Switching Of Optical Pulses Research Articles

Towards Maximum Energy Efficiency of Carrier-Injection-Based Silicon Photonics

We present carrier-injection-based photonic switches, engineered for optical pulse distribution with maximum energy efficiency. We apply small-signal analysis and for the first time large-signal modelling to methodically optimize the switches for minimum energy consumption and to classify the electronic contributions from resistance, capacitance, and diode. We present optimized electronic switch activation, which yields a sixfold reduction in energy consumption and we show how static power consumption becomes a negligible factor for optical pulse switching. We demonstrate that with adjusted phase shifter dimensions, MZI-based switches can operate with additional 50% enhanced energy efficiency with down to 4 pJ per switching operation. We show even further efficiency improvement using ring-based designs, allowing an additional improvement of 50% in energy efficiency and we discuss the trade-off between efficiency and optical bandwidth associated to the Q-factor. We benchmark carrier-injection-based switches together with comparable technologies of the silicon photonics platform and identify carrier-injection to be the most suitable technology for pulse switching applications.

The coupled Hirota system as an example displaying discrete breathers: Rogue waves, modulation instability and varying cross-phase modulations

Discrete dynamical systems constitute an elegant branch of nonlinear science, where ingenious techniques provide penetrating insight for vibrations and wave motion on lattices. In terms of applications, such systems can model oscillators with hard quartic nonlinearities and switching of optical pulses on discrete arrays. A two-component Hirota system is investigated as an extension of the widely studied Ablowitz-Ladik equation by including discrete third order dispersion. Breathers (periodic pulsating modes) are derived analytically, and are used to establish conservation laws. Rogue waves (unexpectedly large displacements from equilibrium configurations) exhibit unusual features in undergoing oscillations above and below the mean level, and may even reverse polarity. Coupling produces new regimes of modulation instabilities for discrete evolution equations. The robustness of these novel rogue waves, in terms of sensitivity to initial conditions, is elucidated by numerical simulations. Self-phase modulations and cross-phase modulations of the same or opposite signs will generate nonlinear corrections of the frequency, due to the intensity of the wave train itself and the one in the accompanying waveguide respectively. Such effects have a crucial influence on the evolution of discrete and continuous multi-component dynamical systems.

All-Optical Steering of Light Through Nonlinear Twin-Core Photonic Crystal Fiber Coupler at 850 nm

We intent to investigate the dynamics and steering characteristics of an optical pulse propagation through photonic crystal fiber coupler (PCFC) using the projection operator method (POM) at 850 nm. For the proposed study, we begin with the analysis of silica PCFC design. From the proposed design, we examine the propagation of Gaussian pulse through PCFC, by means of coupled nonlinear Schrodinger equations. By employing POM, we derive the equations of motion describing the dynamics of the pulse parameters, called collective variables (CVs), namely the amplitude, pulse width, phase and chirp. The corresponding results obtained through POM are compared and verified numerically by split step Fourier method (SSFM). Furthermore, we propose a novel chloroform filled PCF structure that operates as a single mode at 850 nm, featuring an enhanced dispersion and nonlinearity for efficient switching, thus enabling to accomplish switching at a low input pulse power and low loss over shorter distances. Efficient optical pulse switching through both the designs are demonstrated through the simulation of the transmission curve. From the transmission curve, we infer that efficient switching can be achieved at relatively low input power in the proposed chloroform filled PCF.

Nonlinear switching of optical pulses in fiber bragg gratings

We study numerically the nonlinear switching characteristics of optical pulses transmitted though fiber Bragg gratings. We consider both the uniform and phase-shifted gratings and compare their performance as a nonlinear switch. The nonlinear coupled-mode equations were solved numerically to obtain the pulse-switching characteristics. The steady-state behavior known to occur for continuous-wave optical beams is realized only for pulses wider than 10 ns with long tails. For pulsewidths in the range 0.1-1 ns, the use of phase-shifted gratings reduces the switching threshold, but the on-off contrast is generally better for uniform gratings. We also quantify the effects of rise and fall times associated with an optical pulse on nonlinear switching by considering the Gaussian pulses with smooth tails and nearly rectangular pulses with sharp leading and trailing edges.

Short Optical Pulse Switching in Three-core Nonlinear Fiber Couplers

The propagation and switching of short optical pulses in a three-core nonlinear fiber coupler have been investigated with a variation method within the framework of the Lagrangian density formulation.The analytical solutions were directly obtained from the coupled nonlinear Schr?dinger equations.It is shown that the soliton switching behavior predicted by the present analytical method agrees well with the results from numerical analysis.In addition,the coupling length and the switching threshold of solitons in a nonlinear coupler were obtained.

Dispersion-imbalanced nonlinear optical loop mirrorwith lumped dispersive elements

Self switching of optical pulses by a dispersion-imbalanced nonlinear optical fibre loop mirror is analysed. The loop mirror consists of an anomalous-dispersion fibre and a lumped dispersive element, such as a chirped fibre grating, which is required to brake the symmetry of the loop for self-switching operation. It is shown that a higher switching contrast and a smaller switching power can be achieved compared with those for a standard nonlinear optical loop mirror.

Experimental demonstration of a Raman effect–based optical transistor

We demonstrate optical pulse switching and amplification based on simultaneous Raman and Kerr effects in a fiber-loop mirror. Stimulated Raman scattering is shown to play a dominant role in the transfer function of the loop with highly germania-doped fibers, in agreement with theoretical predictions. Optical switching of a 100-ps signal pulse with an amplification factor of 10 was demonstrated in a 20-mol.% GeO(2)-doped fiber.

Nonlinear switching of optical pulses through stimulated Raman scattering: self-scattering of solitons in optical fibers

We propose a new method for nonlinear switching of optical solitons in a Sagnac interferometer. In contrast to the traditional switching of pulses, by means of a nonlinear phase shift due to the Kerr effect, we propose to use the nonlinear frequency shift of optical solitons as a mechanism for switching via stimulated Raman scattering. The switching energy can be substantially reduced as a result.

Ultrafast all optical switching in two wavelength amplifying nonlinear optical loop mirror

An ultrafast optical switch is described based on optical pulse switching in a nonlinear loop mirror incorporating an erbium doped fibre amplifier. Semiconductor laser diodes are used throughout, emphasising the practical applicability of this device. A 10 bit/s pulse stream comprising 20 ps pulses is modulated by a −7.4dBm, 10 Gbit/s NRZ optical data stream.

Demonstration of optical switching by means of solitary wave collisions in a fiber ring reflector

We have demonstrated the use of solitary wave collisions in optical pulse switching. Our apparatus consisted of a fiber ring with 11 sections of polarization-maintaining fiber, with successive sections fusion spliced with the axes rotated 90 deg. The configuration yielded enhanced transmission (autocorrelation contrast ratio 2.82:1), in agreement with expectation for this number of sections and the unoptimized fiber coupler that was used. Design criteria for complete switching are presented.

Very low threshold Sagnac switch incorporating an erbium doped fibre amplifier

Fast, very low threshold optical pulse switching, in a nonlinear loop mirror incorporating an erbium doped fibre amplifier (EDFA) operating at 1.536 μm with a gain of 46 dB is reported. For a 336 m Sagnac loop, the input switching power is 200 μW, which is 5×103 lower than the best previously reported.