This disclosure presents a method of measuring the strain response of a test material remotely by optical devices using a thin multi-layer assembly, called an optical strain gauge, which is attached directly to the test specimen by pair of adhesive patches built into the assembly. The optical strain gauge assembly attaches quickly and easily by just pressing it onto the specimen by virtue of the two pressure-activated adhesive patches. There is typically no surface preparation necessary for the test specimen. The spatial separation between the two patches adhered to the specimen surface serves to establish an initial gauge length for calculating strain by measuring the stress induced changes to this separation when a load is applied to the test specimen.