Multimode optical fibers (MMF) recently attracted a renewed attention, because of their potential for spatial division multiplexing, medical imaging and high-power fiber lasers, thanks to the discovery of new nonlinear optical effects, such as Kerr beam self-cleaning, spatiotemporal mode-locking, and geometric parametric instability, to name a few. The main feature of these effects is that many transverse modes are involved in nonlinear interactions. To advance our understanding, it is necessary to analyse the modal content of beams at the output of MMFs. In this work, based on a computer digital holography method using a phase-only spatial light modulator (SLM) as a correlation filter, we experimentally demonstrate a method of mode decomposition involving a large (≃80) number of fiber modes. To obtain this, we carried out a SLM calibration, and numerically investigated the most critical parameters which affect the fidelity of the decomposition, by comparing experimental and reconstructed beam patterns in both the linear (speckled structures) and in the nonlinear (self-cleaned beams) propagation regime.

多模光纤（MMF）最近因其在空分复用，医学成像和高功率光纤激光器方面的潜力而引起了新的关注，这要归功于发现了新的非线性光学效应，例如Kerr光束自清洁，时空模式锁定和几何参数不稳定，仅举几例。这些效应的主要特征是非线性相互作用涉及许多横向模式。为了加深我们的理解，有必要分析MMF输出处光束的模态含量。在这项工作中，基于使用仅相位空间光调制器（SLM）作为相关滤波器的计算机数字全息方法，我们实验证明了一种涉及大量（≃80）光纤模的模分解方法。为此，我们进行了SLM校准，