Single‐mode fiber transmission using edge‐emitting led for broadband subscriber loops

Abstract

The edge‐emitting LED, which is less expensive and more reliable than the laser diode, is studied for use in the broadband subscriber loop in combination with a single‐mode fiber. In comparison to the conventional surface‐emitting LED, the present device has a better efficiency in coupling with a single‐mode fiber and has a narrower emission spectrum. In this paper, a method of simple time domain calculation is proposed for the S/N ratio taking into account the wavelength dependence on the dispersion and loss of the fiber, the emission spectrum profile of the edge‐emitting LED, and the pulse response speed. The validity of the computation method and the high‐speed modulation characteristics of the edge‐emitting LED are confirmed through the optical transmission experiment of 600 Mbit/s and 20 km with a simple waveform compensation circuit. Further, the temperature characteristic of the edge‐emitting LED is studied since it is important in the application to a practical system. A method for temperature compensation is investigated. Finally, based on these studies, the maximum transmission distance is studied in which the temperature variations of the optical output, center emission wavelength and the spectral width as well as the device fluctuation are considered. It is shown that the present edge‐emitting LED is capable of an application to broadband ISDN and optical CATV subscriber loops.