Head for an evanescent-wave fibre-optic sensor

Head (500, 900) for a sensor (100) comprising two sections of optical fibre (11, 12) for propagating infrared light at at least one infrared wavelength and generating evanescent waves to the outside in order to detect infrared signatures of an external medium, said head (500, 900) comprising:

• an optical fibre forming a curved part (15) intended to connect the two sections of fibre (11, 12) and to come into contact with the external medium in order to detect the infrared signatures interfering with the propagation of the evanescent waves propagating along the fibre, and
• means (504, 506) intended to protect the curved part (15) against external mechanical stresses, while guaranteeing a contact area (30) between the external medium and said curved part (15),
• wherein said means (504, 506) intended to protect the curved part (15) comprise a first plate (504) and a second plate (506) parallel to said first plate (504) and comprising a stud (502) with an axis which is perpendicular to said second plate (506), said first plate (504) comprising a flow conduit (508) intended to allow a flow of a liquid external medium between the plates (504, 506),
• wherein said curved part (15) is placed between said first plate (504) and said second plate (506),
• wherein said curved part (15) of the fibre comprises a turn wound around the stud (502), wherein each plate (504, 506) has two protrusions, each being designed to come opposite a protrusion on the other plate (506, 504), and in that one end of the curved part (15) is housed between each pair of protrusions.