  Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) based
Elastic Optical Network (EON) is one of the emerging technologies being
considered for next generation high data rate optical network systems. Routing
and Spectrum Allocation (RSA) is an important aspect of EON. Apart from
spectral fragmentation created due to spectrum continuity and contiguity
constraints of RSA, transmission impairments such as shot noise, amplified
spontaneous emission (ASE) beat noise due to coherent detection, crosstalk in
cross-connect (XC), nonlinear interference, and filter narrowing, limit the
transmission reach of optical signals in EON. This paper focuses on the
cross-layer joint optimization of delay-bandwidth product, fragmentation and
link congestion for RSA in CO-OFDM EON while considering the effect of physical
layer impairments. First, we formulate an optimal Integer Linear Programming
(ILP) that achieves load-balancing in presence of transmission impairments and
minimizes delay-bandwidth product along with fragmentation. We next propose a
heuristic algorithm for large networks with two different demand ordering
techniques. We show the benefits of our algorithm compared to the existing load
balancing algorithm.
