Abstract: A system for monitoring a distributed Raman optical transmission line to optically amplify a signal light having a signal wavelength by pumping with a Raman pumping light having a Raman pumping wavelength comprises an optical demultiplexer to demultiplex an output light from the distributed Raman optical transmission line into the signal wavelength component and the Raman pumping wavelength, an optical power measuring unit to measure the optical powers of the signal wavelength component and the Raman wavelength component demultiplexed by the optical demultiplexer, and a judging unit to judge whether a fault exists in the Raman amplification in the distributed Raman optical transmission line and the cause of the fault.

Abstract: An optical signal processor is disclosed comprising a first optical path having a first electroabsorption optical modulator to be applied with a constant voltage and to absorb light of a signal wavelength, a second optical path having a fixed phase relation with the first optical path relative to a probe wavelength, a probe light introducer for dividing probe light of the probe wavelength into two portions and feeding them respectively into the first and second optical paths, an original signal light introducer for introducing original signal light of the signal wavelength into the first electroabsorption optical modulator, and a combiner for combining both light of the probe wavelength passed through the first and second paths.

Abstract: A nonlinear optical element is disclosed for reducing intensity noise of both mark level and space level, and being stable, miniaturized and low-priced. Signal light enters a semiconductor waveguide layer (14). The semiconductor waveguide layer (14) has a band gap wavelength shorter than a wavelength of the signal light. A diffraction grating (12), having a Bragg wavelength close to the wavelength of the signal light, is disposed adjacent to the semiconductor waveguide layer (14). DC voltage is applied to the semiconductor waveguide layer (14).

Abstract: The present invention provides a semiconductor memory capable of retaining information after removing a power supply and of storing information with an optical input. A memory cell is comprising an n-InP substrate, a first semiconductor (n-InGaAs) layer, a second semiconductor (i-InGaAs) layer, a third semiconductor (p-InGaAs) layer, a fourth semiconductor (i-InGaAs) layer and a fifth semiconductor (n-InGaAs) layer. The first to fifth semiconductor layers are stacked in this order on the n-InP substrate. A bias voltage is applied between the n-InP substrate and the fifth semiconductor layer to control a height of a TBD formed in the above multi-layer structure so that carriers may move and electrons can be stored in one of the second and fourth semiconductor layers.

Abstract: A functional semiconductor element, which is designed to perform an ultrafast amplifying, bistable, similar functional operation by initiating and stopping an avalanche multiplication in one of i-type layers of what is called a triangular barrier diode (TBD) structure having an n-i-p-i-n, p-i-n-i-p, n-i-p-i-p, n-i-n-i-p, n-i-n-i-n, p-i-n-i-n, p-i-p-i-p, or p-i-p-i-n configuration. By forming a light absorbing layer and a light emitting layer or light modulating layer in this structure, it is possible to function the element as an optical functional element. Furthermore, the addition of a resonant tunneling diode implements a novel function.

Abstract: An optical functional semiconductor element which performs ultrafast, high-contrast logic operation through utilization of the high speed of light velocity. A resonant-tunneling diode having a negative resistance characteristic is provided apart from a light absorbing layer formed by one of i-type layers of what is called a triangular barrier diode of an nipin or pinip structure, by which as the quantity of incident light increases, the quantity of transmitted current is switched from increase to decrease, the amount of change is made high-contrast and an ultrafast logic operation can be performed.