The need for high bandwidth has been the expectation of network users for a long time, but this year it seems particularly impendent. As the coronavirus outbreak spreads, everyone is turning to stay at home. From office staff working from home to kids continuing coursework online, the number of people who are web browsing and gaming online is shooting up day by day. What about traffic congestion as everyone needs access to the internet? There is a future-proof option to cope with these troublesome problems and enable a better experience of remote working from home: fiber to the home (FTTH).
FTTH defines an access network architecture in which the final connection to the subscriber’s premises is an optical fiber. It is an alternative to the traditional copper network. Aside from bringing fiber to the end-users’ home, there are other FTTx such as fiber to the building (FTTB), fiber to the office (FTTO), etc. according to the specific architecture used.
There are two main FTTH network architectures that can be implemented when deploying an optical fiber network. These FTTH network architectures are active optical network (AON) and passive optical network (PON). AON is a point-to-point (P2P) network structure covering powered switching equipment while PON is a point-to-multipoint (P2MP) network structure that one fiber feeds many without powered electrical devices. In the post AON vs PON Networks: Which One to Choose for FTTH Systems, you can see more differences in these two network structures.
In order to get more clear about FTTH cabling, it is important to know the components in the FTTH network.
OLT: Optical line terminal in a PON system, located in the central office (CO) or hut, is the interface to the subscriber and provides the subscribed services.
ONU: Optical network unit, used to convert optical signals via fiber to electrical signals.
ONT: Optical network terminal, electronics generally located on subscriber premises, basically the same device as ONU.
Splitter: Passive device that splits the light source in sperate paths in a PON system.
More introduction about the PON equipment and relative terms have been included in ABC of PON: Understanding OLT, ONU, ONT and ODN.
From the FTTH cabling network system shown in the fiber below, there are three main FTTH fiber cables implemented to build up FTTH networks: FTTH feeder cables, FTTH distribution cables, and FTTH drop cables. The following figure of a typical PON network will help you better understand them.
Figure: FTTH PON system
FTTH feeder cables connect the central hub to fiber distribution hub, where the splitter is housed in the PON system and it may cover a distance up to several kilometers before termination. Feeder optical cable, also called trunk cable, offers the highest packing density. The number of fibers in feeder cables varies depending on the building type, typically of 12 fibers. For AON deployments, a feeder cable contains hundreds of fibers to provide necessary fiber capacity. For PON deployments, the usage of passive splitters enables smaller fiber count cables.
FTTH distribution cable connects the fiber distribution hub to the fiber access termination (FAT) and the distance is usually no longer than 1km. In the PON system shown in the figure, the distribution cable begins at the splitter. When the distribution cable is near a user, the FAT is used to access a small number of optical fiber in the cable. Distribution cables can be aerial, ducted, directed buried, or grouped. Distribution cables are typically smaller in size than feeder cables and the total fiber count is 48 to 216.
Drop optical fiber cables are used in the last mile to connect subscriber’s ONT to the FTTH network. They can be designed for aerial, directed buried, or ducted installations. FTTH drop fiber cables are usually available in less fiber count, often 1 or 2 fibers, providing the only link to the subscriber. The main characteristics of drop fiber cables are lightweight, small diameter, flexibility, and the fatigue lifetime of them is several hundred times longer than other standard single mode fibers.. The termination of drop cables is often a disturbing problem. If you are interested, you can refer to Drop Cable and Its Termination in FTTH.
When choosing the three optical fiber cables in FTTH cabling, there are some general elements that you should pay attention to which influence the method of cabling deployment.
Type of FTTH architecture: The FTTH architecture implemented will influence the data rate and the optical power budget, which will affect the choice of FTTH fiber optic cable. The cable cost and the additional labor cost for deployment caused by different types of FTTH architecture should also be taken into account.
Fiber type of existing network: If an existing network is expanded, make sure your hardware can integrate seamlessly with the existing infrastructure. It will save you labor and material costs if the optical fiber in the new network segments can be compatible with the fiber in the existing network.
Expected lifetime: An FTTH network is a long-term investment with a lifespan of at least 30 years since the fiber implemented in the FTTH network is supposed to degrade slower than copper cables and less sensitive for interferences from the surroundings. So it is imperative that investments to the FTTH infrastructure are suitable for future needs. Once you decide to start an FTTH project, the FTTH fiber you choose will have long term consequences.
Installation environment: No matter indoor or outdoor applications, there are always different environments where your fiber will be installed. For example, in rugged spaces that your fiber may suffer damage, such as basements or in conduits sharing space with electrical or other wirings, you may choose a rugged sheathed cable that is flexible and crush resistant. There are many variables that will determine which types of fiber are most appropriate in the different parts of the installation. In most cases, one type will not fit all.
FTTH cabling is future-promising because it owns the unique characteristics to which other techniques can not compare and meet the users’ current and possible future needs.
First of all, it is related to the trend that the access and backbone bandwidth requirements are expected to continue to grow rapidly for the next months or even years. For the current home network users, concerns around network performance are serious. When you have video calls with your friends or coworkers, I am certain you do not want to see their faces froze. But that may be the fact you’ve experienced. Therefore it is the overall trend to higher speed Internet access and smoother video streaming, of which FTTH cabling is more capable than the traditional copper one.
Advantages FTTH broadband connection has over other techniques are the key factor why FTTH cabling is a promising future technique.
One of the key benefits is it can provide unlimited bandwidth with a long reach. The development of technology, video applications such as video streaming, IPTV, high-quality video conferencing, smart home technology, IP video home surveillance, and games are gradually permeating into people's daily lives leading to further expansion of people’s demand for bandwidth. At present, only the optical network can assume responsibility.
Another benefit is its reliability. The transmission performance of other technologies such as DSL is subject to the random noise or crosstalk while optical fiber is immune to EMI, which improves the overall throughput. Furthermore, fiber optic cables in FTTH installation are safer compared with the DSL or coaxial cable, since they will not be easily corroded by lightning or rain, or cause leakage.
What’s more, FTTH network construction is more secure than other technologies. Since there are no radiated magnetic fields around fiber cables, it is impossible to tap the signal transmitted through a fiber unless it is cut. Therefore, FTTH cabling can help protect the data from leaking or other virtual threats.
Updated May 12th, 2020