A surface plasmon resonance-based fiber-optic sensor for simultaneous measurement of refractive index and temperature of liquid samples is proposed and experimentally demonstrated. The sensor consists of a gold-coated MM-SM-MM optical fiber structure, whose sensitive section was partially covered with polydimethylsiloxane (PDMS) to generate two independent SPR resonance dips in the fiber transmission spectrum. One of the dips is generated by the bare gold-coated fiber section whose wavelength resonance is tuned by the refractive index and temperature of the surrounding medium. The other dip that is exclusively used to monitor the temperature variations of the liquid sample, whose central wavelength at 900 nm corresponds to PDMS refractive index at 20 °C, is produced by the polymerized gold-coated fiber section. The high refractive index and temperature sensitivity achieved, 2323.4 nm/RIU and −2.850 nm/°C respectively, the small size, the ease fabrication process, and the bio-compatibility of the proposed device are appealing characteristics that makes it ideal for practical bio-sensing applications.

Simultaneous measurement of refractive index and temperature using a SPR-based fiber optic sensor

A Review of advancements (2007–2017) in plasmonics-based optical fiber sensors

This paper presents a highly-sensitive, miniature, all-silica, dual parameter fiber-optic Fabry-Perot sensor, which is suitable for independent measurement of the refractive index and the temperature of the fluid surrounding the sensor. The experimental sensor was produced by a micromachining process based on the selective etching of doped silica glass and a simple assembly procedure that included fiber cleaving, splicing and etching of optical fibers. The presented sensor also allows for direct compensation of the temperature’s effect on the fluid’s refractive index change and consequently provides opportunities for the detection of very small changes in the surrounding fluid’s composition. A measurement resolution of 2x10−7RIU was demonstrated experimentally for a component of the refractive index that is related purely to the fluid’s composition. This resolution was achieved under non-stabilized temperature conditions. The temperature resolution of the sensor proved to be about 10−3°C. These high resolution measurements were obtained by phase-tracking of characteristic components in a Fourier transform of sensor’s optical spectrum.

High resolution, all-fiber, micro-machined sensor for simultaneous measurement of refractive index and temperature

An alternative method to build point and sensor array based on photonic crystal fibers (PCFs) is presented. A short length (in the 9-12 mm range) of properly selected index-guiding PCF is fusion spliced between conventional single mode fibers. By selective excitation and overlapping of specific modes in the PCF we make the transmission spectra of the sensors to exhibit a single and narrow notch. The notch position changes with external perturbation which allows sensing diverse parameters. The well-defined single notch, the extinction ratio exceeding 30 dB and the low overall insertion loss allow placing the sensors in series. This makes the implementation of sensor networks possible.

Photonic crystal fiber sensor array based on modes overlapping

In this work, we have demonstrated a cladless few-mode fiber grating sensor for simultaneous measurement of refractive index (RI) and temperature. The proposed sensor is fabricated from an etched few-mode Fiber Bragg Grating (FMFBG) that can support two Bragg wavelengths, in which the sensitivities for each Bragg wavelength to the changes of RI and temperature are different. A mode coupling theory is used to describe the sensing principle of the proposed sensor and the simulation result finding that an etched diameter of 14.1 μm can get the better performance for optimal the power confinement of etched FMFBG. Experimental results show that the proposed sensor has the RI sensitivities for both λ 01 and λ 11 are estimated to be 1.183 nm/RIU and 4.816 nm/RIU respectively, and temperature sensitivities for λ 01 and λ 11 are 9.62 ± 0.08 pm/°C and 9.52 ± 0.13 pm/°C respectively. With the assistance of 3 × 3 characteristic matrix, discrimination measurements of temperature and RI has been demonstrated and the deviations in RI and temperature measurements are ±8 × 10 −4  RIU and ±1 °C respectively.

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

A fiber-optic sensor for simultaneous measurement of refractive index (RI) and temperature was proposed and demonstrated. It was fabricated by cascading two sections of specialty double cladding (DC) fibers which presented a pair of well-separated resonant spectra dips. The sensing properties of temperature and ambient RI were investigated theoretically based on the coupled mode theory. Experimental results indicated that these two resonant spectra shifts were linearly dependent on the variation of the RI in the range of 1.3333~1.4118 and on the temperature in the range of −10°C~ + 80°C. Such a fiber-optic sensor is simple and easy for mass production and has potential applications for biosensors or chemical sensors.

In-series double cladding fibers for simultaneous refractive index and temperature measurement

The invention relates to a coaxial optical fiber-based temperature and stress dual-parameter optical fiber sensor which is formed by sequentially connecting a single mode input optical fiber, a first coaxial optical fiber, an intermediate single mode optical fiber, a second coaxial optical fiber and a single mode output optical fiber, wherein the single mode input optical fiber, the first coaxialoptical fiber and the intermediate single mode optical fiber are sequentially welded to form a first sensing unit; and the intermediate single mode optical fiber, the second coaxial optical fiber andthe single mode output optical fiber are sequentially welded to form a second sensing unit. The first coaxial optical fiber and the second coaxial optical fiber have different structural parameters, the first sensing unit and the second sensing unit have resonance filtering spectrums with different wavelengths; and the two resonance filtering spectrums have different sensitivities for two parameters, namely the temperature and the stress, thereby the dual-parameter optical fiber sensor can be realized. The coaxial optical fiber-based temperature and stress dual-parameter optical fiber sensor disclosed by the invention has the advantages of simple preparation process, low cost, compact structure, stable performance, easiness for integration with a standard single mode optical fiber system,and the like.

Coaxial optical fiber-based temperature and stress dual-parameter optical fiber sensor

An optical fiber label-free antigen-antibody immunosensor was proposed and demonstrated. It was fabricated by a
special double cladding fiber (DCF) which presents a band-rejection resonant transmission spectrum. With the 3-
aminopropyltriethoxysilane (KH-550) as the crosslink agent, goat anti rabbit IgG was immobilized on the surface of the
DCF sensor. The whole process of immobilization and the antigen-antibody reaction was monitored through the shifts of
the cladding mode resonant spectrum. Experimental results show that the resonant spectrum shifted toward longer
wavelength during antigen-antibody reaction process. And the spectrum shift presented a saturation trend at high
concentration rabbit IgG.

Wenxin Cao

Papers

In-series double cladding fibers for simultaneous refractive index and temperature measurement

Coaxial optical fiber-based temperature and stress dual-parameter optical fiber sensor

A label-free antigen-antibody immunosensor based on a special double cladding fiber