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Optical sensing offers an attractive solution to the societal concern for prevention of natural and human-generated threats and for efficient use of natural resources. The unprecedented properties of optical fibers make them ideal for implementing a 'nervous system' in structural health monitoring: they are small, low-cost and electrically and chemically inert. In particular, the nonlinear interaction of stimulated Brillouin scattering allows for the distributed measurement of strain and temperature with tens of km range. In this work, a novel, radar-inspired technique for random-access Brillouin scattering-based sensors is shown, making a significant step towards a real optical sensing nerve. The method selectively addresses each fiber segment as a distinct sensing element in a synaptic neuronal system. The measurement principle relies on phase-coding of both the Brillouin pump and signal waves by a high-rate, pseudo-random bit sequence. Temperature measurements with 1 cm resolution are reported. The measurement range is scalable to several km. The precision localization of disturbances has been a mainstay of radar systems since WW-II. A widely employed radar technique relies on the transmission of long sequences of short pulses [1], and their subsequent processing by a pre-designed matched filter at the receiving end. The filtering procedure compresses the sequence of pulses to a temporally-narrow impulse response function, which provides high resolution together with a large signal to noise ratio [1]. Matched filters in radars are realized by correlating the received radar echoes against a replica of the transmitted sequence, which was stored as a reference. The correlation, in turn, is implemented either through ratio-frequency, electrical analogue mixing or via digital signal processing. Correlation coding has been introduced to Rayleigh scattering-based optical time-domain reflectometry, as early as 1989 [2]. In our work, we carry over the principle of match-filtering long pulse sequences to the realm of fiberoptic sensing [3][4][5][6][7], and use it for the unambiguous probing of a random locale. Stimulated Brillouin scattering (SBS) is an ideally suited platform for such random-access sensing system: not only is it inherently dependent on both strain and temperature [8][9][10][11][12], it also allows for the realization of correlation-based matched filtering of pulse sequences directly in the optical domain, as will be described in detail. LETTER ARTICLE RandomIn stimulated Brillouin scattering (SBS), a relatively intense pump wave interacts with a counter-propagating signal wave, which is detuned in frequency [8]. The combination of the two waves generates an intensity beating pattern, whose frequency equals the difference Ω between the two optical frequencies. Through electrostriction, the intensity beat introduces an acoustic wave, which in turn leads to a traveling grating of refractive index variations, due to the photo-elastic effect. The traveling grating can couple optical power between ...

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