The operation of a polarization mode dispersion (PMD) compensator using a polarizer and a Faraday rotator-based polarization controller (FRPC) is analyzed in detail, and the compensation performance is experimentally evaluated in 40 Gbit/s operation. The evaluation results show that a wide range of differential group delay over a bit period can almost be completely compensated using the PMD compensator. The characteristics of electrical spectrum-based signal monitoring methods are investigated in detail, and the results shows advantages of a low frequency band monitoring method that produces about double the wider dynamic range than a fundamental repetition frequency monitoring method. The automated PMD compensator using a polarizer and a FRPC driven by the low frequency band monitoring method is experimentally investigated using a terrestrial 40 Gbit/s wavelength division multiplexing system involving 350-km installed single-mode fibers. The PMD compensator produces highly stable signal performance in the field environment for a long term and reduces the standard deviation of the Q-factor distribution.

A novel polarimetric fiber optics current sensor configuration using an in-line 22.5 degree Faraday rotator is proposed on this paper. The introduction of the 22.5 degree Faraday rotator allows to obtain a sensor configuration that does not require adjustment on most optical elements, resulting in an accuracy immune to manufacturing issues. Two prototypes are presented in this paper that are designed to measure AC current, yielding in an excellent accuracy over more than 3 decades.