Abstract: A method for monitoring a system using optical reflectometry comprises: receiving a first optical response signal coming from the system in response to a first optical excitation signal, said first excitation signal carrying a first numeric sequence (A), receiving a second optical response signal coming from the system in response to a second optical excitation signal, said second excitation signal carrying a second numeric sequence (1A, B), and determining correlations between said optical response signals and said numeric sequences in order to detect a singularity of the system. The first and second excitation signals are transmitted simultaneously within the optical system on separate carrier wavelengths ?0, ?1) by wavelength division multiplexing, and the first and second response signals are received simultaneously on said separate carrier wavelengths.

Abstract: A Raman amplifier for use in an optical fiber communication system with dispersion compensation has a first order Raman pump source and a second order Raman pump source both coupled to the input ports of a four-port optical coupler having two input ports and two output ports. One output port is connected to an optical fiber length to inject a pump light signal into the fiber length for second-order Raman amplification and the other output port is connected to a dispersion compensating fiber.

Abstract: In order to allow transmission of higher bitrate optical wavelength channels (C1-C4) over a transport network designed for the transmission of lower bitrate optical wavelength channels (A1-A8), the wavelengths of the higher bitrate wavelength channels (C1-C4) are detuned by at least 30% of the channel spacing (S2) the lower bitrate wavelength channels (A1-A8) with respect to a predefined ITU wavelength grid.

Abstract: A Raman amplifier for use in an optical fiber communication system with dispersion compensation has a first order Raman pump source and a second order Raman pump source both coupled to the input ports of a four-port optical coupler having two input ports and two output ports. One output port is connected to an optical fiber length to inject a pump light signal into the fiber length for second-order Raman amplification and the other output port is connected to a dispersion compensating fiber.

Abstract: The high or very high voltage DC cable has extruded polymeric insulation made out of a styrene-containing material. The material of the insulation is constituted by a mixture comprising polyethylene, a hydrogenated block copolymer of styrene, and an anti-oxiding agent, with the styrene content by mass being 11% to 18%, and the material is not cross-linked. The cable is suitable for use as a DC power cable.

Abstract: The high or very high voltage DC cable has extruded polymeric insulation made out of a styrene-containing material. The material of said insulation is constituted by a mixture comprising polyethylene, a hydrogenated block copolymer of styrene, and an anti-oxidizing agent, with the styrene content by mass being 11% to 18%, and the material is not cross-linked. The cable is suitable for use as a DC power cable.