Multimode Fiber Speckle Imaging Using Integrated Optical Phased Array and Wavelength Scanning

The silicon optical phased array has emerged as a promising approach for speckle imaging through multimode fibers. High spatial resolution typically requires a large number of phase channels. In this paper, we propose and demonstrate a high-resolution wavelength-scanning multimode fiber imaging system, enabled by an integrated optical phased array with only 8 phase shifters. By scanning 50 different wavelengths within a 10-nm span, the number of linearly independent speckle patterns is significantly increased from 57 to 3000, ensuring high spatial resolution imaging. The speckle imaging model is modified for use with the wavelength-scanning system, and an algorithm based on particle swarm optimization is proposed for the automatic multiwavelength compensation. Two algorithms are used for image reconstruction. The pseudo-inverse method is computationally efficient and suitable for real-time imaging, while the iterative algorithm based on total-variation regularization can provide better image quality. An equivalent spatial resolution of 1.75 mu m is experimentally achieved with a field of view diameter of 105 mu m. The number of resolvable points is estimated to be similar to 3000, which is two orders of magnitude greater than the number of phase shifters.