This work shows a developed wearable elongation sensor based on an optical fiber. The presented approach to sew a fiber optic into a lycra textile enables the modulation of light amplitude in respect to textile strain. This apparatus in combination with small-size instrumentation enables the development of a wearable textile garment capable of monitoring and acquiring strain data, and send it wirelessly to a base station. The light amplitude increases with the increment of textile strain. The output voltage remains stable over time for the resting and maximum textile strain position.