KEYWORDS: Magnetism, Magnetic sensors, Sensors, Ferromagnetics, Polymers, Nanocrystals, Manganese, Single mode fibers, Reflectivity, Temperature metrology
In this paper, a three-beam Fabry-Perot interferometric senor for magnetic field and temperature measurement is proposed, which is based on a polymer capped on the cleaved end of a single mode fiber and another SMF is aligned with it. The employed polymer is polydimethylsiloxane (PDMS) incorporated with ferromagnetic nanocrystals (Mn3O4). The proposed structure is compact and easy to fabricate, which can improve the sensitivity. The measured sensitivity of magnetic field is -560 pm/mT around 1550 nm. The proposed sensor possesses the following potential applications, such as petroleum survey, electric power industry, biomedicine, aerospace engineering and other fields.
We demonstrate a fiber-optic magnetic field sensor based on a micro-optical resonator. The optical resonator is formed by nanocrystals-incorporated PDMS (Ni-PDMS) microsphere. The external magnetic field sets up a body force within the microsphere and a magnetic pressure acting on its surface. The experimental results show that the sensitivity of the 170-μm-diameter microsphere (the ferromagnetic particle mass fraction is 10%) is 20 pm/mT, and gradually tends to be saturated in the magnetic field range of 0 ~ 15 mT.
Fiber optic shape sensing has a great potential for diverse medical and industrial applications to measure curvatures and even shapes. Featuring small footprint, strong immunity to radiation and high flexibility integration, fiber optic shape sensing opens up a new era in the fields of position tracking, human wearable devices, catheter navigation, bending detection and deformation monitoring. This paper focuses on a branch of fiber optic shape sensing techniques, with an emphasis on shape sensing based on fiber Bragg gratings (FBGs). Key technologies of shape sensing based on FBG are introduced in detail together with a critical view of its evolutionary trend. In addition, the major problems that exist in FBG shape sensing have been discussed in the end.
A label-free optical fiber biosensor based on a Mach-Zehnder interferometer for real-time bovine serum albumin (BSA) concentration detection has been proposed and experimentally demonstrated. An air microcavity has been fabricated by means of splicing a segment of microfiber between two single mode fibers (SMFs) with appropriate offset such that it acts as a microfluidic channel, where external media can directly interact with the guided light. Experimental results show a high sensitivity of -15.56 nm/(mg/mL).
This paper investigates optical properties of few-mode fiber with non-uniform refractive index, namely: the few mode fiber with U-shape refractive index and the two-mode and four-mode few-mode fiber with bent radius. Finite element method is used to analyze the mode distributions based on their non-uniform refractive index. Effective mode control can be achieved through these few mode fibers to achieve vector beam generation. Finally, reflection spectra of a few-mode fiber Bragg grating are calculated theoretically and then measured under different bending conditions. Experimental results are in good accordance with the theoretical ones. These few mode fibers show potential applications in generation of cylindrical vector beam both for optical lasing and sensing systems.
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