Abstract: An apparatus for digitizing an optical signal comprises: an optical detector to detect an optical signal and to generate an electric signal corresponding to the optical signal; an envelope curve detector to determine the amplitude of the electric signal or a modified electric signal resulting from the electric signal, and to supply an amplitude signal corresponding to the amplitude; an analog to digital converter to digitize the amplitude signal and to supply a corresponding digitized amplitude signal; and a variable voltage source to calibrate the envelope curve detector.

Abstract: A distributed sensing apparatus based on Optical Time Domain Reflectometry, OTDR, including an optical source; an optical splitter in optical communication with the optical source, the optical splitter having first and second outputs; a sensing fibre in optical communication with the first output of the optical splitter; a combining unit arranged to combine a reference signal derived from the second output of the optical splitter with a backscattered signal derived from the sensing fibre, wherein the combining unit comprises one or more 3×3 fused fibre couplers; and a signal processing unit configured for processing information derived from the combining unit so as to provide distributed sensing data. The combining unit includes a polarization diversity arrangement including one or more polarization sensitive elements.

Abstract: A sensor system for detection and localisation of changes in or values for at least one environmental condition comprises a source of pulses of electromagnetic radiation, wherein the source is configured to emit electromagnetic radiation at a plurality of different wavelengths, an optical fibre in optical communication with the source of pulses, wherein said optical fibre includes one or more fibre Bragg gratings having a reflectance and/or transmittance which varies in dependence on the at least one environmental condition, and a detection unit for detecting, at a plurality of different times, electromagnetic radiation which has been reflected or transmitted by at least one of the fibre Bragg gratings, wherein the detection unit is configured for detecting electromagnetic radiation at the plurality of different wavelengths, such that a spectral response can be determined for different spatial regions along the optical fibre, wherein a change in or value for the environmental condition at a spatial region may

Abstract: Device for monitoring a submarine cable (1) comprising at least one optical fiber (2) which is arranged in or on the submarine cable (1), at least one laser light source (3), the light of which can be coupled into the optical fiber (2), wherein portions of the light back-scattered in the optical fiber (2) can be coupled out from the optical fiber (2), detection and evaluation means (5) capable of detecting the back-scattered light and determining from the detected light spatially resolved the temperature of the optical fiber (2), detection means (6) for the electric current flowing in the submarine cable (1), evaluation means (7) capable of storing the time profile of the detected temperature and the time profile of the detected electric, wherein the evaluation means (7) are capable of calculating from the time profiles of the temperature and the electric current spatially resolved the thermal resistance of the soil surrounding the submarine cable (1) and inferring from the spatially resolved determined therm