The Study Of Partial Time Coherence Of Single-Mode Laser Transmiting In Step Multimode Optical Fiber

Optical fiber is the most important transmission medium of light in optical fiber communication system, So it's great significance to study propagation characteristic of Partial Time Coherent light transmitting in Step-Index Multi-Mode Fiber. In this paper, we study the Single transverse mode laser with Partial Time Coherence transmitting in Step-Index Multi-Mode Fiber, mainly analyze the relation between the coherence of models and the temporal coherence, also study its transmitting law. Because of heterogeneity with inner random and wavelength scale in Step-Index Multi-Mode Fiber and coherence will result in two consequences:one is mode couple, the other is the output light intensity of fiber show as Speckle distribution. These will make the transmission of partial time coherence light more complicated. In order to obtain a simplified analytic conclusions, we started analysis basis on the fully mode coupling (equipartition of energy for all modes). And assuming that the time delay between adjacent mode are equal. Firstly, we study the mode coherence matrix of the Single transverse mode laser transmitting in Step-Index Multi-Mode Fiber. Then, we use discrete Fourier analysis to derive out eigenvalue spectrum with Gaussian distribution, thus we can obtain simple formula of speckle contrast. A agreement is obtained between the formula and experimental results of speckle contrast. Secondly, we introduce time delay into Coherence Matrix, and analyze the change trend of Time Coherent.