PSI - Issue 70

T. Ramya et al. / Procedia Structural Integrity 70 (2025) 469–476

472

λ B =2neffΛ

(1)

where (Λ) is grating period and the (neff) is the effective refractive index of fiber core. 3. Fiber Bragg Grating (FBG) Strain and Temperature Sensing System for HDPE Pipe Testing The FBG based optical sensors are used to measure strain and temperature due to their high sensitivity, stability and immunity to electromagnetic interference (Paolozzi et al.(2016) and Kumar et al.(2023)). In this paper, a FBG based strain and temperature sensing system is deployed at 7m depth ATF – Acoustic Test Facility for evaluating the mechanical behavior of a High-Density Polyethylene pipeline under a 1-ton load. The experimental setup includes an array of FBG strain and temperature sensors integrated with an armored cable and a data interrogator for signal acquisition and analysis. The FBG sensor array was procured for installation in the cold water pipeline of a desalination plant. Prior to deployment in the desalination plant, the system was tested at the ATF facility in National Institute of Ocean Technology (NIOT) to validate its performance.

3.1 FBG Sensor System Description

The sensing system consists of:

• FBG Strain Sensor: Measurement range of ±5000 μm/m. • FBG Temperature Sensor: Operational range -20°C to 80°C, used for thermal compensation of strain measurements. • Data Interrogator: Amplifies and processes the reflected signal, optimizing measured power. • Gain: Amplification value (0 to 255) • Threshold Value: Defines the power level for FBG peak computation (200 to 3200) to eliminate side lobes and ground noise.

Fig.3. HDPE pipe model with FBG Sensor Configuration