Ultrahigh-resolution interrogation of a fiber Bragg grating sensor based on higher order four-wave mixing.

The performance of a highly sensitive strain sensor based on nonlinear four-wave mixing (FWM) using a fiber Bragg grating (FBG) is investigated. The power change due to the wavelength shift induced by very small strain over the FBG is significantly magnified by a higher order FWM process. Strain sensitivity of 5.547  dBm/μϵ is achieved and minimum wavelength shift of 2.18×10-6  nm (which corresponds to a strain of 1.80×10-3  μϵ) is detected with uniform FBG, whereas in case of chirped FBG (CFBG) strain sensitivity of 0.3  dBm/μϵ with minimum detectable wavelength shift of 4×10-5  nm (which corresponds to a strain of 0.033  μϵ) is obtained.