Abstract: A surveillance system for in-service fault identification in an amplified passive branched optical network is provided. This system does not require any wavelength tunable light source as used in multi-wavelength OTDR. Fiber-Bragg gratings are placed at some strategic positions on different fiber branches to slice and reflect the optical amplifier's residual ASE power at some wavelength other than the signal wavelengths. The conditions of the fiber link and optical amplifier at each branch can be monitored by constantly checking the reflected power level of the corresponding wavelength without suspending the in-service channels.

Abstract: Photoconductors with channels that lie in the surface depleted region of a GaAs structure are described. These devices have nanoampere bias current, and exhibit photoconductive gain. In contrast to other photoconductors, their low frequency responsivity is of the same order as that in the GHz region, alleviating problems of equalization necessary in receiver applications. As well, these devices exhibit over 60 dB isolation as optoelectronic switches.

Abstract: An optoelectronic assembly for converting a signal between optical and electrical form, or vice versa, consists of a dielectric substrate and a semiconductor substrate. These substrates are fabricated separately and then brought together with major faces in intimate contact with each other. The dielectric substrate has a pair of metallic electrodes on its surface and a waveguide extending to a coupling region. The semiconductor substrate has an active optoelectronic device, e.g. a photodetector or light emitting device, whose optically active portion is brought into optically coupling relationship with the coupling region of the waveguide. At the same time electrically contacting regions of the optoelectronic device are placed in electrical contact with respective ones of the pair of metallic electrodes on the dielectric substrate.