Single-frequency, linearly polarised fibre laser with spectrally asymmetric fibre Bragg grating mirrors

A new design of a single-frequency fibre laser at a wavelength of 1.55 μm with linearly polarised output radiation is developed and investigated, in which a uniform Bragg grating written in an SMF-28 fibre is used as one mirror and the other mirror is a grating written in a Panda fibre with a small overlap of reflection spectral bands of mirrors and the possibility of fine tuning of the lasing spectral line. The length of the active part of the laser cavity formed by a fibre doped with the low-concentration Er³⁺ erbium ions is 10 cm. At a pump power of 60 mW and a wavelength of 1.48 μm, the lasing power reaches 100 μW and the width of the spectral line is less than 100 kHz.