Research papers - Optics Express Vol. 25, Issue 15, pp. 17936-17947 (2017)
FBGs written in specialty fiber for high pressure/high temperature measurement
Ji-Ying Huang, Jan Van Roosbroeck, Johan Vlekken, Antonio Bueno Martinez, Thomas Geernaert, Francis Berghmans, Bram Van Hoe, Eric Lindner, Christophe Caucheteur
Short description
Pressure monitoring devices for downhole applications can be categorized into two types of working conditions, according to the definitions provided in [1]. The first type are working conditions in ultra-high pressure and high temperature (Ultra HP and HT), which indicates that both the operating pressure and temperature can go up to 1379 bar and 175°C, respectively. The second type are working conditions up to 69 bar and 280°C, which are considered to be low pressure and ultra-high temperature (Low P and Ultra HT). The current market is still dominated by crystalline quartz based sensors that have several shortages such as lifetime reduction when exposed to higher temperature and increased pressure errors when encountering temperature transients [2,3].
In this paper, we evaluate different thermal treatments in order to stabilize fiber Bragg gratings written by a femtosecond pulsed laser in specialty highly birefringent micro-structured optical fiber, targeting pressure monitoring at high pressure and high temperature environments. We have obtained a pressure sensitivity of 3.30 pm/bar up to 1400 bar and 290 °C. An effective thermal treatment has been experimentally implemented, yielding a nearly unchanged reflectivity at high temperature in combination with stable temperature and pressure readings: a standard deviation of 0.42 bar in the pressure reading was observed over 7 days at 280°C.
https://opg.optica.org/oe/fulltext.cfm?uri=oe-25-15-17936&id=369978