Laser Depolarizer Technology And Polarization Interference Filter Theoretical Research

Optical depolarizing technology is an effective method to reduce polarization related effects in single-mode fiber systems, which play an important role in long distance optical fiber communication systems and coherent sensing and measurement systems. Polarization interference optical filter proves to be an efficient kind of optical filters and has numerous applications in optical communication, optical information processing. In this thesis, optical depolarizing technology is investigated carefully and in theory the synthesis of crystal-based polarization interference optical filter is presented. Creative works of the thesis are listed as follows:Principles of depolarization are described in detail and therefore two artificial birefringent structures are presented. Based on this structure several novel depolarizers are devised including: 1) Polarization independent depolarizer. Transmission- and reflection-type polarization independent depolarizers are devised, and a transmission-type depolarizer is developed. In experiment, when depolarizing a laser diode with FWHM of 0.13nm, the degree of polarization (DOP) of output light less than 2%. Additionally, an insertion loss of 1.0dB and a polarization dependent loss of 0.09dB are obtained. Furthermore, the depolarizer after encapsulated is used to depolarize a laser diode with FWHM of 0.2nm and the measurement results are 1.2% and 1.6dB of DOP and insertion loss, respectively. 2) Depolarizers with isolator function. Several depolarizer structures are devised in which depolarization and isolation can be achieved simultaneously. Therefore the devices are more compact and less cost. 3) Depolarizer for linearly polarized light. Adding a quarter waveplate before the entrance of polarization-dependent depolarizer, the dependence on the direction of vibration of incident linearly polarized light is effectively reduced. The DOP of output light is 2.6% when depolarizing a laser diode with FWHM of 0.13nm. 4) Depolarizers for multiple longitudinal mode laser diodes. The parameters of such depolarizers are analyzed and optimized in details. A depolarizer with isolation function and independent of the direction of vibration is developed. In experiment, linearly polarized light from a multiple longitude mode laser diodes with randomly direction of vibration is depolarized efficiently, and the DOP outputlight and isolation are 10.5% and 27dB,...