A high-strain optical fiber sensor system has been developed to provide a cost-effective solution for measurement of very large strain. The measurement of large strain in the order of a few tens of % strain (up to 40 % strain) in geotextile materials has been achieved using an extrinsic plastic optical fiber sensor (POF). Based on this design, the sensor is not limited to operating within the elastic region of the plastic fiber proposed by other workers in the field. The present design allows for compression strains to be measured even after exceeding strain levels of 5% (typical plastic strain values of POFs based on fiber stretching.) The POF were initially calibrated using a linear variable displacement transducer and the results based on tensile tests of a series of geotextile fabrics have shown to compare well with other reference measurements.