研究目的
Investigating the feasibility of a highly sensitive distributed pressure sensing system using side air holes fiber based on phase sensitive optical time-domain reflectometry.
研究成果
The proposed distributed fiber sensor based on frequency-scanning Φ-OTDR using direct-modulation and a side air holes fiber can achieve a kilometer-long 5 cm spatial resolution distributed pressure sensing with a pressure sensitivity of ~2 GHz/bar for a single axis birefringence response and 0.2 GHz/bar for the birefringence response, making a pressure accuracy as low as 10 hPa realistic.
研究不足
The study is limited by the need for temperature compensation in high-accuracy applications and the relatively lower sensitivity when measuring birefringence change compared to single axis response.
1：Experimental Design and Method Selection:
The study employs phase-sensitive optical time-domain reflectometry (Φ-OTDR) with frequency scanning using both polarization axes of side air holes fibers (SAHFs).
2：Sample Selection and Data Sources:
Two SAHFs with different birefringence values are tested. Fiber H has a birefringence of ~10-5 and Fiber L has ~10-
3：List of Experimental Equipment and Materials:
Optical source (DFB laser), electro optical modulators (EOMs), semiconductor optical amplifier, polarization switch and controller, pressure chamber, vacuum pump, precision thermal resistor.
4：Experimental Procedures and Operational Workflow:
Optical pulses are shaped and sent to a polarization switch, aligned with each polarization axis of the fiber under test. Frequency scans are achieved by direct tuning of the laser current.
5：Data Analysis Methods:
The frequency shift induced by temperature or pressure changes is evaluated separately along the two axes. Cross-correlation is used to estimate the frequency shift in the Rayleigh backscattering spectrum.
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