Abstract: A multi-user quantum cryptography system and method are described herein. The system comprises a relay including a quantum information server so configured as to generate quantum information communications having different wavelengths and a multiplexer so configured as to separate the different quantum information communications generated by the quantum information server by their wavelength and to supply each communication to a respective user.

Abstract: A multi-user quantum cryptography system and method are described herein. The system comprises a relay including a quantum information server so configured as to generate quantum information communications having different wavelengths and a multiplexer so configured as to separate the different quantum information communications generated by the quantum information server by their wavelength and to supply each communication to a respective user.

Abstract: A multiport optical waveguide interferometer is provided which comprises at least two N.times.N couplers arranged in series on an array of fibers and separated by a short region such that the phase shift between the couplers is approximately equal to .pi.. A method for making such an interferometer comprises forming such couplers, for instance by a fused taper method with appropriate twist, where the fused, tapered and twisted zone is longer than usual and wherein the couplers are formed in series within such zone, separated by short regions of between 1-2 mm, and adjusted to achieve the flattest possible wavelength response.

Abstract: A tapered optical fiber component is provided that has an optical fiber with a cladded region. An optical core passes through the cladded region. The cladded region has a tapered extended first region drawn down in diameter to form an effective area region that has a predetermined effective area. The tapered extended first region is formed to adiabatically concentrate an optical signal for propagation through the effective area region of reduced diameter. The power density of the optical signal propagating through the effective area region is increased as an inverse function of the effective area.

Abstract: A tapered optical fiber component is provided that has an optical fiber with a cladded region. An optical core passes through the cladded region. The cladded region has a tapered extended first region drawn down in diameter to form an effective area region that has a predetermined effective area. The tapered extended first region is formed to adiabatically concentrate an optical signal for propagation through the effective area region of reduced diameter. The power density of the optical signal propagating through the effective area region is increased as an inverse function of the effective area.

Abstract: The optical waveguide coupler device is formed on two laterally adjacent optical fibers for splitting with wavelength-flattened ratios an incident light intensity into the two fibers. Adjacent sections of the two fibers are fused together and first and second concatenated tapered portions are formed. These two tapered portions are separated by a central optical waveguide portion including two parallel branches of slightly different lengths, each capable of propagating a light signal from either tapered portion to the other. The first and second tapered portions define optical waveguide couplers presenting coupling ratios varying with optical wavelength in accordance with different curves. The different lengths of the two parallel branches of the central portion cause a shift .phi. between the phases of the optical signals propagating through these two branches. The coupling ratios of the tapered portions and the phase shift .phi. are selected to wavelength-flatten the coupling ratios of the coupler device.

Abstract: A wavelength filter is integrated to a single-mode optical fiber capable of propagating a light signal and comprising a longitudinal and opaque outer jacket enveloping the fiber. This fiber is stripped of its jacket on a given length thereof to obtain a non-jacketed length of optical fiber. The so produced non-jacketed fiber length is formed with first and second concatenated biconical tapers separated from each other by a given distance and each having a given profile. By appropriately selecting the distance separating the two tapers and the given profile thereof, the filter will enable transmission of a first, predetermined wavelength of the propagated light signal while it will stop a second, predetermined wavelength of the signal. A method of integrating such a filter to a single-mode optical fiber is also proposed.