Abdosllam M. Abobaker

Design of dispersion-managed fiber systems for transmitting chirp-free Gaussian pulses

We present a general method to analytically design a dispersion-managed (DM) fiber system for any desired fiber (dispersion, nonlinearity and losses) and pulse (width and energy) parameters. This analytical design allows one to transmit chirp-free Gaussian pulses (for very long distances) in almost all kinds of DM fiber systems that have appeared so far in the literature, including systems with dispersion map length greater, equal or shorter with respect to the amplification period.

Large dispersion and high nonlinearity in silicon nanowire embedded photonic crystal fiber

We design a photonic silicon nanowire embedded microstructured optical fiber which is a special class of waveguide whose core diameter is of subwavelength or nanometer size with the air holes in the cladding. We study the optical waveguiding properties, namely, waveguide dispersions and effective nonlinearity by varying the core diameter. The results reveal that the air-clad silicon subwavelength nanowire exhibits several interesting properties such as a large normal dispersion (82385 ps2/km) for 300 nm core diameter and a large anomalous dispersion (-6817.3 ps2/km) for 500 nm core diameter at 1.95 μm wavelength. The structure provides a large nonlinearity (3648 1/Wm) at 0.450 μm wavelength for 300 nm core diameter. These enhanced optical properties might find suitable for various nonlinear applications that include the generation of few cycle pulses, supercontinuum generation and optical processing.

Dynamics of 850 nm optical pulses upon compression in a tapered photonic crystal fiber

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).

Generation of Few-Cycle Laser Pulses Using A Photonic Quasi-crystal Fiber

We explore the optical properties of a proposed solid-core photonic quasi-crystal fiber (SC-PQF) of 10-fold for the wavelengths from 300 to 1100 nm. The proposed SC-PQF exhibits a admissible low dispersion of −8.6481 ps2/km, a third order dispersion of 0.00415 ps3/km and a large nonlinearity of 1684 W−1 km−1 at 450 nm, which turn out to be the desired optical properties for generating the few-cycle laser pulses. By exploiting these optical properties, we numerically demonstrate the generation of few-cycle laser pulses at 450 nm wavelength by means of higher-order soliton effect compression.

Designing a 10-fold photonic quasi-crystal fiber for enhancing the efficiency of second harmonic generation

We design a 10-fold photonic quasi-crystal fiber (PQF) for analyzing the efficiency of second harmonic generation (SHG). In this study we emphasize on lowering two factors, namely, overlap area and wave-vector mismatch which determine the efficiency of SHG. We find a trade off variation between these two factors with increment in pitch. Finally we optimize the relative efficiency of SHG as 84.87 %W-1cm-2 for a 10-fold PQF, which is 35% higher than that of earlier reported relative efficiency of 6-fold PQF (62.96% W-1cm-2).

Six-fold photonic quasicrystal fiber for generating few cycle laser pulses

A solid core photonic quasi-crystal fiber (PQF) is a novel microstructured optical fiber which could provide a large nonlinearity and a low dispersion, which, in turn, could be exploited for generating few cycle laser pulses. We look for the hitherto mentioned optical properties in the proposed PQF by carefully changing the geometrical parameters, namely, core diameter and the pitch. We report a large nonlinearity (γ = 588.2993 W-1 m-1) and a low dispersion (≈ 0.095 ps/nm.m) for operating wavelengths from 1200 to 2000 nm.

Efficient pulse compression in photonic crystal fibre at 850 nm

We theoretically investigate the generation of linearly chirped solitary pulse in photonic crystal fiber (PCF) to obtain very short pulses than adiabatic compression, wherein the effective dispersion decreases but the nonlinearity increases exponentially, by using the self-similar analysis. The dispersion and nonlinearity varying nonlinear Schrödinger (NLS) equation aptly models the pulse propagation in such PCF. Based on the analytical results, we propose the efficient pulse compressor which generates chirp and pedestal free ultrashort pulses at 850 nm in newly designed photonic crystal fiber (PCF) structures. In addition, we apply the projection operator method to derive the pulse parameter equations which indeed very clearly explain the behavior of the adiabatic and self-similar compressed pulses in different parts of the PCF structures. The analytical results exactly match with the results obtained by the projection operator method. Further, we also adopt the split-step Fourier algorithm to investigate the pulse compression process in PCF and we find that the results obtained from direct numerical experiments also exactly match with those of analytical and semi-analytical results. The main advantage of the proposed pulse compressor based on self-similar technique is that the compression factor can be increased enormously when compared to the adiabatic compression.

Generation and dispersion compensation techniques for 10 Gb/s radio-over-long haul fiber span

Multi-gigabits per second millimetre-waves (MMW) have found wide application in a variety of areas. There is always demand for not only discovering costly effective ways of generation, but also carrying high bit rate signals, up to 10 Gb/s, as long as possible. In this paper, developments for generation and dispersion compensation techniques for transmission of optical MMW signals are presented. Optically generated MMW that modulated with 10 Gb/s, could not travel safely through a fibre span up to 60 Km. Applying analytical design for dispersion compensation, it is possible to transmit optical MMW signals through fibre span for several tens of kilometres.

Dispersion-managed optical fiber systems with zero Hamiltonian

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.