A narrow line distributed feedback (DFB) fiber laser based on a 16 mm long Bragg grating, inscribed in a purpose-made strongly activated and highly photosensitive silica fiber, was fabricated and tested. A fiber preform synthesized by means of surface-plasma chemical vapor deposition (SPCVD), and a standard Bragg grating writing technology using an ArF excimer laser and a $\pi$-shifted phase mask, were applied to fiber drawing and grating writing, respectively. A single-mode generation regime of the DFB laser core-pumped at a wavelength of 976 nm was obtained, the measured linewidth being less than 8 kHz.

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.