High-thermal-stability light source for helicopter inertial navigation and test verification method of high-thermal-stability light source

Abstract

The invention belongs to the field of airborne inertial navigation, and relates to a high-thermal-stability light source for helicopter inertial navigation and a test verification method thereof.The high-thermal-stability light source comprises a high-thermal-stability light source light path which comprises an erbium-doped optical fiber, a pumping diode, a wavelength division multiplexer, an optical isolator, a planarization device and an optical coupler; the pumping diode emits laser, the laser passes through the wavelength division multiplexer and then reaches the erbium-doped optical fiber, after erbium ions in the erbium-doped optical fiber absorb the laser, an excited spontaneous radiation phenomenon occurs and superfluorescence is generated, and one part of the superfluorescence is directly output into air through the tail end of the erbium-doped optical fiber. And the other part of the superfluorescence sequentially passes through the wavelength division multiplexer, the polarization independent optical isolator, the flat filter, the main port of the optical coupler and the one-to-three coupler and then is input to three sensitive axes of the gyroscope to provide light energy for the three axes of the gyroscope.

Description

Technical Field

[0001] The invention belongs to the field of airborne inertial navigation and relates to a high thermal stability light source for helicopter inertial navigation and a test verification method thereof. Background Art

[0002] The average wavelength temperature stability is the primary indicator for evaluating the temperature performance of erbium-doped fiber light sources. At the same time, the stability of the light source will directly affect the stability of the temperature-varying scaling factor of the gyroscope. High-precision fiber gyros require the average wavelength temperature stability of the light source to be less than 3ppm / ℃. Therefore, as the source optoelectronic device of the fiber gyroscope, the design of a highly stable light source is the primary task in the design process of the fiber gyroscope.

[0003] At present, the erbium-doped fiber light sources on the domestic market mostly adopt complex optical path structures such as double-stage double-pass and three-stage double-pass, which increases the volume, cost and assembly complexity of the light source to a certain extent. In addition, the light source has only one fiber pigtail output. If it is applied to a fiber optic gyroscope, a 1-to-3 coupler of a fiber optic gyroscope needs to be installed outside the light source to provide light energy for the three axes of the gyroscope. At the same time, the introduction of too many passive optical devices in a multi-stage (two or more) light source will affect the temperature characteristics of the light source. At present, there is no effective measure to improve the temperature characteristics of the light source. For this reason, the present invention proposes a high thermal stability light source for helicopter inertial navigation based on Fresnel reflection, thereby improving the stability of the airborne gyroscope. Summary of the invention

[0004] The purpose of the present invention is to propose a highly stable light source optical path structure based on the Fresnel reflection effect in response to the problem that the average wavelength of the light source changes with temperature. Compared with the traditional complex optical path structure, the solution proposed by the present invention not only reduces the manufacturing cost and volume of the light source, but also integrates the 1-to-3 coupler of the gyroscope into the interior of the light source. The light source directly outputs three pigtails to provide light energy for the three axes of the gyroscope, reducing the volume of the gyroscope and solving the complexity problem of the light source-gyroscope system. Most importantly, its average wavelength thermal stability is better than that of the light source with a traditional complex optical path structure.

[0005] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0006] A high thermal stability light source for helicopter inertial navigation includes: a high thermal stability light source optical path, the optical path includes: erbium-doped optical fiber, a pump diode, a wavelength division multiplexer, an optical isolator, a flattener, and an optical coupler;

[0007] The pump diode emits laser, which reaches the erbium-doped fiber after passing through the wavelength division multiplexer. After the erbium ions in the erbium-doped fiber absorb the laser, stimulated spontaneous radiation occurs and super fluorescence is generated. Part of the super fluorescence is directly output into the air through the tail end of the erbium-doped fiber, and the other part of the super fluorescence passes through the wavelength division multiplexer, polarization-independent optical isolator, flat filter, main port of optical coupler, and one-to-three coupler in sequence, and is input to the three sensitive axes of the gyroscope, providing light energy for the three axes of the gyroscope.

[0008] Furthermore, the length of the erbium-doped optical fiber is 15 m.

[0009] Furthermore, the erbium-doped optical fiber pigtail is vertically cut, and the end face of the cut pigtail is processed by an optical fiber wrapping process.

[0010] Furthermore, the pump diode emits a laser with a central wavelength of 980 nm and a pump power of 100 mW.

[0011] Furthermore, the wavelength division multiplexer is a 980nm / 1550nm wavelength division multiplexer.

[0012] Furthermore, the superfluorescence wavelength is 1550 nm.

[0013] Furthermore, the splitting ratio of the optical coupler is 98:2, wherein the port with a splitting ratio of 98 is the main port.

[0014] A method for testing and verifying a high thermal stability light source for helicopter-borne fiber-optic inertial navigation, the method being used to verify the light source, comprising the following steps:

[0015] A control group was designed. Control group 1 was a light source fused to a Faraday rotator mirror; control group 2 was a light source fused to a fiber optic reflector.

[0016] The light source according to any of the preceding claims and two control light sources are subjected to an average wavelength thermal stability test, and the output spectra of the three light sources are collected by a spectrometer and sent to a computer in real time;

[0017] The three groups of light sources are connected to the same gyro system respectively, and the output voltage of the gyro systems connected with different light sources is monitored respectively; and the gyro systems connected with different light sources are placed statically on a vibration isolation table with an independent foundation for static performance testing;

[0018] Finally, the gyro scale factor stability tests were performed on the gyro systems connected with different light sources.

[0019] Furthermore, the test time for each light source was 8 hours, and the rotation rate of the turntable was set to 10° / s.

[0020] Furthermore, the optical power of the erbium-doped fiber light source was measured at a sampling interval of 20 seconds, and the wavelength was measured at a resolution of 0.1 nm and a sampling interval of 20 seconds.

[0021] Beneficial effects of the invention: The invention combines the performance index requirements of the fiber optic gyroscope and the fiber optic light source, proposes and designs a flat erbium-doped fiber optic light source with good average wavelength thermal stability, and uses the vertical cutting method based on the Fresnel reflection effect to process the erbium-doped fiber pigtail, which not only simplifies the optical path structure and reduces the cost, but also the output power of the light source can be adjusted online and monitored in real time according to the needs of the gyroscope. After testing, a semi-double-pass structure optical path erbium-doped fiber optic light source with a full-temperature average wavelength temperature stability of less than 1ppm / ℃ was finally obtained. Its average wavelength stability is better than that of ordinary light sources by 105-120ppm, and the thermal stability error of the scale factor of the fiber optic gyroscope is reduced by about 185-350ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram for modeling a pigtail.

[0023] Figure 2 Structural diagrams of three types of fiber optic light sources: (a) based on Fresnel reflection effect, (b) pigtail fusion FRM, and (c) pigtail fusion FM.

[0024] Figure 3 Spectra of light sources with erbium-doped fibers of different lengths.

[0025] Figure 4 This is a diagram of the experimental arrangement of a high-stability light source. (a)-(c) respectively represent the three light sources with vertically cut fiber pigtail processing method, FRM and FM placed in the temperature chamber for testing.

[0026] Figure 5 is the variation trend of average wavelength with temperature.

[0027] Figure 6 is the variation trend of gyro scale factor with temperature.

[0028] Figure 7 Simulation diagram for fiber pigtail modeling. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In view of the problem that the average wavelength of the light source changes with temperature, the present invention proposes a highly stable light source optical path structure based on the Fresnel reflection effect. Compared with the traditional complex optical path structure, the solution proposed by the present invention not only reduces the production cost and volume of the light source, but also integrates the 1-to-3 coupler of the gyroscope into the interior of the light source. The light source directly outputs three pigtails to provide light energy for the three axes of the gyroscope, reducing the volume of the gyroscope and solving the complexity problem of the light source-gyroscope system. Most importantly, its average wavelength thermal stability is better than that of the light source with a traditional complex optical path structure. The following is a specific description:

[0031] 1. Theoretical Analysis

[0032] Output optical power, average wavelength stability, and spectrum width are important indicators for evaluating the performance of fiber optic light sources. Fiber optic gyroscopes are angular rate sensors based on the Sagnac effect, and their effect can be enhanced by introducing multi-turn sensitive coils. According to the Sagnac principle, the gyroscope angular rate Ω is related to the phase shift Φ s The relationship between can be written as:

[0033]

[0034] Among them, L = N·2πR, N and R are the length, number of turns and radius of the sensitive coil respectively, c is the speed of light in vacuum, and λ is the average wavelength of the light transmitted in the gyroscope. It can be seen from the above formula that the scale factor K of the gyroscope depends on the average wavelength λ of the light. The angular rate of rotation of the gyroscope can be accurately measured only when the average wavelength is relatively stable. High-precision fiber gyroscopes require that the average wavelength stability of the erbium-doped fiber light source is within 3ppm / ℃. The average wavelength thermal stability is mainly affected by the inherent temperature characteristics of the erbium-doped fiber, the temperature dependence of the pump source output power, the temperature dependence of the pump source output wavelength, the feedback power and the polarization state, but the inherent temperature characteristics of the erbium-doped fiber directly affect the output characteristics of the light source.

[0035] The present invention designs a high-performance, low-cost erbium-doped fiber light source based on the Fresnel reflection effect, aiming to obtain a fiber light source with a wider spectrum, higher output power, and better thermal stability without introducing irrelevant passive optical devices (FRM, ordinary fiber reflector, fiber attenuator, fiber circulator, etc.), and improve the temperature characteristics of the gyroscope by improving the average wavelength stability of the light source. The transmission model of light transmission in the fiber core is as follows Figure 1 As shown, θ is the cutting angle of the end face. The light field in the fiber core can be expressed as:

[0036]

[0037] The light field distribution at the end of the fiber core can be expressed as:

[0038]

[0039] Considering half-wave loss, the reflected light field can be expressed as:

[0040]

[0041] According to the coupled mode theory, the coupling efficiency between the reflected field and the incident field is:

[0042]

[0043] When light passes through the cross section of two media or materials with different refractive indices (the cross section of the fiber core and air in this patent), the Fresnel reflection effect should be considered, and its coupling efficiency can be expressed as:

[0044]

[0045] Among them, θ1 represents the refraction angle from the optical fiber core into the air. The relationship between the refraction angle and the incident angle can be expressed as n1sinθ=n0sinθ1. Through modeling and simulation, Figure 1 The transmission model of the light at the tail end of an angled optical fiber is given. As can be seen from the figure, when the tail fiber is cut vertically, the reflected power is about 4%; and when θ>5°, the reflected power becomes very small, only 0.5%. It is predicted that this semi-double-pass optical path structure based on the Fresnel reflection effect will not only save the cost of the light source, but also greatly improve the average wavelength stability of the light source.

[0046] 2. Highly stable optical path design

[0047] With the increasing maturity of passive device production technology, a single-stage optical path structure light source can meet the performance index requirements of fiber optic gyroscopes for light sources. The present invention designs a high-stability erbium-doped fiber light source based on the Fresnel reflection effect. The light source can be regarded as a semi-double-pass backward structure, and it is predicted that this semi-double-pass structure has the common advantages of double-pass backward and single-pass backward, that is, a wider spectrum, better average wavelength stability and higher photoelectric conversion efficiency. The semi-double-pass backward optical path structure is as follows: Figure 2 As shown in (a), a laser diode with a central wavelength of 980nm emits a laser with a peak wavelength of 974nm and a pump power of 100mW. After passing through a 980nm / 1550nm wavelength division multiplexer, it reaches the erbium-doped fiber. After the 980nm laser is absorbed by the erbium ions in the erbium-doped fiber, stimulated spontaneous emission occurs and super fluorescence of 1550nm is generated.

[0048] Since the light source designed in this patent is based on the Fresnel reflection effect, Japan's Fujikura high-precision fiber cutting machine CT-30 is used to vertically process the erbium-doped fiber pigtail, and a special process of fiber wrapping is used to process the cut pigtail end face. Part of the 1550nm light generated after pumping is directly output into the air through the tail end of the erbium-doped fiber, and the other part of the 1550nm light is then sequentially passed through a 980 / 1550nm wavelength division multiplexer, a polarization-independent optical isolator, a flat filter, a 98% port of a 98:2 optical coupler, and a one-to-three coupler before being input into the three sensitive axes of the gyroscope to provide light energy for the three axes of the gyroscope. In order to increase the comparative nature of the experiment and to verify the effectiveness of this method, the present invention provides Figure 2 (b) and (c) are two other structures, namely, the erbium-doped fiber tail end is processed by fusion FRM and fusion FM respectively.

[0049] After the optical path structure is completed by fusion splicing, the length of the erbium-doped fiber needs to be optimized to obtain a spectrum with higher flatness and wider spectrum. The spectrum debugging process increases in steps of 0.5 meters. Figure 2 (a) Take for example, Figure 3 As shown in the figure, the spectrum of three typical lengths of erbium-doped optical fibers of 10 meters, 15 meters and 20 meters after debugging is given. The red circle line is the spectrum shape of the 20-meter erbium-doped optical fiber fused into the optical path. Due to the high concentration of erbium ions in the 20-meter erbium-doped optical fiber, it presents a strong absorption effect at the wavelength of 1530nm, so the spectrum shows a shape of low near the left peak (1530nm) and high near the right peak (1560nm). Similarly, when the number of meters of erbium-doped optical fiber is low, a spectrum shape with a high left peak (1530nm) and a low right peak (1530nm) will appear. Through spectrum debugging, it can be seen in the figure that when the length of the erbium-doped optical fiber is 15 meters, the spectrum flatness is higher and the spectrum width is the widest. At this time, the spectrum width can reach 37.68nm, which fully meets the spectrum width requirements of the optical fiber gyroscope.

[0050] like Figure 2 As shown in the figure, for the selection of optoelectronic modules, the pump source module uses a 14-pin butterfly package pump source, which integrates a negative temperature coefficient thermistor and a monitoring photodiode, has high output power, and the maximum power can reach 600mW. At the same time, the pump source uses fiber Bragg stabilization technology, which can lock the wavelength in the entire working range, has good average wavelength stability, and is widely used in the field of erbium-doped fiber light sources and optical amplifiers. The photodetector uses an InGaAs planar structure 3-pin single PIN photodetector PDS143-COT-B0110 independently developed by Beijing Shiweitong Technology Development Co., Ltd. This detector has the advantages of adjustable transimpedance, low noise, high sensitivity, good airtightness, etc., and is widely used in the field of weak light detection.

[0051] As for the selection of passive optical devices in the erbium-doped fiber light source, a 980 / 1550nm wavelength division multiplexer with high isolation, high reliability and low insertion loss is selected as the wavelength division multiplexing unit of the light source of the present invention; a C-band 1060-XP erbium-doped fiber independently developed by Nufern Corporation of the United States is selected as the gain medium of the light source of the present invention. The erbium-doped fiber is manufactured using special rare ion doping technology and double cladding design technology, and has high pump conversion efficiency and output optical power. A polarization-independent optical isolator is selected as the isolator for the light source of the present invention. The optical isolator is installed at the tail end of the light source, which can not only prevent the self-excited oscillation inside the light source from generating lasers, but also eliminate the signal instability caused by the high-precision gyroscope feedback light. An LPG flattener is selected as the flattener of the light source of the present invention to meet the flatness and spectrum width requirements of the light source. The flattener is mainly used to compensate for the uneven amplification gain of erbium-doped optical fiber on different wavelength division multiplexing channels, and has the advantages of low insertion loss, good thermal stability, and high planar spectral gain. FRM and ordinary FM are selected as the reflection modules of the light source of the present invention, which have lower insertion loss, higher return loss and extinction ratio. The introduction of the reflection module increases the comparability of the experiment.

[0052] 3. Test Verification

[0053] The optical path device, circuit PCB, circuit chip and mechanical structure slot are integrated into the mechanical structure of the light source. Since the fiber optic gyroscope is sensitive to the angular velocity of the three axes of X, Y and Z, unlike the traditional erbium-doped fiber light source, the high-stability light source designed by the present invention not only simplifies the optical path structure, but also integrates the 1-to-3 fiber coupler of the gyroscope into the mechanical structure of the light source. The light source directly outputs three pigtails to provide light energy to the three sensitive axes of the fiber optic gyroscope, which not only reduces the volume of the gyroscope, but also facilitates the miniaturization and high-precision development of the gyroscope. At the same time, the output power of the light source can be adjusted online in real time according to the specific needs of the gyroscope, and the output parameters of the light source during operation can also be monitored online in real time by the host computer.

[0054] In order to verify the influence of the average wavelength of the semi-double-pass backward structured light source and the light source on the gyroscope performance, the present invention respectively carried out full-temperature performance tests on the above three structured light sources and the light source-gyroscope system. The experimental arrangement is as follows: Figure 4 As shown, Figure 4(a)-(c) respectively show the experimental arrangement diagrams of placing the light source based on Fresnel reflection effect, the light source of fused FRM, and the light source of fused FM in the high and low temperature chamber. The erbium-doped fiber light source is powered by a +5V external DC power supply. The light source optical power is measured using an EXPO PM-1600PM with a sampling interval of 20 seconds, and an Advantest Q8384-OSA with a resolution of 0.1nm and a sampling interval of 20s. PM and OSA are connected to the host computer via GPIB for real-time data storage and subsequent processing.

[0055] Referring to the temperature history of the light source, the thermal stability test of the average wavelength of the light source with three different pigtail processing methods was carried out. The average wavelength of the light source after the pigtail of the light source was processed by vertical cutting, welding FRM, and welding FM respectively changes with temperature as shown in the figure below. Figure 5 As shown, the blue square line, red triangle line and green circle line represent the temperature change of the fiber optic light source processed by the methods of vertical cutting of the pigtail, fusion FRM and fusion FM respectively. It can be clearly seen in the figure that compared with the two methods of fusion FRM and fusion FM, the vertical cutting pigtail processing method based on the Fresnel reflection effect has better thermal stability of the average wavelength. Due to the presence of the temperature control module in the light source circuit, the output wavelength of the LD is almost not affected by the ambient temperature. The change of the average wavelength of the erbium-doped fiber light source with temperature mainly depends on the optical path structure.

[0056] When evaluating the performance of an interferometric fiber gyroscope, zero bias stability, scale factor, and random walk coefficient are three important indicators for evaluating the performance of the gyroscope. Researchers have invested a lot of research on the zero bias stability and random walk of fiber gyroscopes, and the influence of the gyroscope optical path and circuit on the gyroscope zero bias and random walk coefficient noise is also relatively clear. The stability of the gyroscope scale factor is currently the main factor affecting the output performance of the fiber optic gyroscope, which is also a point where the laser gyroscope is superior to the fiber optic gyroscope. In the actual application of gyroscopes, the gyroscope scale factor will drift under harsh conditions such as low speed, humid and hot environment, long start-up, temperature change environment, especially in temperature environment, causing the gyroscope's measured value to deviate from the true value. Therefore, the temperature stability of the scale factor is an important indicator for evaluating the dynamic performance of a high-precision fiber optic gyroscope. After completing the normal temperature and variable temperature performance tests of the light source, it is necessary to verify the performance of the light source on the gyroscope. Before conducting the temperature-variable experiment of the gyro scale factor, it is necessary to monitor the output voltage of the detectors of the three different gyro systems to prevent the light source output power from being too large and exceeding the detection threshold of the detector, causing a large noise signal to be mixed in the gyro output signal. After the voltage magnitude and output waveform of the detector output meet the requirements, the static performance and dynamic temperature performance of the gyro are studied.

[0057] The gyro is placed statically on an independent ground-based vibration isolation table for static performance testing. The voltage conversion module in the gyro circuit board leads to a +5V electrical signal to power the light source. The three pigtails output by the light source are directly connected to the three sensitive axes of the fiber optic gyroscope. The experimental temperature is room temperature +25℃, and the test time is greater than 8 hours. The gyro is powered by an external +24V DC power supply, and the gyro output data is transmitted to the host computer through the high-speed isolator converter serial port. Zero bias stability and random walk are two important index parameters for evaluating the static performance of the fiber optic gyroscope. After the static test at room temperature, the zero bias stability and random walk coefficients of the three axes of the fiber optic gyroscope X, Y, and Z meet the performance index requirements of the high-precision interferometric fiber optic gyroscope, and the gyroscope temperature performance is studied.

[0058] The vertically cut pigtail processing light source based on Fresnel reflection effect is installed and fixed on the fiber optic gyroscope. The light source outputs three pigtails to provide optical signals for the three sensitive axes of the gyroscope X, Y, and Z. The power supply of the light source is provided by the voltage conversion module in the fiber optic gyroscope circuit board. The +24V voltage required by the gyroscope is converted by the +220V standard voltage, and then the +24V voltage is converted by the voltage conversion module to the +5V power supply required by the light source. Since the turntable in the temperature chamber is a single-axis angular rate turntable, the scale factor test of the gyroscope is verified by the Z axis as a representative. Referring to the test specifications of the three-axis integrated fiber optic gyroscope, the gyroscope is fixed to the high and low temperature temperature chamber with an independent foundation vibration isolation single-axis turntable through the installation fixture with the Z axis facing the sky, and is fixed with screws to prevent the gyroscope position from changing when the turntable rotates, and the turntable sensitive axis is zeroed and locked. The data signal line and power supply line of the gyroscope are led out through the slip ring on the single-axis turntable. The slip ring is responsible for connecting with the external PC when the turntable rotates, and transmits the data signal and electrical signal of the gyroscope in real time.

[0059] The other end of the slip ring outside the temperature chamber is connected to the high-speed isolation converter outside the gyro, which is connected to the serial port and USB interface of the computer host respectively. The serial port is responsible for sending the output of the fiber optic gyro to the host computer, and the USB interface is responsible for the power supply of the converter. The temperature chamber turntable uses a 920CT rate position turntable with a high and low temperature chamber. When the turntable rotates at a low speed, the installation error will become the main error in the gyro scale factor test process; when the turntable rotates at a high speed, the installation error can be ignored, and the asymmetry and nonlinear test of the scale factor will not be affected. Referring to a large number of literatures, it is known that the scale factor stability measured when the turntable rotates at a speed of 10° / s is the best, that is, at this rotation rate point, the gyro scale factor error caused by the installation error component and the ground speed error is the smallest and can be almost ignored. At the same time, the same temperature history curve is set for the gyro and light source test, and the test time is greater than 8 hours.

[0060] Generally speaking, considering the thermal expansion of silica, the fiber coil area S should change at a few ppm / ℃ and change positively with temperature. Since the average wavelength of the light source changes negatively with temperature, a more stable average wavelength is required to obtain a more stable gyro scale factor. The light source-gyro based on Fresnel reflection effect, the light source-gyro fused with FRM, and the light source-gyro fused with FM were placed in high and low temperature chambers for testing. The experimental results are shown in Figure 2. Figure 6 The blue square line, red triangle line and green circle line respectively represent the changes in the scale factor of the fiber light source-gyroscope processed by the methods of vertical cutting of the pigtail, fusion FRM and fusion FM. It can be seen from the figure that the better the thermal stability of the light source, the smaller the error of the corresponding gyroscope scale factor. The error of the gyroscope scale factor of the light source processed by vertical cutting of the pigtail based on the Fresnel reflection effect is significantly smaller than that of the other two processing methods. Therefore, the method proposed in the present invention can not only greatly improve the temperature performance of the fiber light source, but also effectively improve the temperature performance of the fiber gyroscope.

[0061] The above is only a specific embodiment of the present invention, and the present invention is described in detail. The unexplained part is a conventional technology. However, the protection scope of the present invention is not limited to this. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A high thermal stability light source for helicopter inertial navigation, characterized in that: include: High thermal stability light source optical path, the optical path includes: erbium-doped optical fiber, pump diode, wavelength division multiplexer, optical isolator, flattener, optical coupler; The pump diode emits laser, which reaches the erbium-doped fiber after passing through the wavelength division multiplexer. After the erbium ions in the erbium-doped fiber absorb the laser, stimulated spontaneous radiation occurs and super fluorescence is generated. Part of the super fluorescence is directly output into the air through the tail end of the erbium-doped fiber, and the other part of the super fluorescence passes through the wavelength division multiplexer, polarization-independent optical isolator, flat filter, main port of optical coupler, and one-to-three coupler in sequence, and is input to the three sensitive axes of the gyroscope, providing light energy for the three axes of the gyroscope.

2. The high thermal stability light source according to claim 1, characterized in that: The length of the erbium-doped fiber is 15m.

3. The high thermal stability light source according to claim 2, characterized in that: The erbium-doped optical fiber pigtail is cut vertically, and the end face of the pigtail is processed by the fiber wrapping process.

4. The high thermal stability light source according to claim 1, characterized in that: The pump diode emits a laser with a central wavelength of 980nm and a pump power of 100mW.

5. The high thermal stability light source according to claim 4, characterized in that: The wavelength division multiplexer is a 980nm / 1550nm wavelength division multiplexer.

6. The high thermal stability light source according to claim 5, characterized in that: The superfluorescence wavelength is 1550nm.

7. The high thermal stability light source according to claim 1, characterized in that: The splitting ratio of the optical coupler is 98:2, wherein the port with a splitting ratio of 98 is the main port.

8. A method for testing and verifying a high thermal stability light source for helicopter-borne fiber-optic inertial navigation, the method being used to verify the light source according to any of the preceding claims, characterized in that: The following steps are involved: A control group was designed. Control group 1 was a light source fused to a Faraday rotator mirror; control group 2 was a light source fused to a fiber optic reflector. The light source according to any of the preceding claims and two control light sources are subjected to an average wavelength thermal stability test, and the output spectra of the three light sources are collected by a spectrometer and sent to a computer in real time; The three groups of light sources are connected to the same gyro system respectively, and the output voltage of the gyro systems connected with different light sources is monitored respectively; and the gyro systems connected with different light sources are placed statically on a vibration isolation table with an independent foundation for static performance testing; Finally, the gyro scale factor stability tests were performed on the gyro systems connected with different light sources.

9. The method according to claim 8, characterized in that The test time for each light source was 8 hours, and the rotation rate of the turntable was set to 10° / s.

10. The method according to claim 8, characterized in that The optical power of the erbium-doped fiber light source was measured at a sampling interval of 20 seconds, and the wavelength was measured at a resolution of 0.1 nm and a sampling interval of 20 seconds.

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