Passive Optical LAN(POL) and application prospect

Preface:At present,most enterprise networks use traditional copper wire LAN, which are showing more and more drawbacks. With the rapid development of cloud computing, big data, and 4K video, more and more businesses are gradually migrating to cloud data centers. Followed by changes in traffic and architecture, the majority of traffic has shifted from a local switching architecture to a cloud switching architecture. On the other hand, with the explosive development of video, IoT, and the Internet, these applications have increasingly higher requirements for high bandwidth and low latency. In the age of digital transformation, enterprises urgently need a network that can carry all “things” access, and the POL network is the best choice.

I. POL Introduction

1.1 POL overview

POL is an enterprise LAN based on PON technology that provides users with integrated data, voice, video and other services through optical fibers. It is not a new technology, but applies the PON network technology that has been proven for a long time in the ISP network to the enterprise network. POL can bring great value to customers, at the same time, it will not change the existing business planning and customers network connection mode, and can provide all the functions provided by the traditional LAN network.

1.2 POL topology

POL provides a Layer 2 transmission network, adopts PON technology to provide gigabit access to user, and uses a single optical fiber to converge sevaral services such as video, data, wireless, and voice.

POL toplogy:


1.3 Comparison between POL and traditional LAN

In the POL network, the aggregation switch in the traditional LAN will be replaced by the OLT, the copper cable will be replaced by the optical fiber, and the access switch will be replaced by the passive optical splitter. The ONU provides Layer 2/Layer 3 functions and provide data, voice and video services by wired or wireless.
The downstream of PON network adopts the broadcast mode: the optical signal is sent by the OLT and divided into multiple optical signals to each ONU with the same information through the optical splitter. The ONU selectively receives its own packages according to the tags carried in the message and discard the packages that tags are not match.

The upstream of PON network: the OLT uniformly allocates a time slice to each ONU. The ONU strictly transmits signals according to this time slice window.ONU will shutdown the optical port when the time slice does not belong to its own time slice. The upstream time window scheduling mechanism is highly dependent on the PON distance measurement technology.
An understanding of PON technology principles will help us to apply this technology more proficiently in network design,In particular, the passive (no power supply required) characteristics of its optical distribution network, and the point distribution planning and design caused by the difference from traditional switches require special attention.To ensure the traffic packets in both directions are forwarded on a single-core fiber, PON uses wavelength division to process two-way signal transmission at the same time. Upstream and downstream signals use different wavelengths, but are transmitted on the same fiber. The direction from OLT to ONU/ONT is the downstream direction, and vice versa is the upstream direction. The downstream direction uses 1490nm and the upstream direction uses 1310nm.
Line structure comparison:


Device selection comparison::

Subsystem Name Traditional solution equipments POL solution equipments
1 Device room/machine house system ODF、Voice distribution frame ODF,Splitter (centrally placed)
2 Backbone wiring/vertical wiring subsystem Most copper cables or indoor multimode optical cables Indoor single-mode optical fiber
3 Floor management/floor machine house system Rack/cabinet, copper cable distribution frame, optical fiber distribution frame Floor distribution box, optical fiber connector, optical splitter (dispersing device)
4 Horizontal wiring subsystem Twisted pair, indoor multi-mode optical cable Butterfly fiber
5 Work area subsystem Copper module, copper panel, copper cable Fiber and fiber connectors

II. POL advantage analysis

Through the comparison between POL and traditional LAN in the previous section, we can find the challenges of traditional LAN and the unique advantages of POL.

Challenges of traditional LAN:

A large number of switches occupy the space of the computer room, high power consumption, and difficult heat dissipation.

The connection between aggregation routers is complicated,and it takes up pipeline space, making wiring and maintenance difficult.

Switch locations are scattered,management is complicated, and a large maintenance team is required.
Transmission distance limitation.
It is complicated to add new network equipment.

It is difficult to upgrade and expand network.

Whether its transmission distance,smooth network upgrades,high reliability,flexible networking,easy deployment,and simplified operation and maintenance,the traditional integrated wiring system has completely lagged behind POL. The POL integrates the transmission of traditional integrated wiring with fiber to the desktop, fiber to user unit, and fiber to the public area and turns the original L3 network into a flat L2 architecture.Enterprises can integrate different systems such as data,voice,video security,and wireless into a single optical fiber network, which has incomparable advantages over traditional integrated wiring.

POL advantage analysis:

Advanced architecture:POL network uses single-mode fiber,with almost unlimited bandwidth potential, and smooth broadband upgrades on demand.

Safe and reliable:Full optical fiber transmission,anti-detection,anti-electromagnetic interference, PON device provides strong DoS defense capabilities, reducing network attacks.

Converged bearer: The POL solution can bear data, voice, video and other services on one network.

Space saving: The POL solution is super convergent. The park only needs to provide a core computer room and don’t need many floor computer rooms.

Wide coverage: Covered distance is 20km,meeting the coverage requirements of super-high buildings and super-large parks.

Green and energy-saving: The POL solution uses passive optical splitters to replace convergence equipment of the traditional network,and the equipment room does not require air conditioning,which is more energy-efficient.

Convenient maintenance: PON technology adopts a centralized management method to avoid the disadvantages of decentralized management of traditional schemes and reduce the difficulty of operation and maintenance.

Cost advantage: Based on past experience, using 1000 points as a sample, choosing POL’s FTTD (Fiber To The Desktop) method will save 15% cost compared to traditional switch networks, and choosing FTTO (Fiber To The Office) will save cost more than 58% compared to switch networks.

III. Prospects of POL Development

POL is in the early development stages currently, and the current utilization rate is not high, but significant changes will occur in the next five years. The degree of POL solutions selection by enterprise users is not high enough,but manufacturers and social groups have been vigorously promoting this technology,and the IoT demand will become an important driving force to promote POL.

When it comes to POL applicable scenarios,most people may think of places such as corporate offices,education parks,and hotels.It cannot be denied that these places are the most widely used places,but from the unique advantages of POL,we can see that POL helps reduce energy consumption and operating costs.The IoT is the key to truly promoting the adoption of POL technology by enterprises. In the IoT application solution,a large number of terminal devices scattered in various places need to be connected to the network,Traditional LAN cannot meet such demand, and POL can serve as a bridge to eliminate the gap in this demand.Therefore,POL will find greater applications in the urban infrastructure, manufacturing,processing,solar,wind,and smart energy fields.The reason is that the current cable lines in these industrial facilities usually extend several miles,while POL can extend a long distance,and nodes can be deployed along the line through multi-fiber co-cables and optical splitters.Take the manufacturing industry as an example,it involves sensors such as flow meters, filters,or temperature,these devices need to be connected to the Internet,and traditional LAN are difficult to meet their networking needs.What is needed is to be able to operate stably in the working environment of these sensor devices.And does not produce electromagnetic interference or radiation.POL is just such a technology.It has a long transmission distance,can be networked through an optical splitter,does not produce electromagnetic interference and radiation,and can be used for the connection of most equipment.It has great needs in manufacturing and processing industries.Play a role in the large area and wide coverag application scenarios.

POL is an amazing technology because it is based on optical fiber transmission,has a simple network structure,is easy to manage,and has certain advantages in both construction and operation and maintenance costs.With the continuous development of enterprises,users put forward higher requirements for bandwidth, and the use of optical fibers will become more and more common,expanding from campus networks,backbone networks to the access field.IT users try to accept it,and good technology will prove its value through time.But I have to admit that there is still huge resistance to POL’s promotion.Enterprises that have invested heavily in traditional LAN may not change to POL,at least not immediately.For small organizations,POL solutions may be not a good idea.Compared with twisted-pair copper-based networks,user may not use all the capacity that POL can provide,and the solution may become very expensive. Therefore,these two technologies may coexist in the future,and POL will be used to make up for the functions that traditional LAN cannot achieve.Moreover,for those who familiar with traditional network technology, it takes time to gradually learn, adapt, master and apply POL technology.


With the intelligentization of cities,the application of cloud computing and big data,and the popularization of IoT,more and more enterprise applications will become cloud-based in the future.For enterprise networks,the digital transformation is imperative,which requires a simple network.POL have the characteristics of one network with multiple services,cost-effectiveness, simplicity, flexibility,safety and reliability,effectively supports enterprise digitization.So it is becoming the best choice for digital transformation in education,hotel,electric power, transportation,smart security,industry and other fields.With the gradual improvement of customer recognition,the ecology is also growing. I believe that the POL will continue to grow rapidly in the future.