Amplification of broadband noise pumped by two lasers in optical fibers

A theoretical and experimental investigation of catastrophic amplification of broadband noise in optical fibers near the zero-dispersion frequency (ν0) pumped by two lasers with frequencies that are symmetrically tuned relative to ν0 is presented. The effect is due to a four-wave mixing (FWM) process, phase matched up to third-order dispersion, between the spectral components of noise and the lasers. We observed a FWM gain of 16 dB (10-dB net gain) over a 22-nm bandwidth (limited by fourth-order dispersion) for 18-dBm power lasers at ±1 THz (8 nm) from ν0 in a 25-km-long dispersion-shifted fiber. A simple analytical model is proposed that will permit us to investigate this effect numerically in amplified links with concatenated amplifiers and consider random fluctuations of ν0 along the fiber.