Compact and fast interrogation unit for fiber Bragg grating sensors


Kiesel, P.; Beck, M.; Schmidt, O.; Johnson, N. M.; Bassler, M.; Ecke, W.; Schroeder, K.; Bartelt, H. Compact and fast interrogation unit for Fiber Bragg grating sensors. Photonics in the Transportation Industry: Auto to Aerospace; 2007 September 9-12; Boston, MA; SPIE Proceedings 6758: 67580A.


We present a compact and fast wavelength monitor capable of resolving pm wavelength changes. A photosensor array or position detector element is coated with a linear variable filter, which converts the wavelength information of the incident light into a spatial intensity distribution on the detector. Differential read-out of two adjacent elements of the photosensor array or the position detector is used to determine the centroid of this distribution. A wavelength change of the incident light is detected as a shift of the centroid of the distribution. The performance of this wavelength detector was tested with a wavelength tunable light source. We have demonstrated that our device is capable of detecting wavelength changes as small as ~0.1 pm. The wavelength monitor can be used as read-out unit for any optical sensor that produces a wavelength shift in response to a stimulus. In particular, changes in the reflection properties of one and two-dimensional photonic crystals can been detected. The performance of this interrogation method has been tested for the case of temperature and strain sensors based on Fiber Bragg Gratings (FBG).

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