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ABSTRACT: We consider the optical pulse propagation in a tapered photonic crystal fiber (PCF) wherein dispersion as well as nonlinearity varies along the propagation direction. The generalized nonlinear Schrödinger equation aptly models the pulse propagation in such a PCF. The design of the tapered PCF is based on the analytical results which demand that the dispersion decrease exponentially and the nonlinearity increase exponentially. By employing the self-similar scaling analysis, we have already proposed the efficient pulse compression scheme with the chirped soliton. In order to get more insight into the dynamics of the pulses (the variations in the amplitude, pulse width and chirp) while being compressed, we adopt the generalized projection operator method (POM) which, in turn, helps arrive at two different sets of pulse parameter equations of Lagrangian variation method (LVM) and collective variable method (CVM).
Electronics, Communications and Photonics Conference (SIECPC), 2011 Saudi International; 05/2011
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ABSTRACT: Nearly pedestal-free optical pulse compression using self-similar chirped optical solitons near the photonic bandgap (PBG) structure of nonlinear fiber Bragg gratings (NFBGs) with exponentially decreasing dispersion is investigated using the gen-eralized nonlinear coupled-mode equations (NLCMEs). The full dispersion characteristics and the effect of PBG are included. We find that the ratio of the frequency detune of the pulse's center frequency from the Bragg frequency of the NFBG to coupling coefficient of the NFBG is an important design parameter of the NFBG optical pulse compressor. We carried out a comprehensive study on the effect of the ratio of frequency detune to coupling coefficient, grating length, initial chirp, initial dispersion, and initial pulsewidth on the self-similar optical pulse compression. We also studied the compression of both the hyperbolic secant and Gaussian-shaped pulses and the effect of variation in the initial pulsewidth on the optical pulse compression. Index Terms—Compression, fiber Bragg grating (FBG), non-linear coupled-mode equations (NLCMEs), self-similar.
01/2011; 29(1).
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ABSTRACT: By using appropriate self-similar scaling analysis, we delineate the generation of linearly chirped solitary pulses in photonic crystal fiber (PCF) at 850 nm to obtain the short pulses with large compression factor and minimal pedestal energy when compared to adiabatic compression scheme. The dispersion and nonlinearity varying nonlinear Schrödinger equation aptly models the pulse propagation in such a PCF. The analytical results demand that the effective dispersion must decrease exponentially while the nonlinearity must increase exponentially in the PCF. Thus, based on the analytical results, we propose the new design of tapered PCF by varying the pitch and diameter of the air hole. We adopt the projection operator method to derive the pulse parameter equations which indeed very clearly describe the self-similar pulse compression process at different parts of the PCF structures. As we are interested in constructing compact compressor, we also introduce another designing of PCF by filling chloroform in the core region. The chloroform filled tapered PCF exhibits low dispersion length for efficient pulse compression with low input pulse energy over small propagation distances.
IEEE Journal of Quantum Electronics 01/2011; · 1.88 Impact Factor
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ABSTRACT: We examine the effectiveness of using nonlinear optical loop mirrors (NOLMs) to reduce the intersymbol interference in dispersion-managed (DM) fiber communication systems compensated by chirped fiber gratings (CFGs) with group delay ripples (GDR). We show that the use of NOLMs can enhance the transmission performance by more than one order of magnitude in the presence of amplifier noise and random variations in the parameters of the GDR in CFGs. We found that transoceanic transmissions can be achieved when NOLMs are included in the DM optical fiber transmission line compensated by CFGs with GDR whose parameters vary randomly along the transmission line.
Journal of Lightwave Technology 01/2009; · 2.78 Impact Factor
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ABSTRACT: We examine the effects of stimulated Raman scattering on ultra-short pulses propagating in optical fiber systems. In particular
we demonstrate that the existing theories for the Raman-induced soliton self-frequency shift give consistent results only
in a restricted domain of pulse width which excludes important practical applications to high-speed soliton transmission systems.
We present a general theory for the soliton self-frequency shift (SSFS), which applies to any pulse whose spectral bandwidth
lies within the third-order telecommunication window. We show that the disastrous impact of the SSFS in high-speed long-distance
transmission lines can be suppressed by use of filters whose central frequency is appropriately up shifted with respect to
the transmission frequency.
10/2008: pages 207-225;
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ABSTRACT: We demonstrate almost chirp-fee and pedestal-free optical pulse compression in nonlinear fiber Bragg gratings with exponentially decreasing dispersion. The exponential profile is well approximated by a number of gratings with constant dispersion.
Opto-Electronics and Communications Conference, 2008 and the 2008 Australian Conference on Optical Fibre Technology. OECC/ACOFT 2008. Joint conference of the; 08/2008
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ABSTRACT: We examine the propagation of ultra-short optical light pulses in dispersion-managed birefringent fiber transmission systems, in which the pulse dynamics is governed by the coupled higher-order nonlinear Schrödinger equations with higher-order linear and nonlinear optical effects. We derive the equations of motion in terms of pulse parameters such as amplitude, temporal position, width, chirp, frequency and phase, using a projection operator method, and we obtain the spatial dynamical behavior of picosecond and femtosecond pulse parameters. From our detailed analysis, we show that the stimulated Raman scattering has a strong impact on the pulse dynamics.
Journal of Optics A Pure and Applied Optics 06/2008; 10(8):085102. · 1.92 Impact Factor
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ABSTRACT: The dynamics of nonlinear pulse propagation in optical fibers is governed by the famous nonlinear Schrodinger equation (NLSE), in which the group-velocity dispersion and self-phase modulation form a basic set of optical processes describing a broad range of realistic physical situations. In this work, by means of variational formalism for the NLSE, we derive exact analytical expressions for the variational equations corresponding to the amplitude, width and chirp of the pulse in terms of initial pulse parameters, fiber parameters and the distance of propagation of the pulse; under the condition when the Hamiltonian of the system is zero. Then, for Gaussian and hyperbolic secant ansatz, we check the validity of the obtained analytical results to describe pulse propagation in optical fiber. As a practical application of our results, we consider the design of the DM fiber systems and we derive an analytical expression for the Gordon-Haus jitter.
Computer and Communication Engineering, 2008. ICCCE 2008. International Conference on; 06/2008
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ABSTRACT: We construct two families of exact periodic solutions to the standard model of fiber Bragg grating (FBG) with Kerr nonlinearity. The solutions are named "sn" and "cn" waves, according to the elliptic functions used in their analytical representation. The sn wave exists only inside the FBG's spectral bandgap, while waves of the cn type may only exist at negative frequencies (omega<0), both inside and outside the bandgap. In the long-wave limit, the sn and cn families recover, respectively, the ordinary gap solitons, and (unstable) antidark and dark solitons. Stability of the periodic solutions is checked by direct numerical simulations and, in the case of the sn family, also through the calculation of instability growth rates for small perturbations. Although, rigorously speaking, all periodic solutions are unstable, a subfamily of practically stable sn waves, with a sufficiently large spatial period and omega>0, is identified. However, the sn waves with omega<0, as well as all cn solutions, are strongly unstable.
Physical Review E 02/2008; 77(2 Pt 2):026602. · 2.26 Impact Factor
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ABSTRACT: Using Lang's equation for the dynamics of injection locking of a laser diode, we show that the hysteresis property of the excess carrier density has direct influence on the mode-shift characteristics, which makes the shift of the slave laser mode to be different from the frequency detune of the external master laser signal within the locking range of the slave laser. The theoretical prediction is experimentally confirmed by the measurement of the mode-shift of an injection locked Fabry-Perot laser diode.
Journal of Nonlinear Optical Physics & Materials 01/2008; 19(17):15-22. · 0.38 Impact Factor
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ABSTRACT: By means of the variational formalism for the nonlinear Schrödinger equation, we find an explicit relation for the power of a pulse in terms of its duration, chirp and fiber parameters (group-velocity dispersion and self-phase modulation parameters). Then, using that relation, we derive the explicit analytical expressions for the variational equations corresponding to the amplitude, width, and chirp of the pulse. The derivation of the analytical expressions for the variational equations is possible for the condition when the Hamiltonian of the system is zero. Finally, for Gaussian and hyperbolic secant ansatz, we show good agreement between the results obtained from the analytical expressions and the direct numerical simulation of the nonlinear Schrödinger equation.
Physical Review E 09/2007; 76(2 Pt 2):026603. · 2.26 Impact Factor
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ABSTRACT: In standard optical fibers with constant chromatic dispersion, modulational instability (MI) sidebands execute undesirable frequency shifts due to fiber losses. By means of a technique based on average-dispersion-decreasing dispersion-managed fibers, we achieve both complete suppression of the sideband frequency shifts and fine control of the MI frequencies, without any compromise in the MI power gain.
Optics Letters 06/2007; 32(10):1287-9. · 3.40 Impact Factor
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ABSTRACT: We present the compression of chirped Bragg solitary pulses near photonic band gap of nonlinear fiber Bragg gratings with exponentially decreasing dispersion. Compression factor of the proposed scheme is two times larger than adiabatic compression.
Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007. OFC/NFOEC 2007. Conference on; 04/2007
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ABSTRACT: We carefully analyse the feasibility of N × 160 Gbit s−1 ultra-long haul transmissions in densely dispersion-managed (DDM) fibre systems. By using a novel analytical approach, we design highly optimized configurations of DDM fibre systems. Transmission performances of the analytically designed DDM fibre systems are evaluated using numerical simulations. We show that single-channel transoceanic transmissions at 160 Gbit s−1 may be achievable in DDM fibre systems, whereas multi-channel transmissions result in dramatically poor performances.
Journal of Modern Optics 12/2005; 52(18):2731-2742. · 1.17 Impact Factor
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ABSTRACT: We address the problem of optical light pulses, called dressed pulses, which do not match the stationary pulse profile of a dispersion-managed (DM) fiber system and we theoretically analyze the associated radiation. Comparing hyperbolic-secant, raised-cosine, and Gaussian pulse envelopes, we show that the general radiation figure is highly sensitive to the input pulse profile. As common general features for these pulse profiles, we find a rich variety of dynamical states that includes weak-, moderate-, and strong-radiation states, depending on the map strength of the DM fiber system. We demonstrate the existence of two intervals of map strengths where the emitted radiation is of considerably low level. The first interval falls in a region of small map strengths where pulses are weakly dressed. In contrast, the second window of low radiation appears in the map strength region corresponding to strongly dressed pulses. As a major difference with respect to the pulse profile, we find that light pulses with Gaussian input profile produce less radiation in the fiber system than hyperbolic-secant or raised-cosine pulses can do. In particular, at the lower edge of the second window of low radiation, Gaussian light pulses with large initial dressing acquire the best ability to execute a stable nonradiative propagation over transoceanic distances.
Physical Review E 10/2005; 72(3 Pt 2):036613. · 2.26 Impact Factor
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ABSTRACT: We show that nonlinear optical loop mirrors can dramatically suppress the side peaks induced by the group delay ripples in chirped fiber gratings compensated dispersion-managed systems and significantly improve the system performance.
Quantum Electronics and Laser Science Conference, 2005. QELS '05; 06/2005
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ABSTRACT: We address the problem of group delay ripples in chirped fibre gratings on dispersion compensation in optical transmission systems. We show that the intersymbol interference, which is a highly harmful effect induced by the group delay ripples in transmission systems, can be substantially reduced by the use of nonlinear optical loop mirrors. This leads to an improvement of the system performance by more than one order of magnitude when compared with a grating-compensated dispersion-managed system without nonlinear optical loop mirrors. We find similar performances irrespective of whether the structure of group delay ripples is modelled by a sinusoidal function or the grating is modelled by the coupled-mode equations.
Journal of Optics A Pure and Applied Optics 06/2005; 7(7):315. · 1.92 Impact Factor
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ABSTRACT: We study the propagation of Gaussian-shaped pulses in grating-compensated dispersion-managed systems with group delay ripples (GDR). We show that the intersymbol interference caused by the GDR in gratings can be substantially reduced by nonlinear optical loop mirrors and the 40-Gb/s system performance can achieve transoceanic transmission in the presence of amplifier noise and random variations in ripple period of the gratings along the transmission line.
IEEE Photonics Technology Letters 06/2005; · 2.19 Impact Factor
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ABSTRACT: We show that the use of nonlinear optical loop mirror can significantly reduce the intersymbol interference induced by group delay ripples in dispersion-managed soliton communication systems compensated by chirped fiber gratings.
Lasers and Electro-Optics, 2003. CLEO/Pacific Rim 2003. The 5th Pacific Rim Conference on; 01/2004
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ABSTRACT: We present a useful method to estimate the soliton energy for a given bit rate in dispersion-managed soliton systems compensated by chirped fiber gratings. The estimates are in good agreement with the numerical results.
Lasers and Electro-Optics, 2003. CLEO/Pacific Rim 2003. The 5th Pacific Rim Conference on; 01/2004
