Photonic bandgap fiber for refractive index measurement

The use of photonic bandgap fibers for refractive index measurement has been demonstrated. The demonstrated PBGF has a wavelength shift of 280 nm in the falling photonic bandgap edge when the ambient refractive indices change from 1.333 to 1.39, which agrees well with the analytical prediction. A sensitivity of 2 × 10−6 RIU is possible to be achieved assuming the demodulation system can resolve 0.01 nm wavelength shift.