High temperature detection inside large-scale plants using distributed sensor fabricated by 10 LPG resonant wavelengths multiplexing

Osanori Koyama, Hikaru Sumiana, Yoshikazu Toyooka, Makoto Yamada

Abstract: Ten resonant wavelengths could be multiplexed successfully by writing long-period gratings (LPGs) with different pitches using a CO2 laser. A preliminary distributed temperature monitoring experiment was conducted, and it was estimated that separation between 2 adjacent resonant peaks was 13.2nm, even when the temperature difference between 2 adjacent LPGs was 150°C. This separation is large enough to distinguish the resonant wavelengths individually. The results clarified that this multiplexing approach enables the LPFG to detect a local high temperature caused by an abnormal reaction inside large-scale plants.