Counter-pumped Raman Amplifiers Research Articles

Exact solution for the gigantic amplification of ultrashort pulses in counterpumped Raman amplifiers

We exactly solve the initial-boundary value problem of interaction of three waves in the limit when one of these waves is strongly damped. The solution is applied to the characterization of transient effects in Raman amplifiers, with a special emphasis on the possibility of generating Stokes pulses with peak powers that are orders of magnitude higher than the input power of the pump beam.

Analysis of combined effect of pump-intensity noise and reflection in counter-pumped Raman amplifiers

We have analyzed the combined effect of pump-intensity noise and reflections on the performance of counter-pumped Raman amplified systems. The required level of pump-intensity noise was evaluated for negligible enhancement of multi-path interference (MPI). We have also investigated the enhancement of pump-to-signal crosstalk caused by the reflections occurring within transmission fiber. We found that a high reflection (larger than -20 dB) within effective length of fiber could increase the effect of pump-to-signal crosstalk even for the counter-pumped Raman amplifiers.

System impairment caused by combined effect of pump-intensity noise and reflection in Raman amplified systems

The combined effect of pump-to-signal crosstalk and reflections in Raman amplified systems is investigated. The system's performance has been measured using two different pump modules in co- and counter-pumped configurations. The results show that the high reflection occurring within the transmission fibre could enhance the pump-intensity noise even in counter-pumped Raman amplifiers.

Design of double-pass discrete Raman amplifier and the impairments induced by Rayleigh backscattering

We report on the investigation of discrete Raman fiber amplifier in double-pass configuration based on the dispersion-compensated fiber and high reflection FBG. We proved in simulation and experiments that the double-pass configuration requires nearly 50% less pump power and the same fiber length to provide the same Raman gain and double-dispersion-compensation performance compared to the typical counter-pumped Raman amplifier. We also analyzed the equivalent noise figure (NF) and the Rayleigh backscattering impairments. The theoretical results shown that the impact of multipath interference (MPI) noise is the dominating limitation factor of this system operated at very high Raman gain region.

Gain transients in copumped and counterpumped Raman amplifiers

Gain transients in both copumped and counterpumped distributed Raman amplifiers were investigated as a function of signal launch power, fiber type, and surviving signal wavelength for the first time. We found that gain transients are much more pronounced in a copumping scenario than in a counterpumping scenario for the same operating conditions. We also found that the dependency of gain transients on signal launch power, fiber type, and surviving channel wavelength follows the pump-depletion theory. A simple transient suppression technique with better than 0.2-dB ripple capability was also demonstrated.

Pump to signal RIN transfer in Raman fiber amplifiers

We present an analytical model and measurements of the pump to signal relative intensity noise (RIN) transfer characteristics of copumped and counterpumped Raman amplifiers. We give a quantitative analysis of noise averaging from chromatic dispersion in copumped systems and from different propagation directions in counterpumped systems. It is shown that nondispersion-shifted fibers and other fibers with high dispersion between the signal and pump wavelengths give a greater potential for use in copumped Raman amplified systems.

Pump to signal RIN transfer in Raman fibre amplifiers

An analytical model and measurements of the pump to signal relative intensity noise transfer characteristics of co- and counter-pumped Raman amplifiers is presented. Quantitative analysis of noise averaging from chromatic dispersion in co-pumped systems, and from different propagation directions in counter-pumped systems is given.