Optical fiber strain sensor with extended dynamic range based on specklegrams

•Achieving high resolution measurements using a low cost technology.•The design of a complex algorithm that can extract useful information from the great amount of available data within specklegrams.•The successful test of the proposed algorithm in an experimental setup.

In this paper, a processing scheme based on the morphological similarities of speckle patterns is proposed to extend the dynamic range of Fiber Specklegram Sensors (FSS). The method has been applied to a low cost FSS demonstrating its good performance to extend the dynamic range of strain measurements. The scheme analyzes the pattern energy distribution to establish the current modal state of the FSS and employs the correlation value with the reference modal state specklegram to determine the fine strain measurements. The achieved results exhibit a very high performance, making this low cost technology applicable to structural monitoring.