Optical polarization mode dispersion compensators for high-speed optical communication systems

This paper details and describes optical polarization mode dispersion compensators (PMDCs) for high-speed optical communication systems. We begin with a general discussion of the PMDC, including its operating principle, practical implementation considerations, and its performance evaluation methods. We then describe an optical PMDC with fast tracking speed for a 40 Gb/s non-return-to-zero differential phase shift keying (NRZ-DPSK) system. The performance of the PMDC is tested in both back-to-back operation and a 1,100 km transmission system. Back-to-back measurements show that the PMDC can increase the polarization mode dispersion tolerance of a 40 Gb/s NRZ-DPSK system to about an 8 ps mean differential group delay at an optical signal-to-noise ratio (OSNR) margin of less than 1.5 dB. It is able to track principal state of polarization changes as fast as 45°/ms. Fiber nonlinear effects on the PMDC are investigated in the 1,100 km transmission system with neighboring 10 Gb/s on-off keying (OOK) channels with 50 GHz channel spacing. Applications of the optical PMDC to other modulation formats such as differential quadrature phase shift keying (DQPSK) are also discussed. é 2010 Alcatel-Lucent.