ONU Interconnection for Reducing Latency in TWDM-PON Based Mobile Front- and Middle-Hauls by using Wavelength Mobility

Due to the demands of ultra-large bandwidth and much reduced latency for current 5G and future 6G mobile networks, the fixed network infrastructure for mobile services is evolving rapidly to meet the needs of mobile operators [1]. The passive optical network (PON) is emerging as a very promising solution for 5G/6G mobile transport networks to provide the best total cost ownership (TCO) for its all-passive photonics (APP) nature. The time wavelength division multiplexing (TWDM-PON) can provide a larger capacity and more flexible bandwidth management than the legacy TDM-PON [2]. Here, a time/wavelength-division-multiplexing passive optical network (TWDM-PON) with virtual interconnection among optical network units (ONUs) is proposed to realize all-photonic networks providing large capacity, flexible bandwidth provisioning, and much reduced latency among the network nodes. The virtual interconnect among ONUs (vONUI) is achieved by simply adding a reflective channel filter at the remote node of the TWDM-PON and maintains its APP nature, as shown in Fig. 1. With this approach, the interconnect can be applied to all ONUs, not limited to adjacent nodes. The vONUI-enabled network can be used to serve as the middle-haul to connect the centralized unit (CU) and distributed units (DUs) as well as the front-haul to connect a DU with many radio units (RUs) for the 5G and beyond 5G mobile networks. The role of DUs in the functional split of 5G and beyond 5G era is to support low-latency for time-sensitive services. The RU interconnect (RUI) can help to achieve this goal by enabling direct communications among RUs, forwarding of timely data to neighboring RUs, and providing real-time up-stream bandwidth management. If the TWDM-PON is applied to serve as the middle-haul to connect CU and DUs, it forms an all-photonic switching networks among ONUs to provide direct interconnect among DUs (DUI) if each ONU is equipped with an extra wavelength for providing DUI. The DUI can improve mobile network performance by reducing latency, increasing flexibility, and enhancing reliability and security.