Abstract: Apparatus and a method for increasing the optical measurement range in optical time domain reflectometers in which a fibre laser amplifier is used to amplify the optical time domain reflectometer pulses launched into a waveguide. This apparatus and method have particular usefulness for branched local networks. The signal returning to the optical time domain reflectometer is amplified as well as the outbound signal.

Abstract: Apparatus and a method for increasing the optical measurement range in OTDRs in which amplification is used to amplify the OTDR pulses launched into a waveguide. The waveguide may be part of a waveguide or fiber under test and the gain is distributed and substantially balanced by propagation losses so that the maximum signal level returning to the OTDR is not substantially greater than in the absence of the amplification, thereby not requiring enhanced electrical dynamic range of the receiver. Raman amplification is particularly suitable. The signal returning to the OTDR is amplified as well as the outbound signal.