High sensitivity evanescent field fiber Bragg grating sensor

Increased sensitivity to change in surrounding index is shown by etching the core of a fiber Bragg grating. A maximum sensitivity of 1394 nm/riu is achieved as the surrounding index approaches the core index. Assuming a detectable spectral resolution of 0.01 nm realized in the experiment, the sensor achieves a minimum detectable index resolution of 7.2/spl times/10/sup -6/ when the index of the surrounding medium is 1.44. The sensor can be used as a chemical and biosensor and multiple sensors can be multiplexed and interrogated along a single fiber.