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This paper reports experimental results on distributed strain measurement in GI fibers with a sub-meter spatial resolution by using a DP-BOTDR system. A spatial resolution of 40 cm was achieved with a RMS strain error of 7.1 μe.

Ten resonant wavelengths could be multiplexed successfully by writing long-period gratings (LPGs) with different pitches. A preliminary distributed temperature monitoring experiment was conducted, and it was estimated that separation between 2 adjacent resonant peaks was 13.2 nm apart, even when the temperature difference between 2 adjacent LPGs was 150°C. The results clarified that this multiplexing approach enables the LPFG to detect a local high temperature caused by an abnormal reaction inside in a large-scale plant.

We propose two kinds of probe typed, microcavity fiber Fabry-Perot interferometers (MCFFPIs) for high temperature measurement (HTM). Experimental results show high stable sensing properties with linear spectral responses of the MCFFPIs for the HTM.

Whispering gallery modes (WGMs) of microcavities are extremely sensitive to their size and the refractive index. WGMs of micrometer-sized spheres and cylindrical fibers are used for sensing applications by comparing with theoretical simulations.

A novel sideband interrogation method was developed for precise measurement of resonance frequency difference between interferometers. Frequency resolution better than 29 kHz was experimentally demonstrated with a pair of fiber Fabry-Perot interferometers.

A temperature insensitive strain sensor using two multimode fibers of opposite temperature sensitivities in series is proposed and demonstrated. The proposed scheme can also make various other multimode interference based fiber-optic devices temperature insensitive.

We demonstrate miniature Mach-Zehnder-interferometer with a device length of 179.5 μm using two micro-abrupt-tapers in a cladding-depressed strongly-guiding fiber. The index variation of 2×10−3 from a 6.3 picoliter optical liquid can cause 1.6 nm wavelength-shift.

A novel temperature sensor based on fiber Bragg grating (FBG) in micro/nanofiber (MNF) immerged in the refractive index oil with high thermo-optic coefficient is proposed and simulated. A sensitivity of 0.4168nm/°C can be achieved.

Based on simple fiber-optic approaches, we present some advanced nanobiophotonics methods for ultrahigh-resolution bioimaging and biosensing beyond the diffraction barrier in the subwavelength nanometric range at cellular, intracellular and bulk tissue level.

A novel optical coherence domain reflectometry (OCDR) by use of an optical frequency comb source is proposed and demonstrated with high spatial resolution ( 45 dB), and short measurement time (≤10 s).

The main fiber optic and other non contact Photonic technologies used in Structural Health Monitoring (PSHM) will be reviewed, several case study and several additional sector applications addressed and, finally, the conclusions will be summarized.

We have been developing "fiber optic nerve systems" for "smart structures and smart materials," in which an optical fiber acts as sensor to measure distribution of strain and/or pressure along it. By embedding the fiber in structures and materials, such as buildings, bridges, aircraft fuel-tanks and pipe-lines, we can realize health monitoring function for these. We have created an original technology to analyse the distributed optical parameters along the fiber by use of synthesis of correlation characteristics of continuous lightwave. Adopting this technology, "fiber optic nerve systems," which have quite a high spatial resolution and measurement speed, have been established.

A self-healing multipoint mesh sensing system is proposed by arranging the wavelengths of FBG sensors corresponding to the FSR of an AWG with three 2×2 optical switches in remote nodes to construct the healing links.

Distributed optical fiber temperature sensor (DTS) for underground coal gasification (UCG) system using is studied in this paper. By measuring temperature of reacting mine gasification process can be controlled. Calibration of DTS and experiment result are introduced. The results show that, DTS can play an important role in UCG systems.

This paper reviews the scientific, technical and applications of fibre optic sensors as they enter their fifth decade and considers future prospects triggered by new science and new needs.

Using simple fiber-optic based approaches, we have developed some advanced biophotonics and nanobiophotonics combined imaging and sensing techniques that can be exploited for high-resolution bioimaging and biosensing at cellular, intracellular and bulk tissue level.

Growth in fiber optic sensing in the geophysical sector, predominantly in downhole oil and gas applications, has spurred refinement of optical fibers primarily to endure the harsh high temperature, hydrogen-rich well environment. This paper reviews advanced sensing fiber design and field performance under these conditions, as well as some new fiber and waveguide designs for enhanced sensor functionality and performance.

Tapered fibres with waist diameters down to 0.7 µm embedded in hydrophobic aerogel are demonstrated as evanescent-field gas sensors. The porous aerogel is permeable to gases but protects the sub-micron fibre from contamination and damage.

We report doubling of sensitivity for tapered fiber-optic sensors with logarithmic detection when light passes through the tapered region twice. Further sensitivity enhancement is possible with multiple passes through the taper.

We present a novel technique for measuring the characteristics of a cloud of cold atoms by monitoring the spontaneous emission coupled into the guided mode of a nanofiber. We show that the fiber is very sensitive to the atoms close to its surface.

We use frequency-shifted interferometry to detect the concentrations of the same gas species at different locations and in different mixtures by accurately correcting the spectral shadowing effect. Different gas species are also detected.

We show that the propagated beams in the silicon nano fiber with a silver clad are localized at two metal-dielectric interfaces with a sub-wavelength diameter. We promise this nano fiber acts as an optical sensor.

A novel multiplexing technology was proposed for fiber Bragg grating (FBG) sensors. This technology is based on a frequency-shifted asymmetric Sagnac interferometer incorporating an acousto-optic modulator (AOM).

A novel all-fiber asymmetrical Sagnac loop interferometer is proposed to measure the chromatic dispersion of a multichannel fiber Bragg grating (FBG). This method has the advantages of simple configuration, low cost, and high tolerance for the characteristics of FBG as well as the ability to uniquely determinate the phase delay.

This paper presents a fibre optic sensor for a multipoint density measurement inside a lead acid battery at several heights. The sensor was optimized with an electrolyte level fibre for easier battery maintenance.

Photonic crystal fibers having a microstructured air-silica cross section offer new optical properties compared to conventional fibers for telecommunication, sensor, and other applications. Recent advances within research and development of these fibers are presented.

With the increasing market for smart structures there has come a need to develop fast and accurate multichannel sensor systems for the measurement of strain, in particular. One potential alternative to fullfill this demand is distributed fibre-optic sensing which enables measurement of strain distributively along the whole fibre length.

The fibre optic sensor market (unlike the fibre optic communications market) is highly heterogeneous and diversified in both sensor types and application areas. Sensors vary widely in their measurand function, basic technology, performance, construction and end user market. As such, it is difficult to describe this activity in broad generalisations. Fibre optic sensors are finding their way into specialised applications where they offer specific advantages over conventional instruments. Examples of different fibre sensors are to be found in many varied domains. Specific examples cited indicate some of the types becoming available.