Analysis of laser phase noise effect in direct-detection optical OFDM transmission

Abstract—In this paper, we characterize the impact of laser phase noise (PN) in direct-detection optical OFDM (DDO-OFDM) and identify its many differences from those in coherent optical OFDM (CO-OFDM). The analytical models for the diverse PN effects, including power degradation, phase rotation term (PRT), and inter-carrier interference (ICI), are given in terms of critical system parameters with or without the small PN assumption. In particular, the analytical upper-bound of the ICI power with a simple form is also provided. We also present a bit error rate (BER) estimation approach which is proven to be reliable for an optical signal-to-noise-ratio (OSNR) penalty lower than 2 dB. In addition, the PN tolerances, in terms of OSNR penalty, are also numerically analyzed and discussed with different QAM formats, data rates, laser linewdiths, and subcarrier numbers. Index Terms—Direct detection, optical fiber communication, or-thogonal frequency division multiplexing (OFDM), optical modu-lation, phase noise. I