Abstract-Distributed temperature sensors (DTS) measure temperatures by means of optical fibers. Those optoelectronic devices provide a continuous profile of the temperature distribution along the cable. Initiated in the 1980s, DTS systems have undergone significant improvements in the technology and the application scenario over the last decades. The main measuring principles are based on detecting the back-scattering of light, e.g., detecting via Rayleigh, Raman, and Brillouin principles. The application domains span from traditional applications in the distributed temperature or strain sensing in the cables, to the latest "smart grid" initiative in the power systems, etc. In this paper, we present comparative reviews of the different DTS technologies, different applications, standard, and upcoming, different manufacturers.
In recent years, microspectrometer systems fabricated by the LIGA technology for use in the visible wavelength range increasingly made their way to the market. For spectral analysis in the infrared range, a highly transmissive hollow waveguide has now been developed and demonstrated successfully. In combination with linear detector arrays, the hollow waveguide microspectrometer allows to design portable near infrared spectrometer systems. Such a system has now been applied to evaluate the spectrum from 0.9 jim to 1 .15 tm in second order and from 1.15 im to 1.75 im in first order. Due to its outer dimensions of 54 x 36 x 7 mm3 and a low power consumption, it can be integrated in portable spectral analysis systems. It exhibits a high sensitivity (NEP below 1 1 pW) due to a fiber-optical entrance with a fiber core diameter of 300 rim. An indium-gallium-arsenide linear detector array based on a novel setup concept is incorporated in the system. Furthermore, units for pre-amplification of the signal and 16-bit AD conversion are contained. In the present paper, the setup and fabrication of the whole microspectrometer system, its optical features and the detectorspecific solutions are described. The fabrication process which is based on molded polymer parts is presented. Using the experimental results of the electro-optical tests and the polymer spectra measured, the performance of the system will be demonstrated.
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