Title: Sound Reconstruction via Optical Multi-Mode Fiber

Abstract: Sound reconstruction via arbitrary objects has been a popular method in recent years, based on the recording of scattered light from the target object with a high-speed detector. In this work, we demonstrate the use of multi-mode fiber as a medium that enables reconstruction at a much further distance. By placing a speaker near the fiber and using a high-speed camera with a maximum region of interest, we show that it is possible to reconstruct the sound without relying on specific grain information in the speckle. Basic filtration techniques and spectral subtraction methods are employed to improve the signal quality. After applying band-stop and high-pass filters, the magnitude-squared coherence between the original sound and captured data is 0.8 at fundamental frequencies. The proof-of-concept method that we introduce here can be extended to monitor the vibrations of earth's crust and civilian buildings for structural safety.