Periodic Reporting for period 3 - PULSe (Pervasive Ubiquitous Lightwave SEnsor)
Reporting period: 2018-09-01 to 2019-12-31
Brillouin Distributed Optical Fibre Sensing is a powerful lightwave technology for measuring and mapping temperatures, deformations and pressures in thousands of industrial, civil and environmental applications using a sensing fibre cable installed along the asset to be monitored and an interrogator equipment to sweep a “virtual sensor” and measure temperature (strain) individually at any cable point.
Brillouin can be an ideal pervasive sensor for long-range distributed sensing (simultaneous individual measurements at different locations) using inexpensive fibres; it can be also an ideal ubiquitous solution because of its intrinsic safety (no sparks in explosion/fire risk areas), immunity to high-voltage and interferences, resistance to moisture and corrosion, bio-compatibility and miniaturization.
The first generations of novel Brillouin equipment could not match the price reduction expectations for a wider ‘mass-scale’ market. The synergy of cost-effective equipment, easy-to-apply sensors, processing software and accessible know-how could boost the diffusion of Brillouin sensing in a range of different markets with well-established and new application domains.
PULSe main goals are to optimize, industriale and secure the market uptake of a Brillouin distributed sensing solution based on a synergy of innovative interrogator equipment, strain sensing cable, data processing software and open-access support tools.
PULSe partners covers the full value chain of development, manufacturing, commercialization and service. PULSe partners have established experience on Brillouin and project management, a captive market ready for immediate exploitation of the project results cooperation with already established external foreign support partners geographically consistent with the market segmentation.
The physical principles underlying the PULSe project sensor system are based on stimulated Brillouin scattering effect along single-mode optical fibers, and the sensing system exploits a technology called Brillouin optical time-domain analysis (BOTDA).
A Brillouin sensing solution comprises a sensing fibre cable, that has to be installed or displaced along the asset to be monitored, and a sensor interrogator equipment that creates the “virtual sensor” that is swept along the cable length to measure the distribution of deformation, temperature or pressure along its whole length.
The technology is based on the Brillouin effect, an interaction between lightwaves and mechanical vibrations in which the striction induced by the electrical field of the lightwave excites mechanical waves (phonons) inside the fibre at the expense of the wavelength of the light that is interacting, with a linear dependence from the temperature and strain in the fibre. By analysing the Brillouin scattered light point-by-point along the fibre, the deformation or temperature is continuously measured just as if a “virtual” sensor would have been swept along the whole fibre length .
State-of-the-art of this technology are Brillouin Optical Time-Domain Analyser (BOTDA) based on Stimulated Brillouin Scattering (SBS). The basic working scheme of a BOTDA is presented in Figure 1 and works as follows: (1) a pulse of “pump” light is injected at a first end of the sensing fibre and creates a travelling virtual sensor that moves along its length, while at the opposite end of the fibre (2) the “probe” light having a specific wavelength is continuously injected. When the “travelling” sensor (3) sweeps a region of the sensor that has the temperature (or strain) characteristics tested by the specific “probe” wavelength in use, the probe light results perturbed by stimulated Brillouin amplification. In our employed low-cost dual lightwave source , the pump and probe lights are generated with a special technique. Perturbed light (4) is then analysed in the time-domain in order to locate the position of the perturbed region.
 Horiguchi, T. et al., IEEE Photonics Technology Letters, 1, pp. 107-108, (1989).
 D. Marini, M. Iuliano, F. Bastianini and G. Bolognini, Proc. SPIE, vol. 10323, p. 509 (2017).
Throughout the project final period, the technical activities have consisted in finalization of the industrialized interrogator equipment and sensing cable, the use of developed the data management platform and the implementation of the field-trial tests with the developed sensing system.
The dissemination and exploitation activities have mostly focused on promotion activities for the developed industrialized sensing system, on scientific publications and white papers, on technical certifications and standardization, on involvement of external exploitation partners and participation/product presentation to meetings and events involving industrial rather than academic audience, most notably the organization of the final workshops presenting the sensing system and project results.
The main achieved results at project completion are: the development and in-field test of an industrial optical fiber sensing system comprising an interrogator and a specifically-developed sensing cable, together with a developed data management platform to be used in industrial application monitoring. Their exploitation and dissemination involved in particular promoting at industrial events and meetings, setting up of business contacts with industrial stakeholders in order to foster developed system installation, and organization of two specific PULSe project workshops presenting project developed products and attained results.
PULSe interrogator is based on a novel patented BRL system in which part of the pump light sourced by a master laser is injected into a ring circuit in counter-propagation with some Brillouin-shifted light initially produced by spontaneous scattering and successively by self-sustained stimulated scattering.
Moreover, bare optical fibre is generally unsuitable for strain sensing in industrial applications because of no protection, handling issues and non-uniform stress transfer, and a fiber cable must be used with optical fiber sensors. Most strain sensing cables reported in literature show low market availability, high price and large Minimum Order Quantity (MOQ). To sense strain, the optical fibre must be tightly glued to the cable sheath but this makes the cable difficult to handle because any bending can damage the fibre. In the specialty cable under development with PULSe project, the fibre coupling is loose until the product is installed on the final application.
The synergy of cost-effective equipment, easy-to-apply sensors, processing software platform and accessible know-how will help boosting the diffusion of PULSe solution in a market of already validated applications and with wider cross-sector impact in environmental protection, CO2 and greenhouse gas reduction, social costs and public health.