Linear network coding and parallel transmission increase fault tolerance and optical reach

Modern optical network systems are evolving toward more spectral flexibility and efficiency driven by the ever-increasing need for high-speed transmission. In spectrally efficient elastic optical networks, a more integrated, fault tolerant transmission system is becoming critical, due to the accompanying optical impairments and the resulting limitations in optical reach. Previous work has addressed the issue of optical reach and transmission tolerance to faults (errors) in the physical layer by deploying various forward error correction schemes. This paper proposes a different approach, complementary to the error correction mechanisms in the physical layer. In our approach, we apply randomized linear network coding (RLNC) at the source node to encode all data in the electronic layer before all-optical transmission. To achieve fault tolerance, a coded auxiliary optical channel is used in parallel with the main path. With the auxiliary path and RLNC, as shown analytically, the system is able to use more advanced modulation formats in the main path, while being highly tolerant to bit errors and packet loss caused by optical impairments. The results show that the system can alleviate the constraints on optical transmission quality and achieve better optical reach and spectral efficiency.