“…Note that the use of FBGs as selective reflectors permits one to assemble FL cavity in a robust all-fiber geometry; they also may modify the laser operation mode after a correspondent fiber treatment related, for instance, to the novel materials based on the nonlinear electromagnetically induced transparency [36,37]. Also note that the term "effective" length of a FBG placed inside a short Fabry-Pérot laser cavity, introduced in our earlier works [38,39], defines the factual length of the laser cavity and, consequently, the real optical frequencies of longitudinal modes established in it.…”