Carl E. Soccolich

Soliton intensity-dependent polarization rotation

We show experimentally and numerically that intensity-dependent polarization rotation does not lead to pulseshape distortions for fundamental solitons because the soliton rotates as a unit. We demonstrate an optical limiter based on nonlinear polarization rotation in a standard, single-mode fiber followed by a polarizer. The output pulse shape from the limiter resembles that of the input, although the pulse width may be different.

All-optical time-domain chirp switches

We describe a novel architecture for an all-optical time-domain chirp switch in which digital logic is based on timeshift keying. This architecture is a generalization of fiber soliton-dragging logic gates that have a switching energy approaching 1 pJ. By using solitons we separate the nonlinear chirping from the time shifting and, consequently, reduce the required phase shift during the nonlinear interaction. We discuss the scaling laws for energy and latency versus pulse width and show that the chirp switches have low switching energies for high-bit-rate applications.

Cascade of ultrafast soliton-dragging and trapping logic gates

As part of the header decoding circuit for a 100-Gb/s ring local area network, a soliton-dragging NOR gate followed by a soliton-trapping AND gate that can operate up to bit rates of 0.2 THz was demonstrated. The soliton-dragging NOR gate has a time-shift-keyed output, while the soliton-trapping AND gate converts the time shifts to an energy contrast. Even with timing jitter and coupling losses, the measured output energy contrast is approximately 12:1. The experimental results are in good agreement with numerical simulations of the nonlinear Schrodinger equation.<<ETX>>

All-optical timing restoration using a hybrid time-domain chirp switch

We demonstrate a hybrid time-domain chirp switch (TDCS) in which the nonlinear chirper is an AlGaAs waveguide and the soliton dispersive delay line is a polarization-maintaining fiber. The hybrid TDCS can restore timing in a switching or transmission system, and when combined with an optical amplifier, it can act as an ultrafast, all-optical regenerator for soliton pulses. The timing restoration concept is applicable to other non-linear materials with negligible walk-off, and the acceptable time window can be tailored by adjusting the width and intensity of a reference pulse.

Reduction of Bragg Grating-Induced Coupling to Cladding Modes

We discuss fiber designs that have been suggested for the reduction of Bragg-grating-induced coupling to cladding modes. The discussion is based on a theoretical approach that includes the effect of asymmetry in the UV-induced index grating, made by UV-side writing. Experimental results from gratings in a depressed-cladding fiber are compared with simulations. The model gives good agreement with the measured transmission spectrum and accounts for the pronounced coupling to asymmetrical cladding modes, even when the grating is written with smallest possible blaze. The asymmetry causing this is accounted for by the unavoidable attenuation of the UV light. It is found for the considered fiber designs that a high numerical-aperture fiber increases the spectral separation between the Bragg resonance and the onset of cladding-mode losses. A depressed-cladding fiber reduces the coupling strength to the lower order cladding modes, and the UV-sensitive cladding design reduces the cladding-mode coupling loss. The a...

Bragg grating induced cladding mode coupling due to asymmetrical index modulation in depressed cladding fibers

Summary form only given. UV-written Bragg gratings find wide spread use as wavelength selective components. In reflection high extinction ratios are routinely obtained. However, coupling to cladding modes gives excess loss on the short wavelength side of the main reflection. Different fiber-designs have been proposed to reduce this problem. None of these designs seems to give complete solutions. In particular, the otherwise promising depressed cladding design gives a pronounced coupling to one LP/sub 01/ mode, this has been referred to as a Ghost grating. To find the modes of the fiber we have established a numerical mode-solver based on the staircase-approximation method. The Bragg grating causes coupling between the fundamental LP/sub 01/ mode and higher order LP/sub 1p/ modes that satisfy phase-matching. The coupling strength is determined by the overlap integral of the LP/sub 01/, the LP/sub 1p/ mode, and the UV-induced index perturbation. For LP/sub 0n/ the index perturbation is set to one in the core and zero elsewhere. For LP/sub 1n/ it is simplified to the worst case, i.e., opposite sign of the field.