Abstract

The need to increase reach and capacity of optical communication systems has led to the deployment of distributed Raman amplification, which improves the power budget by lowering the amount of amplified spontaneous emission (ASE) accumulated over the transmission spans. However, distributed Raman amplification also significantly increases the amount of double-Rayleigh backscattered (DRB) power,^1,2 which suddenly becomes an important source of inband crosstalk. Like with other systems suffering from inband crosstalk (e.g., caused by imperfect channel suppression of add/drop multiplexers^3,4 or multiple discrete reflections⁵), the signal not only beats with ASE at the receiver, but also with a superposition of randomly phased data signals falling within the signal wavelength band. In the case of DRB, this superposition turns into multiple-path interference (MPI), interference of the signal with randomly delayed replicas of itself.⁶

© 2002 Optical Society of America