  The digital transformation has been underway, creating digital shadows of
(almost) all physical entities and moving them to the Internet. The era of
Internet of Everything has therefore started to come into play, giving rise to
unprecedented traffic growths. In this context, optical core networks forming
the backbone of Internet infrastructure have been under critical issues of
reaching the capacity limit of conventional fiber, a phenomenon widely referred
as capacity crunch. For many years, the many-fold increases in fiber capacity
is thanks to exploiting physical dimensions for multiplexing optical signals
such as wavelength, polarization, time and lately space-division multiplexing
using multi-core fibers and such route seems to come to an end as almost all
known ways have been exploited. This necessitates for a departure from
traditional approaches to use the fiber capacity more efficiently and thereby
improve economics of scale. This paper lays out a new perspective to integrate
network coding (NC) functions into optical networks to achieve greater capacity
efficiency by upgrading intermediate nodes functionalities. In addition to the
review of recent proposals on new research problems enabled by NC operation in
optical networks, we also report state-of-the-art findings in the literature in
an effort to renew the interest of NC in optical networks and discuss three
critical points for pushing forward its applicability and practicality
including i) NC as a new dimension for multiplexing optical signals ii)
algorithmic aspects of NC-enabled optical networks design iii) NC as an
entirely fresh way for securing optical signals at physical layers
