Demonstration of 400 Gb/s optical PDM-OFDM superchannel unrepeatered transmission by all optical phase-conjugated copy

Abstract

Unrepeatered transmission delivers data over a few hundred kilometers without in-line active elements and it can effectively reduce the line complexity and the overall system cost. In this paper, we propose all optical phase-conjugated copy (OPC) to improve optical signal noise ratio (OSNR) margin and nonlinear tolerance for unrepeatered transmission of polarization division multiplexing (PDM) optical superchannel with EDFA only amplification. Orthogonal pumps FWM scheme is utilized to generate the optical phase-conjugated copy. The original superchannel and the phase-conjugated copy are simultaneously transmitted and received. The phases of the copy symbols are conjugated and summed with the original superchannel symbols to suppress both linear noise and nonlinear phase noise at the receiver. The proposed OPC scheme is simple and effective in phase-conjugated copy generation and digital signal processing (DSP). What is more, it is transparent to signal bit rate and modulation format, which applies to optical superchannel transmission. We experimentally verify the proposed scheme on a 400Gb/s optical polarization division multiplexing orthogonal frequency division multiplexing (PDM-OFDM) superchannel. A Q-factor improvement of 2.1dB is achieved after 180km SSMF unrepeatered transmission. The optimum launch power in OPC scheme increases from −3dBm to −2dBm. To verify the maximum reach, we extend fiber length and realize 240km SSMF unrepeatered transmission.