FIELD: fiber optics, design of fiber-optical gyroscopes and fiber transducers of physical quantities such as pressure pickups, temperature-sensitive elements, magnetic field sensors, etc. SUBSTANCE: process of manufacture of radiation input-output device in ring interferometer of fiber-optical gyroscope consists in formation of biconical constriction on twin light guide produced by polishing of two workstocks for single-mode light guides with large linear birefringence, in cutting of lateral grooves in polished surfaces, in alignment of these workstocks with their flat surfaces and in drawing of twin light guide from produced workstock. Prior to polishing workstocks are placed inside and then fused together with bearing quartz tube on which internal surface there is deposited layer of quartz glass with refractive index less by (2-4)10-3 than refractive index of pure quartz glass and thickness ensuring 
, where Dsh is diameter of sheath formed by layer of quartz glass with reduced refractive index; Dw is diameter of starting workstock. After drawing of twin light guide section on which biconical constriction is formed is placed in advance into etching solution to etch away external layer of twin light guide made of pure quartz glass. Later formed biconical constriction is covered with protective-reinforcing optical coat. EFFECT: reduced size and mass characteristics of radiation input-output device, raised zero stability of ring interferometer. 3 cl, 14 dwg
