Design and characterization of dual D-shaped no-core fiber based SPR sensor for refractive index and temperature measurement

We report an optical fiber multiparameter sensor for refractive index and temperature measurements. The proposed sensor is composed by a microcavity in multimode fiber, assisted by Bragg gratings (FBGs) in singlemode fiber. The microcavity is engraved in a multimode optical fiber by using the femtosecond laser micromachining. The sensor is characterized through microcavity immersion in water and based on its temperature variation. The results show that it is possible to obtain refractive index and temperature measurements with sensitivities of 1625 μW/RIU (refractive index unit) and of 0.23 μW/°C, with resolution of 1.8 × 10−4 RIU and of 1.3 °C.

Simultaneous measurement of refractive index and temperature based on tapered no-core fiber cascaded with a fiber Bragg grating

We propose and demonstrate a compact all-fiber sensor for simultaneous measurement of temperature and refractive index (RI), which is based on a no-core fiber (NCF) and fiber Bragg grating (FBG). Two segments of NCF used as beam splitter and combiner are embedded on the two ends of an FBG, which constitute a Mach-Zehnder (MZ) interferometer susceptible to the temperature and an ambient RI. With the change of RI and temperature, MZ interference and Bragg reflection result in the variation of transmission spectrum. The experimental results show that the sensitivity of RI is -109.573 nm/RI in the range from 1.333 to 1.398, and the sensitivity of temperature ranging from 10 °C to 70 °C is 0.014 nm/°C, respectively. The feasibility of simultaneous measurement of an external RI and the temperature with this configuration has been demonstrated experimentally.

A fiber ring cavity laser sensor for refractive index and temperature measurement with core-offset modal interferometer as tunable filter

A fibre optical sensor for the simultaneous measurement of pressure, temperature and refractive index has been demonstrated. The sensor is based on a multi-cavity design and employs a monolithic sapphire transducer element.

Simultaneous measurement of strain, temperature and refractive index based on a fiber Bragg grating and an in-line Mach–Zehnder interferometer

A fiber-optic sensor for simultaneous measurement of refractive index and temperature is described. The refractive index measurement is based on the visibility variations of a Fabry-Pérot interferometer. It is formed with the interfering waves generated from a low reflectivity Bragg grating inscribed on a Panda fiber and from the fiber end tip (Fresnel reflection) in contact with the liquid. The sensor is characterized by immersing the fiber tip in distilled water with different concentrations of ethylene glycol. A linear relation of the interferometer fringe visibility with refractive index variation is observed. The temperature is determined by the wavelength shift of the FBG peaks. Results show the feasibility of simultaneous measurement of refractive index and temperature and also the possibility of adjusting fringe visibility via polarization control.

Femtosecond laser pulses induced ultra-long-period fiber gratings for simultaneous measurement of high temperature and refractive index

ABSTRACTA novel fiber optic sensor for the simultaneous measurement of refractive index and temperature is reported. The sensor consists of a high-birefringence fiber loop mirror and a section of single mode-coreless-single mode fiber structure. The single mode-coreless-single mode fiber structure served as a refractometer while the high-birefringence fiber loop mirror was used to measure temperature. The multimode interference valley of the single mode-coreless-single mode fiber structure was sensitive to the surrounding refractive index of liquids (96.42 nm/refractive index unit) and had almost no response to temperature fluctuations. The high-birefringence fiber loop mirror was highly sensitive to temperature (1.98 nm/°C) but was insensitive to changes in refractive index. The theoretical and experimental results demonstrated simultaneous measurement of temperature and refractive index. The optimum resolution was 2.07 × 10−4 refractive index units and 0.01°C.

Experimental study on ultra-high sensitivity gold-based SPR sensor for refractive index and temperature measurement

We presented a hybrid sapphire dual-Fabry—Perot- cavities sensor for high temperature and refractive index measurement. A double-sided polished sapphire solid wafer is connected in series with a double-sided parallel sapphire C-ring and a single-sided polished sapphire mirror to form the hybrid Fabry—Perot interferometer. The double-sided polished sapphire solid wafer acts as the first Fabry—Perot cavity for temperature sensing, and the sapphire hollow C-ring cavity constitutes the second Fabry—Perot cavity for measuring the refractive index of external environment medium. The single-sided polished sapphire mirror serves as the most distal reflector. Heterogeneous fiber splicing between sapphire fiber and multimode silica fiber is realized to achieve long-distance transmission of interference signals. A series of high temperature measurement experiments range of room temperature to 1080 °C in an air environment and refractive index measurement experiments in a liquid environment were carried out. Based on the changing rates of corresponding Fabry—Perot cavity optical path difference against refractive index and temperature, we calculated the sensitivities of the sensor. The refractive index and temperature sensitivities were 2.0659 × 105 nm/RIU in the RI range of 1.3330∼1.3741 and 7.837 nm/ °C at 1080 °C.

Cladless few mode fiber grating sensor for simultaneous refractive index and temperature measurement

An interrogation scheme for an in-series double cladding fiber (DCF) sensor is proposed and demonstrated, which can be used for simultaneous refractive index (RI) and temperature measurement. It utilizes two commercial distributed feedback lasers to match two cascade DCF sensors which have two band-rejected filtering spectra at different wavelengths. The two lasers were intensity modulated by different frequencies and demodulated by a lock-in amplifier. Experimental results indicated that a resolution of ±2×10-5 in RI and ±1.2dCin temperature were achieved. Based on the simple and low cost interrogation scheme, the dual parameters sensor system will find potential applications in chemical sensors and biosensors.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Research on simultaneous measurement of refractive index and temperature comprising few mode fiber and spherical structure

Integrated FPI-FBG composite all-fiber sensor for simultaneous measurement of liquid refractive index and temperature