Timing and phase jitter suppression in coherent soliton transmission.

We have revisited soliton transmission in the new context of coherent optical detection optimizing and comparing digital backward propagation and in-line optical filtering as a means to suppress soliton timing and phase jitter. We find that in-line optical filtering allows one to improve the reach of the soliton system by up to the factor of 2. Our results show that nonlinear propagation can lead to performance beyond the nonlinear Shannon limit.

Nonlinear inverse synthesis and eigenvalue division multiplexing in optical fiber channels.

We scrutinize the concept of integrable nonlinear communication channels, resurrecting and extending the idea of eigenvalue communications in a novel context of nonsoliton coherent optical communications. Using the integrable nonlinear Schrödinger equation as a channel model, we introduce a new approach-the nonlinear inverse synthesis method-for digital signal processing based on encoding the information directly onto the nonlinear signal spectrum. The latter evolves trivially and linearly along the transmission line, thus, providing an effective eigenvalue division multiplexing with no nonlinear channel cross talk.

Random walks and random numbers from supercontinuum generation.

We report a numerical study showing how the random intensity and phase fluctuations across the bandwidth of a broadband optical super-continuum can be interpreted in terms of the random processes of random walks and Lévy flights. We also describe how the intensity fluctuations can be applied to physical random number generation. We conclude that the optical supercontinuum provides a highly versatile means of studying and generating a wide class of random processes at optical wavelengths.

Nonlinear Optics for High-Speed Digital Information Processing.

Recent advances in developing nonlinear optical techniques for processing serial digital information at high speed are reviewed. The field has been transformed by the advent of semiconductor nonlinear devices capable of operation at 100 gigabits per second and higher, well beyond the current speed limits of commercial electronics. These devices are expected to become important in future high-capacity communications networks by allowing digital regeneration and other processing functions to be performed on data signals "on the fly" in the optical domain.

Experimental investigation of resonant enhancement of the acoustic interaction of optical pulses in an optical fiber.

The acoustic interaction of optical pulses in optical fibers is investigated directly by time-resolved pump-probe measurements of the transmission of a fiber Sagnac-loop interferometer. Resonant enhancement of the refractive-index change deltan(ac) induced by the acoustic waves is observed when the repetition frequency of the pulse train is close to a vibrational eigenfrequency of the fiber. For standard fiber deltan(ac) is enhanced by a factor of ~3 at the 465-MHz eigenmode frequency, and this factor increases to ~10 when the polymer jacket is removed from the fiber.

Measurement of the refractive-index modulation generated by electrostriction-induced acoustic waves in optical fibers.

The refractive-index modulation generated in optical fibers by electrostriction-induced acoustic waves is investigated directly by a pump-probe measurement technique in a 1-km-long fiber Sagnac-loop interferometer. Pump pulses propagating unidirectionally around the loop generate transverse acoustic waves that produce a time-dependent relative phase shift for the probe pulses. The consequent interferometer transmission changes are used as a measure of the acoustic interaction.

Suppression of soliton interactions by periodic phase modulation.

We study analytically and numerically the interaction of adjacent solitons under the influence of a phase modulator. Above a critical value, a bifurcation takes place and the interaction-free lengths are considerably increased.

Average soliton dynamics of a high-gain erbium fiber laser.

Soliton propagation in a fiber described by the nonlinear Schrödinger equation in the presence of large periodic energy variations is examined. Stable propagation can be achieved provided that the soliton period is long compared with the period of energy variation and the (associated) average soliton (peak) pulse power equals the fundamental soliton (peak) pulse power. The result is used to interpret recent experiments on mode-locked, high-gain erbium fiber lasers.

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.

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.

Improved mode locking of an F-center laser with a nonlinear nonsoliton external cavity.

We demonstrate that solitons are not essential for the operation of the soliton laser. The external cavity employed contains an optical fiber with negative group-delay dispersion and therefore does not support bright solitons. Thus the improved mode locking cannot be attributed to the injection of an N = 2 soliton.

Trapping of energy into solitary waves in amplified nonlinear dispersive systems.

A number of examples have recently been found in which stable, highly compressed pulses are produced in fibers on much shorter length scales than those present initially. These systems involve energy flow among different nonlinear waves. We present numerical model calculations that exhibit this compression when energy is pumped into the nonlinear wave.

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.

All-fiber pulse compression at 1.32 microm.

We have constructed a pulse compressor using two different optical fibers. By adjusting the waveguide dispersion it has been possible to produce fibers with positive and negative dispersion at 1.32 microm.