Shaping of coherence function of sources used in low-coherent measurement techniques

Abstract
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.