Compact and fast interrogation unit for fiber Bragg grating sensors

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).

Citation

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.