A 1.3-\mu m wavelength vertical-mesa ridge waveguide mulitple-quantum-well (MQW) distributed feedback (DFB) laser with high directly modulated bandwidth and wide operation temperature range is reported. With the optimization of the strained-layer MQWs in the active region, the surrounding graded-index separated-confinement-heterostructure waveguide layers, together with the optimization of the detuning and coupling coefficient of the DFB grating, high directly modulation bandwidth of 16 GHz at r