Optical switching in InGaAsP amplifiers

Future optical communications networks will require large bandwidth, high capacity switching systems that can be controlled as easily and flexibly as possible; in a variety of applications involving high bit rate systems, photonic switching appears to offer advantages in the provision of space, time and wavelength switching. Optical amplifiers based on InGaAsP material technology are proving to be very flexible when employed in such switching devices. As well as offering compact, readily controlled gates with a considerable on/off ratio, their inherent gain can overcome splitting losses in spatial switching arrays, while their nonlinear and spectral properties allow a range of functions to be implemented suitable for high speed and multi-wavelength systems. Means of exploiting these properties can roughly be divided into devices where the optical path is controlled electronically via the injection current, and those with a d.c. injection current where incoming intense optical pulses cause modulation via nonlinear effects in the device active region. Examples of both will be discussed in this paper