A 10-Gbit/s, 1.58-mu m, InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser (EML) with a twin waveguide (TWG) structure is operated experimentally over a wide temperature range of 0 to 80degC. We introduce an InGaAlAs multi-quantum well (MQW) system for both LD and EAM MQWs, because this material has temperature-tolerant characteristics. These layers are grown using single step epitaxial growth, and the device was fabricated with a very simple process. Moreover, successful transmission through an 80-km single-mode fiber (SMF) was achieved with the device running at up to 80degC. These results confirm the suitability of this type of laser for use as a cost-effective and low-power consumption light source in 10-Gbit/s optical network systems.