A fiber optic gyroscope comprising: at least one optical device (100, 130), the optical device (100, 130) comprising at least one of a recirculator or an integrated optics chip; a fiber optic coil (83, 140) comprising a hollow core optical fiber with first and second ends; at least one coupling device for connecting one of the ends of said hollow core optical fiber to said at least one optical device (100, 130), characterised in that: the coupling device comprises a sleeve, a ferrule and a glass plate, said sleeve having a first end and a second end and both said sleeve and ferrule including a hollowed out cavity, the hollow core optical fiber being positioned within the ferrule with said one of the ends of the hollow core optical fiber extending from an end of the ferrule, wherein the end of the ferrule is attached to the first end of the sleeve and one side of the glass plate is attached to the second end of the sleeve so that said one of the ends of the hollow core optical fiber is rigidly held within the cavity of the sleeve at a position having a predefined distance from the side of the glass plate, wherein the hollow core fiber is configured to be glued or sealed in the ferrule in such a manner that the glue or sealant will not wick, whereby the cavity within the sleeve becomes a sealed cavity. at least one optical device (100, 130), the optical device (100, 130) comprising at least one of a recirculator or an integrated optics chip; a fiber optic coil (83, 140) comprising a hollow core optical fiber with first and second ends; at least one coupling device for connecting one of the ends of said hollow core optical fiber to said at least one optical device (100, 130), characterised in that: the coupling device comprises a sleeve, a ferrule and a glass plate, said sleeve having a first end and a second end and both said sleeve and ferrule including a hollowed out cavity, the hollow core optical fiber being positioned within the ferrule with said one of the ends of the hollow core optical fiber extending from an end of the ferrule, wherein the end of the ferrule is attached to the first end of the sleeve and one side of the glass plate is attached to the second end of the sleeve so that said one of the ends of the hollow core optical fiber is rigidly held within the cavity of the sleeve at a position having a predefined distance from the side of the glass plate, wherein the hollow core fiber is configured to be glued or sealed in the ferrule in such a manner that the glue or sealant will not wick, whereby the cavity within the sleeve becomes a sealed cavity. the coupling device comprises a sleeve, a ferrule and a glass plate, said sleeve having a first end and a second end and both said sleeve and ferrule including a hollowed out cavity, the hollow core optical fiber being positioned within the ferrule with said one of the ends of the hollow core optical fiber extending from an end of the ferrule, wherein the end of the ferrule is attached to the first end of the sleeve and one side of the glass plate is attached to the second end of the sleeve so that said one of the ends of the hollow core optical fiber is rigidly held within the cavity of the sleeve at a position having a predefined distance from the side of the glass plate, wherein the hollow core fiber is configured to be glued or sealed in the ferrule in such a manner that the glue or sealant will not wick, whereby the cavity within the sleeve becomes a sealed cavity.