Abstract

Erbium fiber amplifiers are demonstrated to have low distortion especially at video or higher frequencies. Prior measurements have shown an upper limit of -60 dBc of composite triple beat (CTB) and -59 dBc of composite second order distortion (CSO).¹ Video distribution requires -106 dBc for two-tone third order intermodulation distortion (IMD) at frequencies above 50 MHz. It is important to understand the nature and the frequency dependence of the various distortions in multichannel subcarrier applications. The fundamental distortion is caused by stimulated emission, similar to that in a laser diode. We have developed a theoretical model for predicting harmonic and intermodulation distortions based on a perturbation approach similar to prior work in laser diodes² The spatial dependence of various pump and signal quantities along the length of the fiber are taken into account. Basic rate equations with amplified spontaneous emission (ASE) can be written as³

© 1991 Optical Society of America