Signal Overlap for Elastic Optical Networks

In Elastic Optical Networks, advanced transmission techniques based on coherent detection strategies have been proposed and exploited to provide high flexibility in resource allocation. So far, these techniques have assumed the constraint of each optical signal being transmitted along a dedicated frequency slot, by carefully avoiding frequency overlap with other optical signals. In this study, an overlap technique, that enables uncorrelated optical signals to be superimposed along the same spectrum resources, is designed and validated through simulations, both in terms of performance bounds and bit-error rate in coded transmissions. In particular, it is demonstrated how this technique allows each overlapped signal to be correctly received and detected. The proposed technique is less spectrally efficient and more complex to implement than increasing the constellation size and using non overlapping frequency slots, but it warrants consideration for flexible networking. The proposed technique is first theoretically detailed and justified. Then, networking scenarios and implementation schemes suitable for its effective utilization are identified and applied in the case of two overlapped 112 Gb/s polarization-multiplexed quadrature phase shift keying signals. Simulation results show that, applying 3-dB optical signal-to-noise ratio margin on the achieved bounds, optical reaches of around 800 km can be successfully supported by the proposed overlap technique.