Two-mode Optical Fiber Research Articles

Novel resonant multi-soliton solutions of time fractional coupled nonlinear Schrödinger equation in optical fiber via an analytical method

The aim of this article is to investigate the time fractional coupled nonlinear Schrödinger equation (TFCNLSE) which can be used to describe the interaction among the modes in nonlinear optics and Bose–Einstein condensation. The TFCNLS equation plays a crucial role in soliton wavelength division multiplexing and pulse propagation through a two-mode optical fiber. For the sake of getting different analytical solutions, we capitalize modified version of the extended tanh-expansion method. Fractional nonlinear partial differential equations (FNLPDEs) have become popular because they can explain complex physical phenomena and have dynamic structures of localized wave solutions. The study obtained various soliton solutions including bright, dark, periodic, and singular solitons. The results are presented in graphical form with appropriate parameter values to aid visualization. Such solutions are critical for explaining some mesmerizing and complex physical phenomena. In addition, some results from earlier studies are generalized which justify the novelty of the current study. This study proves that the computational method used is efficient, brief, and widely applicable in finding analytical solutions to diverse complex nonlinear problems arising in the recent era of nonlinear optics, applied sciences and engineering.

Propagation of optical pulses in fiber optics modelled by coupled space-time fractional dynamical system

This article focuses on securing distinct optical solitons to optical fiber with the coupled nonlinear Schrödinger equation. The examined equation is analyzed with the aid of conformable space–time fractional and is known to have a significant role in the propagation of pulses through a two-mode optical fiber and the soliton wavelength division multiplexing. The fractional nonlinear partial differential equations have garnered increased interest since they may be utilized to explain a wide range of complicated physical phenomena and have more dynamic structures of localized wave solutions. New extended direct algebraic method, a relatively recent integration tool, is used to obtain the solutions. The diverse pulses as bright, dark, combo, and singular soliton solutions have been extracted. In addition to aiding in the clarification of fractional nonlinear partial differential equations, the employed method provides previously extracted solutions and extracts new exact solutions. Given the correct parameter values, numerous graph forms are sketched to provide information on the visual presentation of the obtained findings. The achieved solutions are to be attractive to researchers for understanding the complexity of the considered model. The findings of this research validate the effectiveness of the proposed method for increasing nonlinear dynamical behavior. It is anticipated that, the research will be of interest to all engineers who work with engineering models. Results demonstrate the efficacy, simplicity, and generalizability of the selected computational method.

M-truncated optical solitons to a nonlinear Schrödinger equation describing the pulse propagation through a two-mode optical fiber

M-truncated optical solitons to a nonlinear Schrödinger equation describing the pulse propagation through a two-mode optical fiber

Characteristics of higher-order vector rogue waves to a coupled fourth-order nonlinear Schrödinger system in a two-mode optical fiber

Optical fiber communication serves a significant role in recent communication. Investigated in the work is a coupled fourth-order nonlinear Schrodinger system for the ultrashort optical pulses in a two-mode optical fiber. For the complex envelopes of two field polarization components, we work out the Darboux transformation and higher-order vector rogue-wave solutions. The second-order vector rogue waves with the triangle structure, each component of which is composed of three four-petaled rogue waves, are shown. With the strength of the higher-order linear and nonlinear effects increasing, width of the triangle structure along the distance axis decreases, while width of the triangle structure along the time axis increases. We obtain the second-order vector rogue waves with the merged structure and the third-order vector rogue waves with the triangle and pentagon structures. We expect that our results could be helpful in studying the rogue-wave phenomena in the nonlinear optics.

Simultaneous Measurement of Humidity and Temperature with Cytop-reduced Graphene Oxide-overlaid Two-mode Optical Fiber Sensor

A polymer-overlaid two-mode microfiber knot resonator (TMM-KR) was designed to measure relative humidity (RH) and temperature simultaneously in a living condition. The device is composed of two main optical features: two-mode microfiber (TMM, slow-varying term) and two-mode knot resonator (TMKR, fast-varying term). After fabricating a TMM by non-adiabatically tapering a conventional single mode fiber (SMF), we designed C-rGO-overlaid TMM as a polymer-overlaid optical sensor to evaluate the response and recovery times. The effective group refractive index between fundamental and cladding modes, HE11 and HE12, respectively, of the TMM-KR reduced to nearly zero by optimizing the waist diameter of the optical microfiber, and the sensitivities of the proposed sensor remarkably enhanced to 0.603 nm/%, and -0.79 nm/oC, for RH and temperature, respectively. Our calculated and experimental results demonstrated that the proposed micro-structure of the C-rGO-overlaid TMM-KR will provide optical properties that can be applied for practical use of environment sensing.

On-line Writing of Fiber Bragg Grating Array on a Two-mode Optical Fiber for Sensing Applications.

On-line fabricated fiber Bragg grating (FBG) array and its sensing potentials have attracted plenty of attention in recent years. In this paper, FBG arrays are written on-line on a two-mode fiber, and this two-mode fiber Bragg grating (TM-FBG) is further experimentally investigated for temperature and curvature sensing. The responses of this sensor were characterized by 11.2 pm/°C and −0.21 dB/m−1 for temperature and curvature, respectively. Based on the measurements, a dual-parameter fiber sensing system was developed, which can realize the quasi-distributed, simultaneous detection of temperature and curvature, making it suitable for structural health monitoring or perimeter security.

Study of fabrication reproducibility of two-mode optical fibers for mode division multiplexing with MIMO processing.

We propose a two-mode optical fiber (TMF) with a low sensitivity of differential modal group delay (DMD) to change of the core radius and the refractive index of the core in the index profile which are major factors for DMD deviation. This was done to achieve high reproducibility of fiber fabrication. The proposed TMF has a graded index (GI) core and a depressed inner cladding, and we optimize structural parameters. We fabricated different kinds of TMFs to confirm the low DMD sensitivity of our proposed fiber. The fabricated TMF showed that the DMD sensitivity to changes in core radius of the TMF was approximately 8 ps/km/μm which is 98% smaller than that of a GI-TMF without a depressed inner cladding.

Effects of intermode nonlinearity and intramode nonlinearity on modulation instability in randomly birefringent two-mode optical fibers

We analyze in detail the effects of the intermode nonlinearity (IEMN) and intramode nonlinearity (IRMN) on modulation instability (MI) in randomly birefringent two-mode optical fibers (RB-TMFs). In the anomalous dispersion regime, the MI gain enhances significantly as the IEMN and IRMN coefficients increases. In the normal dispersion regime, MI can be generated without the differential mode group delay (DMGD) effect, as long as the IEMN coefficient between two distinct modes is above a critical value, or the IRMN coefficient inside a mode is below a critical value. This critical IEMN (IRMN) coefficient depends strongly on the given IRMN (IEMN) coefficient and DMGD for a given nonlinear RB-TMF structure, and is independent on the input total power, the power ratio distribution and the group velocity dispersion (GVD) ratio between the two modes. On the other hand, in contrast to the MI band arising from the pure effect of DMGD in the normal dispersion regime, where MI vanishes after a critical total power, the generated MI band under the combined effects of IEMN and IRMN without DMGD exists for any total power and enhances with the total power. The MI analysis is verified numerically by launching perturbed continuous waves (CWs) with wave propagation method.

Geometric phase due to orbit–orbit interaction: rotating LP11 modes in a two-mode fiber

Accumulation of geometric phase due to non-coplanar propagation of higher-order modes in an optical fiber is experimentally demonstrated. Vertically-polarized LP11 fiber mode, excited in a horizontally-held, torsion-free, step-index, two-mode optical fiber, rotates due to asymmetry in the propagating k-vectors, arising due to off-centered beam location at the fiber input. Perceiving the process as due to rotation of the fiber about the off-axis launch position, the orbital Berry phase accumulation upon scanning the launch position in a closed-loop around the fiber axis manifests as rotational Doppler effect, a consequence of orbit–orbit interaction. The anticipated phase accumulation as a function of the input launch position, observed through interferometry is connected to the mode rotation angle, quantified using the autocorrelation method.

Multiwavelength Brillouin fibre laser in two-mode fiber

In this paper, a multiwavelength two-mode Brillouin fibre laser generated by two-mode optical fibre (TMOF) is proposed and demonstrated experimentally. The system comprises a 500 m long TMOF. A tunable laser source amplified by a high power erbium doped fibre amplifier acts as the Brillouin pump (BP) followed by a single mode fibre Bragg grating as a reflector in the cavity with a centre wavelength of 1544 nm. The BP is observed in the superposition of and modes in the few-mode fibre. The set-up is capable of generating a maximum of 12 clearly defined Stokes lines at the pump power of 28.6 dBm, spanning from 1543.88 to 1544.92 nm.

Simulation of a long-haul fiber optic link with a two-mode optical fiber

Modern telecommunication networks approach the capacity crunch, which is associated with the so-called nonlinear Shannon limit. So, the passage to fiber optic links with few-mode optical fibers is considered as an alternative solution of the described problem concerned with high nonlinearity of conventional commercial single-mode optical fibers. Presently, various designs of few-mode optical fibers have been known, with the recently published works presenting experimental results demonstrating their potentialities for long-haul fiber optic links. A lot of models of long-haul fiber optic links with few-mode optical fibers have been developed based on which features of a few-mode optical fiber transport network were numerically simulated. This work presents the results of simulation of a 6000-km long-haul fiber optic link with a two-mode optical fiber and 100-km-per-span Erbium doped fiber optic amplifiers system under 100 Gbps DP-DQPSK data transmission. We studied the use of particular linearly polarized modes and optical vortices for signal transmission. The computation results were compared with the simulation of the same fiber optic link with a single-mode optical fiber under the identical conditions.

Modulation instabilities in randomly birefringent two-mode optical fibers**Project supported by the Natural Science Foundation of Jiangsu Provincial Universities (Grant No. 14KJB140009), the National Natural Science Foundation of China (Grant No. 11447113), and the Startup Foundation for Introducing Talent of NUIST (Grant No. 2241131301064).

Modulation instabilities in the randomly birefringent two-mode optical fibers (RB-TMFs) are analyzed in detail by accounting the effects of the differential mode group delay (DMGD) and group velocity dispersion (GVD) ratio between the two modes, both of which are absent in the randomly birefringent single-mode optical fibers (RB-SMFs). New MI characteristics are found in both normal and anomalous dispersion regimes. For the normal dispersion, without DMGD, no MI exists. With DMGD, a completely new MI band is generated as long as the total power is smaller than a critical total power value, named by Pcr, which increases significantly with the increment of DMGD, and reduces dramatically as GVD ratio and power ratio between the two modes increases. For the anomalous dispersion, there is one MI band without DMGD. In the presence of DMGD, the MI gain is reduced generally. On the other hand, there also exists a critical total power (Pcr), which increases (decreases) distinctly with the increment of DMGD (GVD ratio of the two modes) but varies complicatedly with the power ratio between the two modes. Two MI bands are present for total power smaller than Pcr, and the dominant band can be switched between the low and high frequency bands by adjusting the power ratio between the two modes. The MI analysis in this paper is verified by numerical simulation.

Demonstration of Bidirectional PON Based on Mode Division Multiplexing

Recently, mode division multiplexing (MDM) has been introduced into optical transmission systems and networks for capacity enhancement. In this letter, we propose a bidirectional passive optical network (PON) architecture based on MDM. The bidirectional optical distribution network of the MDM-PON consists of few-mode fiber, passive mode multiplexer/demultiplexer, and few-mode circulators, all of which are characterized by low modal-crosstalk. Signals in different modes are able to be transmitted and received independently for both downstream and upstream transmission. We experimentally demonstrate the bidirectional MDM-PON transmission over 10-km two-mode optical fiber. The 10-Gb/s ON–OFF-keying signals can be independently transmitted and directly detected without coherent receiver and multiple-input multiple-output processing. Moreover, nonlinear transmission impairments are experimentally investigated.

Accurate mode characterization of two-mode optical fibers by in-fiber acousto-optics.

Acousto-optic interaction in optical fibers is exploited for the accurate and broadband characterization of two-mode optical fibers. Coupling between LP01 and LP1m modes is produced in a broadband wavelength range. Difference in effective indices, group indices, and chromatic dispersions between the guided modes, are obtained from experimental measurements. Additionally, we show that the technique is suitable to investigate the fine modes structure of LP modes, and some other intriguing features related with modes' cut-off.

Transition, coexistence, and interaction of vector localized waves arising from higher-order effects

We study vector localized waves on continuous wave background with higher-order effects in a two-mode optical fiber. The striking properties of transition, coexistence, and interaction of these localized waves arising from higher-order effects are revealed in combination with corresponding modulation instability (MI) characteristics. It shows that these vector localized wave properties have no analogues in the case without higher-order effects. Specifically, compared to the scalar case, an intriguing transition between bright–dark rogue waves and w-shaped–anti-w-shaped solitons, which occurs as a result of the attenuation of MI growth rate to vanishing in the zero-frequency perturbation region, is exhibited with the relative background frequency. In particular, our results show that the w-shaped–anti-w-shaped solitons can coexist with breathers, coinciding with the MI analysis where the coexistence condition is a mixture of a modulation stability and MI region. It is interesting that their interaction is inelastic and describes a fusion process. In addition, we demonstrate an annihilation phenomenon for the interaction of two w-shaped solitons which is identified essentially as an inelastic collision in this system.

Phenomenological model of stochastic, spatiotemporal, intensity dynamics of stimulated Brillouin scattering in a two-mode optical fiber.

We present a simple numerical model that is used in conjunction with a systematic algorithm for parameter optimization to understand the three-dimensional stochastic intensity dynamics of stimulated Brillouin scattering in a two-mode optical fiber. The primary factors driving the complex dynamics appear to be thermal density fluctuations, transverse pump fluctuations, and asymmetric transverse mode fractions over the beam cross-section.

Two mode optical fibers with low and flattened differential modal delay suitable for WDM-MIMO combined system

We propose two mode optical fibers (TMFs) with minimally low differential modal delay (DMD) slope which are suitable for wavelength division multiplexing and multiple input multiple output (MIMO) combined transmission system. We designed and fabricated three different kinds of TMF, nearly zero-DMD (zTMF), positive-DMD (pTMF) and negative-DMD (nTMF) with a graded index core and a depressed inner cladding. We confirmed that the fabricated zTMF has DMD of below 15 ps/km in the C band and the fabricated pTMF and nTMF have the same degree of effective areas. We also confirmed that a DMD compensation line with a length of 100 km composed of pTMF and nTMF can successfully achieve the best properties of low DMD in the C + L band and low mode conversion.

Stochastic, spatiotemporal intensity dynamics of stimulated Brillouin scattering in a two-mode optical fiber

We report stochastic, spatiotemporal dynamics in stimulated Brillouin scattering from single-mode pump pulses propagating through a fiber that supports LP01 and LP11 modes. Comparison with experiments in single-mode fiber indicates that independent scattering from different modes plays a key role. We also investigate the role of transverse pump fluctuations in driving the observed spatiotemporal intensity dynamics in the scattered beam.

Optimized graded index two-mode optical fiber with low DMD, large A_eff and low bending loss

An optimized two-mode optical fiber (TMF) with the graded index (GI) profile is designed and fabricated. We clarify an appropriate region of GI-TMF satisfying DMD = 0 ps/km, the large effective area A(eff), and the low bending loss for LP(11) at 1550 nm. According to our fiber design, GI-TMF is successfully fabricated to have the large effective area A(eff) of 150 μm(2) for LP(01) mode, and low DMD below 36 ps/km including zero in the C-band. We expect that our design GI-TMF is suitable for MDM and can reduce MIMO-DSP complexity.

All-optical Brillouin dynamic grating generation in few-mode optical fiber

We report, for the first time (to our knowledge), generation of Brillouin dynamic gratings (BDGs) in few-mode optical fibers. A moving acoustic grating is generated by stimulated Brillouin scattering using a writing beam in one fiber mode, which is used to reflect a reading beam at a different wavelength in another fiber mode. With single-end pumping, a BDG with a tunable reflectance of up to 0.1% is demonstrated in a 15km specially designed two-mode optical fiber.