We numerically analyzed reflection spectrum of Brillouin dynamic grating localized by intensity-modulated correlation-domain technique. Furthermore, based on the results, we proposed a novel modulation technique achieving better spatial resolution for distributed fiber sensing along a polarization-maintaining fiber.
We propose and demonstrate a novel method for controlling stimulated Brillouin scattering with light in a phase-sensitive manner. Our results indicate that Brillouin gain can be enhanced or suppressed in a polarization-maintaining fiber via acoustic wave interference by controlling the relative phase of orthogonally polarized light, which induces acoustic waves. This method paves the way for the all-optical control of Brillouin interaction.
Single-photon interference experiments are attempted in the time domain using true single-photon streams. Self-heterodyning beats are clearly observed by letting the field associated with a single photon interfere with itself on a field-quadratic detector, which is a time analogue of Young's two-slit interference experiment. The temporal first-order coherence of single-photon fields, i.e., transient interference fringes, develops as cumulative detection events are mapped point-by-point onto a virtual capture frame by properly correlating the time-series data. The ability to single out photon counts at a designated timing paves the way for digital heterodyning with faint light for such use as phase measurement and quantum information processing.
Brillouin correlation-domain techniques used for fiber optic distributed sensing have been widely studied owing to their unique feature in which the spatial resolution is not limited by the phonon lifetime, unlike with time-resolved methods. This approach can be divided into two main classes according to the scattering type, i.e., spontaneous or stimulated Brillouin scattering. In this study, we derived a formula for the measurement spectrum of the correlation-domain reflectometry using spontaneous Brillouin scattering by considering its stochastic properties. The derived formula is equivalent to the formula of the system using stimulated Brillouin scattering. Our results indicate that the methods developed thus far for improving the system’s performance can be commonly applied.
A method to reconstruct the spatial distribution of Brillouin gain spectrum from its Radon transform is proposed, which is a type of optical computed tomography. To verify the concept, an experiment was performed on distributed Brillouin fiber sensing, which succeeded in detecting a 55-cm strain section along a 10-m fiber. The experimental system to obtain the Radon transform of the Brillouin gain spectrum is based on a Brillouin optical correlation-domain analysis with a linear frequency-modulated continuous-wave laser. Combining distributed fiber sensing with computed tomography, this method can realize a high signal-to-noise ratio Brillouin sensing.
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