Self-homodyne optical orthogonal frequency division multiplexing (OFDM) transmission system is a variant of self-coherent systems with a relaxed laser linewidth requirement as opposed to a full coherent system. The system is designed by transmitting a carrier together with the subcarriers, ensuring a strong phase-correlation between them at a receiver compared to the coherent system where only the subcarriers are transmitted. Despite the strong phase-correlation, the laser phase noise (PN) can still degrade the self-homodyne system performance due to the interaction of the PN with a chromatic dispersion (CD) induces a phase-modulation to intensity-modulation (PM-to-IM) conversion noise which cannot be canceled using a balanced-receiver. This imposes a high noise pedestal underneath each subcarrier, with the highest pedestal's peak imposed beneath the subcarriers that are farthest away from the carrier. This in turn produces a phase-decorrelation between the carrier and subcarriers which degrades the Q-factor between the lowest and highest subcarrier frequencies. In this work, the effect of the PM-to-IM conversion noise is reduced for the transmission of up to 174 Gb/s using a simple delay-line assigned to realign the phase-decorrelation of the subcarriers. With this technique, the subcarriers Q-degradation can be improved and the total transmission length can be tripled with Q-improvements of 5.4, 5.3, and 5-dB for 16-quadrature amplitude modulation (QAM) over 1360 km, 32- QAM over 800 km, and 64-QAM over 480 km, respectively, using 10-MHz LW with a 15-GHz total signal bandwidth. For 29 GHz signal bandwidth, the phase-walk-off of the high frequency subcarrier becomes more severe where the introduced delay can increase the transmission length by 2.5 times than without the delay, which increased the signal tolerance to the conversion noise.

中文翻译：

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使用延迟自同调光学正交频分复用系统将调相转换为强度调制转换噪声的影响

自同调光学正交频分复用（OFDM）传输系统是自相干系统的一种变体，与完整相干系统相比，它具有宽松的激光线宽要求。该系统是通过与子载波一起发送载波来设计的，与仅发送子载波的相干系统相比，确保了接收机之间子载波之间的强相位相关性。尽管相位相关性很强，但是由于PN与色散（CD）的相互作用会引起相位调制到强度调制（PM-to），因此激光相位噪声（PN）仍然会降低自谐系统的性能。 -IM）转换噪声，无法使用平衡接收器消除。这会在每个子载波下方施加一个高噪声的基座，其中基座最高 在远离载波的子载波下方施加的s峰值。这进而在载波和子载波之间产生相位解相关，这会降低最低和最高子载波频率之间的Q因子。在这项工作中，使用分配用于重新对齐子载波相位去相关的简单延迟线，可以降低PM-IM转换噪声对高达174 Gb / s传输的影响。使用此技术，可以改善子载波的Q衰减，并且可以通过在1360 km上进行16正交幅度调制（QAM），在32-QAM上进行16正交幅度调制（QAM）的Q改进5.4、5.3和5dB，将总传输长度增加三倍。使用10 MHz LW且总信号带宽为15 GHz的情况下，分别在800 km和480 km上进行64 QAM。对于29 GHz信号带宽，