Phase noise effects on the performance of joint carrier phase recovery algorithms in phase-locked WDM superchannel transmission systems

Low-Overhead Low-Complexity Carrier Phase Recovery Technique for Coherent Multi-Band OFDM-Based Superchannel Systems Enabled by Optical Frequency Combs

“…1) to estimate the common phase error, which is applied to correct the phase drift of all subcarriers across the different sub-bands within the OFDM-based superchannel. This is similar to the master-slave carrier phase tracking scheme previously demonstrated for comb-based spectral [13], [14], [41] and spatial [6] superchannel transmission systems as well as the multi-band DFT-spread OFDM system in 179 [42]. Since the pilot-subcarriers used occupies a small fraction of the overall OFDM bandwidth, this MS-CPR scheme will ultimately serve as alternative CPR method to achieve reduction in overall pilot-subcarrier overhead plus CC in CO-OFDM systems.…”

“…This is because the higher-order modulation formats with shorter fiber transmission distance suffers stronger effects of differential phase offset, compared to the lower-order modulation formats, indicating that sensitivity of the differential phase offset increases with the order of the modulation formats. Similar to the comb-based Nyquist-WDM superchannel systems [13], [14], it can be observed from Fig. 5 that performance of MS-CPR without the slave DD phase-tracker for the outer OFDM-bands is adversely impacted more by the differential phase offset than the inner OFDM-bands.…”

“…This shared phase evolution among the OFDMbands provides the possibility to reuse the resources needed for phase estimation for other sub-bands within the superchannel spectrum via joint-carrier phase tracking techniques. However, as shown in [13] and [14] and also depicted in this work, there may exist band-dependent phase offset, which degrade the performance of joint-carrier phase tracking schemes. The origin of this phase offset can be traced to the different group velocity delay experienced by each OFDM-band as a result of the fiber CD, which is adequately captured by the baseband frequency domain CD transfer function expressed as [11]:…”

“…To the best of our knowledge, this remains to be investigated especially for long-haul optical fiber transmission of multi-wavelength comb-based orthogonal band-multiplexed OFDM-based superchannel signals. In particular, joint-carrier phase tracking is recently shown to suffer performance degradation due to dispersion-induced phase-offset in comb-based Nyquist-WDM superchannel transmission systems [13], [14]. Since CO-OFDM systems with adequate cyclic prefix (CP) exhibit robust immunity against residual chromatic dispersion (CD) [40], it will be interesting to investigate the joint-carrier phase tracking for multiwavelength OFDM-based superchannel systems enabled by optical frequency combs, which is the focus of this paper.…”

“…As a result of the different group velocity delay experienced by the individual OFDMbands, the bands would gradually walk off each other after fiber transmission and subsequently arrive at the receiver at different time instants and mix with different parts of the LO phase noise. This is because the carrier phase after fiber transmission will have different delays in the different channels, where the relative CD-induced time-delay between the channels can be expressed as [13], [14]:…”