FIELD: fiber optics. SUBSTANCE: filter based on fiber-optical diffraction gratings with large periods includes core carrying fiber-optical diffraction gratings with large periods formed on it, each being formed with preset period, shell surrounding core, coat covering part of shell without fiber-optical diffraction gratings with large periods, second coat covering part of shell having fiber-optical diffraction gratings with large periods. Refractive index of core provides for displacement of coupled length of wave towards short lengths of waves with rise of temperature in correspondence with amount of impurity added into core. Refractive index of second coat diminishes with rise of temperature and coupled length of wave displaces towards long waves. Core develops negative displacement of coupled length of wave by value of positive displacement of coupled length of wave in material of second coat whose refractive index diminishes with rise of temperature. EFFECT: provision for temperature stability of parameters of filter, enhanced resistance of filter to increased humidity. 4 cl, 19 dwg
