An optical device having liquid-core optical fiber, comprising: - at least one first connecting device comprising: a sleeve of tubular structure through which a channel comprising a plurality of superposed and communicating ducts passes, a first duct being formed from one end of the sleeve and being arranged to receive hermetically at the corresponding end of the sleeve one end of the optical fiber, and a second duct being formed communicating with the first duct; closing means hermetically closing the end of the second duct which is opposite the end communicating with the first duct, wherein the sleeve furthermore contains a third duct intended for filling the interior volume of the second duct when the latter is closed at one end by the closing device and the fiber is inserted into the first duct, the third duct connecting transversely the exterior of the sleeve to the interior of the second duct; and a hermetic closing cap for hermetically closing the orifice of the third duct opening onto the exterior of the sleeve; - said optical fiber having a liquid core and a first end inserted into the first connecting device, wherein said optical device is characterized in that the interior volume of the second duct of the first connecting device comprises the liquid and a gas bubble of a maximal size such that it remains approximately spherical under the action of surface tension during the orientation shifts of the sleeve and such that it cannot cover the end of the sleeve, and in that the third duct of the first connecting device is hermetically closed by the closing cap. - at least one first connecting device comprising: a sleeve of tubular structure through which a channel comprising a plurality of superposed and communicating ducts passes, a first duct being formed from one end of the sleeve and being arranged to receive hermetically at the corresponding end of the sleeve one end of the optical fiber, and a second duct being formed communicating with the first duct; closing means hermetically closing the end of the second duct which is opposite the end communicating with the first duct, wherein the sleeve furthermore contains a third duct intended for filling the interior volume of the second duct when the latter is closed at one end by the closing device and the fiber is inserted into the first duct, the third duct connecting transversely the exterior of the sleeve to the interior of the second duct; and a hermetic closing cap for hermetically closing the orifice of the third duct opening onto the exterior of the sleeve; a sleeve of tubular structure through which a channel comprising a plurality of superposed and communicating ducts passes, a first duct being formed from one end of the sleeve and being arranged to receive hermetically at the corresponding end of the sleeve one end of the optical fiber, and a second duct being formed communicating with the first duct; closing means hermetically closing the end of the second duct which is opposite the end communicating with the first duct, wherein the sleeve furthermore contains a third duct intended for filling the interior volume of the second duct when the latter is closed at one end by the closing device and the fiber is inserted into the first duct, the third duct connecting transversely the exterior of the sleeve to the interior of the second duct; and a hermetic closing cap for hermetically closing the orifice of the third duct opening onto the exterior of the sleeve; - said optical fiber having a liquid core and a first end inserted into the first connecting device,