Research On Fast Birefringence Detection Based On Polarization Sensitive Oct And Dual Loop Oeo

Birefringence detection is widely used in jewelry identification.With the development of science and technology and the improvement of medical care level,it was found that the birefringence of biological tissue can be a good representation of tissue state.However,due to the particularity of tissue,traditional birefringence detection technologies is not very useful.Therefore,the study of novel birefringence detection technologies is becoming more and more important.As one of the most popular medical imaging technologies,polarization-sensitive optical coherence tomography(PS-OCT)technology can detect birefringence well due to its unique polarization imaging technology.However,the rendering speed of traditional time-domain polarization-sensitive OCT(TD-PS-OCT)is limited by the mechanical scanning of reference arm;the performance and application of frequency-domain polarization-sensitive OCT(FD-PS-OCT)is limited by the complex algorithm processing.It is necessary to change the structure of PS-OCT to get better performance.Due to the high Q and low phase noise output of an optoelectronic oscillator(OEO),it is widely used in the generation of microwave signals.In addition,considering the close relationship between OEO output signal frequency and OEO loop delay,when any of sample length and sample refractive index is known,another can be measured by detecting signal frequency using OEO structure.In this paper,two novel birefringence detection methods and devices are proposed combining PS-OCT and OEO respectively.The first method improves the rendering speed of TD-PS-OCT by directly changing the injection current of semiconductor optical amplifier(SOA)to realize depth scan instead of mechanical scan of reference arm.The simulation results show that proposed structure can distinguish 10-3 birefringence change of 20?m sample.The second method,using high sensitivity to the short loop delay of a dual-loop OEO composed of polarization controller(PC)and polarization beam combiner(PBC),can detect sample birefringence as long as sample length is known.The simulation results show that 0.012 birefringence change of 10cm sample can be detected under the condition of using 51m long fiber loop,1.02m short fiber loop and 9.984GHz band-pass filter.A higher birefringence resolution can be achieved by increasing the length of long fiber loop or the center frequency of filter.