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Passive Optical LAN

Updated on Jul 8, 2024 by
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What Is Passive Optical LAN?

A Passive Optical Network (PON) utilizes fiber-optic technology to distribute data from one source to multiple endpoints. The term "passive" denotes the use of optical fiber cables linked to an unpowered splitter, which transmits data from the service provider's network to numerous customers.

A Passive Optical LAN (POL or POLAN), short for Passive Optical Local Area Network, is based on the Passive Optical Network (PON) architecture. Like any PON system, POL is a point-to-multipoint indoor network infrastructure that uses optical splitters to distribute data from a single source to multiple user endpoints. It also employs Wavelength Division Multiplexing (WDM) technology to enable bi-directional upstream and downstream communication.

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Why Transition to Passive Optical LAN?

Although Passive Optical LAN (POL) does not have as long a history as PON, it is seen as the next-generation infrastructure to replace traditional copper-based LANs in local area networks. Times are changing, and corporations are exploring artificial intelligence, virtual reality, 5G, and Wi-Fi 6. As more network backbones are built on fiber to meet the demands for higher connectivity density, greater bandwidth, and faster speeds, new opportunities for Passive Optical Local Area Networks (POL) emerge.

  • Changing From Copper to Fiber

Switching from copper to fiber is the primary driver for adopting Passive Optical LAN (POLAN). The competition between copper and optical cable companies has highlighted the limitations of copper. For example, Cat6 cables can achieve speeds of 10Gbps but only up to 55 meters. Even with Cat8, the latest in copper cables, speeds of 10Gbps, 25Gbps, and 40Gbps are limited to a maximum of 30 meters. To support future data rates of 100G, 400G, or higher, fiber is clearly more advantageous.

  • Increase in IoT, Cloud and Video Business

With the advent of 5G and WiFi-6, a revolution in IoT is underway. Enterprise networks need to connect more devices over larger areas with increased bandwidth. Additionally, advanced technologies like cloud computing add pressure on LANs, and the growing demand for network capacity is driven by video streaming, the primary driver of bandwidth increases. Traditional LANs are becoming a significant issue.

The Architecture of Passive Optical LAN

A traditional local area network (one with a 10 Gb/s backbone) relies on copper and is made up of multiple layers or levels of Ethernet cables, routers and active switches. The core layer devices connect to distribution layer switches, which then link to access layer switches in communication closets. Copper cables run from these closets to users' computers.

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Passive Optical LAN (POL) transforms traditional LAN architecture by replacing copper cables with single-mode fiber optic cables, creating an all-fiber connection with minimal copper cables at the endpoints. POL consists of:

  • Single-mode fiber for the backbone

  • Passive optical splitters

  • Optical Line Terminals (OLTs) to manage network intelligence

  • Optical Network Terminals (ONTs) to control devices from a single management console in a flat network architecture

  • Category cabling from PoE-enabled ONTs to end devices

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The Advantages and Disadvantages of Passive Optical LAN

Advantages

Larger Scale and Reach

Compared to traditional LAN infrastructure, Passive Optical LAN (POL) reduces the amount of cables and devices needed in a network. Traditional LANs use copper cables like Cat6 to transmit data, while POL uses single-mode fiber optic cables. These cables are smaller, lighter, and less susceptible to interference, allowing POL networks to cover longer distances and provide more available space. This is particularly beneficial for industries like hospitality, where it can free up space for additional guest rooms.

Higher Efficiency and Security

Unlike traditional decentralized LANs, Passive Optical LAN (POL) centralizes intelligence and management. This allows all services to be delivered through a single infrastructure, eliminating the need for multiple platforms to provide high-quality services. IT administrators can manage and troubleshoot networks remotely, reducing the need for on-site checks. This decreases human intervention, minimizes the possibility of errors, and enhances efficiency and security.

Energy Saving and Environmentally Friendly

POLAN’s small footprint and simplified design contribute to reducing environmental impact. Here's why it is energy-efficient:

  • Lower Cooling Requirements: POLAN’s passive components, placed between the ONT and OLT, emit less heat and operate within a broader temperature range. This reduces the need for power and cooling in telecom rooms.

  • Reduced Power Consumption: The passive components in a POLAN use less power compared to active components, further lowering overall energy usage.

Lower Installation and Operating Expenses

A common misunderstanding about the costs hinders the adoption of Passive Optical LAN (POL). Many people focus solely on the higher cost of fiber optic cables compared to copper cables. However, installers must consider not just the cost of the cables but also the entire infrastructure and operating expenses. When these factors are taken into account, the overall expenses of POL can be more economical.

Longer Lifecycle

A passive optical local area network can extend the network lifecycle to two decades or longer.

While copper cables can theoretically support speeds up to 10 Gb/s depending on the system, fiber remains superior in terms of bandwidth. Fiber performance is limited by electronic components, not the cable itself, allowing existing fiber to support future improvements. Fiber also has lower latency, enabling it to transmit data over longer distances without delays, ensuring fast downloads, uploads, and resource access. A passive optical LAN can easily support faster when higher speeds are required.

Disadvantages

Less Possible to Deploy Immediately

While Passive Optical LAN offers significant benefits for large enterprises, short-term adoption is challenging due to substantial investments in existing copper networks. For small organizations, it is not a cost-effective solution as they do not utilize the full capacity of Passive Optical LAN.

Risk of Single Point of Failure

In Passive Optical LAN, 32 fibers converge into a single splitter module, which is fed by a single feeder fiber. This configuration creates a single point of failure; if the shared fiber or splitter is damaged, it can affect all users. Troubleshooting can be challenging due to this centralized setup.

Primary Components of Passive Optical LAN

Building a Passive Optical LAN requires less equipment. A typical POL is comprised of three main components connected by one single mode fibre.

Optical Line Terminal (OLT)

In Passive Optical LAN, the Optical Line Terminal (OLT) manages both upstream and downstream signals. It connects to the Wide Area Network (WAN) and corporate resources through the core router, receiving data from service providers and transmitting it to ONTs. Conversely, it collects data from ONTs and sends it back to the providers. Typically, one OLT port can connect to 32 ONTs.

Passive Optical Splitter

The passive optical splitter is crucial in Passive Optical LANs. Typically, one or several fiber optic splitters are deployed between the OLT and ONTs. These splitters can be placed anywhere within the optical network's midspan, distributing optical signals equally to end users without needing a power supply. Fiber optic splitters come in various split ratios, fiber types, and package form factors, with PLC splitters being the most commonly used.

Optical Network Terminal (ONT)

ONTs act as the end-user interfaces in a Passive Optical LAN. Since the network primarily uses optical fibers, optical signals must be converted to electrical signals before connecting computers and other devices. ONTs and ONUs perform this conversion, transforming single-mode fiber optical signals into RJ45 Ethernet interfaces for connection to computers and other devices.

In addition to the previously mentioned devices, a high-performance Passive Optical LAN requires connectivity components such as fiber patch cables, copper patch cables, fiber enclosures, connectors, fiber wall plates, pathway support materials, and other cable management components. These elements collectively ensure the network's optimal performance.

The Applications of Passive Optical LAN

Current trends indicate significant growth potential for Passive Optical LAN across various sectors, including hotels, campus buildings, hospitals, and large enterprises. Customers in these industries appreciate the unique advantages POL offers. Overall, Passive Optical LAN is well-suited for these application scenarios due to its specific features.

  • Limited Space for Network Cabling: Passive Optical LAN is ideal for environments with limited space, such as hotels, where space and energy savings are crucial.

  • Need for Converged and Secure Networks: In enterprises requiring video conferencing, wireless access, and monitoring services, Passive Optical LAN can converge all services into a single, secure infrastructure.

  • Centralized Management for Easier Network Support: In campus networks, multiple buildings can be connected to a main computer room with a simpler layout, facilitated by Passive Optical LAN’s centralized management.

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