A prototype optical fiber sensor for monitoring corrosion on large steel structures has been designed and tested with favorable results. The sensor works by pulling a multimode fiber into a tight bend and securing it with a `corrosion fuse.' When the fuse corrodes, it eventually breaks and allows the fiber to straighten. The resulting difference in optical intensity emerging from the fiber is measurable using an OTDR or other optical detector. Initial experiments were carried out to determine the effect of bending fibers in a small radius and showed the feasibility of the device. Following, tests were performed on three in-line sensors in a simulated corrosive atmosphere and showed that this cheap and easily implemented monitoring scheme could be used to infer the presence of corrosion at different locations, and/or the degree of corrosion at a single location.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.