Experimental demonstration of a 400 Gb/s full coherent transmission in an in-field metro-access scenario

The current challenge for the physical layer of next generation optical access network based on PON architectures is to increase the capacity above 100 Gbps per wavelength. This target may require a revolution for PON, moving from direct detection (DD) to optical advanced modulation formats and coherent detection. In fact, the performances of full-coherent systems for ultra-high bit rates are, in terms of receiver sensitivity, significantly better than standard DD receivers, obtaining power budget of more than 30 dB. In this scenario of large available power budget, it will even be possible to envision a convergence of the access with the metro segment, also considering that wavelength routing functionalities based on Reconfigurable Optical Add Drop Multiplexers (ROADM) can be inserted at the boundary between the two network domains. In this future possible scenario, it becomes thus fundamental to study the resulting power budget for both the metro and the access network, in order to optimize the overall optical performance. To this end, we show in this paper experimental results obtained on a 33-km deployed metropolitan fiber link on a PM-16QAM full-coherent transmission at 50 Gbaud (400 Gbps) in terms of BER curves as a function of received optical power in a practical emulation of downstream metro+access transmission. A Reconfigurable Optical Add-Drop Multiplexer is introduced in the middle of the link to implement a wavelength routed metroaccess scenario.