This paper, for the first time to the best of our knowledge, presents a novel fiber-optic refractive-index sensor which is based on an intrinsic Fabry-Perot interferometer (IFPI) formed by a section of endlessly single-mode photonic crystal fiber (EPCF) and conventional single-mode fiber. Such an IFPI sensor has the advantages of easy fabrication, low joint and transmission losses, low-cost and good fringe visibility due to the use of the EPCF. This miniature fiber-optic sensor is demonstrated for the measurement of the refractive index change of glycerin solution by measuring its fringe visibility change solely. The experimental data agree well with the theoretical results and the refractive-index resolution and repeatability of ∼2 × 10−5 and ±0.5%FS in the linear operating range, are achieved. In addition, such a sensor can be used as an excellent temperature sensor with a cavity-length-temperature sensitivity of 4.16 nm/°C and repeatability of ±0.15%FS when tested from 20 °C to 100 °C. Therefore, simultaneous measurement of refractive index and temperature can be realized by determination of the fringe visibility and the cavity length change of such a PCF-based IFPI, respectively, providing a practical way to measure refractive index with self-temperature compensation.

In-line fiber Fabry-Perot refractive-index tip sensor based on endlessly photonic crystal fiber

This study presents design and development of evanescent wave absorbance based U-bent plastic optical fiber (POF) probe with high sensitivity and its applications to refractive index (RI) sensing. The probes were fabricated by a controlled decladding procedure to remove the fluorinated polymer without damaging the poly methyl methacrylate (PMMA) core and a simple and scalable fabrication technique to obtain POF U-bent probes of desired geometry. U-bent probes of fiber diameter from 250 to 1000 μm were fabricated and optimum bend diameter for each fiber diameter was investigated. The sensitivity was found to be maximum when the bend diameter of the probe varies from 2 to 3 times the fiber diameter. Probes with 500 μm core and 1.25 mm bend diameter showed highest sensitivity (5.57Δ A 560 nm /ΔRIU) in the visible region to RI changes from 1.33 to 1.47 with a resolution better than 1 milli RI units. Furthermore, U-bent probes were amine functionalized and coated with gold nanoparticles to obtain a localized surface plasmon resonance (LSPR) based RI sensor that has an 8-fold improvement in RI sensitivity, hence extending their applicability to plasmonic biosensing.

Development of LSPR based U-bent plastic optical fiber sensors

A review of recent developed and applications of plastic fiber optic displacement sensors

A novel intensity modulated fiber optic sensor (FOS) for liquid refractive index measurement is presented in this communication. The sensor principle is based on frustrated total internal reflection effect caused by refractive index change of a medium surrounding an optical fiber tip. Experimental results obtained for liquids of different refractive index confirm the sensor potential to act as a sensitive refractometer.

All-fiber optic sensor for measurement of liquid refractive index

U-bent plastic optical fiber probes as refractive index based fat sensor for milk quality monitoring

An optical fiber, partially stripped of its cladding is shown to sense refractive index of a liquid in which the uncladded sensing region is immersed, to a high degree of precision and over a wide range of refractive index. The slope of sensor response is found to be non linear, can have either sign and can change sign at around refractive index of the fiber. The sensitivity of the sensor to refractive index change is dependent on cladding thickness and is a maximum at an intermediate thickness value. It is insensitive to the presence of absorption at the wavelength at which refractive index is being measured and to the chemical nature of the solute. Experiments designed to show that cladding modes are responsible for sensing are described.

Mrinmoy Chakroborty

Papers

Fiber optic sensing of liquid refractive index