Zhang Q W, Hugues-Salas E, Giddings R P, Wang M, Tang J M
Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, 149 Yanchang Road, Shanghai 200072, China.
Opt Express. 2013 Apr 8;21(7):9167-79. doi: 10.1364/OE.21.009167.
Record-high 19.25Gb/s real-time end-to-end dual-band optical OFDM (OOFDM) colorless transmissions across the entire C-band are experimentally demonstrated, for the first time, in reflective electro-absorption modulator (REAM)-based 25km standard SMF systems using intensity modulation and direct detection. Adaptively modulated baseband (0-2GHz) and passband (6.125 ± 2GHz) OFDM RF sub-bands, supporting signal line rates of 9.75Gb/s and 9.5Gb/s respectively, are independently generated and detected with FPGA-based DSP clocked at only 100MHz as well as DACs/ADCs operating at sampling speeds as low as 4GS/s. The two OFDM sub-bands are electrically multiplexed for intensity modulation of a single optical carrier by an 8GHz REAM. The REAM colorlessness is experimentally characterized, based on which optimum REAM operating conditions are identified. To maximize and balance the signal transmission performance of each sub-band, on-line adaptive transceiver optimization functions and live performance monitoring are fully exploited to optimize key OOFDM transceiver and system parameters. For different wavelengths within the C-band, corresponding minimum received optical powers at the FEC limit vary in a range of <0.5dB and bit error rate performances for both baseband and passband signals are almost identical. Furthermore, detailed investigations are also undertaken of the maximum aggregated signal line rate sensitivity to electrical sub-band power variation. It is shown that the aforementioned system has approximately 3dB tolerance to RF sub-band power variation.
首次在基于反射电吸收调制器（REAM）的25公里标准单模光纤（SMF）系统中，通过强度调制和直接检测，实验证明了在整个C波段实现了创纪录的19.25Gb/s实时端到端双波段光正交频分复用（OOFDM）无色传输。自适应调制的基带（0 - 2GHz）和通带（6.125 ± 2GHz）OFDM射频子带，分别支持9.75Gb/s和�.5Gb/s的信号线速率，由仅100MHz时钟频率的基于现场可编程门阵列（FPGA）的数字信号处理器（DSP）以及低至4GS/s采样速度的数模转换器（DAC）/模数转换器（ADC）独立生成和检测。两个OFDM子带通过8GHz REAM进行电复用以对单个光载波进行强度调制。通过实验表征了REAM的无色特性，并据此确定了最佳的REAM工作条件。为了最大化并平衡每个子带的信号传输性能，充分利用在线自适应收发器优化功能和实时性能监测来优化关键的OOFDM收发器和系统参数。对于C波段内的不同波长，前向纠错（FEC）极限下相应的最小接收光功率在<0.5dB范围内变化，基带和通带信号的误码率性能几乎相同。此外，还对最大聚合信号线速率对电性子带功率变化的敏感性进行了详细研究。结果表明，上述系统对射频子带功率变化具有约3dB的容忍度。
