Limited Feedback of Principal Modes for High Speed Multimode Fiber Links

Multimode fibers are widely used for short and medium haul links. However, the data rates through multimode fibers (MMFs) is limited due to modal dispersion. Recently, it has been shown that signaling in the set of "principal modes" (PMs) of the MMF can reduce dispersion significantly. However, accurate knowledge of the PMs is required at the transmitter to utilize them effectively. In this paper, we propose the use of Grassmannian line packing as a quantization scheme for communicating the PMs to the transmitter, and describe various codebook designs for few-mode and large-core MMFs. Simulations reveal that the channel frequency response can be improved by 5 dB for few-mode fibers and 2 dB for large-core MMFs using quantized PMs.