Amplified spontaneous emission in pulse-pumped Raman amplifiers

• Published in: IEEE photonics technology letters Vol. 15; no. 5; pp. 667 - 669
• Main Authors: Bromage, J., Winzer, P.J., Nelson, L.E., Mermelstein, M.D., Horn, C., Headley, C.H.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2003; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplification; Amplifiers; Fiber lasers; Gain; High power amplifiers; Noise; Optical amplifiers; Optical fiber polarization; Optical noise; Optical pulses; Pulse amplifiers; Pumps; Spontaneous emission; Stimulated emission; Time division multiplexing; Trains; Wavelengths
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2003.809954

We discuss amplified spontaneous emission (ASE) generated in Raman amplifiers that are counter-pumped with trains of pulses. Our experimental and theoretical results show that if the peak power of the pump pulses is too high, the ASE output from the amplifier can be significantly higher than that from a continuous-wave pumped amplifier providing the same gain. This effect places a lower limit on the duty cycle of pump pulses one can use for a given level of Raman gain. Furthermore, we report an additional ASE enhancement if there is insufficient walkoff between the pump pulses and copropagating ASE to average the effects of higher frequency pump intensity noise. As a result, less pump intensity noise can be tolerated when pulse-pumping a fiber having a zero-dispersion wavelength located midway between the pump and signal wavelengths.