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利用光纤偏振分束器和3 dB耦合器搭建偏振分集90°光学混频器,采用单端接收实现了偏振分集的相干接收机。实现了10 Gb/s偏振复用差分相移键控(DPSK)光信号,经过280 km普通单模光纤(SSMF)和掺铒光纤放大器(EDFA)传输后的数字相干接收,测量无误码。研究了数字相干光接收中的各种信号处理算法。采用数字信号处理算法完成载波相位估计,数字滤波器补偿光纤色散,恒模算法进行自适应数字偏振解复用等。研究了90°光学混频器的非理想正交特性,运用统计方法补偿了光学混频器偏离90°的误差,此算法和信号格式以及光纤色散等因素无关。使用恒模算法实现数字偏振解复用,该算法收敛时间小于0.5μs。
Polarization diversity 90 ° optical mixer was constructed by using optical fiber polarization splitter and 3 dB coupler. Single-ended receiver was used to realize the coherent receiver with polarization diversity. A 10 Gb / s polarization-multiplexed differential phase shift keying (DPSK) optical signal is achieved and digitally coherently received after transmission of 280 km normal single-mode fiber (SSMF) and erbium-doped fiber amplifier (EDFA). Various signal processing algorithms in digital coherent light reception are studied. Adopt digital signal processing algorithm to complete carrier phase estimation, digital filter to compensate fiber dispersion, and constant mode algorithm to adaptive digital polarization demultiplexing. The non-ideal orthogonal characteristics of the 90 ° optical mixer are studied. The statistical error of the optical mixer from 90 ° is compensated. This algorithm has nothing to do with the signal format and fiber dispersion. The digital polarization demultiplexing is realized by using the constant modulus algorithm. The algorithm converges less than 0.5μs.