Self-sustained intensity oscillation of a laser diode introduced by a delayed electrical feedback using an optical fiber and an electrical amplifier

Abstract

A self-sustained oscillation of laser light intensity emitted by a laser diode was newly observed by a delayed network using an optical fiber and an electrical feedback system. The time delay (transit time) of the light beam through the optical fiber plus the time delay of the electrical signal in the electrical feedback system determines the oscillation frequency of the light intensity. The oscillation for the fiber length of 7 km was obtained by using an electrical amplifier with large gain. With a wide-band amplifier, harmonic (multimode) oscillations took place where the waveform was almost square.