Linewidth tolerance of digital coherent receiver using Viterbi amp; Viterbi RF carrier recovery for radio-over-fibre links

摘要

Transport and distribution of wireless signals over fibre, so called Radio-over-Fibre (RoF), is an important technology in order to realize converged fibre-optic and wireless networks (1). Recently, we have proposed and experimentally demonstrated a novel DSP based digital coherent receiver for phase-modulated RoF optical links (2). The RF signal processing in (2) is performed using maximum likelihood RF carrier phase estimation (2). In this paper, we investigate the performance of the proposed digital coherent receiver in (2) using feedforward Viterbi & Viterbi RF carrier recovery algorithm in combination with squaring synchronizer. The advantage of the proposed scheme is simplicity since the RF carrier recovery is performed on only one sample per bit due to prior squaring synchronizer which performs timing recovery. We investigate the tolerance of the proposed scheme with respect to laser linewidth using numerical simulations and compare the results to traditional approach using feedforward maximum likelihood RF carrier phase recovery (MLCPE).