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High-temperature operation of 1.3-μm wavelength multiquantum-well (MQW) lasers with an active stripe horizontally tapered over whole cavity, for direct coupling to single-mode fibers (SMFs), are reported. The lasers have reduced the output-beam divergence in a simple structure which does not contain an additional spot-size transformer. To improve high-temperature characteristics, we have investigated the influence of the thickness of separate-confinement-heterostructure layers and the number of quantum wells (QWs) on the threshold current and the output-beam divergence at high temperature. As a result, the fabricated lasers show low-threshold current (∼18 mA) and high-slope efficiency (∼0.4 mW/mA) with narrow output-beam divergence (∼12°) at 85°C. Moreover, we have obtained maximum coupling efficiency of -4.7 dB in a direct coupling to a SMF, and the reliability of longer than 10 5 h (MTTF) by a lifetime test of over 2000 h at 85°C.