The historical beginnings of photosensitivity and fiber Bragg grating (FBG) technology are recounted. The basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described. The many applications of fiber grating technology are tabulated, and some selected applications are briefly described.

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Fiber Bragg grating technology fundamentals and overview

In this paper, we summarize the fundamental properties and review the latest developments in high power fiber lasers. The review is focused primarily on the most common fiber laser configurations and the associated cladding pumping issues. Special attention is placed on pump combination techniques and the parameters that affect the brightness enhancement observed in single-mode and multimode high power fiber lasers. The review includes the major limitations imposed by fiber nonlinearities and other parasitic effects, such as optical damage, transverse modal instabilities and photodarkening. Finally, the paper summarizes the power evolution in continuous-wave and pulsed ytterbium-doped fiber lasers and their impact on industrial applications.

High Power Fiber Lasers: A Review

Random distributed feedback fibre lasers

Room temperature multifrequency erbium-doped fiber (EDF) lasers anchored on the ITU frequency grid and using frequency periodic filters are presented. The multifrequency operation is demonstrated both theoretically and experimentally by adding a frequency shifter in the ring cavity to prevent steady-state laser operation and single-frequency oscillation.

Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid

Fiber lasers have seen progressive developments in terms of spectral coverage and linewidth, output power, pulse energy, and ultrashort pulse width since the first demonstration of a glass fiber laser in 1964. Their applications have extended into a variety of fields accordingly. In this paper, the milestones of glass fiber laser development are briefly reviewed and recent advances of high-power continuous wave, Q-switched, mode-locked, and single-frequency fiber lasers in the 1, 1.5, 2, and 3 μm regions and their applications in such areas as industry, medicine, research, defense, and security are addressed in detail.

Fiber lasers and their applications [Invited]

We have successfully demonstrated a single-frequency distributed-feedback (DFB) thulium-doped silica fiber laser emitting at a wavelength of 1735 nm. The laser cavity is less than 5 cm long and is formed by intracore UV-written Bragg gratings with a phase shift. The laser is pumped at 790 nm from a Ti:sapphire laser and has a threshold pump power of 59 mW. The laser has a maximum output power of 1 mW in a single-frequency, single-polarization radiation mode and is tunable over a few nanometers. To the best of the authors’ knowledge, this is the first report of a single-frequency DFB fiber laser that uses thulium as the amplifying medium. The lasing wavelength is the longest demonstrated with DFB fiber lasers and yet is among the shortest obtained for thulium-doped silica fiber lasers.

Single-frequency thulium-doped distributed-feedback fiber laser

Robust singlemode operation is reported of an Er/sup 3+/-doped distributed feedback fibre laser based on a 36 mm long Bragg grating with a permanently induced /spl pi//2 phaseshift. The laser is integrated into a master-oscillator/parametric-amplifier configuration, which yields an output power of 5.4 mW and has a linewidth of 15 kHz.<
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Distributed feedback Er3+-doped fibre laser

Singlemode UV-induced distributed feedback (DFB) fibre lasers with a linewidth of < 15 kHz and a sidemode suppression better than 61 dB are presented. The stability of the lasers is verified by a 10 Gbit/s transmission experiment. Five DFB fibre lasers are cascaded and pumped by a single semiconductor laser, thereby forming a multiwavelength source for WDM systems.

Five wavelength DFB fibre laser source for WDM systems

A numerical model for erbium distributed feedback (DFB) fibre lasers is presented. The model is used to optimise the location of a discrete phase shift to obtain maximum output power. For DFB fibre lasers of up to 10 cm in length it is shown that the influence of Kerr nonlinearity with respect to output power is negligible.

Design of DFB fibre lasers

A cost-effective wavelength selectable light source comprising a distributed feedback (DFB) fibre laser array is proposed. A large number of wavelengths can be selected via optical space switches using only one shared pump laser. The structure is a good candidate for use as a wavelength selectable backup transmitter for wavelength division multiplexed (WDM) systems.

Poul Varming

Papers

Single-frequency thulium-doped distributed-feedback fiber laser

Distributed feedback Er3+-doped fibre laser

Five wavelength DFB fibre laser source for WDM systems

Design of DFB fibre lasers

Cost-effective wavelength selectable light source using DFB fibre laser array