Figure 8
(a) Schematic of FBG interrogation set-up. The light from superluminescent diode (SLED) is launched into the optical circulator then transmitted to the FBG with the Bragg resonance wavelength of 1070 nm. When strain is applied (in the range 0–25 \(\upmu\)m), the resonance wavelength shifts and the reflected wavelength comes back through the circulator to the flat fiber device which generates speckles from the reflected wavelength and therefore acts as the interrogator. (b) Reflected power spectrum of the tested FBG, showing the peak signal is 30 dB higher than the background noise level.
