Wang, Qirui
(2025)
Low-Cost Distributed Fiber Optic Interrogation Based on Optical Frequency Domain Reflectometry.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
As a highly flexible sensor technique suitable for wide-range real-time detection, with immunity to electromagnetic interference and adaptability to harsh environments, distributed fiber optic sensing has become indispensable in modern industrial fields, playing a key role in process control, fossil fuel management, and energy facility monitoring. Among these technologies, optical frequency domain reflectometry (OFDR) is distinguished by its high accuracy, sensitivity, and spatial resolution. However, its applicability is severely limited by the high cost of instrumentation.
This dissertation investigates the potential of using low-cost telecom distributed feedback (DFB) lasers to perform OFDR measurements. Through direct current modulation, a DFB laser with a 1-MHz linewidth is tuned across 1 nm to achieve a 1.2-mm spatial resolution, providing an affordable OFDR-based light detection and ranging (LiDAR) solution for diverse, complex environments.
The research further explores optical fibers with enhanced Rayleigh backscattering profiles to improve in-fiber OFDR sensing performance while reducing instrumentation costs. Utilizing ultrafast laser direct writing, the Rayleigh backscattering intensity of standard telecom fiber is enhanced by over 40 dB and the signal-to-noise ratio is improved significantly. This enhancement, combined with image processing, enables distributed strain sensing with a 4.8-cm gauge length and an error below 2.7 µε. The study also identifies limitations in the performance improvements associated with higher Rayleigh backscattering enhancements.
Additionally, the dissertation examines the effects of mode hopping in DFB lasers on the performance of low-cost OFDR systems. Numerical simulations reveal that mode hopping has minimal impact on free-space LiDAR measurements and only slightly affects distributed strain sensing, with errors of less than ±1 µε when 100 µε is applied.
These findings highlight the potential of using low-cost 1-nm DFB lasers in OFDR systems while maintaining reliable and accurate sensing performance. The findings detailed in this dissertation enable the development of high-performance optical sensors for a wide range of applications demanding high spatial resolution, which is unattainable with other measurement schemes such as microwave, ultrasonic, and electronic sensors, while offering a significant cost advantage over conventional OFDR instruments.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
7 January 2025 |
| Date Type: |
Publication |
| Defense Date: |
5 November 2024 |
| Approval Date: |
7 January 2025 |
| Submission Date: |
19 October 2024 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
101 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Electrical and Computer Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
distributed fiber optic sensing, optical frequency domain reflectometry, LiDAR, DFB laser, mode hopping |
| Date Deposited: |
07 Jan 2025 21:04 |
| Last Modified: |
07 Jan 2025 21:04 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/47032 |
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