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FTTH Network Topology

FTTH Network Topology : Whenever we talk about the FTTH structure, it means that the network topology is being talked about. In FTTH network topology to specify the difference between passive and active infrastructure, it is important to create a clear distinction between the topology used for the deployment of fiber (passive). Technologies used for data transport on infrastructure and fibers,it means that is active equipment.

In the FTTH structure two most widely used topology are point-to-multipoint, often combined with one Passive Optical Network (PON) technology, and point-to-point, which typically uses Ethernet Transmission technology.

FTTH Network details
FTTH Network Details

Active and Passive Optical Network in FTTH

To understand the FTTH network topology, it is necessary that we first understand active and passive optical networks. In FTTH network topology Point-to-point topology provide dedicated fiber between the POP and the subscriber. Each subscriber has a direct relationship with a dedicated fiber.

In FTTH network topology most existing point-to-point topology deployments use Ethernet, which can be combined with other transmission schemes for business applications (eg fiber channels, SDH / SONET).This type of topology can also include PON technology by placing the passive optical splitters in the access node.

Point-to-multipoint topology are deployed in combination with passive optical splitters in the field With standardized PON technologies - GPON is at the front-runner of being EPON in all over world today. Most popular in Asia - using time-sharing protocols to control access to many shared feeder fiber subscribers.

Active Ethernet technology can also be used to control subscribers in point-to-multipoint. The topology requiring the placement of Ethernet switches in the field. I would like to mention the passive and active optical network through a picture which makes it easy for you all to understand.

Passive and active optical network in FTTH network topology
FTTH network topology

Point to Point (P2P) Network Topology

Point-to-Point network topology is also known as Fiber is dedicated to each user. The use of one fiber and laser per user is knows as the Point-to- Point networks. One defined fiber is terminated at the subscriber and active devices at the central office (CO) for a telecommunications provider. N-fiber line implies to 2N Transceivers.

This is a Centralized Splitter Distribution where the splitter is placed in the exchange & fiber are connected directly to the customers. All work is done only in the Exchange and at subscribers' premises.

Advantages of Point-to-Point Network Topology

Blow mentioned are the the advantages of Point-to-Point network topology.

Simple network planning & design

Maximum optical reach to customers.
Provide maximum bandwidth utilization, high efficiency of PLT cards, maximizes the utilization of expensive OLT cards. Since each home/business directly fiber connected to Fiber Distribution Hub (FDH), there would be no unused ports in the OLT card or and 100% efficiency is achieved. This allows a wider physical distribution of the OLT ports.

Network Testing Ability: One of the benefits of a centralized splitter approach is its ability to provide easy testing and troubleshooting access. Another benefit of one central location is easy to access by maintenance technicians faced with such tasks as location a cable break or dealing with a fiber macro bend issue.

Flexibility: A centralized Fiber splitter (FDH) Cabinet would also create greater flexibility in the distribution network.
Future bandwidth upgrade-ability:
(a) Better option in un-certain growth
(b) Better option in un-predictable market share.
(c) It can also say that better option in low take rate or market share.

Disadvantages Of Point-to-Point Network Topology

Requires large amount of fibers in the exchange.
Increase number of sub-ducts & civil work.
Costly, due to cable & civil work.
Not flexible regarding maintenance.

Point to Multi Point Network Topology

Point to Multi point generally known as single fiber is shared by 2 or 64 users. In PON system optical fiber is design to share between 2 to 128 users, depending upon the availability of splitters.

A Point to Multiple point PON will have less optical reach than a Point-to-point network, which does not use splitters. We already families that typically a PON is capable of reaching subscribers up to 20 kilometers (km) from the OLT which will cover most of the population. N-fiber line implies to N+1 Transceivers.

Local Convergence Point topology : Wherein each fibers connected to OLT ports leave the central office then splitted once, usually in FDT, before being distributed to customers. This topology simplifies network planning, installation & maintenance.

Advantages of Point to Multi Point Network Topology

➤Point to multi-point (on GPON) is the most CAPEX efficient
➤Lower duct occupancy with less fibers
➤Saves OPEX at Central Office
➤There is no foreseeable limitation on Available band width
➤Higher splitter utilization.
➤Simplify maintenance by providing external network test locations.
➤Easy customer management at FDT. (fiber deployment on demand).
➤Trouble shooting is done from one single point.
➤Better overall loss measurements compared to cascaded distribution.
➤Requires less optical devices in the field, thus minimizes the chances of network outages.

Distributed / Cascaded Network topology

In this topology, the signal is splitted more than once before reaching the customer. Splitting is done in the exchange, FDT, FAT, manhole /handhole; or inside a building. Suitable for application in assured high take ratios & in rural areas.

Cascaded and Distributed Splitters could be considered as an option:
(a) If the forecast is accurate and the area is well maintained such as premises and buildings complexes etc. (dust free and clean duct network)..
(b) Community or development only service provider.

Advantages Of Point-to-Multi Point Network Topology

➤Extend customer reach.
➤Easy network upgradeability.
➤Defer cost of downstream splitters if required.
➤Reduce fiber management at the exchange.
➤More effective utilization of optical fibres.
➤Smaller OSP components used to house splitters
➤Splitter 1:16 and 1:32, can be used to concentrate traffic& reduce the GPON port requirements.

You will be very easy to understand by the image given below what is the difference between point-to-multi point and point-to-point network topology. To understand the better configuration details please go through the below image.
Point to multi point and point-to-point network topology
Point to Multi point and Point-to-Point configuration

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