Research On Several Key Technologies Of Polarization Encoding Communication

Realizing polarization coding via Information loaned by polarization of light, which is both an effective solution for power fluctuation and a way to significantly reduce the nonlinear effects in optical fiber communication system and improve the efficiency of spectrum. Undoubtedly it is a research hot spot on realization of high-speed optical fiber communication. The stability of the polarization encoder is one of the key issues affecting polarization coding communication. In this paper, firstly, the stability of the polarization encoder based on Lithium niobate (LN) phase modulator is studied in depth, and is described by time variant vector. The experiment result shows that, for the LN phase modulator, the principal state of Polarization-dependent loss (PDL) is consistent with the principal state of Polarization-dependent phase shift, indicating PDL will not affect the stability of the polarization state. A "inertia" of polarization rotation is observed in experiment, when voltage is increased to a value from OV (and vice versa), the polarization state will not be stable before about30mins. It will have negative effects on low-speed modulation. For high-speed modulation, the changes of the average power will cause polarization jitter. To solve this problem, this article suggests placing the50ohm matching resistor outside the LN, and enhancing heat dissipation to reduce the thermal inertia effects. Secondly, this paper analyzes the feasibility and defects of existing polarization encoding scheme, and then through the production of large dynamic range phase modulator and the phase compensation technology to improve the existing polarization encoding scheme and the stability of polarization encoding. On the one hand, experiments show that the improved scheme can effectively avoid the insertion loss; on the other hand, interference in the arm length difference can also influence on the stability of polarization, but it still needs to continue to improve in order to avoid the signal less susceptible to environmental factors. Finally, this paper studies on the key devices for loop systems and analyzes the performance of related components and parameters to determine the feasibility of the loop system, offering a theoretical basis for rational selection of devices and follow-up experiments. Using coded signal intensity and polarization encoding signal to conduct transmission experiment, not only verifies the feasibility of the loop transmission system, but also finds that the polarization encoding signal problems in transmission experiments, which undoubtedlv indicates the direction for the following work.