Power-referenced refractometer with tilted fiber Bragg grating cascaded by chirped grating

A power-referenced refractometer operating in reflection mode is proposed and experimentally demonstrated based on a tilted-fiber Bragg grating (TFBG) cascaded by a reflection-band-matched chirped-fiber Bragg grating (CFBG). The optical signal reflected by the CFBG passes twice through the TFBG that enhances sensitivity of the refractometer. In addition, the optical signal is propagating all the way in the fiber core so that the extra insertion loss is low. Refractive index measurement with sensitivity up to 597.2 μW/R.I.U. is achieved within the range from 1.333 to ~1.42. The maximum detectable refractive index is ~1.45.