Section Of Optical Fiber Research Articles

Temperature-insensitive relative humidity sensing based on a carrier-suppression-effect-free tunable optoelectronic oscillator using a non-coherent broadband optical source

A relative humidity (RH) sensing scheme with high resolution and high interrogation speed based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. A carrier-suppression-effect-free single bandpass microwave photonic filter (MPF) with no baseband response is employed in the OEO to select the oscillating frequency, which is consisted of a non-coherent broadband optical source, a Mach-Zehnder interferometer (MZI) with one arm embedded a phase modulator, a dispersion compensation fiber and a photodetector. In one arm of the MZI, a section of optical fiber is coated with a polyvinyl alcohol (PVA) film acting as sensing probe, in which the PVA film can convert the RH variation to the strain on the fiber. When the RH changes, the arm-length difference and free spectral range of the MZI is changed, leading to a frequency change of the MPF as well as the oscillating signal of the OEO. By simply monitoring the frequency shift of the oscillating signal in the electrical domain, a high resolution and high interrogation speed RH measurement can be achieved. The temperature cross-sensitivity can be almost eliminated by adding a section of fiber without PVA film coating in the other arm of the MZI. An experiment is performed, and a high RH sensitivity of 2.016 MHz/%RH with a high resolution of 0.17 % is achieved.

Classification of the factors causing the change of the optical fiber strain by using the Brillouin reflectograms

A classification of the factors causing the change of the optical fiber strain by using the Brillouin reflectograms is considered.The differences of Brillouin reflectograms with strain along the optical waveguide are discussed under various impacts: temperature and mechanical longitudinal stretching.Reference Brillouin reflectograms for different kinds of optical fibers from the database are capable of improving a process of classification of potentially hazardous sections (sections of optical fibers with high mechanical strain or changed temperature) in the optical fiber.The results presented in this paper allow us on the basis of the analysis of Brillouin multi-reflectograms to identify a factor that has a predominant impact on the fiber strain in the investigated sections of the optical fibers in fiber optical communication lines.

Performance analysis of Strain sensor based on Fiber Bragg Grating

A fiber Bragg grating can be worked as reflector, it is constructed in a short section of optical fiber that reflects light of specific wavelength and allow to pass remaining wavelengths. This is possible by creating a periodic change in refractive index within the fiber core. The change in the modal index of fiber caused due to strain results in a Bragg wavelength. This work describes performance of Fiber Bragg Gratings as a strain sensor at 1550nm wavelength is considered for simulation, corresponding dynamic strain and wavelength shifts are analysed. This performance analysis is useful especially for intrusion detection system where environments are harsh. This sensor is compatible with data communication system and can be used for remote sensing.

Low-cost optical fiber physical unclonable function reader based on a digitally integrated semiconductor LiDAR.

This paper introduces an integrated fiber physical unclonable function (PUF) verification system based on a semiconductor laser source at substantially lower complexity and cost than existing alternatives. A source sub-section consisting of a linear frequency-swept semiconductor laser is used in combination with an optical frequency domain reflectometry (OFDR)/LiDAR-based measurement sub-section in order to conduct fiber identification via measurement of the unique Rayleigh reflection pattern of a section of optical fiber. When using these Rayleigh reflection patterns as PUFs, this technique results in a maximum equal error rate (EER) of 0.15% for a 5-cm section of optical fiber and an EER of less than 1% for a 4-cm section. These results demonstrate that the system can serve as a robust method fiber identification for device and communication verification applications.

Azimuth-Rotated Splicings of a Four-Core Optical Fiber for Inter-Core Group Delay Compensation

This letter presents an experimental method to compensate for the differential group delay between the core modes in a multi-core fiber. Optical fiber sections are sequentially spliced with azimuthal offsets such that light initially launched to any cores can propagate through the combination of the same lengths of different cores, resulting in ideally uniform group delay. The differential group delays before and after the compensation are measured by wavelength-domain Mach–Zehnder interferometry through multi-core fiber sections. The experimental results show that the group delay compensation is practically limited by non-uniformity of the multi-core fiber.

Fiber optic distributed temperature sensing for fire source localization

A method for localizing a fire source based on a distributed temperature sensor system is proposed. Two sections of optical fibers were placed orthogonally to each other as the sensing elements. A tray of alcohol was lit to act as a fire outbreak in a cabinet with an uneven ceiling to simulate a real scene of fire. Experiments were carried out to demonstrate the feasibility of the method. Rather large fluctuations and systematic errors with respect to predicting the exact room coordinates of the fire source caused by the uneven ceiling were observed. Two mathematical methods (smoothing recorded temperature curves and finding temperature peak positions) to improve the prediction accuracy are presented, and the experimental results indicate that the fluctuation ranges and systematic errors are significantly reduced. The proposed scheme is simple and appears reliable enough to locate a fire source in large spaces.

Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry.

This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment’s shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object.

Temperature Independent Tapered Fiber Bragg Grating-Based Inclinometer

A new concept for an optical fiber inclinometer based on tapered fiber Bragg grating (TFBG) is presented. The sensor was characterized by the experimental measurement of the dependence of inclination angle on the spectral response in fluctuating temperature conditions. The research showed that the TFBG made it possible to simultaneously measure both the inclination angle and temperature, and to operate as a temperature insensitive 0°–90° tilt sensor, in a different interrogation regime. Inscription of the FBG in the tapered optical fiber section offered not only sensor miniaturization, but also the possibility of temperature sensing by the fiber section adjacent to the inclination area. Moreover, due to the reflective mode of the TFBG, the sensor offers excellent sensitivity due to the double-loss operation.

Gigabit passive optical networks and catv over hybrid bidirectional free space optics +20 km single mode fiber

ABSTRACTThis article experimentally shows a gigabit passive optical network (GPON)+ community access television system (CATV) link, transmitting in 20 km of single mode optical fiber section or/and in free space. Bidirectional transmission of GPON traffic and CATV and further experimental apparatus is demonstrated and performed, based on signal transparency through the optical path, without optical‐electrical‐optical signal conversion between different media. The viability of such links is here analyzed by measuring the loss of data packets and the carrier‐to‐noise‐ratio value for the video signal overlay. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2867–2871, 2015

Experimental study of light transmitting cement-based material (LTCM)

Light transmitting cement-based material (LTCM) was prepared by polymethylmethacrylate (PMMA) fibers, Portland cement, aggregates, deforming agent and water reducers in a given proportion. The compressive and flexural strengths of LTCM prepared with different diameters and volume fractions of optical fibers were measured at the age of 28d. The compressive and flexural strengths of LTCM specimens decreased with an increasing volume fraction of fiber. Factors such as distance from the light source to specimen, diameter and volume fraction of fiber, and the variety of light sources that affect the optical power of LTCM were studied in this paper. The experimental results demonstrate that the optical power was significantly affected by the distance from light source and specimen, and the diameter and number of fibers. The matrix material, cross section of optical fiber, and the interface between fiber and matrix were analyzed by SEM.

Dynamics of Laser-Induced Shock Wave in Silica/ Dynamika Laserowa Indukowana W Fali Uderzeniowej W Krzemionce

Abstract The study of detonation-like mode of laser induced damage propagation was considered. Velocity of this propagation is two orders of magnitude faster than known published data on burning fiber glass. The condition of optical fiber and enough long laser pulse let us obtain laser induced damage propagation passing near hundred own core diameters during pulse. The using as target the core of silica-based optical fiber has some diagnostic advantages. It allows spatially splits “start” and “stop” points and to supply the same form of energy deposition in every cross section of optical fiber. Tested regime demonstrates near constant velocities during 250 ns in the range of laser intensity 2-4.5 GW/cm2.

Photonic approach to broadband instantaneous microwave frequency measurement with improved accuracy

A photonic approach for instantaneous microwave frequency measurement over a wide bandwidth is proposed and experimentally demonstrated based on the fading effect of the fiber. In this scheme, three lights with different wavelengths and three sections of optical fiber are used to construct the frequency-dependent amplitude comparison functions (ACFs), using a phase modulation along with an intensity modulation. The unknown microwave frequency can be determined from the intersection of three ACFs. The method can not only provide extended measurable range of the microwave frequency, but also improve the accuracy by choosing an ACF with a large slope. The measurement errors as demonstrated in the experimental results are within ±90MHz in the frequency range of 0.5–20GHz.

A long period grating-based chemical sensor insensitive to the influence of interfering parameters

An optical fibre chemical sensor that is insensitive to interfering parameters including temperature and surrounding refractive index is described. The sensor is based upon a Mach-Zehnder interferometer formed by a pair of identical cascaded long period gratings (LPGs), with the entire device coated with a mesoporous coating of silica nanoparticles. A functional material is infused only into the coating over the section of optical fibre separating the LPGs. The transmission spectrum of the device consists of a channeled spectrum arising from interference of the core and cladding modes within the envelope of the LPG resonance band. Parameters such as temperature, strain and surrounding refractive perturb the entire device, causing the phase of the channeled spectrum and the central wavelength of the envelope shift at the same rate. Exposure of the device to the analyte of interest perturbs only the optical characteristics of the section of fibre into which the functional material was infused, thus influencing only the phase of the channeled spectrum. Measurement of the phase of the channeled spectrum relative to the central wavelength of the envelope allows the monitoring of the concentration of the analyte with no interference from other parameters.

Offset Coupling, Feedback, and Spatial Multiplexing in 4$\,\times\,$4 Incoherent-MIMO Multimode Fiber Links

We experimentally evaluate the performance of incoherent multiple-input multiple-output (MIMO) multimode fiber (MMF) links with different fiber media, link lengths, and modulation techniques. The performance of conventional 62.5 μm diameter silica as well as perfluorinated plastic, graded-index MMF sections of various lengths were evaluated using 1 × 1, 2 × 2, 3 × 3 and 4 × 4 MIMO setups over a range of lengths, with both open-loop equalization and feedback-based spatial multiplexing techniques. The data rate was evaluated over silica fiber sections with lengths ranging between 100 m-3 km using distributed feedback lasers and VCSELs at the transmitters. In addition, plastic optical fiber sections with lengths ranging from 1 m - 100 m were evaluated with Fabry Perot lasers. Axial offsets were introduced while launching into, and detecting from the MMF to enhance modal diversity, and the impact of these offsets on the data rates was measured to obtain optimal launch and detection conditions. With optimized launch conditions and modulation parameters, the silica based systems realized data rates of 16 to 26 Gb/s, representing a bandwidth-length product improvement of 28× over MMF standards such as 10 GBASE-SR. The plastic fiber system reached data rates of 24 to 43 Gb/s, with bandwidth-length product increases of up to 12× of rated parameters. The use of off-axis launch and detection with flexible offsets on all four MIMO streams of the 4 × 4 system would enable further performance improvement.

Optical sensor based on two in-series birefringent optical fibers

An optical fiber sensor based on the combination of two spliced birefringent optical fiber sections is proposed in this paper. The sensor is built up in a Solc-filter-like configuration and a simple theoretical model based on Jones matrices is employed to predict experimental results. By choosing the suitable birefringent optical fibers (e.g., photonic crystal fibers, birefringent microfibers, elliptical core fibers, PANDA fibers, etc.), the sensor described herein allows for probing of two physical parameters (e.g., refractive index and temperature, hydrostatic pressure and temperature) or sensing the same parameter in two disconnected environments. In order to demonstrate the sensor performance, the system response was evaluated in a temperature-sensing measurement.

Mode couplings and elasto-optic effects study in a proposed mechanical microperturbed multimode optical fiber sensor

A step index multimode optical fiber with a perturbation on a micrometer scale, inducing a periodic deformation of the fiber section along its propagation axis, is theoretically investigated. The studied microperturbation is mechanically achieved using two microstructured jaws squeezing the straight fiber. As opposed to optical fiber microbend sensors, the optical axis of the proposed transducer is not bended; only the optical fiber section is deformed. Further, the strain applied on the fiber produces a periodical elliptical modification of the core and a modulation of the index of refraction. As a consequence of the micrometer scale perturbation period, the resulting mode coupling occurs directly between guided and radiated modes. To simulate the transmission induced by these kinds of perturbations, simplified models considering only total mode couplings are often used. In order to investigate the range of validity of this approximation, results are compared to the electromagnetic mode couplings rigorously computed for the first time, to our knowledge, with a large multimode fiber (more than 6000 linear polarized modes) using the Marcuse model. In addition, in order to have a more complete modeling of the proposed transducer, the anisotropic elasto-optic effects in the stressed multimode fiber are considered. In this way, the transmission of the microperturbed optical fiber transmission and, therefore, the behavior of the transducer are physically explained and its applications as a future stretching sensor are discussed.

Carbon coatings on silica glass optical fibers studied by reflectance Fourier-transform infrared spectroscopy and focused ion beam scanning electron microscopy

Carbon coatings applied on optical fibers via chemical vapor deposition were characterized by a resistance technique, focused ion beam/scanning electron microscopy (FIB/SEM), and reflectance Fourier-transform infrared spectroscopy (FTIR). The resistance technique measures the thickness of carbon film by measuring the resistance over a section of optical fiber, and backing out the film thickness. The FIB/SEM system was used to remove a cross section of the optical fiber and carbon coating and using a scanning transmission electron detector the thickness was measured. The FTIR approach is based on the fact that the wavelength of the light in the mid-infrared region (~10μm) is significantly larger than the typical thickness of the carbon coatings (<0.1μm) which makes the coating “semi-transparent” to the infrared light. Carbon coating deposition results in significant transformations of the band profiles of silica in the reflectance spectra that were found to correlate with the carbon coating thickness for films ranging from 0.7nm to 54.6nm. The observed transformations of the reflectance spectra were explained within the framework of Fresnel reflection of light from a dual-layer sample. The advantage of this approach is a much higher spatial resolution in comparison with many other known methods and can be performed more quickly than many direct measurement techniques.

Micromachined optical fiber enclosed 4-electrode IPMC actuator with multidirectional control ability for biomedical application

The present paper examined a novel micromachined column structured Ion Polymer Metal Composite (IPMC) actuator with multidirectional control capability. The developed 4-electrode transducer enclosed a section of optical fiber, thereby allowing electronic directional control of conducted laser light. The fabricated device with IPMC actuator dimensions of 5 mm x 2 mm x 1 mm reached a maximum displacement of 400 μm when a square wave of 9 V was applied to the top-bottom electrode pair. Displacements in different directions and moving angles were characterized with side-side and top-right electrode pairs connected to the actuating signals. Furthermore, the generating moment per volt per second by the transducer was analyzed. The maximum value of approximately 200 μN*m/V/s was displayed when the device actuated with the side-side electrode pair. Controlling the developed IPMC actuator moved the laser beam in multiple directions. This device could be promising for biomedical applications such as microendoscopic ocular surgery.

Distribution of guided mode power flow between the layers of circular and elliptical multilayer optical fibers

An invariant expression in the form of a contour integral for guided mode power flow via an arbitrary area of the cross section of an optical fiber with constant permittivity is presented in polar and elliptical coordinates. Expressions for guided mode power flows via the cross sections of circular and elliptical multilayer optical fibers are obtained.

Selective excitation of whispering gallery modes in a novel bottle microresonator

Selective excitation of spheroidal whispering gallery modes and bottle modes in a robust bottle microresonator fabricated straightforwardly from a short section of optical fiber is demonstrated. Characteristic resonance spectra of long-cavity bottle modes were obtained by using a tapered fiber to excite evanescently bottle microresonator at different points along its axis. Compared to bare-fiber cylindrical resonators, the bottle microresonator results in a 35x increase of the observed Q factor.