The fiber-optic weigh technology is the process to estimate the gross weight of the loads

by measu-ring the loads forces acting on the weigh system with fiber-optic sensing technology. Several fiber-optic weigh system have been reported by prior authors

such as the microbending system

the polarimetric system and the interferometric system. Here

we demonstrate a novel weigh system based on fiber Bragg grating(FBG) sen-sing technology. The sensing principle of FBG is that: when the physical quantity

strain or temperature

monitored by FBG sensors changes

it will cause the reflected wavelength shift of the FBG sensors. This wavelength shift is proportional to the variation of strain or temperature. Compared with other fiber-optic systems

the FBG-based weigh system

which is simpler in design and easier to be integrated

can offer higher accuracy

longer lifetime

and lower costs simultaneously. In the weigh system

the load-supporting structure is very important. In this experiment

a metal cantilever beam was chosen as the elastic body of the weigh system to support the loads. With the theory of the strength of materials

we analyzed the cantilever beam structure and deduced that the force on the free end of the cantilever beam was direct proportion to the deflection variation of the beam. We could use a FBG to detect the deflection of the beam to calculate the force on the free end of the beam. Based on this conclusion

we designed the cantilever beam with special parameters to meet this weigh system. We also used the ANSYS software to calculate the deflection of the designed cantilever beam

and the result showed that this metal cantilever beam was suitable for this weigh system. In this experiment

in order to use the FBG detect the deflection variation of the cantilever beam

one end of the FBG was adhered on the free end of the standard cantilever beam with special gelatin

then the FBG was dragged to make the FBG reflected wavelength shift about 1nm. Finally

the other end of the FBG was adhered on the motherboard of the weigh system. The bonding coefficient of the gelatin is about 0.93. When the loads were applied to the end of the cantilever beam

it caused the deflection of the beam

and this caused the FBG deformation along the fiber longitudinal direction. A fiber grating interrogator was applied to detect the wavelength shift of FBG. The best resolution of the interrogator is 1 pm

and the scan rate of the interrogator can reach 5 000 Hz. According to monitoring the wavelength shift of the FBG

the deflection variation of the cantilever beam could be obtained. After analyzing the cantilever beam structure

we could derive the mathematic relationship between the loads applied to the end of the beam and the flexivity of the beam

and the weight of the applied loads could be made out by the value of the flexivity. The experiment results demonstrated that the weight range of this system could reached about 50 kg

the sensitivity of this system was about 0.05 kg

and the related linear regression coefficient is 0.9997.