High-Spatial-Resolution and Wide-Range Strain Distributed Sensor Based on Exposed-SMF Using Efficient Adaptive Zero Padding

A high-spatial resolution and wide-range distributed strain sensor (DSS) based on UV laser exposed single mode fiber (E-SMF) has been experimentally demonstrated, of which the maximum measurable strain was up to
$9000 \mu \varepsilon $
under a spatial resolution of 1.5 mm. To address the tradeoff between strain resolution and sensing spatial resolution, an efficient adaptive zero padding (AZP) was proposed to calculate the number of padding zeros to optimize the number of zero padding (NZP). Compared with traditional zero padding (TZP), the cross correlation calculation time was improved from 138.842 to 0.476 s using the proposed AZP method under the spatial resolution of 1.5 mm, indicating that the cross correlation calculation time was reduced by nearly
$300\times $
. Moreover, the distance compensation method (DCM) was employed to improve the deteriorated similarity induced by position deviation between the reference (Ref.) and measurement (Mea.) signal, which could be greatly improved by using DCM. The strain property of the E-SMF and SMF was compared and investigated by DCM based on the AZP method. The strain profile of the E-SMF could be successfully and well demodulated in the zero- and stretched-strain section at the spatial resolution of 1.5 mm by using DCM, when the applied strain was increased from 1000 to
$9000 \mu \varepsilon $
.