Waves In Optical Fibers Research Articles

Solitary waves in optical fibers governed by higher-order dispersion

An exact solitary wave solution is presented for the nonlinear Schrodinger equation governing the propagation of pulses in optical fibers including the effects of second, third and fourth order dispersion. The stability of this soliton-like solution with sech2 shape is proven by the sign-definiteness of the operator and an integral of the Sobolev type. The main criteria governing the existence of such stable localized pulses propagating in optical fibers are also formulated. A unique feature of these soliton-like optical pulses propagating in a fiber with higher order dispersion is that their parameters satisfy efficient scaling relations. The main soliton solution term given by perturbation theory is also presented when absorption or gain is included in the nonlinear Schrodinger equation. We anticipate that this type of stable localized pulses could find practical applications in communications, slow-light devices and ultrafast lasers.

Collision properties of rogue waves in optical fiber

Abstract In this paper, we study the collision properties of rogue waves in optical fiber theoretically. Based on the triplet solution of the nonlinear Schrodinger equation with two parameters, the factors that affect the initial conditions of colliding rogue waves are discussed. Meanwhile, the variation dynamics of peak intensity in collision is studied with each parameter, and the approximate formula of this variation law is derived by drawing an analogy between the collision of rogue waves and that of classical particles, which is consistent with the numerical results. The variation with both two parameters is also discussed, which is found the abnormal behavior of peak intensity in this case. This effect can be potentially used to generate rogue waves with higher peak intensity in optical fiber, which is confirmed by our simulation results.

A FRET-based dual-color evanescent wave optical fiberaptasensor for simultaneous fluorometric determination of aflatoxin M1 and ochratoxin A.

A dual-color fluorescence resonance energy transfer (FRET) based aptasensor is described for simultaneous determination of the mycotoxins aflatoxin M1 (AFM1) and ochratoxin A (OTA). Aptamers against AFM1 and OTA were labeled with two fluorophores with different excitation wavelengths (Cy5.5; 675nm; and Alexa 405; 401nm), respectively. They were used as the signalling probes. A compact dual-color evanescent wave all-fiber detection system with two lasers (635nm; red; and 405nm; purple) was used for the simultaneous collection of two-wavelength fluorescence signals. The hybridization of labeled aptamers with complementary sequences (Q-cDNA) labeled with adarkquencher (BHQ3or dabcyl)causes fluorescence to be strongly reduced because of the fluorescence resonance energy transfer. In the presence of AFM1 and OTA, they bind to their respective aptamer and result in the dissociation of double stranded DNA, which induce fluorescence recovery. Under the optimum conditions, AFM1 and OTA can simultaneously and selectively be determined ranged from 1ng·L-1 to 1mg·L-1. The detection limits of AFM1 and OTA are 21 and 330ng·L-1, respectively (S/N = 3). The FRET-based dual-color detection scheme was applied to the simultaneous detection of AFM1 and OTA in milk with good recovery, precision, and accuracy. Graphical abstract Aptamers against AFM1 and OTA were labeled with two fluorophores with different excitation wavelengths (Cy5.5; 675nm; and Alexa 405; 401nm) and then used assignalling probes. A FRET-based aptasensor is described for simultaneous determination of AFM1 and OTA using dual-color evanescent wave system with two lasers (635nm; red; and 405nm).

Dark and antidark solitons for the defocusing coupled Sasa–Satsuma system by the Darboux transformation

In this article, we construct the N-fold Darboux transformation for the defocusing coupled Sasa–Satsuma system which describes the simultaneous propagation of two nonlinear waves in optical fibers with higher order effects. With the non-zero constant background as a seed, we derive the dark and antidark soliton solutions from the once-iterated formula. We find that this coupled system can exhibit the dark–dark, dark–antidark and antidark–dark vector solitons.

Towards self-diagnosis composites: Detection of moisture diffusion through epoxy by embedded evanescent wave optical fibre sensors

This paper reports on an epoxy matrix for glass fibre reinforced polymers equipped with low cost optical fibre sensors for the early detection of water diffusion, with devised applications in the oil and gas industry. Novel evanescent wave optical fibre sensors were designed, fabricated and embedded in epoxy resin samples. The tips of the optical fibre sensors were coated with a silver layer to work in reflection, so that they could be used as probes. Accelerated diffusion tests were performed: the samples were exposed to simulated sea water at 80 °C for up to 148 h. The water diffusion resulted in a remarkable change of the reflected signal from the sensors, a result that was then confirmed through gravimetric measurements and a theoretical prediction, according to Fick's diffusion law. The results corroborate the feasibility of “sensitive” fibre reinforced polymers in harsh environments and that chemicals diffusion in these materials can be remotely and continuously monitored by means of the presented sensing system.

A Theoretical Model of Dual Tunable Optoelectronic Oscillator

A theoretical model of an electronically tunable multi-loop optoelectronic oscillator (OEO) based on photonic and microwave multiferroic delay lines has been developed. The theory takes into account a dispersion of electromagnetic waves in optical fibers and a dispersion of spin-electromagnetic waves in ferrite-ferroelectric structures. An expression for transfer function of the OEO circuitry was derived. The theory enables one to calculate transmission characteristics and suppression of spurious harmonics of the multi-loop OEOs. The features of both magnetic and electric tunabilities are investigated.

Rogue wave generation by inelastic quasi-soliton collisions in optical fibres

We demonstrate a simple cascade mechanism that drives the formation and emergence of rogue waves in the generalized non-linear Schr\"{o}dinger equation with third-order dispersion. This conceptually novel generation mechanism is based on inelastic collisions of quasi-solitons and is well described by a resonant-like scattering behaviour for the energy transfer in pair-wise quasi-soliton collisions. Our results demonstrate a threshold for rogue wave emergence and the existence of a period of reduced amplitudes - a "calm before the storm" - preceding the arrival of a rogue wave event. Comparing with ultra-long time window simulations of $3.865\times 10^{6}$ps we observe the statistics of rogue waves in optical fibres with an unprecedented level of detail and accuracy, unambiguously establishing the long-ranged character of the rogue wave power-distribution function over seven orders of magnitude.

Cherenkov Radiation Control via Self-accelerating Wave-packets

Cherenkov radiation is a ubiquitous phenomenon in nature. It describes electromagnetic radiation from a charged particle moving in a medium with a uniform velocity larger than the phase velocity of light in the same medium. Such a picture is typically adopted in the investigation of traditional Cherenkov radiation as well as its counterparts in different branches of physics, including nonlinear optics, spintronics and plasmonics. In these cases, the radiation emitted spreads along a “cone”, making it impractical for most applications. Here, we employ a self-accelerating optical pump wave-packet to demonstrate controlled shaping of one type of generalized Cherenkov radiation - dispersive waves in optical fibers. We show that, by tuning the parameters of the wave-packet, the emitted waves can be judiciously compressed and focused at desired locations, paving the way to such control in any physical system.

Spectral broadening of picosecond pulses forming dispersive shock waves in optical fibers.

We investigate analytically, numerically, and experimentally the spectral broadening of pulses that undergo the formation of dispersive shocks, addressing in particular pulses in the range of tens of ps generated via electro-optic modulation of a continuous-wave laser. We give an analytical estimate of the maximal spectral extension and show that super-Gaussian waveforms favor the generation of flat-topped spectra. We also show that the weak residual background of the modulator produces undesired spectral ripples. Spectral measurements confirm our estimates and agree well with numerical integration of the nonlinear Schrödinger equation.

Selective Methanol Gas Detection Using a U‐Bent Optical Fiber Modified with a Silica Nanoparticle Multilayer

SUMMARYThe development of an evanescent wave optical fiber sensor modified with an organic–inorganic hybrid nanoporous thin film for the detection of organic solvent vapors was demonstrated. The optical fiber with a core diameter of 200 μm was bent into U‐shape to enhance the penetration depth of light transferred into the evanescent field, and modified with a multilayered thin film of poly (allylamine hydrochloride) and silica nanoparticles (PAH/SiO2)n, via layer‐by‐layer (LbL) film deposition. The mesoporous film structure led to higher molecular diffusion and the highest selectivity to methanol among the six alcohols and water, which were used as target analytes, by the aid of tetrakis (4‐sulfophenyl) porphine (TSPP) infused inside the film.

Single-shot observation of optical rogue waves in integrable turbulence using time microscopy.

Optical fibres are favourable tabletop laboratories to investigate both coherent and incoherent nonlinear waves. In particular, exact solutions of the one-dimensional nonlinear Schrödinger equation such as fundamental solitons or solitons on finite background can be generated by launching periodic, specifically designed coherent waves in optical fibres. It is an open fundamental question to know whether these coherent structures can emerge from the nonlinear propagation of random waves. However the typical sub-picosecond timescale prevented—up to now—time-resolved observations of the awaited dynamics. Here, we report temporal ‘snapshots' of random light using a specially designed ‘time-microscope'. Ultrafast structures having peak powers much larger than the average optical power are generated from the propagation of partially coherent waves in optical fibre and are recorded with 250 femtoseconds resolution. Our experiment demonstrates the central role played by ‘breather-like' structures such as the Peregrine soliton in the emergence of heavy-tailed statistics in integrable turbulence.

Decoupled polarization dynamics of incoherent waves and bimodal spectral incoherent solitons.

We consider the propagation of strongly incoherent waves in optical fibers in the framework of the vector nonlinear Schrödinger equation (VNLSE) accounting for the Raman effect. On the basis of the wave turbulence theory, we derive a kinetic equation that greatly simplifies the VNLSE and provides deep physical insight into incoherent wave dynamics. When applied to the study of polarization effects, the theory unexpectedly reveals that the linear polarization components of the incoherent wave evolve independently from each other, even in the presence of weak fiber birefringence. When applied to light propagation in bimodal fibers, the theory reveals that the incoherent modal components can be strongly coupled. After a complex transient, the modal components self-organize into a vector spectral incoherent soliton: The two solitons self-trap and propagate with a common velocity in frequency space.

Electromagnetic waves in optical fibres in a magnetic field

A new method is reported of recording the secondary radiation of luminescent substances based on the use of capillary fibres of great length. Theoretical analysis of the dispersion curves of electromagnetic radiation in capillary fibres doped with erbium ions Er3+ has been established. The Lorentz model is used for describing the dispersion properties of electromagnetic waves in a homogeneous medium doped with rare-earth ions. The dispersion dependencies of polariton and axion–polariton waves in erbium nitrate hydrate are determined on the basis of the model of the interaction between electromagnetic waves and the resonance electronic states of erbium ions in the absence and presence of a magnetic field.

Simultaneous measurement on strain and temperature via guided acoustic-wave Brillouin scattering in single mode fibers

During the last decade, fiber sensor has drawn extensive attention due to its flexible, insulating, and readily operating in most measurement environment. But generally, fiber sensor is sensitive to more than one environmental parameter at the same time, so the cross sensitivity limits the application of the sensor. In the present work, a novel design scheme of sensing simultaneously temperature and strain via guided acoustic-wave Brillouin scattering is proposed for resolving the cross sensitivity induced by temperature and strain in single mode fibers. In the guided acoustic-wave Brillouin scattering which occurs due to the interaction between two optical co-propagating waves and the transverse acoustic wave in optical fiber, multi spectrum peaks appear when the frequencies of pump and Stokes are appropriate. Brillouin frequency shift is dependent on elastic property of fiber material such as sound velocity, density, Young's modulus, etc. and these elastic properties are influenced by the surroundings. So Brillouin spectrum changes with temperature and strain. Because different acoustic modes of guided acoustic-wave Brillouin scattering have different sensitivities to temperature and strain, characteristic frequencies of different acoustic modes shift at different levels. Then the influences of temperature and strain on elastic property of fiber material, and the relationship between material properties and characteristic frequency of each acoustic mode can be worked out, therefore the temperature and strain can be calculated by the different influences of temperature and strain on each acoustic mode. The simulation results indicate that the temperature sensitivity of R02 mode is 0.86% lower than that of TR25 in the SMF-28 fiber, but the strain sensitivity of R02mode is 54.1% higher than that of TR25. Temperature sensitivity of R02 is approximately equal to that of TR25, but strain sensitivity of R02 is obviously diferent from that of TR25. So the influences of temperature and strain on Brillouin frequency shift can be effectively distinguished, thereby simultaneous measurements of temperature and strain can be realized by guided acoustic-wave Brillouin scattering.

Fast Numerical Nonlinear Fourier Transforms

The nonlinear Fourier transform, which is also known as the forward scattering transform, decomposes a periodic signal into nonlinearly interacting waves. In contrast to the common Fourier transform, these waves no longer have to be sinusoidal. Physically relevant waveforms are often available for the analysis instead. The details of the transform depend on the waveforms underlying the analysis, which in turn are specified through the implicit assumption that the signal is governed by a certain evolution equation. For example, water waves generated by the Korteweg-de Vries equation can be expressed in terms of cnoidal waves. Light waves in optical fiber governed by the nonlinear Schr\"odinger equation (NSE) are another example. Nonlinear analogs of classic problems such as spectral analysis and filtering arise in many applications, with information transmission in optical fiber, as proposed by Yousefi and Kschischang, being a very recent one. The nonlinear Fourier transform is eminently suited to address them -- at least from a theoretical point of view. Although numerical algorithms are available for computing the transform, a "fast" nonlinear Fourier transform that is similarly effective as the fast Fourier transform is for computing the common Fourier transform has not been available so far. The goal of this paper is to address this problem. Two fast numerical methods for computing the nonlinear Fourier transform with respect to the NSE are presented. The first method achieves a runtime of $O(D^2)$ floating point operations, where $D$ is the number of sample points. The second method applies only to the case where the NSE is defocusing, but it achieves an $O(D\log^2D)$ runtime. Extensions of the results to other evolution equations are discussed as well.

Sol-Gel-Based Titania-Silica Thin Film Overlay for Long Period Fiber Grating-Based Biosensors.

An evanescent wave optical fiber biosensor based on titania-silica-coated long period grating (LPG) is presented. The chemical overlay, which increases the refractive index (RI) sensitivity of the sensor, consists of a sol-gel-based titania-silica thin film, deposited along the sensing portion of the fiber by means of the dip-coating technique. Changing both the sol viscosity and the withdrawal speed during the dip-coating made it possible to adjust the thickness of the film overlay, which is a crucial parameter for the sensor performance. After the functionalization of the fiber surface using a methacrylic acid/methacrylate copolymer, an antibody/antigen (IgG/anti-IgG) assay was carried out to assess the performance of sol-gel based titania-silica-coated LPGs as biosensors. The analyte concentration was determined from the wavelength shift at the end of the binding process and from the initial binding rate. This is the first time that a sol-gel based titania-silica-coated LPG is proposed as an effective and feasible label-free biosensor. The specificity of the sensor was validated by performing the same model assay after spiking anti-IgG into human serum. With this structured LPG, detection limits of the order of tens of micrograms per liter (10(-11) M) are attained.

Unified explanation for rogue waves in optical fibers

Unified explanation for rogue waves in optical fibers

Glass optical fibre sensors for detection of through thickness moisture diffusion in glass reinforced composites under hostile environments

A combination of evanescent wave optical sensors (EWOSs) and fibre Bragg gratings (FBGs) were embedded in an epoxy vinyl ester and an epoxy vinyl ester based glass reinforced polymer (GRP) composite to measure fluid ingress that would result in degradation under hostile conditions. Samples were subjected to accelerated aging in the form of single sided exposure to simulated sea water at 120°C in a pressurised stainless steel vessel. Low cost EWOSs were prepared from a standard multimode glass optical fibre and compared to commercially available FBGs. Both sensors were able to detect the early stage of moisture diffusion into the GRP matrix. The evanescent sensors showed a reduction in the transmitted signal intensity between 1500 and 1650 nm with an increasing exposure time due to a change in the optical properties of the polymer, whereas a peak shift was observed for the FBGs due to the swelling of the resin with the absorption of water. Additionally, the glass optical fibre sensors were embedded in a configuration that allowed the extent of diffusion through the thickness of the GRPs to be monitored, with the fibres in the closest position to the exposure face showing a greater signal change than those positioned further away.

The nonlinear Schrödinger equation and the propagation of weakly nonlinear waves in optical fibers and on the water surface

The dynamics of waves in weakly nonlinear dispersive media can be described by the nonlinear Schrödinger equation (NLSE). An important feature of the equation is that it can be derived in a number of different physical contexts; therefore, analogies between different fields, such as for example fiber optics, water waves, plasma waves and Bose–Einstein condensates, can be established. Here, we investigate the similarities between wave propagation in optical Kerr media and water waves. In particular, we discuss the modulation instability (MI) in both media. In analogy to the water wave problem, we derive for Kerr-media the Benjamin–Feir index, i.e. a nondimensional parameter related to the probability of formation of rogue waves in incoherent wave trains.

Dispersive Wave Emission in Dual Concentric Core Fiber: The Role of Soliton–Soliton Collisions

Soliton-soliton collisions have a crucial role in enhancing the spectrum of dispersive waves in optical fibers and collisions among in-phase solitons lead to a dramatic enhancement of the dispersive wave power, as well as to its significant spectral reshaping. We obtained a simple analytical model to estimate the spectral position, width, and amplitude of the dispersive waves induced by a collision of two in-phase solitons. We tested our theory in the case of a dual concentric core microstructured fiber.