Ratiometric interrogation of dynamically strained fiber Bragg gratings

We demonstrate a new and highly flexible technique for high speed dynamic interrogation of fiber Bragg gratings [FBG]. The technique is based on a ratiometric measurement employing a pulsed broad band light source, a single detector and 2 filter FBGs. The filter FBGs are mounted on a temperature controlled cantilever where the strain of the filter FBGs can be adjusted to requirement. The technique can be used on multiplexed FBGs and has been demonstrated here at a frequency of 20kHz although much higher frequencies are possible with a light source of higher power. Sub micro-strain resolution of 0.6 µe at 23 kHz is demonstrated and the noise for strain e(=?L/L) is 5·10^-9 evHz^-1.