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Surveillance is becoming more and more important in the recent years. In many cities, cameras have been set to look after parks, streets, roads, facilities and so on, however this fact is rising concerns about privacy. In this work, an alternative surveillance method which gather at once security and privacy has been propose and tested. Based on fiber optic specklegram technology; a system consisting...
We propose a model-based compressed sensing (MBCS) of FBG arrays (FBGA), interrogated with wavelength scanning incoherent optical frequency domain reflectometry. This method measures the frequency response of a FBGA with an electrical vector network analyzer combined with a tunable laser. Instead of the usual inverse discrete Fourier transform (IDFT), we apply a direct estimation of the grating reflectivities...
We present a distributed fiber optic sensing scheme to study 3D temperature fields inside concrete containers submitted to fire. High spatial resolution (3cm to 13cm), temperature uncertainty better than 3°C and rapid measurements (in the minute range) were required. We thus compared advantages and drawbacks of three sensing chains, based on Rayleigh, Brillouin and Raman scatterings; such distributed...
A 3D FEM model of an FBG in a PANDA fiber with an extended fiber length of 25.4 mm is presented. Simulating long fiber lengths with limited computer power is achieved by using an iterative solver and by optimizing the FEM mesh. For verification purposes, the model is adapted to a configuration with transversal loads on the fiber. The 3D FEM model results correspond with experimental data and with...
This paper describes the application of a commercial distributed optical fiber sensing system to a large scale physical model of landslide. An optical fiber cable, deployed inside the landslide body, is interrogated by means of optical frequency domain reflectometry with very high spatial density. A shallow landslide is triggered in the physical model by artificial rainfall and the evolution of the...
This paper presents a ratiometric optical broad range pH sensor that comprises an optical fiber coated at one end with CdSe/ZnS quantum dots (QDs) and Oxazine 170 perchlorate (O170) embedded in ethyl cellulose (EC) matrix. The feasibility of coating an optical fiber with the sensing film to fabricate a ratiometric fiber optic broad range pH sensor is investigated. Using an LED with a central wavelength...
A new optical carbon dioxide sensor based on the colormetric change of pH indicator α-naphtholphthalein with the internal reference fluorescent CIS/ZnS quantum dots (QDs) was developed. The luminescence intensity of CIS/ZnS QDs increased with increasing carbon dioxide concentration. The sensing films consisting of α-naphtholphthalein in polyIBM and CIS/ZnS QDs in polystyrene layer. The sensitivity...
This paper presents a study for a fibre optic sensor based on quantum wires to detect and measure the amplitude and direction of a static electric field. This study is supported by the analogy of the fluid equations describing the free electrons in the quantum wires and the Madelung formalism of Quantum Mechanics. In this context, it is possible to construct a diatomic plasmonic molecule whose energy...
The impact of Brillouin scattering on the polarisation of pump and probe in a Brillouin optical-time domain analyser is investigated. Experimental results indicate that the Brillouin interaction integrated along the entire sensing fibre produces a polarisation pulling force that changes the pump polarisation. Although this force can be compensated to first order by dual-sideband probes, the Brillouin...
We propose a high speed strain measurement method using an active mode locking (AML) fiber Bragg grating (FBG) laser sensor with a chirped FBG cavity. The mode-locked frequency of the AML laser depends on both the position and Bragg wavelength of the FBG. Thus, the mode-locked frequency of cascaded FBGs can be detected independently along the cavity length of cascaded FBGs. The strain across FBGs...
We present a technique to overcome the random transfer function of fiber-optic direct detection coherent optical time-domain reflectometry (C-OTDR). For this purpose, a standard optical fiber was treated by UV light in order to introduce local strongly scattering segments of definite size and distance to each other. Dynamic strain measurements were performed to demonstrate the sensory benefit in comparison...
In this paper we show a Brillouin optical time-domain analysis (BOTDA) sensing system experiment employing a tunable narrow-linewidth dual pump-probe source based on modified Brillouin ring laser technology. The developed cost-effective source generates a tunable pump-locked probe light, with suitable wavelength shift, large tuning range (∼200 MHz), narrow linewidth (<2.5 MHz) and adequate power...
We propose and demonstrate a miniature Fabry-Perot (F-P) interferometric sensor based on a hollow glass microsphere (HGM) for highly sensitive temperature measurement. The sensor head is fabricated by sticking a HGM on the end face of a single-mode fiber, and it consists of a short air F-P cavity between the front and the rear surfaces of the HGM. A sensor with 135.7280-μm cavity length was tested...
The proposed technique consists in an optical fiber resonator interrogated for sensor characterization, implementing an alternative technique for dynamic range improvement. Such technique relies on the analysis of an added-signal caused by signal saturation, which occurs due to the broadening of the laser pulse. A wide study for different pulse widths is presented in this work, namely for 100 ns,...
We analyze the output signal power spectrum with different initial input signal power spectrum in a long-haul wavelength-division-multiplexed system with backward multiple-pump Raman amplifiers. The genetic algorithm is used to optimize the output signal power. The results using fixed pump wavelengths are compared with the case in which the pump wavelengths are allowed to vary. We experimentally show...
Implementation of Optical Frequency Domain Reflectometry (OFDR) requires a source whose instantaneous frequency can be accurately scanned over a sufficiently wide frequency range. Achieving high repetition rates of accurate linear frequency sweeps can be rather challenging. In contrast, fast and accurate Sinusoidal Frequency Scan (SFS-OFDR) can be easily implemented via direct or external optical...
An interrogation technique based on phase modulation to intensity modulation conversion due to FBG filtering is presented. A 10 GHz tone is used to phase modulate an optical carrier located at the Bragg wavelength of a given FBG. The modulation index is set to a small value to keep Bessel identities close to 0 in order to avoid higher harmonics. Changes of the Bragg wavelength cause a power change...
Graphene has been reported to show polarization-dependent optical absorption in the visible spectral range, that it shows more absorption for s-polarized light than p-polarized light. We study further on it and demonstrate that this unique property can be utilized to design a fiber optic sensor, which works in a similar way of surface plasmon resonance (SPR) fiber optic sensor. However, they are based...
New approach in simultaneous measurement of dynamic strain and temperature has been done by using a high birefringence PANDA fiber Bragg grating sensor. By this technique, we have succeeded in discriminating dynamic strain and temperature distribution at the sampling rate of 800 Hz and the spatial resolution of 1 mm. The dynamic distribution of strain and temperature were measured with the deviation...
FBG inscribed on splice joint is proposed to be used as a sensor. It could realize temperature and strain measurement simultaneously because of the different strain responses of the different parts of the FBG inscribed on splice joint, while the temperature responses are same. The strain responses of four overlap values are discussed, which is used to optimize the discrimination capability of the...
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