Highly sensitive strain sensor based on a long-period fiber grating with chain-shaped structure

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Materials Science

Background:

• Traditional fiber optic strain sensors often face limitations in sensitivity and physical size.
• The development of compact, high-sensitivity sensors is crucial for advanced structural health monitoring and industrial applications.
• Long-period fiber gratings (LPFGs) are known for their sensing capabilities but can be improved for specific applications.

Purpose of the Study:

• To investigate and experimentally demonstrate a novel chain-shaped long-period fiber grating (CS-LPFG) for enhanced strain measurement.
• To improve the strain sensitivity and reduce the physical length of the sensing unit compared to existing fiber strain sensors.
• To evaluate the temperature-strain cross-talk performance of the developed CS-LPFG sensor.

Main Methods:

• Fabrication of the CS-LPFG structure by polishing periodic slant planes onto a single-mode fiber using a high-frequency CO2 laser.
• Experimental characterization of the sensor's response to applied strain.
• Measurement of the sensor's sensitivity to temperature and assessment of temperature-strain cross-talk.

Main Results:

• The CS-LPFG sensor achieved a high strain sensitivity of 34.8 pm/µε within the 0-650 µε strain range.
• The sensing unit length was significantly reduced to 7.5 mm, offering a compact sensor design.
• A low temperature-strain cross-talk of 1.6 µε/°C was recorded, indicating good selectivity for strain measurement.

Conclusions:

• The novel chain-shaped LPFG structure effectively enhances strain sensitivity while enabling a miniaturized sensor footprint.
• The CS-LPFG demonstrates superior performance in strain measurement with minimal length and low temperature cross-talk.
• This technology holds significant potential for applications requiring precise and compact strain sensing.