Distributed sensing of physical and chemical parameters for structural monitoring

Simultaneous recovery of temperature and strain over a single sensor length has been demonstrated using the information recovered from polarimetric measurements on the LP₀₁ and LP₁₁ modes of polarisation maintaining fibre. Temperature information was recovered to within 2°C and strain recovery was better than 10 με. The measurement method is entirely compatible with distributed measurement methods. A novel generic form of sensor capable of performing distributed measurements on a chemical species has been designed. This sensor has been shown to be an efficient means of detecting water ingress. With the use of suitable OTDR instrumentation, wetted sensor lengths of less than one metre, can be detected and located. The sensor has given meaningful information on the location of voided regions during a cement grouting process