High-performance distributed dynamic strain sensing by synthesizing φ-OTDR and BOTDR

Area of Science:

• Optical Engineering
• Materials Science
• Structural Health Monitoring

Background:

• Distributed strain sensing is crucial for monitoring the structural integrity of various infrastructures.
• Existing techniques like φ-OTDR offer high sampling rates but lack absolute strain measurement, while BOTDR provides absolute strain but with lower dynamic range and sampling rates.
• A need exists for a sensing technique combining the advantages of both φ-OTDR and BOTDR.

Purpose of the Study:

• To propose and demonstrate a high-performance distributed dynamic absolute strain sensing technique.
• To synthesize the capabilities of φ-OTDR and BOTDR for enhanced strain measurement.
• To achieve high sensing accuracy, high sampling rates, absolute strain measurement, and a large sensing dynamic range.

Main Methods:

• A hybrid sensing technique is developed by synthesizing φ-OTDR and BOTDR.
• Relative strain data from φ-OTDR is combined with absolute strain signals from BOTDR.
• The initial strain offset is estimated by fitting the relative strain with the absolute strain signal.

Main Results:

• The proposed technique successfully realizes distributed dynamic absolute strain sensing.
• Experimental results demonstrate a sensing dynamic range exceeding 2500 µɛ.
• A peak-to-peak amplitude of 1165 µɛ and a wide frequency response range (0.1 to >30 Hz) were achieved over a 1 km sensing range.

Conclusions:

• The synthesized φ-OTDR and BOTDR technique effectively overcomes the limitations of individual methods.
• The developed method provides both high sensing accuracy and sampling rates, along with absolute strain measurement and a large dynamic range.
• This technique is suitable for advanced structural health monitoring applications requiring precise dynamic strain analysis.