High-efficiency long-lived GaAlAs LED´s for fiber-optical communications

A new fiber-mounted GaAlAs LED has been proposed and developed to satisfy efficient performance and high-reliability requirements in Practical fiber-optical communication systems. By utilizing the lens effect of a spherical-ended fiber, the LED-to-fiber coupling is greatly improved and a coupling efficiency of 8.5 percent is obtained. At a forward current of 100 mA, the output power of 305 µW is obtained from 0.14-numerical-aperture 85- µm-core step-index fiber of 3-cm length. The power in the cladding part of the fiber is almost completely removed by the epoxy. Long-term operating-life tests of LED´s described here are in progress. After about 8000 h of operation, no power reduction has occurred. The accelerated aging at elevated temperatures has also been performed and an activation energy of 0.5 eV has been determined for DLD-free LED´s. A half-life in excess of 10⁶h is estimated for room-temperature operation at a constant-current density of 10 kA/cm².