Self-heterodyne detection for SNR improvement and distributed phase-shift measurements in BOTDA

In this paper we present a Brillouin optical time domain analysis (BOTDA) sensor that takes advantage of the enhanced characteristics obtained employing self heterodyne optical detection combined with synchronous demodulation. By employing this technique we increase the sensitivity of the sensor and demonstrate experimentally a 12.35 dB enhancement in the SNR compared to conventional direct-detection systems. This detection scheme also enables distributed measurements of the Brillouin phase shift in an optical fiber, which can lead to enhanced BOTDA schemes

Brillouin distributed sensor using RF shaping of pump pulses

We introduce a novel configuration for long-range Brillouin optical time domain analysis (BOTDA) sensors that is based on shaping the pump pulses in the radio frequency instead of the optical domain. This results in a simplified setup that uses just one standard intensity modulator to generate pulses with extremely high extinction ratio (60dB in our experiments). We develop a theoretical model for Brillouin interaction in long distance BOTDA and use simulations to demonstrate that the availability of such pure pulses completely suppresses measurement errors caused by pulse leakage. Finally, experimental results are shown to confirm theoretical predictions. A 25 km fibre is measured with our system and the results compared to those obtained using pump pulses with lower extinction ratios

Brillouin spectral scanning using the wavelength dependence of the frequency shift

We present a novel Brillouin spectra characterization method based on the Brillouin frequency shift dependence with pump wavelength. It is applied to a Brillouin optical time domain analysis sensor, resulting in a cost effective experimental setup that also avoids pulse leakage distortion in the measured spectra

Technique for embedding fiber optics in metallic structures for Smart material applications

In this paper a technique to embed fiber optic sensors (FOS) to metallic structures is presented and validated opening possibilities to smart metallic structures. The technique is based in widely adopted and low cost TIG welding. A detailed procedure for scaling up is presented in which, Ni and Cu coated fiber optics at first, and Ni coated FBG sensors at last are embedded in Tin coated forged steel ST-52 with Tin alloy wire. Tensile and temperature tests show stable measurements with 1.3pm/µm and 24pm/ºC sensibility in the embedded sensor in a metallic specimen for strain ranges from 0 to 550µm and temperature ranges from 50 to 200ºC.This paper was supported by the project Unidad mixta de investigación NEXT-BEARINGS with reference IN853A 2015/2, funded by the Spanish general government administration and the Xunta de Galicia through GAIN and the Ministry of Industry, Energy and Tourism of Spain. As requested by the sponsors, the logos are depicted in Figure 7. Ander Zornoza would also like to acknowledge the support received from the MEC through the Torres Quevedo grant with reference PTQ-14-06588

Sensitivity magnification of an interferometric optical fiber sensor with a length-linked virtual reference

Here, it is proposed an alternative to magnify the sensitivity of a single optical fiber interferometric sensor up to two orders of magnitude. The method consists of fabricating the sensing interferometer with a specific length whose spectrum is added to that of a virtual interferometer whose length is linked to the sensing interferometer. In this manner, the spectrum of the sensing and virtual interferometers are made to coincide in a maximum or a minimum. The pattern resulting from said sum has a well-defined envelope that is easy to monitor and correlate with the measurand. Thus, the sensor sensitivity can be magnified as desirable. To demonstrate the method, a microscopic Fabry-Perot interferometer was fabricated and tested as temperature sensor. A temperature sensitivity amplification of 124 times was demonstrated experimentally. The method here proposed may pave the way to practical implementation of the Vernier effect with a single interferometer or resonator.This work was supported in part by the grants PDC2022-133885-100, I + D + i/PID2021-122505OB-C31, TED2021-129959B-C21, funded by MCIN/AEI/10.13039/501100011033, by “ERDF A way of making Europe”, by the “European Union Next Generation EU/PRTR” and by Gobierno Vasco/Eusko Jaurlaritza (IT1452-22); ELKARTEK (KK2021/00082, KK2021/00092, KK2021/108, and KK2022/00080)

Application of remote power-by-light switching in a simplified BOTDA sensor network

We propose and demonstrate the use of spatial multiplexing as a means to reduce the costs of distributed sensing networks. We propose a new scheme in which remote power-by-light switching is deployed to scan multiple branches of a distributed sensing network based on Brillouin Optical Time Domain Analysis (BOTDA) sensors. A proof-of-concept system is assembled with two 5-km sensor fiber branches that are alternatively monitored using a fast remotely controlled and optically powered optical switch. The multiplexed distributed sensor fibers were located 10 km away from the interrogation unit and a Raman pump is used to remotely power the switch. Furthermore, the deployed BOTDA unit uses an alternative configuration that can lead to simplified setups

BOTDA sensor network with power by light remote switching

We present and demonstrate a Brillouin Optical Time Domain Analysis (BOTDA) based long range sensor network with remote switching. Two different 5 km long sections were monitored alternatively by using a fast remotely controlled and optically powered up optical switch. The sensed fibers were located 10 km away from the interrogation unit. The BOTDA unit uses a simplified configuration to reduce the sensor network costs. Proof-of-concept experiments were carried out verifying the capacity of the proposed system.This work was supported by the Spanish Government project TEC2010-20224-C0