Differences between NOVA technology and FBG technology

NOVA SCIENTIA technology introduces a new physics in the optical fibre field that improves all the main characteristics of what is available today with FBG's technology: accuracy, data rate speed, monitoring possibilities and costs.

NOVA Tech goes beyond the limits of FBG technology
Today Optical-fiber sensors based on fibre Bragg gratings (FBG's) is the most used and developed way of using the light reflected in an optical fibre as a sensor. FBG's  rovide remote measurements of temperature, strain, and the derivative information. FBG's find many industrial applications in civil engineering, aeronautics, train transportation, space, naval, bio-medics, green energy and electrical engineering. FBG sensors properly positioned on a component give information about strain, temperature, and all the derivative properties, in a non intrusive way.

NOVA technology is directly compared to FBG's in what are the main characteristics that made the Fibre Optic Bragg Grating sensors very attractive in so many industries.
The direct compare is between NOVA technology and Wavelength Division Multiplexing single point FBG sensor technology that at today is the most used FBG's technique.

NOVA Tech
Strain applied to a NS (NOVA-Segment) induce a phase change to the unique carrier signal for each reflector. In detecting the phase change from the reference it is possible to quantify the elongation and so the strain applied. 

FBGs-TECH
Strain applied to an FBG array induces a wavelength change in the optical return spectrum of the sensor and so detecting the wavelength shift from a starting position it is possible to quantify the applied strain.

NOVA Tech
Laser: standard telecommunications distributed feedback (DFB) this gives advantages in term of power unit performance and costs.
An elongation along fibre axis cause an increase (or decrease) in the NS length. The system is capable of detecting the difference in length of each of the segment from the cleaved end, that act as a reference point. Subtracting the segment delta L from the reference it is possible to have the single segments dL and so the strain generated.

FBGs-TECH
Laser: specific tuneable laser with a wavelength operation window. This is a limitation in term of hardware performance and costs. An elongation along fibre axis induces a strain that applied to an FBG array create a wavelength change in the optical return spectrum of the sensor and so detecting the wavelength shift from a starting position it is possible to quantify the applied strain.

 

NOVA Tech	FBGs-TECH
0.01 microstrain	1.2 microstrain
Minimum dL detectable is in the order of 1e-5 μm that on a short NS sensor (10mm) is equal to 1 nanostrains. Temperature sensing accuracy is 0.005 degC.	Min wavelength shift measurable is 1 picometer that is equal to a strain of 1.2 microstrain in the fibre senor. Temperature sensing accuracy is 0.1 degC.

The accuracy and precision of a measurement process is usually established by repeatedly measuring traceable reference standard.
This applies when measurements are repeated and averaged, the precision of the average (sensitivity) is equal to the known standard deviation of the process divided by the square root of the number of measurements averaged
NOVA Tech sensitivity = 0.22 nε/sqrt(Hz) - FBG sensitivity = 200 nε/sqrt(Hz)

NOVA Tech	FBG's TECH
>200 kHz	max 2.5 kHz
Laser used is a standard telecommunications distributed feedback (DFB) laser, the limit is the FPGA in the hardware that can achieve >1000 kHz	Typical scan frequency is 2.5kHz, the Laser used is a special tunable Laser that has limitation on the achievable acquisition data rate speed.
none	40nm
The wavelength used in the ultrashort grating is unique for each of sensors, this  eliminate the operating window and the strain overlap issue. This gives immense advantages in multiplexing, in sensing layout  definition, design, and in measurements possibilities.	Typical laser wavelength band width is 40k picometers, that are equal to 40k microstrain. The sum of the total measured strain by the sensors must be <40k us and they cannot overlap. This can be a limiting constrain in multiplexing, in  ensing layout and in data reliability.
bond 0.25 mm grating	bond 8 mm grating
The strain transfer tolerance is very high because it needs to be guaranteed mostly where the ultrashort gratings are. Because the gratings are 0.25 mm long the bonding process is simple and reliable.	The strain transfer along the 8 mm fbg length must be perfect otherwise the sensor reads not reliable results due to errors in the peak detection shift. The bonding process quality (shear,thickness, porosity ) is a key factor.
continuos	discrete
Integrate the applied strain field over the sensing fiber. The advantages of long-gauge length sensors for structural health monitoring include the reduced dependence on the local properties at the sensor location of measurements made on a non homogeneous substrates and the absence of sensing gaps, whereby the integrating property of the measurement ensures that a localised strain event  anywhere along the sensing fiber will not be missed.	Highly localised sensors that detect the deformation only in where the sensor is applied, typically on a length of 8 mm. The disadvantage is that the monitoring is discrete on where the sensors are, so a localised strain that is not in the sensor 8 mm length will be missed. This is crucial, for instance, when the structure health monitoring is the objective of the installation, localised stiffness drops due to a growing crack or a temperature hot spot, for example, will not be flagged if not in the 8 mm.
>40 sensors	40 sensors
The limitation is only the FPGA that create the hardware. This can be bespoke for the application. Not having an operation window create space for an high number of sensors.	The laser operation window and the electronics used are key factor for the limitation in term of number of sensors that can be multiplexed in the same channel.