I. Introduction
Clock recovery, which is the process of synchronizing a locally generated clock with incoming data, is a prerequisite for most other optical processing tasks including optical demultiplexing, optical logic, and optical retiming, recompression, and reamplification (3R) regeneration. Although electronic circuits can perform clock recovery at speeds up to 40 Gb/s, in future optical time-division multiplexed networks, the data rate could exceed the speed of conventional electronics. In these systems, the process of clock recovery can be better accomplished in the optical domain.