Transmission Matrix Measurement of Multimode Optical Fibers by Mode-Selective Excitation Using One Spatial Light Modulator

Abstract

Multimode fibers (MMF) are promising candidates to increase the data rate while reducing the space required for optical fiber networks. However, their use is hampered by mode mixing and other effects, leading to speckled output patterns. This can be overcome by measuring the transmission matrix (TM) of a multimode fiber. In this contribution, a mode-selective excitation of complex amplitudes is performed with only one phase-only spatial light modulator. The light field propagating through the fiber is measured holographically and is analyzed by a rapid decomposition method. This technique requires a small amount of measurements N, which corresponds to the degree of freedom of the fiber. The TM determines the amplitude and phase relationships of the modes, which allows us to understand the mode scrambling processes in the MMF and can be used for mode division multiplexing.

Deep Learning for Computational Mode Decomposition in Optical Fibers

“…The approach to perform an MD using DH is based on the linearity of the Maxwell equations [19]. Arbitrary electromagnetic field distributions E arb , with amplitude A arb and phase Φ arb , can be decomposed into a linear series of base functions E i with the individual complex-valued weights a i :…”

“…In Figure 4, the optical setup used to capture the individual mode field distributions purely intensity-based as well as holographically, is demonstrated. As it has already been introduced in prior work [19], the system is originally intended for selective mode excitation with an MMF. A single-mode fiber (SMF) is used for spatial filtering of a laser beam to ensure the best beam profile for the experiments.…”

“…In previous work, the author has shown a technique based on Digital Holography (DH) with which complex-valued MMF speckle patterns can be reconstructed and decomposed into the individual mode components by means of an orthogonal series expansion [19]. However, digital holographic techniques have the drawbacks that they are prone to environmental perturbations and phase instabilities [20,21] and that a reference beam is required.…”

Special Issue on Liquid Crystal on Silicon Devices: Modeling and Advanced Spatial Light Modulation Applications

“…Another interesting application for LCoS devices is described by Rothe et al [15]. Multimode fibers (MMF) are promising candidates for increasing the data rate while reducing the space required for optical fiber networks.…”

Image reconstruction through a multimode fiber with a simple neural network architecture

“…However, there is a serious drawback: due to mode-mixing and modal dispersion, any image coupled into a MMF is transformed into a complex speckle pattern at the output 5 . Researchers have devised various methods for reconstructing the input images from the speckle patterns, based on finding the complex transmission matrix of the MMF [6][7][8][9][10] or phase retrieval algorithms [11][12][13] . However, such methods generally require extra apparatus for measuring the optical phase, or have difficulty scaling to large image sizes.…”