Spectral behaviour of InGaAsP/InP 1.3 mu m lasers and implications on the transmission performance of broadband Gbit/s signals

In connection with the implementation of long-wavelength broadband Gbit/s transmission systems the spectral characteristics of InGaAsP/InP lasers emitting in the 1.3 mu m wavelength region are investigated. The axial mode configuration of the examined lasers is affected by optical feedback from coupling arrangements and broadened as a result of direct modulation. Along with residual material dispersion, polarization dispersion and polarization-mode coupling of the single-mode fiber the laser limits the transmission quality in a transmission system for Gbit/s applications. Considerations about laser spectral behaviour and supporting experimental results are given. Suggestions are made for improving the transmission quality of broadband Gbit/s transmission over long-haul single-mode fibers.