Abstract
A distributed birefringence measurement of a polarization-maintaining fiber (PMF) can be realized by using a Brillouin dynamic grating (BDG). However, the pump depletion decreases the intensity of the BDG along the PMF and limits the measurement range to a few hundred meters. We demonstrate a distributed birefringence measurement of the PMF with an extended range to 3030 m based on an enhanced BDG with an 18.5-ns pump-1 pulse, frequency-upshifted continuous-wave pump-2, and 4-ns read pulse (spatial resolution: 40 cm). The enhanced BDG is promising to characterize the design of a fiber coil to improve the fiber optic gyroscope performance.
Highlights
Since the Brillouin dynamic grating (BDG) in a polarization-maintaining fiber (PMF) was proposed in 2008 [1], extensive studies have been carried out on its fundamental properties [2]–[3] and potential applications, such as all-optical calculus [4], fiber sensing [5]–[9], high-resolution optical spectrometry [10], tunable optical delays [11], distributed birefringence measurement [12]–[13], ultra-wideband communications [14] and microwave-photonics filters [15]
Top views of the measured threedimensional (3D) reflection spectra over the fiber under test (FUT) (PM1550-80, made by YOFC) of the attenuated and enhanced BDGs are shown in Fig. 5(a) and 5(b), respectively, where the shifts of the BDG reflection spectra are attributed to the birefringence fluctuation over the PMF
The intensity of the reflection spectrum slowly increases along the PMF, as shown in Fig. 5(b), because the pump 1 pulse is continuously amplified by the frequency-upshifted continuous wave (CW) pump 2
Summary
Since the Brillouin dynamic grating (BDG) in a polarization-maintaining fiber (PMF) was proposed in 2008 [1], extensive studies have been carried out on its fundamental properties [2]–[3] and potential applications, such as all-optical calculus [4], fiber sensing [5]–[9], high-resolution optical spectrometry [10], tunable optical delays [11], distributed birefringence measurement [12]–[13], ultra-wideband communications [14] and microwave-photonics filters [15]. In the frequency-downshifted CW configuration, the power of the pump pulse continuously transfers to the frequency-downshifted CW through the SBS effect, which leads to an attenuated BDG along the PMF. By using this scheme, a distributed birefringence measurement of a 500-m PMF was realized [17], which is, to the best of our knowledge, the maximum range of a distributed birefringence measurement of a PMF. Brillouin optical time-domain analysis (BOTDA) using Brillouin loss have been widely used for distributed strain and temperature measurement, which rely on mapping the loss spectrum along the sensing fiber [18].
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