MULTIWAVELENGTH DFB LASER ARRAYS WITH INTEGRATED COMBINER AND OPTICALAMPLIFIER FOR WDM OPTICAL NETWORKS

In this paper, we describe the design, fabrication and performance of multiwavelength DFB laser arrays with integrated combiner and optical amplifier built for wavelength-division-multiplexed (WDM) optical netw orks. The goal is to reduce the per-wavelength transmitter cost in bot h initial procurement and subsequent operation. Using photonic integra tion, we have addressed and resolved several important issues related to laser arrays such as wavelength accuracy, output power, high-speed modulation and optical packaging. State of the art results have been o btained. By the use of wavelength redundancy and proximity effect, wav elength deviations of +/-0.2 nm or less from the designated eight-wave length comb have been achieved with high yield. Simultaneous operation of ten wavelengths has also been demonstrated. In spite of the inhere nt splitting loss of 13 dB, high-output powers of about -13 and 0.5 dB m per wavelength have been measured, under simultaneous operation, int o a single-mode fiber (SMF) without and with on-chip optical amplifica tion, respectively. The DFB laser has a 3-dB bandwidth of 9 GHz. A 2.5 -Gb/s (OC-48) error-free transmission through 120 km conventional SMF has been demonstrated under single channel operation. The electrical c rosstalk from neighboring channels cause negligible degradation to the eye diagram and the bit-error-rate (BER) curve at a bit rate of 2.5 G b/s. The optical crosstalk due to four-wave mixing and cross-gain modu lation (XGM) of the semiconductor optical amplifier (SOA) is also char acterized. The impact of this integrated laser array on WDM optical ne tworks is assessed in the conclusion.