search

Press ENTER to search or ESC to close

Introduction

The most complete and accurate knowledge of structures and environments will push engineering to a new level of optimization.

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.)
NOVA technology is based on Fibre Segment Interferometry (FSI)

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.
Introduction
NOVA technology measures the integral of the quantity of interest over a segment

NOVA sensors: more advantages

NOVA fibre sensors will trigger a new era of structural and environmental monitoring also thanks to the several advantages over electrical sensors:
Intrinsically passiveNo power needed at the sensing points
EMI immuneIntrinsically insensitive to electro-magnetic interferences
DurableThe glass fibre is resistant to corrosion, high temperatures, harsh environments
Accessible remotelyLight propagates unperturbed before reaching the sensing area
CompactOptical fibres are as thin as a human hair and can be embedded into composites
MultiplexableSeveral sensors can be arranged along the same fibre
And many more...

Innovation and comparison

Introduction
NOVA technology is sensitive to any external physical change introducing disturbance in the fibre, such as temperature, strain, pressure, vibration, humidity, inclination etc.

Fibre Bragg Grating technology (FBG) represents the most common technology for discrete optical fibre sensing.

Compared to FBG standards, NOVA moves the bar ≈ two order of magnitude higher in respect to the most critical sensing parameters.

NOVA concept merges the features of discrete and distributed fibre sensing techniques, covering a wider range of applications with the same technology.

Comparison FBG-FSI: Strain

Comparison FBG-FSI: Strain
Tensile test comparison between FBG and NOVA FSI sensors.
Load held at 0 N before linear increase.

FBG
  • standard deviation of 0.75 με @ 250 Hz

FSI Nova
  • standard deviation of 0.04 με @ 1 kHz
  • FSI captures the strain oscillation directly caused by our INSTRON calibration machine

Comparison FBG-FSI: Temperature

Comparison FBG-FSI: Temperature
FBG
  • standard deviation of 0.02 °C @ 50 Hz

FSI
  • standard deviation of 0.003 °C @ 1 kHz

FSI vs current fibre sensors: overview

Comparison of the most relevant sensing parameters for NOVA technology1 and the most spread fibre sensing techniques:
Technology
Distributed/ Discrete
Detectable deformation
Data rate
Spatial resolution
Sensors per interrogator - sensing range
FBG2
Discrete
1 µstrain
< 10 kHz
2 - 10 mm
≈40
Rayleigh OFDR3
Distributed
1 µstrain
< 100 Hz
1 - 10 mm
20 - 1000 m
Rayleigh DAS3
Distributed
< 0.1 µstrain
< 5 kHz
> 5 m
10 - 70 km
Brillouin OTDR/OTDA3
Distributed
2 - 10 µstrain
< 1 Hz
0.1 - 5 m
5 - 150 km
NOVA FSI
Discrete/Distributed
< 0.01 µstrain
1 Hz - >200 kHz
0.01 - 100 m
>100
1 Intellectual Property Publication Number: W0 2019/166765/A1
2 Based on typical values for commercial FBG interrogators 
3 Distributed optical fiber sensing: Review and perspective, Ping Lu et al., Appl. Phys. Rev. 6, 041302 (2019)