Research On All Fiber High-speed State Of Polarization Measurement System Of Analog Signal

ABSTRACT:With the development of high-speed optical fiber communication and fiber optic sensing system, the role of polarization (SOP) is increasingly important, especially in the research of how PMD impacts optical fiber communication systems, as well as rapid and accurate measurement of the state of polarization (SOP) of the test signal through polarization time domain reflectometer (P-OTDR). People have increasingly high requirements in high-speed analog measurement. The highest analog signal test rate that the existing commercial polarization analyzer (PA) can arrive is not more than1MHz. So, in this paper, experimental researches is performed on the measurement of SOP about high-speed analog signal.Firstly, deeply research is carried on the circuit of photodetector amplifier. Photodetector that can do four signals differential detection was produced. It can measure0-50MHz analog signal without distortion. High-performance detector was provided to the experimental system.Secondly, operating principle is researched about polarization modulator based on the LiNbO3modulator, simulation is made so that changing curve of Stokes parameters about polarized light after modulation is definite. This provides theoretical basis to the analysis of experiment results.Finally, all-optical high-speed SOP measurement system is designed and produced based on fiber polarization controllers (PC), polarization beam splitters (PBS) and analog photodetectors. The problem of time synchronization and power equalization is solved. Measurements of SOP about0～50MHz analog signal is carried on using the above system, and error analysis is made compared with commercial polarization analyzer. Experiments and analysis show that:this system enables accurate measurement of the Stokes parameters of0～50MHz analog signal, and the error circular radius on the Poincare sphere is less than0.03, which is the same order of magnitude with that of commercial PA. The system has good repeatability, and can measure much higher frequency analog signal compare with current commercial PA. So it provides an effective means for high-speed analog signal SOP measurement.