Author: Huang, Zhenyu
Title: Vital signs monitoring based on Few-mode fiber sensors
Degree: M.Sc.
Year: 2019
Subject: Hong Kong Polytechnic University -- Dissertations
Optical fiber detectors
Optical detectors
Biosensors
Department: Faculty of Engineering
Pages: 51 pages : color illustrations
Language: English
Abstract: In the context of technological development, recent medical institutions require more medical equipment to monitor the patient's vital signs in real time, with breathing and heartbeat being the two most important indicators. This paper discussed in detail and put forward a feasible sensing scheme for vital signs monitoring. Few-mode fibers (FMF) are adapted to build a kind of fibbed-based interferometer. There are two types of the few-mode fibers are studied, Dual-mode fiber (DMF) and Four-mode fiber respectively. DMF support LP₀₁ and LP₁₁. Also, Four-mode fiber support four modes, LP₀₁, LP₁₁, LP₂₁, LP₀₂. To excite the mode other than LP₀₁ in the fiber, a kind of structure adopt with three segments of the optical fibers, SMF (Single-mode fiber)-FMF-SMF. A core-offset distance existence between lead-in SMF and FMF. In this sensing structure, the cores of SMF and FMF are horizontally unaligned and this called core-offset. High-order mode and fundamental mode propagate simultaneously in FMF and produce inter-mode interference. Finally, the interference beam coupled to lead-out SMF. We have numerically optimized the core-offset distance for the two-mode and four-mode core-offset, and the optimized parameters can lead to a desired experimental result. The extinction ratio of the four-mode fiber reached 10 dB. Both of DMF and Four-mode fiber can accurately measure the signals of respiration and heartbeat. All the preliminary steps in the experiment are repeatable, and the fabrication of such fiber-based interferometers is not complicated. From the above viewpoint, this kind of sensor based on the few-mode optical fiber could be worked as a valuable medical sensor in the future.
Access: restricted access

Files in This Item:
File Description SizeFormat 
991022270857903411.pdfFor All Users (off-campus access for PolyU Staff & Students only)1.76 MBAdobe PDFView/Open


Copyright Undertaking

As a bona fide Library user, I declare that:

  1. I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
  2. I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
  3. I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.

By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.

Show full item record

Please use this identifier to cite or link to this item: https://theses.lib.polyu.edu.hk/handle/200/10098