Author_Institution :
Inst. of Radio Eng. & Electron., Acad. of Sci. of the Czech Republic, Prague, Czech Republic
Abstract :
In this article, we investigate, both theoretically and experimentally, transient effects in Raman fiber amplifiers (RFA) caused by channel addition/removal. A comprehensive large-signal numerical model of RFA, which incorporates time variation effects and the downstream and upstream propagation of multiple signals, pumps, and amplified spontaneous emission components, has been used for the theoretical analysis. The effect of pumping scheme, pump power, the length and type of Raman fiber, and number of added and/or dropped channels on the dynamics of surviving channel power fluctuations has been studied. In our experimental setup, signals from two laser diodes (LDs) were transmitted through counterdirectionally pumped RFA consisting of 15.6 km of dispersion compensating fiber (DCF). To simulate channel addition/removal, one signal was square-wave-modulated at 500 Hz. At the output of the RFA, the signal of the continuous-wave LD was selected with an optical bandpass filter, and power fluctuations of the surviving channel were recorded with a high-speed digital oscilloscope. Power fluctuations as high as 0.45 dB with typical saturated amplifier overshoots were observed.
Keywords :
Raman lasers; fluctuations; optical communication equipment; optical fibre amplifiers; optical pumping; superradiance; telecommunication channels; telecommunication network reliability; transients; 15.6 km; Raman fiber amplifiers; Raman fiber length; amplified spontaneous emission components; channel addition/removal response; continuous-wave LD; counterdirectionally pumped RITA; dispersion compensating fiber; downstream propagation; high-speed digital oscilloscope; laser diodes; multiple signals; optical bandpass filter; power fluctuations; pump power; pumps; saturated amplifier overshoots; square-wave-modulated; surviving channel; surviving channel power fluctuations; time variation; transient effects; upstream propagation; Diode lasers; Fluctuations; High speed optical techniques; Laser excitation; Numerical models; Optical fiber amplifiers; Optical filters; Signal analysis; Spontaneous emission; Stimulated emission;
