Solitons are stable localized wave packets that can propagate long distance in dispersive media without changing their shapes. As particle-like nonlinear localized waves, solitons have been investigated in different physical systems. Owing to potential applications in optical communication and optical signal processing systems, optical solitons have attracted intense interest in the past three decades. To experimentally study the formation and dynamics of temporal optical solitons, fiber lasers are considered as a wonderful nonlinear system. During the last decade, several kinds of theoretically predicted solitons were observed experimentally in fiber lasers. In this review, we present a detailed overview of the experimentally verified optical solitons in fiber lasers, including bright solitons, dark solitons, vector solitons, dissipative solitons, dispersion-managed solitons, polarization domain wall solitons, and so on. An outlook for the development on the solitons in fiber lasers is also provided and discussed.

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Recent progress of study on optical solitons in fiber lasers

Manipulation of group-velocity-locked vector solitons (GVLVSs) is numerically proposed and experimentally demonstrated. A pseudo-high-order GVLVS could be generated from a fundamental GVLVS with the help of a polarization-resolved system. Specifically, a pseudo-high-order GVLVS with a two-humped pulse along one polarization and a single-humped pulse along the orthogonal polarization could be obtained. The phase difference between the two humps could be 180°.

Manipulation of Group-Velocity-Locked Vector Solitons From Fiber Lasers

Tunable Metasurfaces Based on Active Materials

Tungsten disulfide (WS2) is a type of anisotropic-layered compound and has broadband saturable absorption features as saturable absorbers (SAs). With WS2-based SAs, dark solitons in erbium-doped fiber (EDF) lasers are first obtained. For the generated dark solitons, the center wavelength is measured to be 1530 nm, and the repetition rate is about 116.5 MHz. A series of optical spectra is exhibited. The electrical signal-to-noise ratio is better than 94 dB. Results in this paper demonstrate that WS2-based SAs are the promising SAs for generating dark solitons in EDF lasers.

Dark solitons in WS 2 erbium-doped fiber lasers

We present a slope-assisted BOTDA system based on the vector stimulated Brillouin scattering (SBS) and frequency-agile technique (FAT) for the wide-strain-range dynamic measurement. A dimensionless coefficient K defined as the ratio of Brillouin phase-shift to gain is employed to demodulate the strain of the fiber, and it is immune to the power fluctuation of pump pulse and has a linear relation of the frequency detuning for the continuous pump and Stokes waves. For a 30ns-square pump pulse, the available frequency span of the K spectrum can reach up to 200MHz, which is larger than fourfold of 48MHz-linewidth of Brillouin gain spectrum. For a single-slope assisted BOTDA, dynamic strain measurement with the maximum strain of 2467.4μe and the vibration frequency components of 10.44Hz and 20.94Hz is obtained. For a multi-slope-assisted BOTDA, dynamic measurement with the strain variation up to 5372.9μe and the vibration frequency components of 5.58Hz and 11.14Hz is achieved by using FAT to extend the strain range.

Slope-assisted BOTDA based on vector SBS and frequency-agile technique for wide-strain-range dynamic measurements

We report numerical simulations on the high-order group-velocity-locked vector soliton (GVLVS) generation based on the fundamental GVLVS. The high-order GVLVS generated is characterized with a two-humped pulse along one polarization and a single-humped pulse along the orthogonal polarization. The phase difference between the two humps could be 180 $^{\circ}$ . It is found that, by appropriately setting the time separation between the two components of the fundamental GVLVS, the high-order GVLVS with different pulsewidth and pulse intensity could be obtained. Either type “1+2” or “2+2” high-order GVLVS could be obtained.

Generation of High-Order Group-Velocity-Locked Vector Solitons

We report results of numerical simulations on the various initial conditions for dark soliton generation in an all-normal-dispersion fiber laser. All the dark solitons generated are odd dark solitons. Differently from the dark soliton generation in fibers, where an arbitrary dip could evolve into a dark soliton, it is found that the dark soliton can originate only from an initial dip with a certain parameter requirement. A bright pulse with either a hyperbolic secant square, Gaussian, or Lorentz profile can be developed into a dark soliton, provided that the parameters of the initial bright pulse are selected. Dark solitons can be generated in fiber lasers only if there is a phase jump, and this phase jump can be maintained and evolve to π during the pulse evolution.

Initial conditions for dark soliton generation in normal-dispersion fiber lasers

We report numerical simulations on the high-order group-velocity-locked vector soliton (GVLVS) generation based on the fundamental GVLVS. The high-order GVLVS generated is characterized with a two-humped pulse along one polarization while a single-humped pulse along the orthogonal polarization. The phase difference between the two humps could be 180 degree. It is found that by appropriate setting the time separation between the two components of the fundamental GVLVS, the high-order GVLVS with different pulse width and pulse intensity could be obtained. 1+2 and 2+2 type high-order GVLVS could be either obtained.

Generation of High-order Group-velocity-locked Vector Solitons

Experimental observations from different fiber lasers or different states within a fiber laser confirm that the fiber dispersion parameter is wavelength-dependent, which suggests that the fiber dispersion measurement based on Kelly sidebands should base on either positive or negative sideband order only rather than sideband orders across zero. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:242–245, 2016

Xinxin Jin

Papers

Manipulation of Group-Velocity-Locked Vector Solitons From Fiber Lasers

Generation of High-Order Group-Velocity-Locked Vector Solitons

Initial conditions for dark soliton generation in normal-dispersion fiber lasers

Generation of High-order Group-velocity-locked Vector Solitons

Revision on fiber dispersion measurement based on Kelly sideband measurement