Abstract: This application relates to methods and apparatus for distributed fibre optic sensing and especially to the processing of signals derived from such sensing techniques to characterise events of interest. The application describes a method of distributed fibre optic sensing, comprising; performing distributed fibre optic sensing so as to generate at least one set of measurement signals from each of a plurality of sensing channels of an optical fibre (101) in response to at least one event of interest. For each set of measurement signals, processing the measurement signals from different sensing channels according to an association metric to determine whether any sensing channels are associated with one another and form at least one association matrix indicative of the sensing channels that are associated with one another.

Abstract: This application relates to methods and apparatus for monitoring data obtained as a train (202) travels on along a rail track (201) to detect the occurrence and/or severity of any significant in-train forces, such as may be caused by heavy braking or excessive acceleration. The method involves taking a first data set corresponding to measurement signals from a plurality of channels of at least one fibre optic distributed acoustic sensor (202) having a sensing fibre (101) deployed to monitor at least part of the rail track. The first data set corresponds to measurement signals acquired as the train passes along the rail track. The method involves analysing the measurement signals to detect a first characteristic signature (402) which consists of a sequence of acoustic transients that appear to propagate rearwards along the train.

Abstract: This application relates to methods and apparatus for distributed fibre optic sensing and especially to the processing of signals derived from such sensing techniques to characterise events of interest. The application describes a method of distributed fibre optic sensing, comprising; performing distributed fibre optic sensing so as to generate at least one set of measurement signals from each of a plurality of sensing channels of an optical fibre (101) in response to at least one event of interest. For each set of measurement signals, processing the measurement signals from different sensing channels according to an association metric to determine whether any sensing channels are associated with one another and form at least one association matrix indicative of the sensing channels that are associated with one another.

Abstract: This application relates to methods and apparatus for monitoring data obtained as a train (202) travels on along a rail track (201) to detect the occurrence and/or severity of any significant in-train forces, such as may be caused by heavy braking or excessive acceleration. The method involves taking a first data set corresponding to measurement signals from a plurality of channels of at least one fibre optic distributed acoustic sensor (202) having a sensing fibre (101) deployed to monitor at least part of the rail track. The first data set corresponds to measurement signals acquired as the train passes along the rail track. The method involves analysing the measurement signals to detect a first characteristic signature (402) which consists of a sequence of acoustic transients that appear to propagate rearwards along the train.