Abstract

Dense wavelength-division-multiplexed (WDM) optical net-works place stringent requirements on the frequency accuracy of signal lasers to avoid optical cross talk and to conform to optical frequency standards defined by the network. Frequency control to within 10% of the channel spacing, i.e., <5 GHz for 50-GHz-spaced channels, may be necessary on each channel. Two-section distributed-Bragg-reflector (DBR) lasers are promising candidates for WDM applications because they offer narrow spectral linewidth, low relative intensity noise, high output power, and stable nanosecond wavelength switching in which discrete longitudinal modes correspond to defined wave-length channels.' However, DBR lasers with intrinsic longitudinal mode spacing exactly matching the channel spacing of WDM systems can be difficult to make with high yield. Furthermore, the output power falls as the Bragg-section tuning current increases. We report that two-section DBR lasers can operate with arbitrarily accurate frequency alignment to WDM channels spaced by 50 GHz, even when their intrinsic cavity mode spacings differ substantially from the networks channel spacing. Moreover, the power reduction with Bragg current can be effectively eliminated over the entire tuning range by using a simple control algorithm.

© 1994 Optical Society of America