The present invention concerns an optical sensor located on a preferred
azimuthal portion of the side of an optical fiber. An optical fiber
having two opposite ends, a core and a cladding and at least one sensing
area is disclosed. Each of the sensing areas is located between the two
opposite ends and each has a longitudinal, a radial and an azimuthal
portion of the fiber that has been removed and replaced by a sensing
material. The sensing collected light is thus representative of a
parameter to be measured, such as temperature. Placing the sensing
material in a lateral side portion of the fiber increases the sensitivity
of the sensor, particularly when it comes to contact temperature
measurement in vivo.