Optical distribution network (ODN) is the final connection between the Internet, cable and telephone services of telecom operators and their customers. In the past decade, ODN has played a key role in the widespread adoption and deployment of passive optical networks, and it is usually ignored. The focus of its development work is to reduce the initial cost, rather than increase the function. However, in order to reduce the operating cost and improve the performance of the access network, the industry is now promoting the introduction of modern technology into ODN. LightCounting released a research report that introduced this topic.

For more than 50 years, the last mile of telecom operators’ access network consists of twisted pair copper cables, one for each household, bundled together with huge cables to form a tree like and branch like physical architecture. Cable operators use coaxial sheathed metal cables in similar tree and branch architectures. Early Internet services were provided through these now outdated technologies, which were often difficult.

Since the beginning of the 21st century, the deployment of PON has officially started to support the “triple play” service package, in which faster network speed, lower latency and more video bandwidth are key selling points. Different from the early access network, the last mile of PON network uses point to multipoint optical fibers. One or a pair of optical fibers originate from the optical line terminal (OLT) and terminate at a passive splitter located somewhere in the external equipment. Multiple optical fibers exit from the splitter and are connected to or near a single house through equipment called optical network terminal (ONT) or optical network unit (ONU). The optical fiber and splitter connecting the OLT and its corresponding ONU are called optical distribution network (ODN).

The first generation ODN (ODN1) is spliced together by highly skilled technicians and expensive welding machines, which requires a controlled environment, usually a van, to prevent dust and other pollutants from entering. Although the cost is high and time-consuming, this approach achieves a low loss optical link with good performance.

From around 2018, the second generation ODN (ODN2) will be deployed, using various pre connected components provided by Corning, CommScope, Huber+Suhner, Huawei, Fenghuo, Guhe and other companies. These products are described in ETSI TR 103 775 released in August 2021. The term “QuickODN” is used to describe an ODN built using pre connected components. The main advantage of ODN2 is that there is no need for optical fiber splicing on site, the installation speed is faster, and the cost is lower.

In addition to pre connection, another major innovation of ODN2 is the use of barcode or QR code for each optical fiber and port, which can be easily input into the intelligent database to create a digital optical distribution network. This “Digital Quick ODN” uses the unique identity of ODN passive components to create intelligent management functions, such as automatic storage of optical fiber location information, automatic identification of optical fiber connection, optical fiber calibration information and visual guidance for field operation.

The emergence of pre connected and digitally labeled optical fibers, splitters, optical fiber processing trays, cross connections and junction boxes has greatly reduced the deployment time and costs of operators, but has hardly solved the problem of operating costs. Today, the third generation ODN (ODN3) is under development. It aims to solve the operating costs of ODN by introducing active, automatic monitoring and intelligence.

The use of some type of optical monitoring system (based on reflection, introduced delay or others) will allow the intelligent management system to automatically identify and locate defects and faults up to specific fiber and port levels in a single network element. The information is then provided to the centralized network operation center and the handheld devices in the hands of on-site technicians. The advantage of being able to “see through” the 1xN splitter in ODN is significant. Fiber breaks can be pinpointed to a single fiber, and unused ports and full ports can be identified before service calls. In addition, service uptime/downtime can be monitored at a single ONU/ENT level.

As FTTx has become a mature network architecture in the top CSP (communication service provider), the industry has finally begun to focus on reducing operating costs through more accurate and automated monitoring achieved through the third generation ODN. We expect that other suppliers will follow Huawei’s example and develop products similar to optical fiber iris to supplement their own products.