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- OTDR (4)
- Strain sensor (4)
- Temperature sensor (4)
- Composite structures (3)
- Distributed acoustic sensing (3)
- Distributed fiber sensing (3)
- Distributed fibre optic sensors (3)
- Fibre optic sensor (3)
- Gamma radiation (3)
- Long period grating (3)
Organisationseinheit der BAM
We investigate two real-time strain sensing principles based on the optical time-domain reflectometry
(OTDR) in polymer optical fibres (POF). The first sensing principle uses the increase of the level of backscattered light
in a stretched POF. The second sensing principle uses the effect of losses due to bending.
The versatility of MPOF offers a variety of sensing applications. In this paper the influence
of strain, temperature and humidity is investigated. The results show that MPOF LPGs are well suited
for strain sensing. Further investigations have to be made to clarify the behaviour on temperature and
humidity in more detail.
The principle of a low-cost but nevertheless powerful POF elongation sensor has already been described in the recent years [1, 2, 3]. The measurement of the phase shift of a signal of a modulated light source which is coupled into two different POF, one being stretched, yields information of the elongation with a resolution of up to 10-5. Analyzing the temporal or frequency behaviour of the signal gives additional information. Since the phase measurement can allow for frequencies up to 2 GHz, the vibrational analysis of macroscopic structures can be extended to several kHz very easily, limited mainly by the signal processing electronics. Thus we processed data of a sensing system applied to a 39 m rotor blade of a wind power generator and could resolve the various frequencies related to different exciting conditions, e.g. the appearance of a beat signal when the blade was externally excited by a mechanical system with a frequency close but not identical to the Eigen frequency of the blade.
A long period grating (LPG) mechanically imprinted in a microstructured polymer optical fibre (mPOF) is embedded in a carbon fibre reinforced polymer (CFRP) unidirectional laminate. Processing steps were established in order to ensure that mPOF does not suffer significant degradation. The strain and temperature responses of the embedded mPOF-LPG were then investigated.