Nature of wavelength chirping in directly modulated semiconductor lasers

Relations are derived concerning the inherent connection between frequency deviations and the optical power wave-form of a directly modulated semiconductor laser, providing for the first time a quantitative assessment of inherent optical fibre dispersion penalties of directly modulated lasers. The relations also indicate that control of chirp involves only the control of the intensity modulation characteristics and proper current drive of semiconductor lasers. Experimental measurement of FM and IM characteristics of a 1.55 μm DFB laser support the results.