Research On Signal Processing Technology Of Resonant Fiber Optic Gyroscope Based On Self-Injection Locking

Optical gyroscope is an inertial sensor that can accurately measure the angular velocity and position information of objects.It is one of the mainstream instruments in the field of inertial measurement and guidance.Resonant fiber optic gyroscope is based on the principle of resonant frequency difference detection,and its accuracy has nothing to do with the cavity length.Using a few meters of optical fiber or even micro ring cavity can achieve navigation level accuracy,so it is regarded as an ideal choice for the new generation of optical gyroscope.However,the low signal-to-noise ratio of the traditional signal processing methods of the resonant fiber optic gyroscope limits its development,and the narrow linewidth laser required by the traditional resonant fiber optic gyroscope has large volume and high cost,which is not in line with the development trend of miniaturization.Aiming at these problems,this paper uses wide-spectrum DFB laser and ring resonator to realize self injection locking,and uses differential frequency signal detection to replace the traditional strength detection method to carry out the research of a resonant fiber optic gyro signal processing platform based on self injection locking.Frequency detection can obtain a higher signal-to-noise ratio than intensity detection.Theoretically,the measurement accuracy is higher,the angular rate measurement range is larger,and the requirements on the laser are reduced,which is more conducive to miniaturization and cost reduction.The main work of the thesis is as follows:(1)The sensing mechanism of resonant fiber optic gyroscope is introduced in detail,the transmission characteristics of ring resonator are theoretically analyzed,the principle of self injection locking technology is introduced,and the generation of differential frequency signal and the detection mechanism of high-precision differential frequency signal are introduced.Finally,the system structure of traditional resonant fiber optic gyroscope is compared,The overall scheme of resonant fiber optic gyroscope based on self injection locking technology is designed.(2)The laser locking technology based on self injection light is studied.Through the theoretical analysis and Simulation of the rate equation of semiconductor laser and the transfer function of ring resonator,the parameter conditions and locking effect of self injection locking are obtained.And the driving system of semiconductor laser is designed.The driving system is mainly composed of constant current source driving module,power detection feedback module and temperature control module.Through appropriate power feedback,the frequency stability and linewidth narrowing effect of output light are improved,which provides necessary conditions for stable and effective self injection frequency locking.(3)Aiming at the problem of low signal-to-noise ratio of traditional resonant gyroscope output signal strength detection,a high-precision difference frequency signal detection technology scheme is proposed.The scheme mainly includes a difference frequency signal conditioning circuit and a difference frequency signal detection circuit.By designing a difference frequency signal conditioning circuit,the difference frequency signal output by the gyro is filtered and shaped to obtain a square wave signal suitable for frequency detection,and then a chip based on TDC-GP22 is used The high-precision difference frequency signal detection scheme detects the difference frequency signal.Experiments show that compared with the traditional digital frequency measurement method,the frequency measurement accuracy can be improved by about an order of magnitude.(4)Realize the specific hardware circuits of the signal processing platform based on the self-injection locking resonant fiber optic gyroscope scheme and complete the test of the gyroscope’s performance.The signal processing platform includes:laser temperature control,constant current source drive,power detection and other modules designed with LTC1923,LTC2053,AD,DA and other chips,difference frequency signal conditioning and high-precision difference frequency signals composed of FPGA and TDC-GP22 chips Detection Systems.Then,the test environment of the gyroscope system was built,and the self-injection locking effect,laser drive,difference frequency signal conditioning circuit,difference frequency signal detection circuit and other modules in the system and the overall performance of the gyroscope were experimentally tested.The experimental results showed that the designed All system modules are in line with the expected results,and the initial bias instability of the gyro output can reach ldeg/s.This paper has certain innovation and engineering significance for the new resonant fiber optic gyroscope in miniaturization,low cost and high precision.