We report a fiber-optic sensor based on silicon Fabry-Pérot cavity, fabricated by attaching pillar the tip of single-mode fiber, for high-resolution and high-speed temperature measurement. The large thermo-optic coefficient thermal expansion material give rise to an experimental sensitivity 84.6 pm/°C. excellent transparency refractive index over infrared wavelength range result in visibility 33 dB reflection spectrum. A novel average tracking method has been proposed demonstrated...

We propose and study an optical microfiber coupler (OMC) sensor working near the turning point of effective group index difference between even supermode odd to achieve high refractive (RI) sensitivity. Theoretical calculations reveal that infinite sensitivity can be obtained when measured RI is close value. This diameter-dependent corresponds condition equals zero. To validate our proposed sensing mechanism, we experimentally demonstrate ultrahigh 39541.7 nm/RIU at a low ambient 1.3334...

We present a systematic study on the spectral characteristics and ultrahigh sensitivity near dispersion turning point (DTP) of optical microfiber couplers. Numerical simulations reveal that DTP exists when group effective refractive index (RI) difference between even mode odd equals zero, where both positive RI sensitivities negative can be achieved. The position is dependent coupler width, it always over surrounding (SRI) range 1.333-1.41, which enables ultrasensitive sensing in this wide...

We report an ultrasensitive gas refractive index (RI) sensor based on optical nanofiber couplers (ONCs). Theoretical analysis reveals that a dispersion turning point (DTP) exists when the diameter of coupler is below 1000 nm. Leveraging this DTP, RI sensitivity can be significantly improved to infinity. Then we experimentally demonstrate DTP and achieve ultrahigh sensitivities 46,470 nm/refractive unit (RIU) -45,550 nm/RIU around using ONC with 700 More importantly, unique twin dips/peaks...

We report a novel fiber-optic anemometer with self-temperature compensation capability based on Fabry-Pérot interferometer (FPI) formed by thin silicon film attached to the end face of single-mode fiber. Guided in fiber are visible laser beam from 635 nm diode used heat FPI and white-light infrared wavelength range as signal light interrogate optical length FPI. Cooling effects heated sensor head wind is converted blueshift reflection spectral fringes Self-temperature-compensated measurement...

We demonstrate a fiber-optic acoustic emission (AE) sensor system that is capable of performing AE detection, even when the experiencing large quasi-static strains. The Fabry-Perot interferometer formed by cascaded chirped fiber-Bragg gratings (CFBGs). reflection spectrum features number narrow spectral notches equally spaced within bandwidth CFBG. A semiconductor laser whose wavelength can be fast tuned through current injection used to lock line center slope notch. When notch knocked out...

We report a miniature fiber-optic water vector flow sensor based on an array of silicon Fabry-Perot interferometers (FPIs). The is composed four FPIs, one in the center with other three equally distributed around it. FPI heated by cw laser at 980 nm, which guided through lead-in single mode fiber. temperature structure established within head due to heating function (speed and direction), can be deduced from wavelength shifts FPIs. Theoretical analysis has been conducted illustrate operating...

The paradox between a large dynamic range and high resolution commonly exists in nearly all kinds of sensors. Here, we propose fiber-optic thermometer based on dual Fabry-Perot interferometers (FPIs) made from the same material (silicon), but with different cavity lengths, which enables unambiguous recognition dense fringes associated thick FPI over free-spectral determined by thin FPI. Therefore, sensor combines To verify this new concept, one 200 μm silicon cascaded another 10 was...

We propose a novel structure that can achieve extraordinary optical absorption over the visible spectrum, based on guided-mode resonance effect. An metal grating with moderate thickness and high filling factor lead to coupling between quasi-guided-mode cavity mode. The resonant interaction two modes influence field distribution, such as magnetic near grating, which results in absorption. Absorption efficiency be optimized up 99.16%. also show peak readily tuned just by varying subwavelength period.

We report a novel fiber-optic sensor for measurement of static gas pressure based on the natural convection heated silicon pillar attached to fiber tip functioning as Fabry-Perot interferometer (FPI). A visible laser beam is guided by efficiently heat pillar, while an infrared whitelight source, also fiber, used measure temperature FPI, which influenced both power and through convection. theoretically experimentally show that, monitoring fringe shift caused heating, air sensing with little...

Wavelength tracking method is widely used for fiber-optic sensors based on Fabry-Pérot interferometers (FPIs). Although wavelength provides high resolution, it encounters the well-known problem of direction ambiguity when spectrum shifts by more than half free-spectral range. In this paper, we propose a new signal processing that can unambiguously recognize spectral peaks silicon FPI obtaining their unique order values to overcome and achieve measurement over extended New elements proposed...

A fiber-optic refractive index (RI) sensor based on a π-phase-shifted fiber-Bragg-grating (πFBG) inscribed side-hole fiber is presented. The reflection spectrum of the πFBG features two narrow notches associated with polarization modes and spectral spacing used for high-sensitivity RI sensing little temperature cross-sensitivity. maintains its outer diameter mechanical strength. also naturally integrated into microfluidic system convenient sample delivery reduced amount. novel demodulation...

A fiber-optic Fabry-Perot interferometer (FPI) is proposed and demonstrated as an electric current sensor based on ohmic heating with temperature self-compensation. The sensing head fabricated by attaching a silicon pillar the fiber tip FPI inserted into molten tin (Sn) sphere conducting medium. Two copper electrodes are also Sn serve for measurement. loaded will lead to rise that measured high resolution FPI. Bragg grating incorporated in vicinity of compensation. Both theoretical analysis...

The work presented in this paper shows that Fiber Bragg Grating (FBG) optical fiber sensors can potentially be used as receivers a long-range guided wave torsional-mode pipe inspection system. Benefits over the conventional pulse-echo method arise due to reduced total travel distance of ultrasonic reflections, since reflections from defects and structural features do not need propagate full round trip back transmitting collar. This is especially important configurations with high...

We report a fiber-optic micro-heater based on miniature crystalline silicon Fabry–Perot interferometer (FPI) fusion spliced to the endface of single-mode fiber. The FPI, having diameter 100 μm and length 10 or 200 μm, is heated by 980 nm laser diode guided through lead-in fiber, leading localized hot spot with temperature that can be conveniently tuned from ambient >1000°C in air. In meantime, using white light system operating 1550 wavelength window where transparent, FPI itself also serves...

We propose and demonstrate the use of a single-frequency laser an acousto-optic modulator (AOM) for quadrature demodulation fiber-optic ultrasonic sensors whose spectrum features sinusoidal fringes. The light from is split into two channels, before it combined fiber leading to sensor, with AOM in one channels introducing frequency shift light. Thus, contains wavelengths difference designed be odd number times quarter free spectral range so that at least them located on slope fringes...

A kind of biconically-tapered optical fiber (BTOF) modified by silica nanospheres is proposed to implement detection refractive index (RI), especially low RI, with strong nonlinearity and enhanced sensitivity; this idea arose from an interesting experiment a BTOF whose surface was very rough. The mechanisms the nonlinear characters are investigated explained coupling effects Mie scattering multimode propagation, phenomenon repeated in several experiments different fibers. Measured...

By observing the activity of anti-cancer agents directly in tumors, there is potential to greatly expand our understanding drug response and develop more personalized cancer treatments. Implantable microdevices (IMD) have been recently developed deliver microdoses chemotherapeutic locally into confined regions live tumors; tissue can be subsequently removed analyzed evaluate response. This method has rapidly screen multiple drugs, but requires surgical removal only evaluates at a single...

We report an ultrasonic sensor system based on a low-finesse Fabry-Perot interferometer (FPI) formed by two weak chirped fiber Bragg gratings (CFBGs) coiled single-mode fiber. The has several desirable features for practical applications in detecting ultrasound solid surface. By controlling the birefringence of coil during fabrication, is made insensitive to polarization variations laser source. circular symmetric structure also renders omnidirectional response ultrasound. While bonded...

Systems that can image in three dimensions at cellular resolution and across different locations within an organism may enable insights into complex biological processes, such as immune responses, for which a single location measurement be insufficient. In this Letter, we describe vivo two-site imaging probe (TIP) simultaneously two anatomic sites with maximum separation of few centimeters. The TIP consists identical bendable graded index (GRIN) lenses is demonstrated by two-photon two-color...