Koch Benjamin, Noé Reinhold, Sandel David, Mirvoda Vitali
Opt Express. 2014 Apr 7;22(7):8259-76. doi: 10.1364/OE.22.008259.
Following an initial discussion of control error signal generation, we present new developments and applications of automatic endless optical polarization control based on a commercial electrooptic LiNbO(3) polarization transformer: (i) Fast tracking and subsequent demultiplexing of DPSK/DQPSK/QAM polarization channels was hitherto limited to a fairly fixed optical input power. With APD photoreceivers used for residual interference detection, we demonstrate here an optical level tolerance of at least 7 dB, compared to only 3 dB for PIN photoreceivers. DPSK channel polarizations are tracked at up to 40 krad/s and higher speed on the Poincaré sphere. (ii) High-order optical modulation schemes require increased accuracy of the polarization controller in the demultiplexer. This is possible at the expense of a reduced tracking speed. We achieve a mean polarization extinction ratio of >40 dB or <0.02 rad error while tracking arbitrary endless polarization changes of up to 1000 rad/s. (iii) While electronic polarization tracking in coherent receivers is currently limited to a symbol rate of about 28 GBaud we show optical polarization tracking of a signal with 1 THz bandwidth.
在初步讨论控制误差信号生成之后，我们展示了基于商用电光铌酸锂（LiNbO₃）偏振变换器的自动无限光偏振控制的新进展和应用：（i）迄今，DPSK/DQPSK/QAM偏振通道的快速跟踪及后续解复用仅限于相当固定的光输入功率。使用雪崩光电二极管（APD）光接收器进行残余干扰检测，我们在此展示了至少7 dB的光电平容限，而PIN光接收器仅为3 dB。DPSK通道偏振在庞加莱球上以高达40 krad/s及更高速度进行跟踪。（ii）高阶光调制方案要求解复用器中偏振控制器的精度提高。这可以通过降低跟踪速度来实现。在跟踪高达1000 rad/s的任意无限偏振变化时，我们实现了平均偏振消光比>40 dB或误差<0.02 rad。（iii）虽然相干接收器中的电子偏振跟踪目前限于约28 GBaud的符号率，但我们展示了对具有1 THz带宽信号的光偏振跟踪。
