Nick Doran

Experimental demonstration of optical soliton switching in an all-fiber nonlinear Sagnac interferometer

We demonstrate, for the first time to our knowledge, the switching of optical solitons. We observe switching of 93% of the total reflected energy in a partially transmitting integrated fiber loop mirror that makes up the interferometer. This result demonstrates the potential of solitons as the natural bits in ultrafast optical processing.

Average soliton dynamics and the operation of soliton systems with lumped amplifiers

It is shown that the dynamics of optical pulse propagation in lumped amplified systems is described by the lossless nonlinear Schrodinger equation under the condition that the amplifier spacing is short compared to the nonlinear evolution length scale. The errors involved in this description are quantified and are on the order of the square of the amplifier spacing. The authors also consider an alternative method of pulse preemphasis which has been proposed, and they show how it relates to the average soliton method presented.<<ETX>>

Energy-scaling characteristics of solitons in strongly dispersion-managed fibers.

We present an empirical scaling law that models the increased energy required for launching a soliton into an optical system with sections of both normal and anomalous dispersion fiber. It is shown that the inclusion of periodic attenuation and amplification can be handled as separate problems, provided that the interval between optical amplifiers is substantially different from the period of the dispersion map. These concepts are illustrated by reference to an example system comprising dispersion-shifted fiber combined with anomalous standard fiber.

Polarization instabilities for solitons in birefringent fibers

We examine the propagation of solitons in the two linearly polarized modes of a birefringent fiber. The behavior of single solitons is similar to that of continuous waves, and the nonlinear effects make the fast mode unstable when the beat length between the modes is long. Even with the instability, nondispersive pulses can still propagate. Highorder solitons break up and can transfer most of the energy into a single, highly compressed soliton.

UV-written in-fibre Bragg gratings

The techniques for fabrication and the properties of periodic and aperiodic fibre Bragg gratings produced by UV exposure in photosensitive optical fibres are reviwwed with an emphasis on applications.

Two-wavelength operation of the nonlinear fiber loop mirror

We describe the two-wavelength operation of the nonlinear fiber loop mirror. In this mode of operation a high-power signal at one wavelength switches a low-power signal at another wavelength. This device is investigated both theoretically and experimentally. The experimental results show that the nonlinear loop mirror performs as an optical modulator that consists of all-fiber components.

Soliton transmission using periodic dispersion compensation

We examine the behavior of solitons in optical fibers where the dispersion is alternated between the normal and anomalous regimes. The periodic nature of the system strongly modifies the shape of the stable soliton (solitary wave) pulses, and increases their energy when compared with solitons in equivalent uniform fibers. Power enhancement factors of up to 70 are numerically observed. This leads to both an increased signal-to-noise ratio (SNR) at the receiver and reduced Gordon-Haus timing jitter. The interaction between pairs of isolated pulses is examined. We also examine implementations including periodic amplification, and show that the energy scalings introduced by the amplification and the dispersion management are independent provided that the periods of the two processes are dissimilar. We show that there is an optimum dispersion compensation ratio which minimizes the received Gordon-Haus jitter. A diagrammatic technique is presented for estimating the performance of dispersion compensated soliton transmission systems.

Pulse shaping, compression, and pedestal suppression employing a nonlinear-optical loop mirror.

We study the shaping of picosecond-duration optical pulses by the intensity-dependent transmission characteristics of a fiber loop mirror in the normally dispersive region. Experimental results for sech(2) intensity input profiles are in good agreement with the theoretical predictions. In addition, input pulses with substantial background radiation emerge both compressed and pedestal free.

Power dependence of dispersion-managed solitons for anomalous, zero, and normal path-average dispersion.

We determine the power dependence of dispersion-managed solitons on map strength and average dispersion, using a combination of numerical simulations and the variational approach. In particular, we investigate the behavior near zero dispersion and identify the region of existence of dispersion-managed solitons in the average normal-dispersion regime.

Compensating for dispersion and the nonlinear Kerr effect without phase conjugation.

We propose the use of a dispersive medium with a negative nonlinear refractive-index coefficient as a way to compensate for the dispersion and the nonlinear effects resulting from pulse propagation in an optical fiber. The undoing of pulse interaction might allow for increased bit rates.