Research On High-birefringent Fiber Based Sagnac Loop Interleaver

Optical interleaver possesses an imperative perspective of applications in DWDM (Dense Wavelength-Division-Multiplexing) system. Its application can decreae the costs of system upgrade and mitigate the rigid requirements of ultra-narrow bandwidth filter to a large extent. So extensive attention has been paid to this field.This thesis is supported by Tianjin Key Project of Applied and Basic Research Programs under Grant No. 043800911. In this thesis a novel and functional interleaver is presented. This type of interleaver is based on Hi-birefrigenct fiber Sagnac loop interferometer, bearing many attractive features, such as polarization independence, ultra-low CD and PMD, flat top, all-fiber, tunable central wavelength, etc.. So this interleaver has a promising future.Based on the theory of Jones matrix, the theoretical model of Sagnac interferometer based on High-birefringent fiber loop is constructed. Starting from this point, a large amount of numerical simulations and experimental researches have been taken, based on which the prototype machine named BFSI-I is assembled and triumphantly passes the project appraisal presided by Tianjin Municipal Science and Technology Commision.Main parts of my work are listed as follows:First, theoretical analyses of transfer functions of the HBF Sagnac interferometer are rigorously and systematically developed using Jones matrix method. There is a great difference between our conclusions and outcomes in some paper. It's been certified that our conclusions can depict the experimental results more perfectly.Second, transfer functions of high-order HBF Solc-Sagnac interferometers and Lyot-Sagnac interferometers are derived based on those above conclusions. And many simulations are done also.Third, a new sort of interleaver based on the HBF Sagnac interferometer is demonstrated. Transfer functions of this interleaver are derived and verified with simulations and experiments. According to simulations and experimental results, the channel isolation of this HBFSI-based interleaver reaches 25dB.Fourth, a novel three-stage HBFSI-based interleaver based on the three-stage HBF Sagnac interferometer is proposed. Simulations and experimental results demonstrate that the three-stage HBFSI-based interleaver has flat-top passband and itschannel isolation exceeds 28dB. Compared with the one-stage HBFSI-based interleaver, the passband width @ 0.1dB of the three-stage HBFSI-based interleaver is extended more than 65%. The passband width @ 0.5dB of a three-stage HBFSI-based interleaver whose channel spacing is 100GHz is about 0.22nm.Fifth, some factors which affected transmission performance of the HBFSI-based interleaver such as the power coupling rate and the reflectivity of output ports are studied and mended with proper schemes that have been proofed in experiments. Characteristics of the three-stage HBFSI-based interleaver including center wavelength tuning, polarization independency and high stability are discussed and certified through simulations and experimental results.Finally, dispersion measurement methods are studied and Chromatic Dispersion and Polarization Mode Dispersion measurements are carried on, laying a good foundation for next study on dispersions in optical communication.