scholarly journals Time Domain Referencing In Intensity Modulation Fiber Optic Sensing Systems

1986 ◽  
Author(s):  
Grigory Adamovsky
Keyword(s):  
Time Domain ◽  
Fiber Optic ◽  
Intensity Modulation ◽  
Sensing Systems ◽  
Fiber Optic Sensing

Multiplexed Fiber Optic Temperature Monitoring Sensor Using Hard-Polymer-Clad Fiber and an Optical Time-Domain Reflectometer

2013 ◽  
Author(s):  
Hyeong Cheol Kim ◽  
Jung-Ryul Lee
Keyword(s):  
Time Domain ◽  
Fiber Optic ◽  
Optical Loss ◽  
Sensor Nodes ◽  
Optical Time Domain Reflectometer ◽  
Sensing Systems ◽  
Hard Polymer ◽  
Optical Time ◽  
Time Domain Reflectometer ◽  
Fiber Optic Temperature

Optical fiber temperature sensing systems have incomparable advantages than the traditional electric cable based monitoring systems. As of now, fiber Bragg grating (FBG) sensors are most popular because of its wavelength domain multiplexing capability. However, grating writing process is complex and takes long time and photosensitive fibers for the typical grating writing process are expensive. In addition, sensing systems for FBGs are also expensive. Therefore, this study proposes multiplexed fiber optic temperature monitoring sensor system using an economical Optical Time-Domain Reflectometer (OTDR) and Hard-Polymer-Clad Fiber (HPCF). HPCF is a specific type of optical fiber, in which a hard polymer cladding made of fluoroacrylate acts as a protective coating for an inner silica core. An OTDR is an optical loss measurement system that provides optical loss and event distance measurement in real time. Multiplexed sensor nodes were economically and quickly made by locally stripping HPCF clad through photo-thermal and photo-chemical processes using a continuous/pulse hybrid-mode laser with 10 m intervals. The core length exposed was easily controlled by adjusting the laser beam diameter, and the exposed core created a backscattering signal in the OTDR attenuation trace. The backscattering peak was sensitive to the temperature variation. Since the elaborated HPCF temperature sensor was insensitive to strain applied to the sensor node and to temperature variation in the normal HPCF line, neither strain compensation nor isolation technique are required. These characteristics are important advantages for the use as structure-integrated temperature sensors. The performance characteristics of the sensor nodes include an operating range of up to 120 C, a resolution of 1.52 C, a tensile strain resistance of 13%.

Detection and Localization of Micro-Leakages Using Distributed Fiber Optic Sensing

2008 ◽  
Author(s):  
Daniele Inaudi ◽  
Riccardo Belli ◽  
Roberto Walder
Keyword(s):  
Fiber Optic ◽  
Field Trials ◽  
Natural Gas Pipelines ◽  
Sensing Systems ◽  
Detection Volume ◽  
Temperature Contrast ◽  
Fiber Optic Sensing ◽  
Detection And Localization ◽  
Single Instrument ◽  
Better Than

Distributed fiber optic sensing offers the ability to measure temperatures and strain at thousands of points along a single fiber. This is particularly interesting for the monitoring of pipelines, where it allows the detection and localization of leakages of much smaller volume than conventional mass balance techniques. Fiber optic sensing systems are used to detect and localize leakages in liquid, gas and multiphase pipelines, allowing the monitoring of hundreds of kilometers of pipeline with a single instrument and the localization of the leakage with a precision of 1 or 2 meters. This contribution presents recent testing results on controlled field trials. The tests demonstrate that it is possible to reliably detect oil leakages of the order of 10 liters to 1’000 liters per hour, corresponding to 0.01% to 0.1% of the pipeline flow. Tests were performed with small temperature differences between liquid and ground. The detection time was between 1 minute and 90 minutes. All simulated leakages were detected and localized to better than 2m accuracy. The paper describes the main parameters that affect the response time and detection volume, including the relative position of the leak to the sensing cable, temperature contrast and instrument performance. We also briefly report on relevant full-scale installations for the permanent monitoring of oil, brine and natural gas pipelines.

Novel long-distance fiber-optic sensing systems based on random fiber lasers

2012 ◽  
Author(s):  
Zinan Wang ◽  
Xinhong Jia ◽  
Yunjiang Rao ◽  
Yun Jiang ◽  
Weili Zhang
Keyword(s):  
Fiber Lasers ◽  
Fiber Optic ◽  
Long Distance ◽  
Sensing Systems ◽  
Fiber Optic Sensing
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