Measuring with light
In this perspective, optical fibre sensing represents the best performing solution to acquire precise data in challenging environments. How?
1. Light propagating through an optical fibre is affected by the surrounding environment
2. By measuring specific light parameters, one can reconstruct what happened to the fibre
3. One can infer with extremely high accuracy the conditions of the structure under monitoring and its environment, if the fibre is integral with it (i.e., deformation, temperature, strain, displacement, pressure, etc.)
FSI (Fiber Segment Inteferometry)
Partially reflecting elements are integrated into the sensing fibres. The distance between two consecutive reflective elements is a segment. The segment length L (from 10 mm to tens of meters) defines the spatial resolution.
Strain (∆L) or a temperature difference (ΔT) applied to a segment induces a phase change to the light carrier signal for each reflector. From the measurable phase change, it is possible to quantify the deformation.
From the phase shift associated to each segment (sensing element), measured with dedicated Photonic Control Units (PCU), is possible to derive and visualise the real time 3D deformation of the element to which the FSI optic fibers is integral with, through the development of different kind of transducers.
Each sensor is composed by a certain number of gratings which are continuous sensing elements and not discrete. Therefore, FSI 3D shape sensing is continuous, highly precise and with high resolution.
FSI sensors differ from the other (optical or electrical) sensors existing in the market allowing spatial continuity of the shape variation measurement of the elements to which they are attached to.
*installation of sensors in series on a single cable, unlike traditional sensors which all have a double dedicated wiring for each single sensor.
FSI sensors give accurate information regarding the modal and vibration analysis and the thermal behaviour. Therefore, they can be used beside shape sensors as temperature sensors and accelerometers.
Advanced algorithms accurately track changes in vibration modes and can provide acoustic sensing during life cycle of complex structures.
FSI sensors are immune to humidity, sea environment corrosion, lightings and EMI emissions. They can operate in ATEX environment and immerse in liquids.