Due to its tremendous information-carrying capacity, single-mode fiber has become the dominant transmission medium for new fiber-optic system installations. Since the optical coupling efficiency between LEDs and single-mode fiber is substantially less than that of diode lasers, it was until recently assumed that single-mode systems would require diode laser sources. A number of recent experiments1–3 have demonstrated that light-emitting diodes can be used instead of diode lasers to satisfy many short to medium distance single-mode system requirements. When compared with diode lasers, LEDs offer the advantages of higher reliability, reduced temperature sensitivity, less complicated drive circuit requirements, immunity to optical feedback, and lower cost due to high yields and simpler packaging technology. These issues are critical to the introduction of single-mode fiber into subscriber loops, where LEDs can be used to satisfy economically present requirements, and diode lasers can be used for future service upgrades.
© 1986 Optical Society of AmericaPDF Article