Chat with us, powered by LiveChat

How is the DTG wavelength changing with temperature and strain?

对不起,此内容只适用于美式英文。 For the sake of viewer convenience, the content is shown below in the alternative language. You may click the link to switch the active language.

An FBG is sensitive to both strain (ε) and temperature (T) changes. In a simplified approximation, one can write:

Wwere λ is the FBG-wavelength; λ0 the wavelength at an arbitrary reference strain ε0 and a reference temperature TSε  the strain sensitivity or gage factor; ST  the temperature sensitivity; Δε = ε – ε the strain change with respect to the reference strain and ΔT = T – T0  the temperature shift with respect to the reference temperature.

The above formula holds for free FBGs and not for FBGs which are fixed to a structure, like for strain gages. In this case, formula (1) should be modified slightly due to the influence of the thermal expansion of the structure. If the structure has a linear expansion coefficient αt , then the thermal expansion of the structure is given by α. ΔT.  If this expansion exceeds the thermal expansion of the fiber glass, which is αf  ΔT , the structure exercises an extra strain on the fiber which is given by  αf) ΔT. Notice that the difference of the thermal expansion coefficients has to be taken because only the excess expansion will be transferred into strain. This strain gives an additional wavelength shift corresponding to Sε  αf) ΔT. The modified formula thus is given by:

It needs to be noticed that a more accurate approximation of the DTG® response is given by the following function:

where λ  is the DTG® wavelength; λ0 the nominal wavelength i.e. the wavelength at zero strain and at a fixed reference temperatureT0   S1 and Sthe temperature sensitivities and k  the strain sensitivity or gage factor. The strain ε is the mechanical strain that is experienced by the fiber. Due to the quadratic nature, the calibration parameters S1 and S2  are depending on the used reference temperature. For strain gauges supplied from FBGS,  the parameters S1 and S2  are determined for a reference temperature of 22.5°C.

This more complex formula is important to use when large temperature variations are expected and is standard implemented for strain gauges in the Illumisense software of FBGS.

Typical values for S1, S2 and k are:

S1 = 6.37E-06

S2 = 7.46E-09

k = 0.772

assuming T expressed in °C and ε expressed in strain.

The thermal expansion coefficient of te fiber αf  is typical around 0.5 μstrain/°C

Notice: Parameters S1, S2 and  αf do not take into account the influence of the coating.  

 

登记并获取简讯
联系我们

我们如何使用您的信息

我们承诺尊重您的隐私,保护您的个人信息。在我们的隐私申明中,您可以了解我们如何处理您的数据,以及我们如何使用这些数据为您提供更好的服务

通过提交本表格,您同意按照我们的隐私声明使用您的数据

Germany

FBGS Technologies GmbH
Winzerlaer Straße 2
D-07745 Jena

Belgium

FBGS International NV
Bell Telephonelaan 2H

B-2440 Geel

China

X2 Suzhou Electronic Technology
Room 103, No. 388
Xinping Str. SIP, Suzhou