7 It is shown that, optionally, the wavelength control module further comprises a temperature detection unit (not shown in the figure), and the temperature detection unit is connected with the control unit. After step S205, the driving method further comprises:

[0099] S207, receiving the working temperature of the sensitive ring of the fiber optic gyroscope in the current working state output by the temperature detection unit.

[0100] Specifically, the working temperature, i.e., the external temperature, in the working of the fiber-optic gyroscope sensitive ring, the temperature detection unit monitors the external temperature in the current working state of the ultra-high precision fiber-optic gyroscope sensitive ring in real time, and transmits the monitored external temperature to the control unit, and the control unit processes and stores the received external temperature in the current working state.

[0101] S208, according to the comparison result of the working temperature and the temperature compensation model, controlling the laser output end to output a compensation light beam corresponding to the current working temperature.

[0102] The input end of the fiber-optic gyroscope sensitive ring is connected with the laser output end of the fiber-optic light source; the temperature compensation model refers to the corresponding relationship between the working temperature of the fiber-optic gyroscope sensitive ring and the center wavelength of the laser light beam in the ring.

[0103] Specifically, the change of the external temperature can cause the deformation of the fiber in the sensitive ring and the colloid filled in the ring, resulting in the change of the average wavelength and the spectrum of the light wave transmitted in the sensitive ring. According to formula (2), the angular velocity Φ of the fiber-optic gyroscope sensitive is related to the average wavelength, and the present application can set the parameter of the transmission spectrum center wavelength of the F-P filter in the C+L band fiber-optic light source by using the temperature and the temperature change rate, and adjust the average wavelength output of the C+L band fiber-optic light source by using the set parameter, compensate the average wavelength change caused by the temperature input of the sensitive ring, and improve the performance of the ultra-high precision fiber-optic gyroscope.

[0104] According to the combination of Figure 3 and Figure 7 , for example, the initial working temperature of the sensitive ring is T0, the center wavelength of the incident laser at the incident end of the sensitive ring is λ0, and with the change of the external temperature, the working temperature T of the sensitive ring changes, at this time, the angular velocity Φ of the fiber-optic gyroscope sensitive changes positively, and the center wavelength λ0 of the incident laser cannot meet the requirement of the center wavelength of the laser of the sensitive ring.

[0105] At this time, the control unit 37 adjusts the triangular wave signals required by the first piezoelectric ceramic 33 and the second piezoelectric ceramic 34 based on the average wavelength FPGA compensation logic of the temperature model, according to the correspondence between the acquired external temperature under the current working state and the working temperature of the fiber-optic gyroscope sensitive ring and the central wavelength of the laser beam in the ring, in combination with the laser output by the F-P tunable filter and the laser power collected by the polarization maintaining fiber photoelectric detector, so that the first piezoelectric ceramic 33 and the second piezoelectric ceramic 34 generate stress under the driving of the external triangular wave signal, and the central wavelength and the spectrum of the first fiber grating 16 and the second fiber grating 25 are changed, so that the angular velocity Φ sensitive to the fiber-optic gyroscope is compensated and output, and after temperature compensation, the central wavelength λ of the compensation light beam output by the fiber-optic light source meets the requirement of the central wavelength corresponding to the current working temperature, the fiber-optic light source itself closed-loop control provided by the embodiment of the application can improve the full-temperature wavelength stability, thereby improving the scale factor and the zero bias performance of the gyroscope.

[0106] Optionally, before step S208, the control method further comprises:

[0107] The fiber-optic gyroscope test is performed in advance to obtain the correspondence between the working temperature of the fiber-optic gyroscope sensitive ring and the central wavelength of the laser beam in the ring, and the temperature compensation model is established.

[0108] In the application, the control unit can adopt an FPGA digital processing circuit as a control core, and the control unit 37 is further connected with the first pump source 13 and the second pump source 23. The fiber-optic light source real-time closed-loop control circuit and the fiber-optic light source driving circuit are relatively independent, the FPGA digital processing circuit controls the output power of the pump laser and the central wavelength and the spectrum of the fiber-optic light source by controlling the fiber-optic light source driving circuit. The fiber-optic light source driving circuit is divided into a temperature control part and a power control part, and the temperature and the output power of the pump laser are controlled under the control of the FPGA digital processing circuit, so as to control the laser parameters of the fiber-optic light source output laser.

[0109] Through the closed-loop control of the C+L band super wide spectrum fiber-optic light source in the above embodiment, on the one hand, the performance of the fiber-optic light source can be improved; on the other hand, by modeling the performance change of the sensitive ring caused by temperature change of the ultra-high precision fiber-optic gyroscope, the performance change of the sensitive ring is actively compensated from the light source end by using the closed-loop control function of the C+L band super wide spectrum fiber-optic light source, so as to greatly improve the scale factor and the zero bias stability of the fiber-optic gyroscope.

[0110] Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, reconfigurations, combinations and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. A fiber optic light source based on a fiber optic gyroscope, characterized in that, Includes a two-way forward module and a backward module; The two-way forward module includes an optical fiber circulator, a first wavelength division multiplexer, a first pump source, a first erbium-doped fiber, a first isolator, and a first fiber grating; the backward module includes a second erbium-doped fiber, a second wavelength division multiplexer, a second pump source, a second isolator, and a second fiber grating. The first end of the first wavelength division multiplexer is connected to the fiber optic circulator; the second end of the first wavelength division multiplexer is connected to the excitation light output end of the first pump source; the third end of the first wavelength division multiplexer is connected to the first end of the first erbium-doped fiber; the second end of the first erbium-doped fiber is connected to the input end of the first isolator; the output end of the first isolator is connected to the first end of the first fiber grating; the second end of the first fiber grating is connected to the first end of the second erbium-doped fiber; the second end of the second erbium-doped fiber is connected to the first end of the second wavelength division multiplexer; the second end of the second wavelength division multiplexer is connected to the excitation light output end of the second pump source; the third end of the second wavelength division multiplexer is connected to the input end of the second isolator; the output end of the second isolator is connected to the first end of the second fiber grating; the second end of the second fiber grating is a laser output end; the laser output end is used to output the laser beam for the fiber optic gyroscope. It also includes a wavelength control module; the wavelength control module includes a coupler, an FP tunable filter, a first piezoelectric ceramic, a second piezoelectric ceramic, a photodetector, an A / D converter, a control unit, a first D / A converter, a second D / A converter, a piezoelectric ceramic driving unit, and an FP filter driving unit; the first piezoelectric ceramic covers the sidewall of the first fiber grating, and the second piezoelectric ceramic covers the sidewall of the second fiber grating; The first end of the coupler is connected to the output end of the second isolator; the second end of the coupler is connected to the first end of the second fiber grating; the third end of the coupler is connected to the optical signal input end of the FP tunable filter; the optical signal output end of the FP tunable filter is connected to the input end of the photodetector; the output end of the photodetector is connected to the signal input end of the A / D converter; the signal output end of the A / D converter is connected to the signal input end of the control unit; the first piezoelectric signal output end of the control unit is connected to the input end of the first D / A converter; the output end of the first D / A converter is connected to the input end of the FP filter drive unit; the drive signal output end of the FP filter drive unit is connected to the drive signal input end of the FP tunable filter; the second piezoelectric signal output end of the control unit is connected to the input end of the second D / A converter; the output end of the second D / A converter is connected to the input end of the piezoelectric ceramic drive unit; and the drive signal output end of the piezoelectric ceramic drive unit is connected to both the first and second piezoelectric ceramics.

2. The fiber optic light source according to claim 1, characterized in that, The 3dB bandwidth of the transmission spectrum of the FP tunable filter is less than the 3dB bandwidth of the reflection spectrum of the second fiber grating.

3. The fiber optic light source according to claim 1, characterized in that, The length of the second erbium-doped fiber is greater than that of the first erbium-doped fiber; the doping concentration of erbium in the second erbium-doped fiber is greater than that in the first erbium-doped fiber.

4. The fiber optic light source according to claim 1, characterized in that, The optical power of the second pump source is greater than that of the first pump source.

5. The fiber optic light source according to claim 1, characterized in that, The control unit is also connected to the first pump source and the second pump source, respectively.

6. A control method for an optical fiber light source based on an optical fiber gyroscope, used to control the optical fiber light source according to any one of claims 1-5, characterized in that, The control method includes: Determine the laser parameters of the first laser beam used in the fiber optic gyroscope; the laser parameters include the center wavelength and spectral linewidth; According to the laser parameters, the pump light parameters of the first pump source and the second pump source are controlled respectively so that the first laser beam is output from the laser output end; wherein, the pump light parameters include the pump light center wavelength and the pump light power.

7. The control method according to claim 6, characterized in that, Based on the laser parameters, the pump light parameters of the first pump source and the second pump source are controlled respectively, so that after the first laser beam is output from the laser output terminal, the process further includes: Receive the output power of the photodetector; Based on the correspondence between the output power and the center wavelength driving model of the transmission spectrum of the FP tunable filter, the FP filter driving unit is controlled to adjust the cavity length of the FP tunable filter. When the center wavelength of the transmission spectrum of the FP tunable filter coincides with the center wavelength of the reflection spectrum of the second fiber grating, the first center wavelength of the first laser beam is determined.

8. The control method according to claim 7, characterized in that, After determining the first center wavelength of the first laser beam, the process further includes: Based on the comparison result between the first center wavelength and the center wavelength within the ring, the first center wavelength of the first laser beam output from the laser output terminal is switched to the center wavelength within the ring. Wherein, the center wavelength within the ring is the center wavelength of the laser beam within the sensitive ring of the fiber optic gyroscope.

9. The control method according to claim 8, characterized in that, The wavelength control module also includes a temperature detection unit, which is connected to the control unit. Based on the comparison result between the first center wavelength and the center wavelength within the ring, after controlling the first center wavelength of the first laser beam output from the laser output terminal to switch to the center wavelength within the ring, the method further includes: The operating temperature of the fiber optic gyroscope's sensing ring under the current operating state is received from the temperature detection unit. Based on the comparison results between the operating temperature and the temperature compensation model, the laser output terminal is controlled to output a compensation beam corresponding to the current operating temperature; The input end of the fiber optic gyroscope sensing ring is connected to the laser output end; the temperature compensation model refers to the correspondence between the operating temperature of the fiber optic gyroscope sensing ring and the center wavelength of the laser beam inside the ring.

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