Polarization-mode dispersion (PMD) is one of the important limiting factors for high-speed optical transmission system. To overcome this limitation, there have been numerous efforts to compensate the PMD of transmission fiber. However, for the efficient PMD compensation, it is essential to develop an accurate monitoring technique. PMD could be monitored by measuring the degree of polarization (DOP) of optical signal. This technique is attractive since it does not require any high-speed circuits and is independent of the bit rate and chromatic dispersion. Recently, it has been reported that the sensitivity of this technique could be substantially improved by filtering out the carrier in the optical signal. To achieve this, the optical spectrum was partially filtered by using a narrow bandpass filter.
In this thesis, we investigated the effects of partial spectrum filtering on the DOP-based PMD monitoring technique. The results showed that, although the partial-spectrum filtering technique could improve the sensitivity of the DOP-based monitoring technique, it deteriorated the performance of PMD compensation under all-order PMD environment. This was mainly because the information on the higher-order PMD was diminished by the partial-spectrum filtering. To solve this problem, we proposed to use a notch filter, such as fiber Bragg grating filter, instead of an optical bandpass filter for the suppression of carrier in the optical signal. This technique could improve the sensitivity of DOP-based monitoring technique without degrading the performance of PMD compensation.
