In fact, low coherence interference is equivalent to cross-correlation process. First, you need to use a broadband light source. For example, if you want to obtain the plate spacing of a Fabry-Perot interferometer from the light reflected by the Fabry-Perot interferometer, you can obtain the emergent fringe from the reflected light through a low-coherence interference device, wherein the low-coherence interference device provides a continuously variable optical path difference. When the optical path difference of the low coherence interferometer matches the optical path difference of the Fabry-Perot interferometer, the position reflects the plate spacing of the Fabry-Perot interferometer. This principle can be obtained by integrating the intensity of a broad spectrum. Here, you can refer to the doctoral thesis of Xinmeile Co., Ltd., which I have also read. Please forgive me if there are any mistakes.