Abstract

Signal and amplified-spontaneous-emission (ASE) double Rayleigh scattering in erbium-doped fibers (EDFs) can increase the intensity noise of erbium-doped fiber amplifiers (EDFAs).^1,2 We show that amplified-signal Rayleigh backscattering from the EDF reflected back by discrete reflection points inside the EDFA or by Rayleigh backscattering from a feeder line causes an increase in relative intensity noise (RIN). This multiple-path-interference RIN increase makes low-reflection EDFA components and the use of an input isolator imperative for inline EDFAs used in externally modulated lightwave AM CATV systems. We present, for the first time to our knowledge, a theory to calculate the RIN caused by these phenomena that takes into account both coherent and incoherent signal redirected Rayleigh scattering (SRRS), and we support this theory with experimental evidence.

© 1994 Optical Society of America