Abstract:We have realized and studied the fiber laser based on 4-core Yb-doped fiber and multimode Bragg grating as the input reflector. The lasing efficiency slope of 55% was measured. An investigation of the output emission has shown that the far-field pattern constitutes an interference picture. That allows us to conclude that the multimode Bragg grating provides phase locking of 4 lasers utilizing the different active cores. A coherent length of laser is longer than possible difference between optical ways of different active cores.Far-field interference pattern for 2-core lasing

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The properties of optical fibres with an array of fibre Bragg gratings written directly during the fibre drawing are considered. Such optical fibres offer new possibilities for producing new types of active and passive fibre elements due to the enhanced back-reflected signal of the so-called artificial Rayleigh scattering, and are of interest for modelling physical phenomena associated with the statistics of reflecting centres in optical fibres, such as, e.g., localisation of photons. We studied fibres with an array of Bragg gratings written in photosensitive fibres, ordinary single-mode optical fibre of the SMF-28 type and in fibre with a core doped with erbium ions. To control the spectrum width of the reflected signal, we used chirped phase masks, as well as writing arrays of gratings in tapered optical fibres.

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