1,720,970 research outputs found
Dataset for Optimisation of Amplitude Limiters for Phase Preservation Based on the Exact Solution to Degenerate Four-Wave Mixing
No full textAdopting an exact solution to four-wave mixing (FWM), wherein harmonic evolution is described by the sum of two Bessel functions, we identify two causes of amplitude to phase noise conversion which impair FWM saturation based amplitude regenerators: self-phase modulation (SPM) and Bessel-order mixing (BOM). By increasing the pump to signal power ratio, we may arbitrarily reduce their impact, realising a phase preserving amplitude regenerator. We demonstrate the technique by applying it to the regeneration of a 10 GBaud QPSK signal, achieving a high level of amplitude squeezing with minimal amplitude to phase noise conversion.
Dataset for Bottrill, Kyle, Hesketh, Graham, Parmigiani, Francesca, Richardson, David and Petropoulos, Periklis (2016) Optimisation of Amplitude Limiters for Phase Preservation Based on the Exact Solution to Degenerate Four-Wave Mixing. Optics Express</span
Nonlinear effects in multimode optical fibers
No full textUtilizing the modes of a multimode fiber forms a frontier between what is achievable with current fibre technology and what is required for the remainder of the 21st century. Large mode area multimode fibers accommodate the high power delivery demanded by fiber lasers used in industry for precision cutting, welding and drilling functions, and used elsewhere for the generation of white light sources used in fiber communication, medical and precision time keeping applications. This thesis explores the theory of nonlinear effects in multimode fibers with the intention of optimizing existing applications, whilst simultaneously identifying new ones.A generalized multimode nonlinear Schrodinger equation is numerically solved to explore the phenomenon of self-focusing in multimode fibers, with peak powers in the megawatt regime. Temporal effects compress femtosecond pulses launched into the fundamental mode, driving peak powers up and coupling power into higher order modes; a process identified with transverse spatial contraction and increased intensity. Parameter regimes in which damage may be avoided are identified. The nonlinear interaction of two modes under continuous wave pumping is solved analytically in terms of elliptic functions.The nonlinear multi frequency dynamics describing the optical regeneration of optical communication signals are researched in a scalar single mode scenario, before nonlinear effects in polarization modes are explored. In the scalar case, a modification to a phase sensitive amplifier from the literature solves the problem of phase to amplitude noise conversion during regeneration. Improved bit error rates in three modulation formats are simulated as a result and experimental collaboration demonstrates proof of principle. Polarization assisted phase sensitive amplification (PAPSA) for signal regeneration is then introduced. Polarization mode benefits include operating power and fiber length reduction, simultaneous regeneration of signal phase and amplitude, and a simple way to decompose the signal into quadrature and in-phase components. An approximate analytic theory of PAPSA is developed. Experimental collaboration demonstrates that PAPSA offers significant signal bit error rate reduction<br/
General complex envelope solutions of coupled-mode optics with quadratic or cubic nonlinearity
No full textThe analytic general solutions for the complex field envelopes are derived using Weierstrass elliptic functions for two- and three-mode systems of differential equations coupled via quadratic chi2 type nonlinearity as well as two-mode systems coupled via cubic chi3 type nonlinearity. For the first time, a compact form of the solutions is given involving simple ratios of Weierstrass sigma functions (or equivalently Jacobi theta functions). A Fourier series is also given. All possible launch states are considered. The models describe sum- and difference-frequency generation, polarization dynamics, parity-time dynamics, and optical processing applications
Reducing bit-error rate with optical phase regeneration in multilevel modulation formats
Full text linkWe investigate theoretically the benefits of using all-optical phase regeneration in a long-haul fiber optic link. We also introduce a design for a device capable of phase regeneration without phase-to-amplitude noise conversion. We simulate numerically the bit-error rate of a wavelength division multiplexed optical communication system over many fiber spans with periodic reamplification and compare the results obtained with and without phase regeneration at half the transmission distance when using the new design or an existing design. Depending on the modulation format, our results suggest that all-optical phase regeneration can reduce the bit-error rate by up to two orders of magnitude and that the amplitude preserving design offers a 50% reduction in bit-error rate relative to existing technology
Minimizing inter-channel cross-phase modulation with optical phase conjugation in asymmetric fibre links
Full text linkUsing analytic and numerical modelling of fibre transmission systems that employ optical phase conjugation (OPC), we show inter-channel cross-phase modulation depends on the integrated square error between nonlinear profiles before and after OPC and that arranging amplifiers and tuning power levels is crucial to minimizing noise. We derive modulation transparent formulas for phase noise and optimal power settings. Examples are shown for 16 and 64 quadrature amplitude modulation
Spatio-temporal self-focusing in femtosecond pulse transmission through multimode optical fibers
Full text linkWe numerically investigate ultra-short pulse propagation in multimode optical fibers with launch peak powers approaching the critical power for self-focusing using a generalized multimode nonlinear Schrödinger equation approach. Nonlinear spatial and temporal effects combined with fiber dispersion govern pulse compression in space and time which can result in damage inducing intensity levels. Here we identify pulse parameters for which damage is avoided and high-power delivery through optical fiber is possible near the fiber zero-dispersion wavelength
Modal decomposition of self-focusing effects in optical fibres
No full textWhen an intense beam with a transverse intensity gradient propagates in a medium with positive Kerr nonlinearity n2, the induced refractive index profile actuates a lens, focusing the beam itself. For input powers above a critical threshold, P > Pcrit, self-focusing can subjugate beam divergence, resulting in catastrophic collapse and material failure [1]. For P < Pcrit diffraction deflects energy from the focal point, and in a fibre, divergence is reflected at the core/cladding boundary instigating a periodic transverse beam profile
Overcoming deleterious effects in FWM-based all-optical signal regenerators
No full textAlthough methods of all-optically regenerating the phase and amplitude of various signal formats have been proposed and demonstrated, their performance is often blighted by some undesirable concomitant distortion of the signal. In this talk, we shall review these undesirable effects and the techniques which have been demonstrated to overcome them
Full quadrature regeneration of QPSK signals using sequential phase sensitive amplification and parametric saturation
No full textWe demonstrate all-optical regeneration of both the phase and the amplitude of a \,GBaud quadrature phase shift keying (QPSK) signal using two nonlinear stages. First we regenerate the phase using a wavelength converting phase sensitive amplifier and then we regenerate the amplitude using a saturated single-pump parametric amplifier, returning the signal to its original wavelength at the same time. We exploit the conjugating nature of the two processing stages to eliminate the intrinsic SPM distortion of the system, further improving performance.</span
Full quadrature regeneration of QPSK signals using sequential phase sensitive amplification and parametric saturation
No full textWe demonstrate all-optical regeneration of both the phase and the amplitude of a 10 GBaud quadrature phase shift keying (QPSK) signal using two nonlinear stages. First we regenerate the phase using a wavelength converting phase sensitive amplifier and then we regenerate the amplitude using a saturated single-pump parametric amplifier, returning the signal to its original wavelength at the same time. We exploit the conjugating nature of the two processing stages to eliminate the intrinsic SPM distortion of the system, further improving performance
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