Laser phase noise effect and reduction in self-homodyne optical OFDM transmission system

Abstract

We present a laser phase noise (PN) induced effect of a phase-modulation-to-intensitymodulation conversion noise and noise pedestals underneath each of the orthogonal frequency division multiplexing (OFDM) subcarriers in a selfcoherent optical OFDM transmission using a self-homodyne technique. We provide a statistical analysis on the received symbols using a histogram to demonstrate the effect of a phase rotation term and inter-subcarrier interference individually and collectively. The PN is then compensated using a simple time delay to realign the phase walk-off of the subcarriers relative to the carrier. Significant quadrature improvements of 6.82 dB using 5 MHz laser linewidth over a 720 km transmission length and 5.38 dB using 20 MHz over 240 km have been obtained with 16 quadrature amplitude modulation (QAM) over 15 GHz OFDM signal bandwidth. The technique also significantly reduced an optical-signal-tonoise ratio requirement at the bit error rate of 1 × 10−3 by 16.15 dB for 64-QAM over 160 km. With the delay, the system can tolerate three times the chromatic dispersion-length product..

Key Technologies and Development Trends of 5G Optical Networks

“…Therefore, some optical communication discussions have been initiated to solve the bandwidth and latency problems faced by future 5G networks. Solutions that have been proposed include a dense wavelength-division-multiplexed passive optical network [14], orthogonal frequency division multiplexing [15,16], and space division multiplexing [17]. Future 5G optical network operators should work toward establishing the large bandwidth and low latency required for the efficient transmission of user data.…”