Abstract

A wide-range of optical comb generators have been proposed in recent years, with applications varying from wavelength division multiplexing (WDM) to photonic microwave filters. In ultra-dense WDM systems, for example, spectrally sliced comb generators are used in order to produce a signal containing a number of closely spaced optical channels [1], More recently, a technique called Coherent WDM (CoWDM) made use of an optical comb generator, where each adjacent channel is phase-locked to each other, in order to increase the information spectral density (ISD) in a compact and cost-effective configuration. Many of the current comb generation techniques require high optical launch powers and/or precise control of certain device parameters and are used in combination with optical filtering in order to shape the comb appropriately, thus increasing the complexity and reducing the overall power efficiency of the generator. In this paper we show that a simple and cost-effective comb generator, where adjacent channels are phase- locked, can be readily achieved. The combination of low drive voltage and the additional degree of freedom offered by the use of two amplitude modulators enables demonstration of 11 comb lines at a spacing of 42.6 GHz for the first time.

© 2007 IEEE