U-shape core-offset fiber sensor with submicrostrain resolution over a 35 millistrain range

Abstract

Large strain with submicro resolution is essential for steel structural monitoring; however, the fiber base sensors are limited by the glass extension to be less than 1%. Here, we propose a U-shape core-offset fiber sensor including four fiber segments to realize a large strain sensor. Four fiber segments with slight length differences in between are core-offset fused together to achieve U-shape spring-like microstructure fiber for large transverse bending radius. The reflected high-order modes at three silica/air interfaces interfere to give a broad spectrum due to unequal segment length, which enables continuous strain detection over 35 mɛ. The air and glass hybrid structure of the device enables the large bending, and hence compression and tension measurement can be achieved simultaneously. The strain sensitivity is up to 20.75 pm/µɛ with the strain accuracy of 0.5 µɛ. This novel, to the best of our knowledge, core-offset fiber has high strain sensitivity and large strain range for compression and tension strain measurement. Furthermore, the proposed strain sensor can be fabricated easily for practical applications where large strain with high strain accuracy is needed.

Graphene-coated three-twisted-taper and four-twisted-taper for highly sensitive temperature and strain sensing

“…For another potential application, graphene-coated three-twisted-taper is also specially suitable for tensile strain sensing considering tapered fiber with ultra-small diameter and ultra-sensitive to the surrounding variation. The experimental setup is the same as [25]. Two displacements with distance of 1 m in between is used to fix SMF and have a minimum step of 10 µm, corresponding to strain accuracy of 10 µε.…”

Novel Optical Fiber-Based Structures for Plasmonics Sensors

“…This new structure not only has good sensitivity, but also has the advantages of compact structure, easy to fabricate, low cost, etc. Fan et al [ 131 ] proposed a new U-shaped core biased fiber-optic sensor with four optical fiber segments for strain detection. The structure and manufacturing process of the U-shaped optical fiber made of four SMF segments welded on the core offset are shown in the Figure 10 B.…”

“…Reprinted with permission from IEEE Sensors , Copyright 2021, IEEE [ 129 ]; ( B ) schematic diagram of the off-set U-shaped optical fiber structure. Refer to [ 131 ]; ( C ) unique micro-bent core structure. Refer to [ 40 ]; ( D ) micro-fiber MZI (MMZI) with two spindle-shaped structure.…”