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Optical Coherent Tomography is a measurement technique, which enables us to visualize the internal structure of the investigated object with very high resolution. In OCT systems on order to detect the measured signal the measurement techniques such as: optical frequency domain reflectometry (OFDR) and optical low-coherent reflectometry (OLCR), are employed. In both methods it is necessary to use at least one interferometer. Up today a few topologies for Optical Coherent Tomography have been employed. Still, the most popular is configuration with Michelson interferometer, but also Fizuea is performed as well. Furthermore, it is known that using balanced configuration interferometer topologies is possible to effectively reduce noise-to-signal ratio. Hence, the use of the second interferometer is necessary. In this situation a few of interferometer topologies can be used. In this article the theoretical and experimental investigation of interferometer topologies for Optical Coherent Tomography will be analyzed. The optimal configuration of the designed system has been presented. By the use of a special configuration, our OCT system is sensitive to change of polarization of measured signals.

In low-coherent measurement techniques two kinds of optical signal processing can be used -spectral and temporal. When the temporal signal processing is used, the most critical problem is to identify the position of the central fringe in the interference fringe pattern. It is so important because this position corresponds to the zero of optical path difference and gives information about a measurand. Therefore, it is necessary to use the low-noise optical signal detection set-up in the low-coherent measurement systems. One of the most effective methods of noise-reduction in low-coherent system is using detection system in balanced configuration. In this article, authors present the designed low-coherent optical signal detection system. This system enables us to perform balanced and un-balanced detection, which allows to compare parameters of both configurations. The authors describe theoretical and experimental investigation of balanced and un-balanced low-coherent optical signal detection system.

In low-coherent measurement techniques, such as: low-coherent interferometry, low-coherent reflectometry and low-coherent optical tomography, the coherence length of the source is one of the critical parameters of the designed system. The coherence length of the source effects the resolution of the measurement system. Commercially available low-coherent sources, as the most popular one - SLDs, have the coherence length at the range of 20-40??m. In many applications it is too little to get the required resolution of the measurement. Hence, it is necessary to use some techniques to change the coherence length of the source. It is possible to do so by shaping the spectral characteristic of the source. One of the most effective methods is to use a combination of a few properly chosen sources called synthesizing multiwavelength combination of sources.?In this article, authors analyses the dependence between the spectral characteristic of the synthesized source and the coherence length. The result of theoretical investigation and simulations will show that the use of synthesized source can greatly reduce the coherence length. Additionally, it will be presented that it is possible to reduce the source coherence length by changing its spectral shape.