A long-wavelength ($1. 3mum$) multimode fiber-optic transmission system has been developed and the field trial system has been installed over 17.3km distance in Daejeon Area by KETRI. The 45Mb/s and 90Mb/s system operate with BER $10^-9$over 17.3km distance, and they successfully operate on the route of 34. 6km length when the fiber cable is simply connected at one end. Average loss of the fiber cable shows 0. 81dB/km including splice loss and the average bandwidth over the 17. 3km distance is 170MHz.