Optical PSK Synchronous Heterodyne Experiments at 560 Mbit/s through 4 Gbit/s

Abstract

A synchronous optical heterodyne receiver was constructed using an optical phase-locked loop based on a 1320nm diode-pumped Nd:YAG laser. Using that receiver and a transmitter based on another Nd: YAG laser, PSK synchronous heterodyne experiments were demonstrated at 560 Mbit/s, 2 Gbit/s and 4 Gbit/s. The receiver sensitivity at the three bit rates was -48.7 dBm (159 photons/bit), -41.7 dBm (225 photons/bit), and -34.2 dBm (631 photons/bit), resepctively. Performance degradations due to an insufficient local iscillator power, a finite intermediate frequency (IF) and a sub-optimum coupler splitting ratio were investigated. compact, robust and can generate highly coherent 1320 nm radiation with linewidths of the order of 1 Hz [13].Recently, optical PSK synchronous heterodyne experiments at 560 Mbit/s have been reported by several groups [14][15][16][17]. In this paper, we demonstrate a synchronous heterodyne receiver using an optical phaselocked loop and report experimental results at bit rates of 560 Mbit/s [17], 2 Gbit/s [18] and 4 Gbit/s [19]. To achieve the higher bit rates (2 Gbit/s and 4 Gbit/s), we use a simple broadband receiver (p-i-n/100-Ω photodetector). In addition, we investigate the impact of the finite IF, the coupler splitting ratio (for the single-ended receiver with the available LO power of 3.3 dBm) and the insufficient LO power on the system performance.