Brillouin distributed time-domain sensing in optical fibers: state of the art and perspectives

Optical fiber sensors based on stimulated Brillouin scattering have now clearly demonstrated their excellent capability for long-range distributed strain and temperature measurements. The fiber is used as sensing element, and a value for temperature and/or strain can be obtained from any point along the fiber. After explaining the principle and presenting the standard implementation, the latest developments in this class of sensors will be introduced, such as the possibility to measure with a spatial resolution of 10 cm and below while preserving the full accuracy on the determination of temperature and strai

Vector analysis of stimulated Brillouin scattering amplification in standard single-mode fibers

The polarization properties of stimulated Brillouin scattering (SBS) amplification or attenuation in standard single-mode fibers are examined through vectorial analysis, simulation and experiment. Vector propagation equations for the signal wave, incorporating SBS and birefringence, are derived and analyzed in both the Jones and Stokes spaces. The analysis shows that in the undepleted pump regime, the fiber may be regarded as a polarization-dependent gain (or loss) medium, having two orthogonal input SOPs, and corresponding two orthogonal output SOPs, for the signal, which, respectively, provide the signal with maximum and minimum SBS amplification (or attenuation). Under high Brillouin gain conditions and excluding zero-probability cases, the output SOP of arbitrarily polarized input signals, would tend to converge towards that of maximum SBS gain. In the case of high SBS attenuation the output SOP of an arbitrarily polarized signal would approach the output SOP corresponding to minimum attenuation. It is found that for a wide range of practical pump powers (<= 100 mW) and for sufficiently long fibers with typical SBS and birefringence parameters, the signal aligned for maximum SBS interaction will enter/emerge from the fiber with its electric field closely tracing the same ellipse in space as that of the pump at the corresponding side of the fiber, albeit with the opposite sense of rotation. The analytic predictions are experimentally demonstrated for both Stokes (amplification) and anti-Stokes (attenuation) signals

Optical Fibre optimized for the Reduction of Nonlinear effects

An optical fibre designed to simultaneously attenuate the effect of modulation instability and stimulated Raman scattering. A first solution proposes to use non-zero dispersion shifted fibres in the normal dispersion regime to reduce both influences at the same time. A further solution proposes to implement corresponding filter elements in the signal line. A still further solution proposes to additionally provide absorber elements for the Raman wavelengths or to design the core as a leaky one for these wavelengths

Achievements in slow and fast light in optical fibres

The ubiquitous role occupied by optical fibres in modern photonic systems has steadily stimulated research to realize slow and fast light devices directly in this close-to-perfect transmission line. This potentially offers the key advantage of a direct and flexible integration in most existing optical systems. The recent progress in the realization of optically-controlled delays in optical fibres, under normal environmental conditions and in the high-transparency spectral region, has paved the way towards real applications based on slow and fast light. This presentation shows the state-of-the-art research in this fascinating field and the possible outcomes in the near future

Slow and fast light in optical fibres

The ubiquitous role of optical fibres in modern photonic systems has stimulated research to realize slow and fast light devices directly in this close-to-perfect transmission line. Recent progress in developing optically controlled delays in optical fibres, operating under normal environmental conditions and at telecommunication wavelengths, has paved the way towards real applications for slow and fast light. This review presents the state-of-the-art research in this fascinating field and possible outcomes in the near future

Slow Light in Optical Fibers: State-of-the-Art and Perspectives 10 Years After the First Demonstration

The possibility to directly realize all-optical delay lines in optical fibers has triggered efforts of research during the past decade, with few practical outcomes. The reason is fundamental, caused by the unescapable relation between delay and distortion

Review and Progress on Distributed Fibre Sensing

Optical fibers have crucially contributed to promote the concept of distributed sensing with a large impact. The different types of fiber optics distributed sensing techniques are reviewed and their performances and limits are presented

Brillouin distributed time-domain sensing in optical fibers: state of the art and perspectives

Optical fiber sensors based on stimulated Brillouin scattering have now clearly demonstrated their excellent capability for long-range distributed strain and temperature measurements. The fiber is used as sensing element, and a value for temperature and/or strain can be obtained from any point along the fiber. After explaining the principle and presenting the standard implementation, the latest developments in this class of sensors will be introduced, such as the possibility to measure with a spatial resolution of 10 cm and below while preserving the full accuracy on the determination of temperature and strain

Brillouin Distributed Fibre Sensing: State of the Art and Perspectives

Developed societies require more and more information for their safety and for their economic development. Recent disasters due to landslides, fires in tunnels and collapses of bridges are a source of serious concern on the part of the public which seeks for more safety and for an efficient prevention of these frequent recurrences of dangers. Sensing in adverse environment and extreme conditions requires dedicated techniques. Quite recent technologies may offer novel valuable solutions and give rise to a strenuous research effort. Optical technologies are an essential actor owing to their tremendous capability to transmit and process a high density of information. Optical fibre is a key component for these technologies and its potential for optical processing and for collecting information as sensing probe is still widely unexplored. The development and the popularity of telecommunications have entirely screened the fact that optical fibres may be efficiently used for sensing purposes. In this paper we present applications of a novel technique using optical fibres to monitor large structures for safety purpose. The fibre is used as sensing element and can provide distributed measurements of quantities like temperature or strain. In other words a value of temperature and/or strain can be obtained for any point along the fibre. This is made possible by using a nonlinear optical effect in the fibre called Stimulated Brillouin Scattering (SBS). Optical fibre sensors based on stimulated Brillouin scattering have now clearly demonstrated their excellent capability for long-range distributed strain and temperature measurements. The Brillouin interaction causes the coupling between optical and acoustic waves when a resonance condition is fulfilled. It turns out that this resonance condition is strain and temperature-dependent, so that determining the resonance frequency directly provides a measure of temperature or strain. The resonance frequency is an intrinsic property of the material that may be observed in any silica fibre. This is very attractive since the bare fibre itself acts as sensing element without any special processing or preparation on the fibre. Standard optical cables may thus be used, resulting in a low-cost sensing element that may be left in the structure. Since the optical effect only depends on the fibre material, it is absolutely stable in time and independent of the instrument. Different measurements performed over a long-term period are thus fully comparable. The latest developments in this class of sensors will be shown, such as the possibility to measure with a spatial resolution of 10 cm and below, while preserving the full accuracy on the determination of temperature and strain. Illustrative examples of site measurements will be presented and future prospects will be discussed

Next generation of optical fibre sensors: new concepts and perspectives

Fibre sensing has reached an interesting turning point today: a clearer assessment about promises that were really held and those that failed to convince can be envisioned. A choice of key fibre sensing techniques will be reviewed and a critical discussion about their real impact will be presented. The promising potentialities of distributed sensing in its different flavours will be addressed, without omitting perspectives on other major techniques, such as Bragg gratings and chemical sensors