The linewidth and wavelength tuning characteristics of single wavelength semiconductor laser diodes are described. Continuously tunable sources of this type are useful for multichannel coherent transmission systems.
Niloy K. Dutta, Niloy K. Dutta,
"Semiconductor lasers for coherent lightwave communcation", Proc. SPIE 1372, Coherent Lightwave Communications: Fifth in a Series, (1 January 1991); doi: 10.1117/12.24904; https://doi.org/10.1117/12.24904