All-order polarization mode dispersion sensing and compensation in optical fiber communication systems
Abstract
Polarization Mode Dispersion (PMD) is considered a major obstacle for ultrahigh-capacity fiber communication systems at 40 Gbaud/s and above. It arises from the residual birefringence of the optical fiber, and causes a differential group delay between different polarizations. If the delay is comparable to a significant fraction of the bit period, adjacent bits may overlap, leading to an increase in bit error rate. Moreover, for polarization multiplexing (Pol-Mux) used in ultrahigh-capacity fiber systems as an important method to improve spectral efficiency, PMD not only couples polarization-multiplexed channels, but also lowers transmission tolerance to fiber nonlinearity and chromatic dispersion. Therefore, for fiber spans in which the PMD is not very small, PMD compensation (PMDC) is required. PMD monitoring is an essential part of PMDC. Since PMD can occasionally vary on a millisecond scale, and the frequency dependence of the PMD becomes important, a fast frequency-resolved monitoring tool is preferred. We experimentally apply a unique high-speed spectral polarimeter to realize near-real-time broadband Polarization Mode Dispersion (PMD) measurements. Based on PMD sensing work, our group has previously performed all-order PMD compensation via hyperfine resolution optical pulse shaping for isolated short pulses. This scheme works more efficiently than the traditional compensators that are limited to the low-order PMD regime and valid only for small distortion compared with pulse width. Here for the first time, we apply this technique in optical fiber communication system experiments: (1) 40 Gbit/s systems; (2) 10 Gbit/s×2 Pol-Mux systems. For the 40 Gbit/s system, we construct a test-bed realized by 10 Gbit/s × 4 optical time division multiplexing (OTDM). With this system, employing an optical pulse shaper with 128 pixels to control 200 GHz range, we demonstrate all-order PMDC with over 50 ps mean differential group delay. For the 10 Gbit/s × 2 Pol-Mux (10% RZ) system, with the same shaper we compensate PMD with over 40 ps mean differential group delay. Both experiments can readily be extended to higher symbol rate (pulses down to sub-ps range).
Degree
Ph.D.
Advisors
Weiner, Purdue University.
Subject Area
Electrical engineering
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