Hetero-core structured fiber optic surface plasmon resonance sensor with silver film

A new optical fiber sensing structure is described, which is capable of refractive index detection based on surface plasmon resonance (SPR) interrogation. The sensor simply consists of two different core diameter fibers, which are connected by thermal fusion splicing, in order to deliberately leak the transmitted light wave into the cladding layer of the sensing fiber region. Silver film was uniformly deposited around the cladding surface for SPR excitation. Experiment to measure the SPR resonance wavelength for the refractive index ranging from 1.333 to 1.398 was carried out, by using a white light source and a spectrum analyzer. Sensor response exhibited characteristic spectrum which has a minimum in a specific wavelength for a given refractive index. Sensitivities obtained from an experimentally derived curve were 2.1×10−4 and 1.5×10−4 at refractive indices of 1.333 and 1.398, respectively. It has been demonstrated that the developed hetero-core fiber structure is one of promising techniques for remote monitoring systems as a SPR refractive index sensor.