Active Optical Fibers Research Articles

Few-cycle dissipative solitons in active nonlinear optical fibres

The propagation of self-induced transparency video pulses is studied in a waveguide containing two-level atoms of two types, which can either amplify or absorb pulses. It is shown that the amplified pulse can be compressed down to the duration comparable with the inverse frequency of the atomic transition (a few femtoseconds) along with the increase in the peak amplitude. The mechanisms restricting the compression of amplified self-induced transparency pulses are analysed (the introduction of the third atomic level and the use of the Bragg grating of the waveguide refractive index).

Active control of long-period fiber-grating-based filters made in erbium-doped optical fibers

Integrating an active medium with a filtering component can bring new functionalities compared with configurations where the two stages (units) are placed in series. We exploit this phenomenon and demonstrate all-optical tunable filters based on long-period fiber gratings written in an active optical fiber. The tuning is obtained via optical pumping at 980 nm.

Dynamics of pulses in optically coupled active optical fibres with different parameters

The dynamics of a wave packet formed by two modes propagating in optically coupled channels with different mode gain increments is studied. It is shown that in the case of a linear intermode coupling, radiation in such structures is decomposed into two autonomous partial pulses with different values of the effective dispersion parameters determining their dynamics. The conditions of the temporal compression and realisation of the superluminal velocity of the envelope maximum for partial pulses and the wave packet as a whole are also investigated.

Active polymer fibres doped with organic dyes: Generation and amplification of coherent radiation

The technology is developed for manufacturing active polymer optical fibres doped with organic dyes. Stimulated emission and amplification in the long-wavelength part of the visible spectrum is studied for rhodamine 11B, phenalemine 512 and substituted DCM pyran in polymer optical fibres. Lasing was observed upon longitudinal and transverse pumping by the second harmonic of a Nd:YAG laser. The gain in polymer fibres was estimated by measuring the intensity ratio of radiation of a master oscillator (dye laser) propagated through the excited (pumped) and unexcited (not pumped) fibre pieces doped with organic dyes. It is shown that the lasing efficiency of rhodamine 11B in a transversely pumped polymer fibre can achieve 36%. The maximum gain (25 dB m-1) is obtained in fibres doped with phenalemine 512.

Nonreciprocal effects in active nonlinear optical fibers with nonlinearity dispersion

The nonreciprocity of the dynamics of Gaussian optical pulses propagating in inhomogeneous nonlinear active optical fibers with nonlinearity dispersion is considered. A substantial nonreciprocity of the time of pulse propagation along the optical fiber in the forward and backward directions is revealed. The possibility of realizing the regime of superluminal propagation of a pulse in one of the directions of the optical fiber is indicated.

Propagation of short pulses in an active nonlinear two-core optical fiber

The switching dynamics of short pulses in an active nonlinear two-core fiber coupler is investigated theoretically. The analysis takes into account the effects of coupling-coefficient dispersion, gain bandwidth, and gain saturation. In particular, we demonstrate that the pulse breakup effect due to coupling-coefficient dispersion can be suppressed by limiting the bandwidth of the linear gain, whether gain saturation is considered or not.

Diffusion of phosphorus doped silica for active optical fibers

The diffusion of phosphorus in P2O5–SiO2 glass has been investigated by annealing of doped layers on the inner surface of quartz glass tubes between 1700°C and 2000°C and measuring radial phosphorus profiles by X-ray microprobe analysis and refractive index profiling, respectively, subsequent to the tube collapse. By comparison with calculated profiles, diffusion coefficients could be determined, which are fitted by an Arrhenius function, where the preexponential D0=10−0.18cm2s−1 is constant but the activation energy decreases with increasing concentration as E=(454–56c0.32)kJmol−1K−1, valid for a concentration range, c, between 0.04 and 10mol% P2O5. The diffusion resembles that earlier determined for aluminium in SiO2 glass, but with smaller diffusivities and activation energies.

Particle size effect on porous Sol–Gel doped cladding U-shaped optical fiber critical micelle concentration (CMC) sensor

In this paper, a sol–gel derived coating U-shaped optical fiber sensors for measurement of critical micelle concentration of surfactants has been studied. The doped sol–gel cladding fiber was used to construct an active cladding U-shaped optical fiber CMC measurement sensor. The porous sol–gel film was deposited a 1000 μm core plastic clad silica fiber after removing the cladding of the fiber at the middle portion nearly 6 cm and bending in U-shaped design. CMC detection is based on an adsorption effect in sample solution of sodium dodecylbenzenesulfonate. Three different types of particles size of sol–gel porous cladding were tested in our lab. Test results show that the sensitivity of the small particle size porous sol–gel cladding U-shaped optical fiber in sensing region is higher than that of large particle size sol–gel cladding based U-shaped.

About the use of entanglement in the optical implementation of quantum information processing

AbstractWe review some applications of entanglement to improve quantum measurements and communication, with the main focus on the optical implementation of quantum information processing. The evolution of continuos variable entangled states in active optical fibers is also analyzed.

Amplified spontaneous emission-based technique for simultaneous measurement of temperature and strain by combining active fiber with fiber gratings

This article reports on an optical fiber-based sensing system for carrying out the simultaneous measurement of temperature and strain. The sensor design is based on the combination of active doped optical fiber and fiber gratings. Erbium/ytterbium co-doped fiber is used to meet the requirements for both high temperature responsivity and small sensor size to address smart structure applications. The temperature dependence of the amplified spontaneous emission power under different pump wavelengths is used as the basis of the sensor and an optical reference to enhance the measurement resolution is discussed. The feasibility of this technique for simultaneous measurement of temperature and strain is demonstrated.

Electrodynamic approach to the estimate of the pumping efficiency of double cladding active optical fibres

A method of increasing the pumping efficiency of active optical fibres doped with Er3+ ions by decreasing the diameter of the inner cladding is analysed. An active optical fibre is described by using the electrodynamic model of a three-layer dielectric waveguide. The dependence of the average pump power flux through the core on the ratio of the radii of the core and the inner cladding is obtained. It is shown that this dependence can also be interpreted as the dependence of the damping constant averaged over all the waves in the core and the cladding.

New stable fluoroindate glasses

Potential applications of fluoride glasses are centered upon passive and active optical fibers. In various cases, phonon energy is a sensitive factor for the efficiency of the optical components. Because of their lower phonon energy, fluoroindate glasses offer some advantages over fluorozirconate glasses. However, the fiber-drawing ability and the resistance against devitrification are higher in InF 3-based glasses. New compositions have been investigated in order to extend IR transmission and enhance thermal stability. Various compositions are reported in the multicomponent system containing In, Ga, Y, Zn, Sr, Ba and Na. A typical composition is 30% InF 3-10% YF 3-25% BaF 2-5% SrF 2-10% NaF-10% ZnF 2-10% GaF 3. This InYBSNZnGa glass has a good stability exemplified by the value of the stability factors: T x− T g=108 K, S=4.1 K. Glass transition temperature, T g=309 °C. Thermal, optical and physical properties of these glasses are reported and the effects of materials purity and processing on these properties are discussed. These glasses corrode less in aqueous solutions than other fluoride glasses.

Nitrate fluorimetric analysis using an active optical fiber

These last past years, nitrate ions have been in vogue pollutants because often incriminated in aquatic pollutions. Very currently used as chemical fertilizers, nitrate can be transformed, when ingested, into carcinogenic nitrosamines in the human body. So it is necessary to monitor the concentrations of these anions, even as traces, particularly in drinking waters or in order to prevent pollution accidents in environmental waters. We recall that the recommanded nitrate concentration by the European Community for drinking water is less than 50 mg NO3 ‐ L ‐1 .

Active and passive chalcogenide glass optical fibers for IR applications: a review

Chalcogenide glass fibers based on sulfide, selenide, telluride and their rare earth doped compositions are being actively investigated worldwide. Great strides have been made in reducing optical losses using improved chemical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite these problems, current single mode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy/spectroscopy, fiber IR sources/lasers, amplifiers and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements in the optical quality of the fibers and the performance of the fibers in existing and future applications.

Piezoelectric coatings for active optical fiber devices

A new class of active fiber devices based on piezoelectric coated optical fibers is currently being developed. The piezoelectric coating is used to produce acoustic waves within the optical fiber and these acoustic waves interfere with optical signals passing through the fiber waveguide. Optical phase modulation devices based on piezoelectric coated fibers have been demonstrated and the behavior of these devices will be reviewed. A second type of active optical fiber device has been fabricated by integrating a piezoelectric fiber coating with an intra-core Bragg grating, which acts as a reflection filter. The primary interest of this work is to produce a piezoelectric fiber optic tunable filter. These types of active all-fiber devices show promise for a variety of applications including telecommunications and sensing networks. The performance of active optical fiber devices that use piezoelectric coatings is dependent on the device structure and the piezoelectric properties of the fiber coating. Several important geometric parameters (e.g. coating thickness and device length) that influence device performance have been experimentally identified. Additionally, several relationships between the fiber coating sputter deposition process, microstructure, and properties have been observed for piezoelectric ZnO fiber coatings. Recent advances in the development of active all-fiber devices are presented.

Stochastisation of optical solitons by the spontaneous luminescence noise in active optical fibres

A theoretical investigation is reported of coherent amplification of solitons in active optical fibres in the presence of the spontaneous luminescence noise. An analysis is made of fluctuations of the soliton parameters and limits on the data transmission rate (bit rate) are identified.

Crystallization in fluoride glasses

Fluoride glasses which are used for passive and active optical fibers are subject to devitrification, especially during fiber-drawing. Kinetic parameters may be obtained through isothermal and nonisothermal methods. Basic relations deriving from the Mehl-Avrami-Johnson approach allow the determination of activation energy E a and Avrami exponent n. The paradox of activation energy is expressed in terms of correlation between E a value and binding energy, which raises the question of the physical meaning of activation energy. Various stability factors are listed and their validity discussed. The important problem of nucleation in fluoride glasses emphasizes the role of anionic oxygen in the nucleation mechanism. The crystallization behavior of the main fluoride glasses, including cadmium fluorochloride glasses, is reported in relation to fiber-drawing ability.

Application of reduced-pressure plasma CVD technology to the fabrication of Er-doped optical fibers

For the first time the reduced-pressure plasma CVD technology was applied to fabrication of active silica optical fibers with all-depressed index structure. Using surface plasma CVD method, fiber preforms with an Er-doped silica core and fluorine doped silica cladding have been prepared and tested. A possibility of high performance active fiber fabrication using the SPCVD has been demonstrated. An influence of fluorine co-doping on luminescence features of Er3+ ions in a silica host has been examined. The erbium concentration-associated clustering effects in pure silica host synthesized by the SPCVD were compared with those in germanosilicate host synthesized by the MCVD.

Optical fibre amplifiers: physical model and design issues

The development of optical fibre amplifiers has caused an impressive evolution in optical telecommunications systems since the end of the 1980s. The widespread application of active fibre amplifiers requires accurate tools to design and simulate these devices in very different operating conditions. The present work describes some physical aspects of active fibre amplifiers and a numerical model for the analysis of active optical fibres that can be applied to investigate spatial and spectral properties of amplifiers for the transmission windows of optical fibre telecommunications. Finally, various design issues relevant to the investigation of optimal fibre design of silica, fluoride erbium-doped and fluoride praseodymium-doped fibres are discussed and illustrated by means of examples.

Fiber-optic fluorescing sensors for nitrate and nitrite detection

Fiber-optic sensors allow remote analyses of chemical substances and they now find many applications in chemistry and biology [1,2]. The purpose of this short report is to give our first results in the development of optical-fiber chemical sensors. Among the numerous known spectrometric methods, we chose the fluorometric one, generally described as a suitable method for determining substances at the parts per million or parts per billion level, with the objective of analyzing nitrate and nitrite anions, using modifications of the fluorescence emission of suitable dyes. The detection of nitrates is based on the irreversible nitration of fluorescein, which leads to a subsequent inhibition of fluorescence emission [3]; determination of nitrites corresponds to their addition on 2,3-diaminonaphthalene, which on the contrary, improves the fluorescence emission [4]. To set up simple instrumentation, we are developing fiber-optic sensors. This consists of (i) realizing an extrinsic active optical fiber by chemical linkage of suitable fluorescent dyes on silica fiber involving silanization reaction (APTES) and chemical methods and (ii) designing an optical device which is appropriate for measurements with optical fibers. The threshold of detection, coating efficiency, and stability with time are presented.