Korean researchers break fibre optic sensor distance record

To describe a new technique, developed in Korea, which extends the operational length of fibre Bragg grating strain and temperature sensors to approximately 50 km. It is based on distributed Raman amplification.Design/methodology/approach – The system uses a single pump source to achieve distributed Raman amplification in the transmission optical fibre and does not employ an additional broadband light source, as the residual pump power after the transmission fibre is recycled to generate broadband amplified spontaneous emission in an erbium‐doped fibre.Findings – The temperature and strain response of the system was tested by measuring changes in reflection from the sensor which were captured on an optical spectrum analyser, located at the end of a 50 km length of fibre. The thermal sensitivity was found to be 8.2 pm/°C over the range 30‐100°C and a strain sensitivity of 1.1 pm/με was exhibited between 0 and 1,700 με. The measurement resolutions of the system for temperature and strain were estimated at 0.7°C and 8.64 με, respectively. The signal‐to‐noise ratio was approximately 11 dB.Originality/value – This work has shown that the use of distributed Raman amplification can extend the operational length of fibre Bragg grating sensors from around 25 km to at least 50 km, whilst achieving good strain and temperature sensitivities.