  Recently, physical layer security in the optical layer has gained significant
traction. Security treats in optical networks generally impact the reliability
of optical transmission. Linear Network Coding (LNC) can protect from both the
security treats in form of eavesdropping and faulty transmission due to
jamming. LNC can mix original data to become incomprehensible for an attacker
and also extend original data by coding redundancy, thus protecting a data from
errors injected via jamming attacks. In this paper, we study the effectiveness
of LNC to balance reliable transmission and security in optical networks. To
this end, we combine the coding process with data flow parallelization of the
source and propose and compare optimal and randomized path selection methods
for parallel transmission. The study shows that a combination of data
parallelization, LNC and randomization of path selection increases security and
reliability of the transmission. We analyze the so-called catastrophic security
treat of the network and show that in case of conventional transmission scheme
and in absence of LNC, an attacker could eavesdrop or disrupt a whole secret
data by accessing only one edge in a network.
