Two-section InGaAsP DBR-lasers at 1.55 /spl mu/m wavelength with 31 GHz direct modulation bandwidth

The small signal modulation response of two-section InGaAsP DBR-lasers at 1.55 /spl mu/m wavelength was investigated. The response was fitted to a general transfer function and it was found that for almost all lasers the response could be described by a three pole model consisting of the laser response from the standard rate equations and an additional first order low pass roll-off. The lasers exhibited reduced damping and increased resonance frequency due to what we believe is detuned loading. This led to a maximum bandwidth of 30 GHz for lasers described by the three pole model. Some lasers exhibited an additional effect which we believe is cavity resonant enhancement of one of the modulation side-bands. This effect increased the maximum -3dB bandwidth to 31 GHz but could not be described by a three pole model.