Single DPLL Joint Carrier Phase Compensation for Few-Mode Fiber Transmission

A carrier phase estimation and compensation algorithm using a digital phase locked loop is proposed which exploits the common-mode impairment from the shared local oscillator at the receiver side in a few-mode fiber transmission system. We verify that the proposed algorithm is more tolerant to phase-mismatches than earlier work. The carrier phase estimation (CPE) scheme is evaluated for a 3$,times,$ 112 Gbit/s dual polarization quadrature phase shift keying mode division multiplexed transmission over 80 km including an in-line multimode erbium doped fiber amplifier. The digital signal processing computational complexity is reduced in comparison to a traditional CPE stage. In addition, the proposed scheme is shown to perform similarly with respect to the $3.8times 10^{-3}$ forward error correcting limit optical signal to noise ratio tolerance of the traditional CPE scheme.