Optoelectronics will undoubtedly playamajor role in the applied sciences
of the next century. This is due to the fact that optoelectronics holds
the key to future communication developments which require high data
transmission rates and of a extremely large bandwidths. For example, an
optical fiber having a diameter few micrometers has a bandwidth of 50
THz, where an impressive number of channels having high bit data rates
can be simultaneously propagated. At present, optical data streams of
100 Gb/s are being tested for use in the near future. Optoelectronics
has advanced considerably in the last few years. This is due to the fact
that major developments in the area of semiconductors, such as hetero-
structures based on III-V compounds or mesoscopic structures at the
nanometer scale such as quantum weHs, quantum wires and quantum dots,
have found robust applications in the generation, modulation, detection
and processing of light. Major developments in glass techniques have
also dramaticaHy improved the performance of optoelectronic devices
based on optical fibers. The optical fiber doped with rare-earth
materials has aHowed the amplification of propagating light,
compensating its own los ses and even generating coherent light in fiber
lasers. The UV irradiation of fibers has been used to inscribe gratings
of hundreds of nanometer size inside the fiber, generating a large class
of devices used for modulation, wavelength selection and other
applications.