An inexpensive fiber-based noncontact distance sensor specific for monitoring short-range displacements in micromachining applications is presented. To keep the overall costs low, the sensor uses plastic optical fibers and an intensiometric approach based on the received light intensity after the reflection from the target whose displacement has to be measured. A suitable target reflectivity compensation technique is implemented to mitigate the effects due to target surface nonuniformity or ageing. The performances of the sensor are first evaluated for different fiber configurations and target reflectivity profiles and positions using a numerical method based on Monte Carlo simulations. Then, experimental validations on a configuration designed to work up to 1.5？mm have been conducted. The results have confirmed the validity of the proposed sensor architecture, which demonstrated excellent compensation capabilities, with errors below 0.04？mm in the (0-1)？mm range regardless the color and misalignment of the target. 1. Introduction Fiber Optic Sensors (FOSs) have gained an ever increasing attention in recent years due not only to the their excellent performances with respect their electromechanical counterparts, but also to the availability of high-quality off-the-shelf photonic components as side products of the enormous progress in optical communications. FOSs are typically characterized by a high sensitivity joined with other unique characteristics such as lightweight, resistance to corrosion, immunity to electrostatic discharges, impossibility to start fires, and capability of remote operation using the same fiber both for sensing and for data transmission. However, despite the many sensing principles and implementations already proposed in the literature, their diffusion in everyday use is still confined to niche applications, mainly because of the high costs of the interrogators and of the complexity of optical layouts and interconnections. Today, commercial FOSs are based on glass fibers similar to those used for high-performance optical communications, although Plastic Optical Fibers (POFs) are emerging as an alternative technology for the realization of inexpensive fiber sensors and interconnections [1]. The “low cost” aspect is a crucial point to open up new market perspectives, since budget limitations often prevent permanent monitoring from being set up using fiber sensors even in cases where fibers are known to provide superior performances. Examples are in cultural heritage preservation (where, e.g., the intrinsic fire safety is a key
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