Abstract

Double Rayleigh scatter noise (DRS) has been shown to be an important limiting factor in optical transmission systems employing Raman amplification.^1,2 This is a consequence of the low value of the Raman gain coefficient in germano-silicate fiber which necessitates the use of long fiber lengths in order to achieve significant gain. DRS is particularly important when Raman-pumping dispersion-compensating fiber,³ and in transmission systems employing distributed amplification and a high Raman gain.⁴ The time-domain-extinction method is gaining acceptance as a technique for the measurement of Raman amplifier noise.⁵ One advantage of this method is that it can measure the DRS noise and the ASE noise separately. In this work we have used this technique to measure the noise from a fibre Raman amplifier pumped by an intensity-modulated Raman fibre laser. We show that intensity noise on the pump laser causes an increase in the DRS noise output of the amplifier and a corresponding degradation of the output signal to noise ratio.

© 2002 Optical Society of America