Corrosion of the reinforcement is one of the major deterioration of reinforcedconcrete structures. The cause of corrosion can be either due to carbonation orchloride attack. The product of corrosion increases the reinforcement volume,hence causing cracking of concrete cover. With the advancement in thetelecommunication industry, fiber optic has proven good track record to beresilient and durable to exposure even to extreme environment. The aim of thisresearch is to look at the possibility of using fiber optic sensor to sense theoccurrence of reinforcing steel corrosion. The Y-shape fiber optic bundle sensorwas attached on a steel plate surface for corrosion determination. This corrosionsensor technique work is based on the detection of the colour changes of the steelplate surface from silvery to brown during the corrosion process. From theresearch, it was found that the Y-shape optical fiber corrosion sensor was capableto sense the occurrence of corrosion process in concrete.