Distributed feedback and distributed Bragg reflector lasers: comparisons of performance and use

The distributed feedback (DFB) laser has emerged as the clear choice for high-bit-rate point-to-point links based on today's systems demands and in-place laser manufacturing technology. However, other laser geometries have also proved capable of a high degree of spectral purity, in particular, the distributed Bragg reflector (DBR) semiconductor laser. The advent of high-quality vapor and beam growth techniques in the InGaAsP/InP system now permits both precise layer composition and thickness control and the utilization of ultrathin etch-stop fabrication techniques, which are essential in achieving reproducible high-performance active-passive DBR transitions. Current trends suggest that DFBs may have a stable role as the workhorse in high-bit-rate, point-to-point, single-channel or coarsely spaced wavelength-division-multiplexed (WDM) applications. However, the versatility of the DBR combined with other basic design features suggests that it may dominate in future densely spaced WDM and coherent applications.