Magneto-resistance is the most important characteristic of spintronic materials. This is usually measured using electrical contact probe testing. In this paper, we discuss a simple optical infrared (IR) experiment that allows the non-contact measurement of the magneto-resistance of spintronic materials and devices. The results are compared with characteristic electrical giant magneto-resistance (GMR) curves and show good agreement. The instrument is simpler and more compact than previous demonstrators, offering the possibility of routine measurement. The ability to measure a GMR profile using a non-contact, non-destructive IR technique has important implications, enabling in situ sample testing, non-contact profiling of the GMR at a wafer level and spatial resolution GMR measurements.