Abstract
Multi-core fibers are needed for expanding the transmission capacity of submarine optical communication
because submarine transmission and cable technologies have advanced, leaving scant room for capacity
expansion by enhancing spectral efficiency or increasing the number of fibers per cable. 2-core fibers
for submarine cable are becoming the first commercial applications of multi-core fibers because of
their optical characteristics that are competitive to those of single core fibers as well as availability of
mass-produced fibers.
