Optical amplifiers could be used in repeaters for wavelength-division- multiplexed (WDM) systems; however, the interaction between multiple signals in optical amplifiers is not well understood. Gain saturation In optical amplifiers is mediated by the carrier density.1,2 Thus the gain of one channel in a multiwavelength amplifier will be affected by the power present In other channels. This will cause crosstalk in amplitude-modulated systems. Similarly, changes in the index of refraction caused by fluctuations in carrier density will cause crosstalk in phase-modulated systems. We have measured changes in the small-signal gain spectrum of an optical amplifier induced by the presence of an intense signal at a different wavelength. We found that three separate mechanisms influence two-color gain saturation in optical amplifiers.
© 1987 Optical Society of AmericaPDF Article