The Equilibrium Mode Distribution (EMD) is a steady modal state of a multimode fiber that describes the relative power distribution among modes without any dependence on the length of the fiber. It is an important concept in fiber optics communications, as it determines the performance of the fiber and the data transmission rate.
The EMD is determined by the optical properties of the fiber, such as the core diameter and numerical aperture (NA). It can also be affected by factors such as fiber length, bending losses, and mode-dependent losses. In multimode fibers, multiple modes of light can propagate in the core and the power of each mode is determined by the EMD. The power distribution of the modes determines the overall performance of the fiber, such as the bandwidth and data rate.
Given the power distribution of the modes, the EMD is determined by the mode field diameter (MFD), which is the average of the maximum and minimum field radii of the modes at the fiber output. The MFD is determined by the optical properties of the fiber and is independent of the length of the fiber.
The EMD is also used to characterize the coupling between multimode fibers. By measuring the power distribution of the modes at the fiber output, it is possible to determine how efficiently power is transferred from one fiber to another, regardless of the length of the fibers.
In conclusion, the EMD is an important concept in fiber optics communications, as it determines the performance of the fiber and the data transmission rate. The EMD is determined by the optical properties of the fiber and is independent of its length. It is also used to characterize the coupling between multimode fibers, as it allows for measuring the power distribution of the modes at the fiber output.
