Nowdays, polymers like hydrogels that respond to well defined stimuli, have a particular interest in fields like optoelectronics, biotechnology, materials, etc. One of this polymers is the NIPAAM, that posses thermo optics properties. This work is oriented to the design and implementation of a temperature sensor using fiber optics and having as sensitive part a sintetized hydrogel of polyNIPAAM and MeOXA of reversible thermosensible characteristics. For this setup we use a glass ampoule which is coupled to two pieces of plastic, inside the ampoule it is placed the hydrogel. The working principle relies in the turbidity changes in a well known temperature called critical. We present the experimental results of the designed and implemented device.