160Gb/s OTDM clock recovery

Abstract

ABSTRACT In this work, we demonstrate clock recovery from a patterned 160Gb/s optical-time-division-multiplexed (OTDM) return-to-zero (RZ) data stream. A cascaded LiNbO 3 Mach-Zehnder modulator is employed as an efficient optical-electrical mixer. A phase-locked-loop (PLL) is used to lock the cross-correlation component between the optical signal and a local oscillating signal. As a result, clock signal at 10GHz is extracted from the 160Gb/s optic al TDM signal. The measured root-mean-square (RMS) timing jitter of the 10GHz clock signal is ~ 130 fs. Keywords : Clock Recovery, Cascaded Modulator INTRODUCTION In ultra high speed optical communication networks, clock recovery is an essential element for any optical access node because it synchronizes the receiver decision circuitry with the incoming data stream 1 . Therefore, a stable clock source with low jitter characteristic 2 at the receiver end is required. However, due to the speed limitation of electrical circuits, at data rates beyond ~ 40 Gb/s, it becomes increasingly difficult to perform the stable clock recovery electronically. Optical clock recovery techniques that can be scaled to data rates of many tens of Gb/s to > 100 Gb/s will be a prerequisite to high data rate communication links of the future. For the optical clock recovery systems, the key steps are Optical-Electric (OE) mixing and cross-correlation detection. One approach to high-speed clock extraction is the injection mode locking technique, in which optical clock signal is obtained by launching the pulse trains into the cavity of a self-pulsating laser