Fiber optic point temperature sensor

An optical sensor for monitoring point temperature in remote and in situ reactions, said sensor comprising:

• a glass capillary tube having a top end closed with a cap and a bulb at a bottom end for holding a liquid having good thermal expansion properties, said capillary tube having an outer and an inner vertical surface, wherein the outer vertical surface is provided with a groove and a hole is provided within the height of the groove;
• a right angled prism formed by a hypotenuse, a base reflective surface and an upright reflective surface being placed in the groove formed so as to locate the reflective surface of the prism close and parallel to the inner surface of the capillary tube,
• a fiber holding plate covering a hypotenuse surface of the right angle prism and provided with two holes for holding fibers, one of which is connected to a light source and one being connected to a photo detector, the fibers connected to the light source and the photo detector are located on the holding plate such that under normal conditions, the light emitted by the light source undergoes total internal reflection (TIR) at the two reflecting surfaces of the prism and is coupled back to the fiber connected to the photo detector and at the desired point temperature, the light emitted by the light source does not undergo TIR and passes through the upright reflecting surface.