Abstract: A pressure sensor for connection to a transmission optical fiber which allows the transmission of a light beam. The pressure sensor comprises a material which is essentially elastic to deformation and optically transparent to the wavelengths of light used. The material includes at least two inclusions, each comprising an optical fiber segment. The distance between the inclusions varies when a deformation is exerted on the pressure sensor. This, in turn, modifies the focal length of the optical system defined thereby, and leads to a variation of the light energy collected by a transmissive optical fiber. The pressure sensor is suitable for detectors or measuring devices for medical use, and in this regard, a method for measuring blood or respiratory pressure is also provided.