High Sensitivity Fiber Bragg Grating Humidity Sensors Made With Through-the-Coating Femtosecond Laser Writing and Polyimide Coating Thickening

Durable fiber Bragg grating (FBG) relative humidity (RH) sensors are fabricated in commercially available polyimide (PI) coated 50-µm diameter Ge-doped silica optical fibers using an infrared femtosecond pulse duration laser and a phase mask. FBGs are inscribed directly through the 10-µm thick PI co...

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Bibliographic Details
Published in:IEEE sensors letters 2024-06, Vol.8 (6), p.1-4
Main Authors: Mihailov, Stephen J., Ding, Huimin, Szabo, Katherine, Hnatovsky, Cyril, Walker, Robert B., Lu, Ping, De Silva, Manny
Format: Article
Language:English
Subjects:
Bragg gratings
C band
Coatings
Femtosecond pulses
fiber bragg gratings (FBG)
Fiber gratings
Germanium
Humidity
Infrared lasers
Optical fiber polarization
optical fiber sensor
Optical fiber sensors
Optical fibers
photonic sensors
Pulse duration
Relative humidity
relative humidity (RH) sensor
Sensitivity
Sensor integration
Sensors
Silicon dioxide
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Summary:Durable fiber Bragg grating (FBG) relative humidity (RH) sensors are fabricated in commercially available polyimide (PI) coated 50-µm diameter Ge-doped silica optical fibers using an infrared femtosecond pulse duration laser and a phase mask. FBGs are inscribed directly through the 10-µm thick PI coating, which is subsequently thickened with PI using a customized fiber recoating system. Devices with varying PI thicknesses are evaluated for their response to RH. For telecom C-band wavelengths, FBG sensor sensitivities vary from 2.4 to 19 pm/%RH for 10 to 60-µm thick PI coatings, respectively. The 19 pm/%RH response represents the highest sensitivity reported for a PI coated silica FBG RH sensor. RH sensors with thinner coatings respond more rapidly to small changes in humidity and show smaller hysteresis when compared with devices with thicker coatings.
ISSN:2475-1472
2475-1472
DOI:10.1109/LSENS.2024.3398432