dispersive waves (original) (raw)

Definition: a linearly propagating wave which is split off by a soliton wave under certain conditions

Category: article belongs to category light pulses light pulses

Related: solitonschromatic dispersionKelly sidebands

DOI: 10.61835/0nn Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn

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What are Dispersive Waves?

When a light pulse is launched into a fiber with anomalous chromatic dispersion so that the pulse parameters do not exactly match those of a soliton, the pulse will evolve (within some propagation distance in the fiber) into a soliton pulse and some temporally spreading background. The latter is called a dispersive wave because it is spreading due to the effect of chromatic dispersion, and this is not compensated by the fiber nonlinearity, since the peak power is too low. The closer the parameters of the initial pulse are to the parameters of a soliton, the higher is the percentage of the pulse energy which ends up in the soliton rather than in the dispersive wave.

A dispersive wave can also be formed when the soliton is disturbed in some way, e.g. by a localized loss in the fiber (causing a deviation from the soliton condition by suddenly reducing the pulse energy) or by the transition into a fiber with modified parameters. Similar effects occur for quasi-soliton pulses circulating in the resonator of a mode-locked laser, where dispersion and nonlinearity usually occur in discrete packages rather than smoothly distributed as in a fiber. The circulating soliton is thus subject to periodically occurring disturbances, which couple the soliton to the copropagating dispersive wave. This also happens in a mode-locked fiber laser, even if its laser resonator is made from fibers only, since the pulse energy usually undergoes large changes in each round trip and also because fibers with different dispersion and/or nonlinearity may be used within the resonator. The periodic disturbance of the circulating soliton can result in the formation of Kelly sidebands.

Frequently Asked Questions

What is a dispersive wave in fiber optics?

A dispersive wave is the portion of a light pulse's energy that spreads out temporally due to chromatic dispersion. This occurs when the pulse's peak power is too low for the fiber's nonlinearity to counteract the dispersive broadening.

Under what conditions are dispersive waves formed?

Dispersive waves are formed when an initial pulse does not perfectly match soliton conditions, or when an existing soliton is disturbed. Such disturbances can be a sudden loss or a change in the fiber's properties.

How do dispersive waves relate to mode-locked lasers?

In mode-locked fiber lasers, circulating solitons are periodically disturbed, coupling energy into a dispersive wave. This continuous, periodic process can lead to the formation of spectral sidebands known as Kelly sidebands.

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