The Methods Of Fiber Optical Angular Sensor Drift And Noise Suppression

The fiber optical angular velocity sensor is a kind of sensors based on Sagnaceffect to measure the rotational speed of the optical fiber coil by measuring theoptical path shift of the two beams of light along the optical fiber coil clockwise andcounterclockwise. In recent years, because of its high accuracy, high sensitivity,dynamic range wide, small size, light weight, easy to integrate, etc., as well as itsbroad application prospects in the military and civilian fields such as satellitepositioning, missile guidance, aircraft navigation, it become a hot research topic inthe field of fiber optic sensors. Based on the domestic and international fiber researchresults and research progress, to achieve a large dynamic range fiber optic and highprecision measurement requirement, we mainly do the following work:Firstly, we analysis the optical angular velocity sensor measuring principle andthe characteristics of the interferometer output signal. Based on modulation anddemodulation of closed-loop sensors, we establishment a dynamic model of thesensor system and carry out simulate result by using matlab’s Simulink software.According to the simulation results，we select the actual parameters.Secondly, we study the closed-loop demodulation system key parameters,including optical signal gain bandwidth selection, A/D converter bits, D/A converterbits and feedback circuit parameters. According to the above hardware parametersrequirements, we complete the FPGA-based digital closed-loop demodulationhardware circuit build by selecting a suitable device, and test all aspects of the circuitnoise.Thirdly, on the basis of the hardware circuit we achieve programming algorithmusing Verilog HDL hardware description language, including fiber optic ring transittime test algorithm, Y-waveguide half-wave voltage test algorithms and sensorsystem testing algorithms. Based on the software and hardware, we actual test thefiber optic ring transit time and the Y waveguide half-wave voltage, while testing thefour-state wave modulation of the output of the sensor system, we mainly test theoutput of the sensor system in the case of open and closed loop, and test the sensoroutput when the rotation sensor system different angles in the closed-loop case. We program the LabVIEW software for data display and storage convenience, andachieve the PC and machine communication through the RS485serial interface.Finally, we analysis the RIN characteristics and the RIN suppression methods.RIN suppression subtraction and RIN suppression sum scheme are analyzed inhardware. Based on noise suppression circuit built, we respectively write programsprocedures for testing the two sources RIN noise suppression method, and give theactual test results.In summary, depending on the chosen simulation parameters, the dynamic modelof the sensor system step response time is0.4ms or so, it shows the parameterselection is reasonable and the system can stable and reliable. Based on the simulationparameters, we select the actual device, set up the hardware circuit of the sensorsystem and prepare test procedures. The test results show that: fiber-optic ring transittime measurement accuracy within2.6ns range; half-wave voltage accuracy3mvrange; when the location of the sensor axis corresponds to the north-south direction,,the stability of the zero drift stability is0.0148o/h; when the sensor axis correspondsto the location of the east-west direction, the zero drift stability is0.00689o/h; lightRIN noise suppression enable the system to get a better improvement. It can achievethe system specifications.