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We present and demonstrate a novel fiber Michelson interferometer based on cascaded twin core fiber (TCF) and side-hole fiber (SHF) for curvature measurement. The interferometer is fabricated by fusing the TCF and SHF. The interferometer can measure curvature and temperature by monitoring the wavelength change of interferometer spectrum. The experiment investigated sensor's spectral responses to the...
Temperature and strain discrimination is experimentally demonstrated in an elliptical-core polarization-maintaining fiber by making use of Rayleigh-based distributed birefringence measurements and the frequency shift of the correlation peak obtained by standard coherent optical time-domain reflectometry. The high sensitivity of coherent Rayleigh sensing and the very distinct behavior of birefringence...
Blueberry juices produced in China and in Italy were analyzed by means of Raman spectroscopy. The reference data of important nutraceutical indicators such as degrees Brix and carbohydrates were available. Some juices were produced from fresh organic fruits, while others were industrial grade, differing in qualities and prices. Raman spectra obtained with excitation at 1064 nm were acquired using...
A cantilever structure in 3D printed based on a fiber Bragg grating (FBG) sensor embedded in polymer material is proposed. The FBG sensor was embedded in 3D printed coating and was tested under three physical parameters: displacement, temperature and vibration. The sensor was tested in displacement in two different regions of the cantilever, namely, on its midpoint and end point. The maximum displacement...
We have developed a chip-scale optofluidic sensor for biomolecular detection, by tapering laterally aligned silica microfiber and capillary to form a modal interferometer. With the pre-immobilization of DNA probes, the sensor is capable of selectively detecting single-stranded microRNA-let7a (molecular weight: 6.5 k) by measuring the spectral shift of the interferometric spectrum. A log-linear response...
Surface plasmon resonance has found plenty of sensing applications on various platforms from label-free biosensing to surface-enhanced spectroscopies. Quasiperiodic nanohole arrays with patterns such as the Penrose tiling have been demonstrated with surface plasmon resonance enhanced optical transmission. Here we transfer quasiperiodic nanohole arrays onto optical fibers and measure their optical...
A simple, low cost technique to fabricate a ratiometric optical fiber ammonia (NH3) sensor has been presented. The ratiometric optical fiber ammonia sensor was based on the ammonia induced absorbance change of sensing material Oxazine 170 perchlorate (O170) in ethyl cellulose (EC) with the luminescence intensity of 7-amino-4-trifluoromethyl coumarin (AFC). The observed luminescence intensity from...
Sensitivity of two commercial perfluorinated (PF) polymer optical fibers (POFs) to gamma radiation was measured, compared and exploited for dosimetry purposes. Fiber radiation induced attenuation (RIA) was found to be highly wavelength dependent and pronounced towards the UV part of the spectrum. PF-POFs were shown to be highly radiation sensitive and RIA-based on-line radiation monitoring with sensitivity...
Distributed fiber-optic sensing (DFOS) has drawn great attention in both academic research and industrial applications due to its unique advantages. Recent progress at University of Electronic Science and Technology of China (UESTC) in DFOS, mainly on ultra-long-distance Brillouin optical time-domain analysis (BOTDA) and phase-sensitive optical timedomain reflectometry (Φ-OTDR), is discussed in this...
Optical fibres have been explored widely for their sensing capability to meet increasing industrial needs, building on their success in telecommunications. This paper provides a review of research activities at City University of London in response to industrial challenges through the development of a range of fibre Bragg grating (FBG)-based sensors for transportation structural monitoring. For marine...
Forward phase-matched Brillouin optomechanical resonance, excited by a tapered fiber, in a graphene inner-deposited whispering-gallery-mode microfluidic cavity, is demonstrated for the first time. The generated Brillouin optomechanical modes with Q factor ∼ 47000 show extremely high sensitivity (200kHz/ppm) for absolute gas detection based on frequency variation, achieving a detection limit down to...
We demonstrate a novel distributed fiber sensing technique with a record broadband sensitivity of 10nε/VHz at a sampling rate of 1MHz. A standing acoustic wave is generated by all-optical excitation of two simultaneously counter-propagating Brillouin dynamic gratings. A dual-tone readout probe pulse is used for the distributed measurement of strain-induced nonlinear phase-shifts of the acoustic wave...
We propose and demonstrate the use of cross recurrence plot analysis (CRPA) to accurately determine the Brillouin shift due to strain and temperature in a Brillouin distributed fiber sensor. This signal processing technique, which is implemented in Brillouin sensors for the first time relies on apriori data i.e, the lineshape of the Brillouin gain spectrum and its similarity with the spectral features...
The robustness of the BOTDA method based on dual-tone probe wave with fixed frequency separation is studied. It is verified that when the sensing fiber consists of two fiber segments with large Brillouin frequency shift difference (>100 MHz), the non-local effect would take place in the front fiber segment, which gives rise to frequency error on the determination of hotspot. Aiming at solving this...
Brillouin optical time domain analysis (BOTDA) enhanced by the tailored compensation for the propagation loss of a pump pulse is experimentally demonstrated for long-distance and high-resolution distributed sensing. Distributed Brillouin amplification (DBA) of the pump pulse is applied in addition to an ordinary BOTDA configuration, where the frequency modulation with time-dependent amplitude variation...
We numerically analyzed the refractive index sensing performance of the two-dimensional array of plasmonic V-shaped grooves. The structural parameters are optimized to show a sharp and large reflectance dip with desired sensing region (n=1.33). Acquiring the sensitivity of the environmental refractive index as 400 nm/RIU in the visible region, FWHM of the dip is ∼5 nm. It shows that the proposed structure...
We proposed a refractive index sensor using a phase-compensated cavity whose resonant wavelength can be tuned by the alignment between layers. The structures are composed of double-layered nanoslit array, which has total thickness of 100 nm while the cavity length is 30 nm thick. Using nanoslit array as a reflector has made it possible to design the phase shift carefully so that the subwavelength...
In this work, the impact of the laser phase noise on chirped-pulse phase-sensitive OTDR signals is theoretically and experimentally analyzed. In particular, it is shown that the noise in the readings of strain/temperature changes along the fiber scales directly with the frequency noise power spectral density of the laser. The effect of the pulse chirp on the signal to noise ratio is also investigated...
We present the coherent anti-Stokes Raman scattering (CARS) microscopy system that has been implemented by using a photonic crystal polarization maintaining optical fiber. Free space CARS system is hard in alignment and unstable in harsh environment. To overcome this problem the femto-second laser pulses of pump and the Stokes beams were delivered through the optical fiber, so that the system became...
A precise measurement technique of long period of fiber grating sensor (LPG) is demonstrated by employing a cascaded chirp LPG (C-CLPG) as a sensing device and by adopting a Fourier transform method for an interrogation technique. In this approach, transmittance of the C-CLPG exhibits periodic channeled spectrum and its strain- and/or temperature-dependent wavelength shift is analyzed by obtaining...
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