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 13.2 nm, 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.
