Passive optical networks (PONs) have been widely deployed: their flexibility and multiservice transmission means they can potentially deliver more than just Internet access. A shared PON fibre can also support voice and video services, allowing communications service providers to deliver all three services at a high-quality service level with one shared network.
PON technology connects multiple users to a single fibre from a broadband service provider using unpowered optical splitters — passive components used to avoid electromagnetic interference in the network. A PON system can terminate at multiple locations, delivering fibre to a subscriber’s home, an office building, a kerb, a shared point in a residential neighbourhood or a business campus, making it a flexible network architecture for a range of service options.
These networks have many advantages aside from just high bandwidth: data transmission is symmetrical, meaning that it’s still fast whether the data is travelling upstream or downstream. This can be highly beneficial for businesses because of download and upload traffic demands. Also, a PON isn’t only cost-effective in terms of cost per bit, but equipment costs too. Because of its point-to-multipoint topology, in which multiple optical network units are connected to the same PON port, the amount of fibre and centralized equipment required is lower than with point-to-point architectures.
Bandwidth is vital to accommodate the rapidly growing demands for home broadband, campus access and enterprise connectivity, so the next wave of optical access networks needs to increase capacity to 50 Gbps. Having a road map for upgrading system capacity from 10G-PON to 50G-PON simply and efficiently is now an absolute necessity.
There are two potential methodologies to address 50 Gbps bandwidth requirements. The first is to improve the single wavelength rate, and the second is to increase the total rate through multi-wavelength multiplexing and channel binding technology. The evolution of PON-based standards is very complex, but essentially, the industry has chosen to focus on the single wavelength method in formulating the next standard after 10G-PON, now known as 50G-PON. It uses the uplink for the service network and downlink for users through various user interfaces, supporting symmetrical 50 Gbps/50 Gbps rates or asymmetrical 25 Gbps/50 Gbps rates over a single wavelength.
Single-wavelength 50G-PON supports a point-to-multipoint topology as well as video, data and voice services. It uses wavelength division multiplexing to implement two-way transmission for a single fibre; time-division multiplexing for downstream traffic; and time-division multiple access to modulate upstream traffic and enable point-to-multipoint communication. Other improvements include dynamic bandwidth allocation, quality of service and increased security and data encryption.
With 10G-PON now in mass-market deployment, single-wavelength 50G-PON is the next step, and is essential to ensure a smooth path for communications service providers. The two will coexist for a long time to meet a variety of networking needs. Both PON standards use voice over IP and proprietary encapsulation for voice, and Ethernet for data, supporting existing infrastructure. This sharing of resources is critical — it saves deployment space in equipment rooms, lowers the energy usage of optical access equipment and reduces network construction costs in upgrades for broadband providers.
This means that it’s vital to have products that support the coexistence of different generations of technology. One recent example is ZTE’s 50G-PON, 10G-PON and GPON Combo solution with multimode optical transceiver modules, designed to handle the transition to 50G-PON while continuing to support 10G-PON and GPON standards. ZTE claims to be the first provider to deliver this precise technology, with lower latency, low jitter, support for virtual network slices and energy savings.
And there’s a growing number of operator customers adopting 50G-PON across different segments. For example, ZTE and China Telecom’s Guangdong branch have launched China’s first 10G-to-the-enterprise application with 50G-PON technology at the Nanshan Science and Technology Park in Shenzhen as part of its plan for advancing the development of new information infrastructure, focused on supporting small and medium enterprises. The aim of this is to spearhead a 10G-to-the-enterprise vision, establishing high-speed and low-latency deterministic networks in the enterprise campus to improve production and operations efficiency.
Another example is communications service provider True, which launched Thailand’s first 50G-PON prototype as part of its continuous upgrading of fixed-network broadband infrastructure in support of the country’s “Thailand 4.0” strategy for industrial development and the evolution of the digital economy.
True has already deployed 1G-PON in its consumer network, with the upgrade to 10G-PON now underway, so the pathway to 50G-PON is a logical next step — particularly if True wishes to support a range of scenario-specific applications and services such as 5G, cloud gaming, virtual and augmented reality, digital health and intelligent manufacturing.
Developing broadband services that are fit for the future is complicated for providers, and network capabilities will be at the heart of their competitiveness and value. But the introduction of new technologies such as 50G-PON shouldn’t be solely based on hunger for more capacity or speed. They should also consider compatibility with existing networks and enhanced capabilities for a better user experience — such as quality of service, lower latency and better security. These features make 50G-PON applicable to an increasingly broad range of market and service segments across industrial, mobile network and consumer domains.
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