A new method to monitor the polarization mode dispersion(PMD) is proposed by calculating the energy difference between two polarization states forPM-QPSK system. The results demonstrate that the first order PMD ranging from 1ps to 19ps can be effectively monitored with the interference of CD and the monitoring error is only 0.5ps. In addition, the proposed method is also cost effective as the bandwidth of coherent receiver is only 1.5 GHz and the sample rate is 1 GHz.
Holographic grating can be used widely in optical fields, especially in wavelength division multiplexer and optical fibre
network. In this paper, a new kind of water resisting photopolymer which is sensitive to the red light of 632.8nm and
green light of 514.5nm is made into double holographic grating by exposure twice. The resolution of this grating is
above 4000line/mm. The principle of manufacture and technology of the new style grating is simple; it doesn't need the
second treatment. The grating has many other merits, such as lower cost high diffraction efficiency, better stability and
so on. Based on the study, the holographic grating can be used for wavelength-division demultiplexer for it is lower loss
and narrow-band width.