在长距离光通信系统中,差分相移键控( differential phase shift keying,DPSK)调制和解调技术是针对色散补偿而提出的一种技术方案。其中差分正交相移键控( differential quadrature reference phase shift keying,DQPSK)技术通过采用不同的调制技术如非归零( non-return to zero,NRZ)、归零( return to zero,RZ)、载波抑制归零( carrier sup-pressed return to zero,CSRZ)调制。但由于差分相移键控的频谱功率较低,误码率更高高,噪声干扰更大等缺点。提出了载波抑制归零-差分正交相移键控( CSRZ-DQPSK)调制方式,具有更好的抗色散和抗偏振膜色散的能力,它可以弥补差分相移键控的缺点。以眼图张开代价( EOP)、眼图和误码率( BER)作为性能评价指标,研究了这3种调制格式对色散( chromatic dispersion,CD)、偏振膜色散( polarization mode dispersion,PMD)和非线性效应的抑制作用。经测试CSRZ-DQPSK调制方式的功率损耗相对较低,具有更窄的频谱,在色散容限与非线性效应容忍度方面具有很大提升,性能更加优越。因此可作为长距离波分复用无源光网络( wavelength division multiplexing-passive optical net-work,WDM-PON)的一个简单高效的方案。%The differential phase shift keying ( DPSK) modulation and demodulation technique was em-ployed for dispersion compensation in long haul optical communication systems. Since there have been extensive innovation towards development of differential quadrature phase shift keying ( DQPSK) that are more suited for different modulation formats including non-return to zero ( NRZ) , return to zero ( RZ) , and carrier suppressed ( CSRZ) . The DPSK had less spectral efficiency, probability of error was higher and noise interference was stronger. The proposed technique CSRZ-DQPSK modulation format had the tolerance of anti-dispersion and anti-PMD ( polarization mode dispersion) . It could mitigate the drawback of DPSK. The tolerance of the three types of modulation formats to polarization mode dispersion ( PMD) and nonlinear effect was evaluated by means of EOP, eye diagrams and bit error rate ( BER) . It was ob-served that power penalty of the proposed modulation format was comparatively less. The results indicated that CSRZ-DQPSK had very good tolerance to chromatic dispersion, polarization mode dispersion and nonlinear effect. Hence it could be used in a simple and cost-effective design of wavelength division mul-tiplexing passive optical network ( WDM-PON) .
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