Abstract

Future wavelength-division-multiplexed (WDM) networks will need an optical power amplifier to boost signal levels. For these applications, multiple-quantum-well (MQW) optical amplifiers are promising due to their inherently larger saturation output powers compared to conventional bulk semiconductor amplifiers [1]. A MQW power amplifier integrated with several tunable lasers has been already demonstrated for the use in future WDM networks [2]. However, a significant limitation on the amplifier performance in these applications is imposed by the intermodulation distortion (IMD) generated by the nonlinear interaction between multiple input signals. When multiple input signals are applied to an amplifier and the channel separations between the signals are less than the reciprocal of the carrier lifetime, the carrier density is modulated at the beat frequency between pairs of input signals. This is the dominant third-order nonlinearity in a semiconductor amplifier [3]. The carrier-density modulation causes gain and refractive index fluctuations at the beat frequency, which, in turn, results in the generation of the intermodulation products. This effect has been extensively studied for the conventional buried heterostructure amplifiers [4]-[5]. However, the IMD in a MQW amplifier can be quite different due to the larger saturation output power and smaller mode confinement factor. In this paper, we report the first measurement of the IMD in a MQW amplifier.

© 1990 Optical Society of America