A Design And Implementation Of The Polarization Extinction Ratio Measurement Sysytem

With the development of optical communication technology, polarizing technology is widely used in Academia and Industry. At the same time, people put forward higher requirement for the control and measurement technology of the polarization properties. As one of important parameters for evaluating the polarization properties, polarization extinction ratio (PER) describes the performance of the polarizing device. Many applications require polarizing device with high PER, such as quality-testing of polarizing device and optical sensing technology. Therefore, it is very important to research the methods of measuring the PER.At present, there are many methods of measuring the PER at home and abroad. Considering the complexity and stability of the system, this dissertation described two methods of measuring the PER including Poincare sphere method (PSM) and rotating polarizer method (RPM). The PSM method indirectly calculated the PER with Stocks parameters. And the RPM method measured the PER by using a high-speed rotating polarizer to detect light power.This dissertation mainly makes a deep research on the above two methods. Based on analyzing the two methods theoretically, a simulation and experiment platform of measurement system with the PSM method is built, and the software and hardware of measurement system with the RPM method is designed and implemented. The testing result of the systems’functions and performance shows that the two systems both have a good performance. The main research work and innovations of this dissertation are as follows:1. Based on Stocks parameters that are used to represent the polarization state, a simulation system by the PSM method is built. The simulation system completed the program of data acquisition and signal processing using OPTISYSTEM and MATLAB. The simulation results show the measurement system is feasible in theory.2. Based on the studies of the performance of the polarization beam splitter (PBS) and the polarization beam combiner, the optical system by the PSM method is built. And the data processing uses the plane geometry algorithms. Experiments show that increasing sample points or adding polarization rotation module can both improve the performance of the PER. The experimental data shows the PER is above36dB. In addition, the method is weakly depended on optical power.3. Based on the research on the single coupling point theory, a measurement system by the RPM method is built. The optical system, the hardware system and the software system are designed in this dissertation. The systems not only achieve the closed-loop position control for polarizer by motor, but also implement the full touch LCD display innovatively. Experimental data shows that when the optical power is between-25dBm and-5dBm, the PER is between0and30dB, and the PERs measurement errors can be limited in±0.15dB; when the optical power is between-5dBm and10dBm, the PER is between0and50dB, and the PERs measurement errors can be limited in±0.3dB.