Passive Optical Network with Modular Optical Line Terminal in Software Defined Environment

Broadband services have become an important part of our lives. The demand for fast and reliable bandwidth has put a lot of pressure on the telecom and cable industry to build a sustainable, flexible, and future-proof network [1]. Passive optical networks (PON) has become a technology of choice as future proof solution [2], however traditional PON with proprietary active solution still poses some challenges in providing flexibility and scalability. This reinforces the idea of using open software and white-box hardware converged with software-defined networking and network function virtualization (NVF) to add flexibility and scalability to the passive optical network (PON) [3]. With the advent of 5G mobile and the role that PON must play in the x-haul of 5G networks, this scalability and flexibility becomes even more important [4]. Looking at the mobile network, where the trend toward flexibility and simplicity also appeared in the radio access network (RAN) as an open radio access network (Open RAN) a few years ago, these trends are also evident in the optical access network. In the Open RAN of the 5G network, there are two primary technological requirements that provide flexibility and simplicity to the network. First, network function virtualization (NFV) abstracts the legacy, purpose-built network hardware functions used in previous generations (2G, 3G, and 4G) [5] into virtualized, software-based network functions (VNFs). The VNF architecture is hardware independent and can be hosted on any hypervisor and hardware [6]. This enables fast and dynamic deployment, less complex hardware lifecycle management, and lower costs. Second, Software Defined Networking (SDN) is used to decouple the user plane from the control plane and enable centralized management and programmability of network resources through SDN controllers. In the traditional PON, the optical line terminal (OLT) supports multiple layers of traffic management and shaping, as well as Layer 2 and 3 switching functions. In most cases, the network management systems (NMS) for conventional OLTSs are proprietary. This means that the OLT functionality includes the control software, Layer 2/3 switching, the PON medium access control (MAC) layer, and the PON physical (PHY) layer. These functions can be split into several parts so that PON specific functions such as MAC and physical layer optics as well as generic network functions can be enabled. This concept helps us to create modular OLT. A comparison of the differences between traditional and modular OLT is presented in Figure 1. The main difference is that the PON MAC functions are moved from the PON line card to the enhanced small form-factor pluggable (SFP+), which supports specific PON functions such as bridging, MAC layer, and physical layer optics. Integrating these specific PON functions into an SFP+ module allows the use of a non-proprietary white-box switch environment to accommodate these micro-OLTs. The management interface could be a Telecom Element Management System (EMS) or an SDN that supports NECONF and RESTAPI interfaces. This will provide much-needed flexibility to telecom operators and the cable industry to meet the ever-increasing demand for higher broadband services