Experimental Demonstration of the Tradeoff Between Chromatic Dispersion and Phase Noise Compensation in Optical FBMC/OQAM Communication Systems

Filterbank multicarrier based on offset quadrature amplitude modulation (FBMC/OQAM) is a promising candidate for optical fiber communication systems, thanks to its better time/frequency confinement compared to other multicarrier modulations. Among linear impairments, the compensation of fiber-induced chromatic dispersion (CD) and laser-induced phase noise (PN) in FBMC/OQAM systems induces a compromise in terms of the number of used subcarriers. Considering a fixed dedicated signal bandwidth, the number of subcarriers is expected to be large enough to allow a better frequency-domain CD compensation. On the other hand, it should be sufficiently small in order for the compensation of common phase error inherent to the PN to work properly. In this paper, we experimentally demonstrate the tradeoff between CD and PN compensation that we previously highlighted by simulations. More specifically, considering a 20-GHz FBMC/4-OQAM modulation and an aggregated laser linewidth of about 200 kHz, we show that the maximum transmission distance reaches 3100 km with nearly 512 active subcarriers and three-tap equalizers, when a maximum 1-dB optical signal-to-noise ratio penalty at a bit error rate of 3.8 × 10
^-3
can be tolerated. Moreover, we propose and validate a frame structure and an integrated synchronization/channel equalization architecture to implement a standalone demodulation system.