Abstract
We have demonstrated a double-modulation scheme to enlarge the measurement range of Brillouin optical correlation-domain reflectometry for fiber-optic distributed strain sensing. In this scheme, the frequency of the laser output is simultaneously modulated with two different frequencies. In the experiment, 53-cm resolution and 1.5-km measurement range were simultaneously obtained. Furthermore, 27-cm resolution and 1.5-km measurement range were also simultaneously achieved when a noise-floor compensation technique was employed.
Highlights
Among various kinds of fiber-optic sensors, Brillouin optical correlation-domain reflectometry (BOCDR) [1] has the capacity to measure the distribution of strain and/or temperature along a fiber under test (FUT) from a single end
13-mm spatial resolution has been obtained in a silica fiber [2], which is the best result ever reported in spontaneous Brillouin scattering-based reflectometers
In the case of Brillouin optical correlation-domain analysis (BOCDA) systems [9], a multiple-modulation scheme is known to be an alternative method to obtain higher NR [10], where the frequency of the laser output is simultaneously modulated with multiple different frequencies
Summary
Among various kinds of fiber-optic sensors, Brillouin optical correlation-domain reflectometry (BOCDR) [1] has the capacity to measure the distribution of strain and/or temperature along a fiber under test (FUT) from a single end. BOCDR suffers from a trade-off between the measurement range and the spatial resolution Their ratio NR is fixed at approximately 570 due to the limitation caused by Rayleigh scattering-induced noise [1]. To obtain higher NR, a temporal gating scheme was implemented [8], where any correlation peak within the FUT can be arbitrarily selected by a time-domain technique. In the case of Brillouin optical correlation-domain analysis (BOCDA) systems [9], a multiple-modulation scheme is known to be an alternative method to obtain higher NR [10], where the frequency of the laser output is simultaneously modulated with multiple different frequencies. By modulating the laser output at 2f0 and 3f0 simultaneously (where f0 is a fundamental frequency), NR was enhanced by three times.
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