LightTrends Newsletter

A third generation of Optical Distribution Networks (ODN) is emerging

October 2022

The residential optical distribution network (ODN) is the final connection between a telecom operators’ internet, cable, and telephone services and its customers. Over the past decade, and often out of the spotlight, ODNs have played a critical role in the widespread adoption and deployment of Passive Optical Networks, and development efforts have focused on reducing upfront costs rather than increasing functionality. Now however, there is a push by industry to introduce modern technology to the ODN in order to reduce operating expense and increase performance of access networks. LightCounting has published a research note today providing an introduction to this topic.

For fifty years or more, the ‘last mile’ of telecom operators access networks consisted of twisted pairs of copper cables, one per household, bundled together in massive cables, in a tree and branch physical architecture. Cable operators used coaxial sheathed metallic cable in similar tree and branch arrangements. Early internet services were delivered, often painfully, over these now archaic technologies.

Starting early in the 21st century, deployment of Passive Optical Networks began in earnest, in support of ‘triple play’ service bundles, in which faster internet speeds, lower latency, and more video bandwidth were all key selling points. Unlike earlier access networks, the ‘last mile’ of PON networks utilize point-to-multipoint optical fiber, with a single or pair of fibers originating at an Optical Line Terminal (OLT), terminating at a passive optical splitter located somewhere in the outside plant, with multiple fibers exiting the splitter and connecting to or near individual residences in a device called an Optical Networking Terminal (ONT) or Optical Networking Unit (ONU). The fiber and splitter connecting an OLT with its subtending ONUs is called the Optical Distribution Network, or ODN.

First generation ODNs (let’s call them ODN1) were spliced together using highly skilled technicians and expensive fusion splicing machines which needed a controlled environment, usually a van, to keep dust and other contaminants away.  While expensive and time consuming, this practice resulted in low-loss optical links that performed well.

Starting around 2018, a second generation of ODN (ODN2) started deployment, using various pre-connectorized components made available by Corning, CommScope, Huber+Suhner, Huawei, Fiberhome, Furukawa and others. These products are described in ETSI TR 103 775, published in August 2021.  The term ‘QuickODN’ is used to describe ODNs built with pre-connectorized components. The main advantage of ODN2 is that no fiber splicing is required in the field, and installation can be done more quickly and less expensively.

 Along with pre-connectorization, another major innovation in ODN2 is the use of bar codes or QR codes for each fiber and port that can be easily entered into a smart database creating a digitalized Optical Distribution Network. This ‘Digital Quick ODN’ uses the unique identities of ODN passive elements to create intelligent management functions like automatic storage of optical fiber location information, automatic identification of optical fiber connections, optical fiber calibration information and a visual guide for onsite operations.

The advent of pre-connectorized and digitally labeled fiber, splitters, and fiber handling trays, cross-connects, and boxes greatly reduced deployment time and expense for operators, but did little to address operating expense. Today a third generation ODN (ODN3) is being developed which aims to address the operational expense of ODNs by introducing active, automated monitoring and intelligence.

Using an optical monitoring system of some sort (based on reflections, introduced delay, or other), will allow an intelligent management system to automatically identify and locate impairments and failures down to the level of specific fibers and ports in an individual network element. This information is then provided to a centralized network operations center and to handheld devices in the hands of field technicians. The benefits of being able to ‘see through’ the 1xN splitter in the ODN are significant. Fiber breaks can be accurately located down to individual fibers, and unused ports and full ports can be individually identified ahead of a service call. And service uptime/downtime can be monitored on the level of individual ONU/ONT.

With FTTx now a mature network architecture among Top Tier CSPs, attention is finally being paid to lowering the operational costs via more accurate and automated monitoring, made possible by third generation ODNs. We expect other vendors will follow Huawei’s lead in developing products similar to the Fiber Iris to supplement their own product offerings.

The full research note is now available for download: if you are a LightCounting client login to your account to access it; if you are not a LightCounting client you can create an account and read this research note in the Resources page on the website (

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