160-Gb/s Optical Time-Division Demultiplexing Using a Mach–Zehnder Modulator in a Fiber Loop

Optical switching a 160-Gb/s signal using a LiNbO Mach-Zehnder modulator (MZM) is enabled by a novel method of connecting it within an optical fiber-loop mirror. The principle of operation exploits the unidirectional optical modulation of the MZM such that counterpropagating waves within the loop experience unequal amplitude modulation leading to output transmission of a high-quality 40-GHz pulse train of duration shorter than if using just the MZM alone. Measurements employing a commercially available MZM modulated at 40 GHz in a fiber-loop show generation of a 5.3- to 5.9-ps-wide gate pulse at a 40-GHz repetition rate with center wavelength tunable from 1535 to 1565 nm. Application to optical time-division demultiplexing of a 160-Gb/s return-to-zero format signal achieves less than 1-dB bit-error-rate power penalty for all four of its 40-Gb/s tributaries.