E10190-000816
FOS
Page 14
3 DATA READINGS AND ANALYSIS
Method for interpreting readings with the FOS Fabry-Perot strain gauge
The following method is proposed as a tool for properly interpreting readings but the
manufacturer should in no way be considered responsible if results obtained do not meet
expectations.
Relation between the length of the cavity (L
cavity
) and the strain (
) is determined by the
following formula:
gage
o
cavity
gage
L
L
L
L
L
)
(
(1)
where:
cavity
L
=
Length of the Fabry-Perot cavity, in nanometers (varies
between 8 000 and 23 000 nm)
gage
L
=
Gauge length (space between the fused weldings), in
millimeters
0
L
=
Initial length of the Fabry-Perot cavity, in nanometers
=
Total strain measurement, in
strains
Total strain
Total strain
is the raw strain obtained directly from FOS readings with all ROCTEST's
fiber-optic readout units after the gauge factor has been defined in readout memory and
selected.
1
0
(2)
where:
=
Total strain measurement, in
strains
Gage length (L
gage
)
Cavity Length (L
cavity
)
Incoming fiber
Fused weldings
Semi-reflecting
mirrors
Micro-capillary
