Research Of Low-cost Open-loop Fiber Optic Gyro Demodulation Circuit

Aiming at the interferometric fiber optic gyroscope based on Sagnac effect,this paper mainly studies and designs from the circuit direction,aiming to realize the openloop fiber optic gyroscope with lower cost and higher precision.Compared with the closed loop,the open-loop fiber optic gyroscope has the advantage of its price,which makes it possible to popularize and use in the civil field.Firstly,the basic principle of optical path sensing and the existing modulation and demodulation methods are analyzed and introduced in this paper.Secondly,according to the characteristics of the signal detection theory,the system output signal using coherent demodulation scheme is determined,and the current mainstream of the closed loop demodulation circuit scheme and the open loop demodulation circuit compares the advantages and disadvantages and applicable system of reasoning,analysis the main source of open loop system error,designed with FPGA as the core of open loop demodulation circuit;For coherent demodulation is the most critical phase sensitive detection module using multiplier and electronic switch to design respectively,and has carried on the experiment and theory analysis,in addition,also set the open-loop fiber optic gyroscope light path part of the piezoelectric ceramics(PZT)phase modulator driver module,will not part optical path open-loop fiber optic gyroscope integrated on a circuit board,form a complete circuit.Finally,according to some problems existing in the experiment process and the demand for low cost and high precision of the system,the direction that can be further optimized and some methods that can be tried to solve the problem are proposed.Final experimental result: Tested on an open-loop fiber optic gyroscope prototype with a length of 275 meters,an outer diameter of 33 mm,and an inner diameter of 22 mm using the zero-crossing demodulation method under normal temperature conditions.The scale factor nonlinearity is 930 ppm and zero offset It is6.4°/h,and the zero-bias instability is 0.052°/h.The main innovation of this paper:In view of the low-cost requirements of open-loop fiber optic gyroscopes,this paper designs a signal demodulation circuit system with an electronic switch-type analog lock-in amplifier as the core.Under the premise of low precision requirements,the overall cost of the system is greatly reduced,and for the first time A low-cost demodulation method for dual-axis fiber optic gyroscopes is proposed without increasing the circuit complexity.