Abstract
Recent developments in fiber-optic sensing have involved booming research in the design and manufacturing of novel micro-structured optical fiber devices. From the conventional tapered fiber architectures to the novel micro-machined devices by advanced laser systems, thousands of micro-structured fiber-optic sensors have been proposed and fabricated for applications in measuring temperature, strain, refractive index (RI), electric current, displacement, bending, acceleration, force, rotation, acoustic, and magnetic field. The renowned and unparalleled merits of sensors-based micro-machined optical fibers including small footprint, light weight, immunity to electromagnetic interferences, durability to harsh environment, capability of remote control, and flexibility of directly embedding into the structured system have placed them in highly demand for practical use in diverse industries. With the rapid advancement in micro-technology, micro-structured fiber sensors have benefitted from the trends of possessing high performance, versatilities and spatial miniaturization. Here, we comprehensively review the recent progress in the micro-structured fiber-optic sensors with a variety of architectures regarding their fabrications, waveguide properties and sensing applications.
Highlights
Fiber-optic sensors have attracted intensive attentions during the past decades due to their unparalleled advantages over the conventional sensors such as immunity to electromagnetic interference, capability of measuring multiple measurands, high resolution, high accuracy, small footprint (~μm), long-distance sensing, ability for high temperature measurement (>300 ◦ C), ability of sensor networking, etc. [1,2,3,4,5]
Compared with conventional fiber-optic point sensors, for example, the Mach-Zehnder interferometer (MZI) with cumbersome structures consisting of two beams of optical fibers or the extrinsic Fabry-Perot interferometer (FPI) by packaging two fiber ends together, the micro-structured fiber optic sensors are able to realize the interferometric schemes with an in-fiber configuration through tapering, laser micro-machining and so on, which makes the sensor more compact and reliable
The paper is arranged as follows: the introduction is presented in Section 1; followed by the fundamental physics and principles in Section 2; Abrupt taper structure and long taper structure will be introduced in Sections 3 and 4; Resonator-type micro-structure and micro-machined devices will be covered in Sections 5 and 6; the grating-based microstructures and some mode-mismatched and hybrid micro-structures will be described in Sections 7 and 8; In Sections 9 and 10 we will provide the future prospect and conclusions of the paper
Summary
Fiber-optic sensors have attracted intensive attentions during the past decades due to their unparalleled advantages over the conventional sensors such as immunity to electromagnetic interference, capability of measuring multiple measurands, high resolution, high accuracy, small footprint (~μm), long-distance sensing, ability for high temperature measurement (>300 ◦ C), ability of sensor networking, etc. [1,2,3,4,5]. Micro-structured fiber gratings mainly include the microfiber-based fiber Bragg grating (FBG), long period grating (LPG) and the recently-emerged random gratings. This paper reviews various micro-structured optical fiber sensors that have been designed and manufactured in different sensing configurations, their working principles, as well as the typical applications. The paper is arranged as follows: the introduction is presented in Section 1; followed by the fundamental physics and principles in Section 2; Abrupt taper structure and long taper structure will be introduced in Sections 3 and 4; Resonator-type micro-structure and micro-machined devices will be covered in Sections 5 and 6; the grating-based microstructures and some mode-mismatched and hybrid micro-structures will be described in Sections 7 and 8; In Sections 9 and 10 we will provide the future prospect and conclusions of the paper
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