NOVA strain sensing technology

NOVA Strain Sensing is a patented application based on Fiber Segment Interferometry (FSI), a novel range-resolved signal processing technique.
The fiber segment enclosed between two broadband in-fiber reflectors represents the strain sensing element. Strain applied to a NOVA-Segment induces a phase change to the carrier signal of the reflectors. By detecting the phase change from the fibre cleaved end, acting as the reference mirror, it is possible to directly quantify the elongation.
FSI collects the advantages of both discrete (FBG) and distributed (Raman or Brillouin) fiber sensors. The resulting measurement represents the integral of the applied strain over each segment. The segment length sets the spatial resolution (from 10 mm to 100 m)

Working principle

An elongation along the fibre axis or a temperature variation causes a phase difference for the light propagating over the fiber segment.
The Photonics Control Unit (PCU, the NOVA FSI interrogator) detects the phase difference for each segment using the cleaved fiber end as reference mirror. this way, it is possible to retrieve the integral of the strain or the temperature variation for each individual segment.

RESOLUTION
the smallest change in the underlying physical quantity that produces a response in the measurement

dL = 1 e-5μm to 1 e-3μm

the path length of the interferometer and sensors installation.

ACCURACY & PRECISION
Accuracy is the degree of closeness of measurements of a quantity to that quantity's true value.
Precision is the degree to which repeated measurements under unchanged conditions show the same results. The accuracy and precision of a measurement process is usually established by repeatedly measuring some 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.

sensitivity = 0.22 nε/sqrt(Hz)