  Technology is moving towards space division multiplexing in optical fiber to
keep up the trend in rate increase over time and to avoid an imminent capacity
crunch. Thus, it is of paramount interest to estimate the potential gains of
this approach. As more spatial channels are being packed into a single fiber,
the increased crosstalk necessitates the use of MIMO to guarantee reliable
operation. In this paper, we exploit the analogy between an optical fiber and a
model from mesoscopic physics - a chaotic cavity - to obtain a novel channel
model for the optical fiber. The model captures both random distributed
crosstalk and modedependent loss, which are described within the framework of
scattering theory. Using tools from replica theory and random matrix theory, we
derive the capacity of the fiber optical MIMO channel model.
