"基于多模光纤扩展光源的干涉仪相干噪声抑制技术研究"

Abstract: In laser interferometers, defects, bubbles, and dirty spots on optical elements can introduce coherent noise resembling "bullseye rings" in interference patterns. To address this issue, a method for suppressing coherent noise based on a multimode fiber expanded light source is proposed. This method utilizes an expanded light source to suppress coherent noise, selects the optimal multimode fiber core to ensure good interference fringe contrast, and utilizes composite speckle suppression technology to reduce speckle contrast by using a multimode fiber and rotating ground glass, thereby suppressing speckle noise generated by multimode fiber mode interference. Simulation analysis and experimental verification were performed in a 300 mm diameter interferometer. The results demonstrate that in a 300 mm diameter Fizeau plane interferometer with a cavity length of 500 mm and a camera exposure time of 5 ms, controlling the diameter range of the multimode fiber core within 0.52-1.70 mm ensures interference fringe contrast greater than 0.75. The speckle contrast of the final image in the interferometer is maintained around 0.04, with a minimum of 0.044. The multimode fiber expanded light source further improves the uniformity of the light source, leading to a more uniform background in imaging within the interferometer. Experimental results demonstrate that the proposed method effectively suppresses coherent noise in interference patterns.