An Ultradense Wavelength Switched Network

We propose and investigate an ultradense wavelength switched network (UD-WSN) for metro and regional applications. The UD-WSN provides all-optical switching and end-to-end wavelength connections at fine granularity (e.g., 12.5 and 6.25 GHz, or lower), and thus can carry high-bandwidth services directly in the optical layer with low latency and low power consumption. Two typical UD-WSN architectures, i.e., symmetric and asymmetric, are introduced. The symmetric architecture is applied in the core segment of optical metro network, where a coherent transceiver is used at each node to send and receive multiple ultradense-wavelength subchannels. The asymmetric architecture is applied in the aggregation or access segment of optical metro network, where multiple subchannels are transmitted between a high-bandwidth coherent transceiver at a metro core node and multiple low-bandwidth noncoherent transceivers at dispersed metro access nodes. Techno-economic analyses show that the UD-WSN is effective in both aspects of cost and power consumption compared to existing solutions. To verify the concept, we also experimentally demonstrate the asymmetric UD-WSN system, in which four optical subchannels with 12.5-GHz frequency spacing are transmitted between a coherent transceiver and four noncoherent transceivers. 20 Gb/s 4-ary pulse-amplitude modulation bidirectional signals in each subchannel are successfully transmitted over 300-km single-mode fiber.