Abstract
By effectively suppressing the nonlinear sweep noise and random range of wavelength sweep in the optical frequency domain reflectometer, the theoretical spatial resolution and uniform sweep distribution are delivered for high sensing accuracy. A strain accuracy of ±0.51 μϵ is realised with a 5 mm sensing resolution, while the accuracy is ±5.89 μϵ with a 1 mm sensing resolution. Theoretical limitation between the strain accuracy and sensing resolution is further studied for the sub-millimetre resolution sensing. It is found that signal to noise ratio and frequency bandwidth of the calculated cross-correlation are critical factors in measuring accuracy. Increasing the sweep range can provide a better spatial frequency step for a high signal to noise ratio in the cross-correlation. With a 130 nm sweep range, the measurement accuracy is limited to ±19.31 μϵ with a 0.5 mm sensing resolution. Besides, for the long-distance sensing of 104 m, the measurement accuracy is ±8.72 μϵ with a 1 mm sensing resolution.
Highlights
Optical frequency domain reflectometer (OFDR) is one of intrinsic-scattering based distributed optical fibre sensing (Rayleigh, Brillouin, et al.)[1,2,3]
As we have obtained the theoretical-level spatial resolution in the previous work [15], we further investigate the sensing accuracy with the ultimate sensing resolution
By introducing high order Taylor components of frequency distribution to compensate for this nonlinear sweep noise, we proposed an equal frequency resample to efficiently suppress the nonlinear sweep noise for better spatial resolution [15]
Summary
Optical frequency domain reflectometer (OFDR) is one of intrinsic-scattering based distributed optical fibre sensing (Rayleigh, Brillouin, et al.)[1,2,3]. Due to the excellent spatial resolution and dynamic range by tuning the laser wavelength, OFDR is becoming one of the most attractive ways to realise high precision sensing. It is mainly used in the optical components metrology for the measurement of transmission loss and link diagnosis in the optical network [4]. An ultimate 0.5 mm resolution and a long-distance distributed sensing of 100 m are represented to demonstrate the efficient suppression of the nonlinear sweep noise and randomly distributed sweep range for the high accuracy with the sub-millimetre resolution
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