Operation of a 25-Gb/s Direct Modulation Ridge Waveguide MQW-DFB Laser up to 85 $^{\circ}$ C

We demonstrated a 25-Gb/s direct modulation up to 85degC with a 1.3- mum InGaAlAs ridge-waveguide multiple-quantum-well distributed-feedback laser. The dependence of the relaxation oscillation frequency on current was 3.3 GHz/mA
^1/2
, and this is the highest value ever reported for 200-mum-long lasers in the 1.3-mum wavelength region. The alpha parameter was around 2.7 at 25degC, and an error-free operation after a 10-km single-mode fiber transmission was obtained up to 85degC.