Frequency modulated continuous wave technique for referencing and multiplexing intensity based fibre optic sensors

We report on the use of a frequency-reflectometry domain technique for referencing optical intensity sensors located between two fibre Bragg gratings. The experiment combines the concept of frequency modulated continuous wave with the spectrally selective mirror properties of fibre Bragg gratings to interrogate with referencing properties intensity based sensors. Multiplexing two of these sensors using this technique in a parallel topology system was also experimentally demonstrated. Due to the use of different fibre lengths (delay lines), signals from the fibre Bragg gratings located at different positions in an array are separated in the frequency-domain.