Single longitudinal mode operation of cleaved‐coupled‐cavity lasers formed by recleaving of 1.5‐&mgr;m InGaAsP buried crescent lasers is investigated as a function of bias current, temperature, and modulation frequency. The two‐cavity lasers are made to operate in a stable single mode by adjusting the bias levels of the electrically isolated and optically coupled sections. The wavelength stability with temperature results in a change of only 0.48 A˚/°C over a range of 14 °C. Single mode operation is preserved under direct modulation at rates as high as 1 Gb/s. The reduction in linewidth and the absence of partition noise makes these lasers useful for optical transmission through highly dispersive single mode fibers.