Direct observation of soliton and normal pulse propagation by spectral domain reflectometry.

We report what are to our knowledge the first continuous observations of optical fiber solitons and nonsoliton pulses in the spectral domain. Using a novel optical time-resolved spectral ref lectometer that measures the backscattered light spectrum, we directly observed (with 200-m spatial resolution) the propagation of ~8.5-ps solitons and nonsolitons traveling down 5-km fibers. Spectral breathing and the recovery of the original spectral widths are clearly seen for higher-order solitons. Possible applications include in situ measurements of soliton parameters, fiber dispersions, and nonlinearities, experimental verifications of pulse propagation theories, and optical sensing.

High-power erbium-doped fiber laser mode locked by a semiconductor saturable absorber.

Using an erbium-doped fiber laser (EDFL) passively mode locked by a semiconductor saturable absorber, we generate 5.5-ps pulses of a 2.3-nJ/pulse, which are more than three times higher in energy than for other reported EDFL's. We show that, by introduction of a linear loss element within the cavity, multiple pulsing behavior at high pump powers can be suppressed. We also determine the saturable-absorber characteristics-absorbance versus wavelength near band gap-that are necessary to produce short mode-locked pulses.

Collision-induced pulse shortening in a mode-locked linear-cavity NaCl color-center laser with an InGaAs/InP multiple-quantum-well saturable absorber.

We report collision-induced reduction of pulse widths in a linear-cavity passively mode-locked NaCl color-center laser. Colliding-pulse operation reduced the pulse widths from 800 to 430 fs. Pulses collided in the InGaAs/InP multiple-quantum-well saturable absorber if the round-trip time from the absorber to the output coupler was less than 1.3 ns, which implies carrier recombination times of that order. Measurements of the gain experienced by two successive pulses indicated partial saturation of the NaCl gain medium.

Soliton fusion and steering by the simultaneous launch of two different-color solitons.

Two optical solitons with different center frequencies simultaneously launched into an optical fiber are considered. By numerical simulation and by experiment, it is shown that if their frequency separation is small, they will either merge into a single pulse (fusion) or form two pulses with different velocities (steering), depending on their phase difference. With a 400-m fiber and ~2.5-ps solitons at 1457.7 and 1460.7 nm, fusion and steering of as much as 7 ps are demonstrated.

Soliton-collision interferometer for the quantum nondemolition measurement of photon number: numerical results.

Using analytic theory and numerical experiments, we show that a quantum nondemolition measurement of the photon number of optical solitons in a single-mode optical fiber can be made. We describe the soliton-collision interferometer with which we propose to make this measurement and discuss simulations of the performance of this interferometer.

Femotosecond switching in a dual-core-fiber nonlinear coupler.

We report all-optical switching of 100-fsec pulses in a fused-quartz dual-core-fiber directional coupler. The length of the device is 0.5 cm, and the switching power is 32 kW. Pulses are routed to either of two separate fiber guides, depending on the input power. Measurements of pulse reshaping by the nonlinear coupler provide compelling evidence of the device's ability to response on a femotosecond time scale.