Regeneration of fiber Bragg gratings inscribed following the point-by-point method with femtosecond laser radiation

The relevance of studies on the thermal stability of fiber Bragg gratings arises from the prospects of their applications in difficult operating conditions at elevated temperatures. One of the highest-temperature types of such structures formed in silica glass fibers are regenerated Bragg gratings. Generally, the regeneration effect is observed in gratings inscribed in molecular hydrogen-loaded fibers and/or in highly-doped germanosilicate fibers. This paper describes the first reported regeneration of gratings created via point-by-point inscription with femtosecond laser radiation in standard telecommunication fiber Corning SMF-28 without the presence of hydrogen in technological processes. The paper proposes an explanation of the possible mechanism for the formation of such regenerated structures.