Fiber-optic urine specific gravity sensor based on surface plasmon resonance

A fiber-optic urine specific gravity sensor based on surface plasmon resonance is first presented in this paper. We have proposed a novel side coated Au film fiber-optic surface plasmon resonance sensor, which is much easier to fabricate than other fiber-optic surface plasmon resonance sensors, for urine specific gravity detection. We made a sensor with 48-nm thickness of sensing layer and 15-mm length of sensing region. The experimental results are satisfactory. In the urine specific gravity detection, we use wavelength and intensity modulations to extract sensing information and their detection results show good linearities. The urine specific gravity sensitivities in glycosuria detection are obtained to be 856.09 nm/SG (in wavelength modulation) and 183.31%/SG (in intensity modulation), respectively. While they are ultra-high in albuminuria detection, the wavelength sensitivity is 12,645 nm/SG and the intensity sensitivity is 1410%/SG.