Optical refractometer based on a birefringent Bragg grating written in an H-shaped fiber.

An optical refractometer based on a birefringent (Hi-Bi) fiber Bragg grating (FBG) written in a new H-shaped fiber structure is proposed. This structure is formed by opening the two holes of a side-hole fiber using chemical etching. When the Hi-Bi FBG is immersed in different liquids, different responses of the slow and fast wavelengths are obtained. The refractometer is also capable of simultaneous measurement of refractive index and temperature.