Optical Fiber Interferometer Signal Detection And Demodulation

The Optical-Fiber Interferometer has been widely used in signal detection. This thesis mainly focus on modulation-demodulation technique of the Optical-Fiber Interferometer,especially the core technique of Lock-In demodulation. In this thesis, several double beam Optical-Fiber Interferometers are studied. By searching their basic structures and principles,the basic generality of their demodulation is found and an analog-digital mixed demodulation system is designed and implemented .In this thesis,this demodulation system is used in an open-loop Sagnac Optical-Fiber Interferometer system. The demodulation results are got by experiments and The output datas are analized.The double beam Optical-Fiber Interferometers have some characteristics: their output signal has a form of 1 + k cosφ. This output is periodical and has a nonlinearity with the mput. When the demodulation result gets the special points of different periods ofφ,or different quadrants ofφ,some tests must be implemented to check that if an error result will be given by the demodulation system. Using the Optical-Fiber Interferometer for this test, the design of Testing Scheme is very complex,and need a huge amount of test work.An integrate circuit chip is used to design a Virtual Optical-Fiber Interferometer. The Virtual Optical-Fiber Interferometer has a simple circuit structure and can instead the optical structure of the double beam Optical-Fiber Interferometers to generate the output electronic signals with high stability and high precision. It can be used to test the special points easily by adjust the input reference voltage.In this experiment,a virtual Sagnac Optical-Fiber Interferometer is designed and used to test the analog-digital mixed demodulation system.This virtual Sagnac Optical-Fiber Interferometer is also tested in experiment.The experimental results indicate that the zero drift of the analog-digital demodulation system is(1.5526×10^-4)°; Tested by this demodulation system,the zero drift of the Optical-Fiber Sagnac Interferometer is (3.5081×10^-4)°, The angular velocity measurement resolution of the Optical-Fiber Sagnac Interferometer is 1.5197°/h ; Tested by this demodulation system, the zero drift of the Virtual Optical-Fiber Sagnac Interferometer is 0.0022°, The angular velocity measurement resolution of the Virtual Optical-Fiber Sagnac Interferometer is 9.5265°/ h. The nonlinear degree of the Virtual Optical-Fiber Sagnac Interferometer's scale factor is 1670ppm,the Scaling Symmetry of the Virtual Optical-Fiber Sagnac Interferometer is 880.62ppm.Usmg this Virtual Optical-Fiber Sagnac Interferometer, a special phase point test is also implemented to the demodulation system and the validity of the analog-digital mixed demodulation system has been proved.