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LC: The third generation optical distribution network is on the rise

A residential optical distribution network (ODN) is the ultimate connection between a telecom operator’s Internet, cable and telephone services and its customers. Over the past decade, ODNs have played a key role in the widespread adoption and deployment of passive optical networks and have generally been overlooked, with development efforts focused on reducing upfront costs rather than adding functionality. However, now, in order to reduce operating costs and improve access network performance, the industry is pushing to introduce modern technologies into ODN. LightCounting has released a research report that covers this topic.

  For more than 50 years, the “last mile” of telecom operators’ access networks has been composed of twisted-pair copper cables, one for each household, bundled together with huge cables to form a tree-like and branched physical architecture. Cable operators use coax-jacketed metal cables in similar tree and branch architectures. Early internet services were delivered through these now obsolete technologies, often with great difficulty.

  From the beginning of the 21st century, the deployment of passive optical network officially began to support the “triple play” service package, in which faster network speed, lower latency and more video bandwidth are key selling points. Unlike earlier access networks, the “last mile” of a PON network utilizes point-to-multipoint optical fibers, with one or a pair of optical fibers originating at an optical line terminal (OLT) and terminating at a passive optical splitter located somewhere outside the equipment. Multiple fibers exit the splitter and are connected to or near a single residence through a device called an Optical Network Terminal (ONT) or Optical Network Unit (ONU). The optical fibers and splitters that connect the OLT to its corresponding ONU are called an Optical Distribution Network (ODN).

First generation ODNs (let’s call them ODN1) were spliced together by highly skilled technicians and expensive fusion splicers, which required a controlled environment, usually a van, to keep out dust and other contaminants Enter. Although costly and time-consuming, this practice results in a low-loss optical link with good performance.

  From around 2018, the second-generation ODN (ODN2) began to be deployed, using various pre-connected components provided by companies such as Corning, CommScope, Huber+Suhner, Huawei, FiberHome, and Furukawa. These products are described in ETSI TR 103 775 published 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 on-site fiber splicing, faster installation and lower cost.

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

  The advent of pre-connected and digitally labeled fibers, splitters, fiber handling trays, cross-connects, and junction boxes has greatly reduced deployment time and expense for operators, but has done little to address operational expense. Today, the third generation of ODN (ODN3) is being developed, which aims to solve the operational expenses of ODN by introducing proactive, automatic monitoring and intelligence.

  Using some type of optical monitoring system (based on reflections, introduced delays, or other) will allow intelligent management systems to automatically identify and locate defects and faults down to specific fiber and port levels within individual network elements. This information is then made available to centralized network operations centers and handheld devices in the hands of field technicians. The benefit of being able to “see through” a 1xN splitter in an ODN is significant. Fiber breaks can be pinpointed to individual fibers and unused and full ports can be identified separately prior to service invocation. And service uptime/downtime can be monitored at the individual ONU/ONT level.

   With FTTx now a mature network architecture among top CSPs (Communication Service Providers), the industry has finally started to focus on reducing operating costs through more accurate and automated monitoring enabled by third-generation ODN. We expect other suppliers to follow Huawei’s example and develop fiber-optic iris-like products to complement their own offerings.