Abstract

A concern in digital systems is the possible system failure due to a large increase in noise, i.e., signal variance, generated by the discrete reflection of a fiber cleave within an amplifier. The noise results from a cavity, hereafter called a Rayleigh cavity, formed by the discrete reflection and the Rayleigh backscatter of the fiber span. Only the case where the gain-producing erbium-doped fiber is between the cleave and the fiber span is considered. In this work the noise for the Rayleigh cavity is measured for a single amplifier and for a Rayleigh cavity within a chain of amplifiers. The noise has been shown to be proportional to the round trip gain of the cavity and that for two discrete reflectors the proportionality constant, Rc, is 2.¹ For a Rayleigh cavity Rc is found to be 1/3 to 2/3 Vs Rc = 1 inferred from existing analysis.² The new estimates come from, (1) a previously unrecognized reduction of 1/2, which occurs because the Rayleigh backscatter must be computed using average power and (2) the degree of polarization is 1/3,³ rather than 0 as had been assumed previously.

© 1996 Optical Society of America