FTTH Feeder Network Details

FTTH Feeder Network Details: Feeder cables are Fiber Optic Cables (FOC) that run out from the Access Node into the FTTH area up to the primary fiber concentration point up to the FDT. The number of fibers in the FOC will depend on the number of the end-user service points,it is also depend upon the telecom operator standard.

Feeder cables can be laid as a simple Point-to-Point topology, from the Access Node to the FDT. Mainly telecom operators use the protected architecture in which the feeder cables are laid in a way that a number of FDT’s are interconnected in a ring shape to the Access Node, providing a diversity solution for the feeder network. READ MORE ABOUT FTTH

The entry of Feeder cables into the cable vault of the Central Office can be performed in two ways. There are two ways that feeder cable can be enter in the central office up to the ODF. For details see the below image.

Feeder Cable Entry

Feeder Cable Entry in FTTH

From (suppose MH No.) MH000 next to the Exchange or the vault underneath, a length of “fire retardant” conduit containing micro-ducts can be provided and will be “cable tied” or “laced” to cable trays and risers allowing the fiber to be blown from outside the exchange to the ODF were it will be terminated.

A length of fire retardant indoor fiber optic cable can be provided from the ODF in the exchange to the first splice point in a MH located out in the fiber optic route. Now I would like to explain about FDT.

FIBER DISTRIBUTION TERMINAL (FDT) 

The feeder cabling will eventually need to convert into smaller distribution cables. This is achieved at the first point of flexibility within the FTTH network which is generally known as the Fiber Distribution Terminal (FDT). At this point, the Feeder cable fibers are separated and spliced into smaller groups for further routing via the outgoing Distribution cables.

Providing environmental and mechanical protection, the FDT shall be used to accommodate and provide optical termination points between the feeder and distribution network with flexibility of fiber cross-connection between them. The FDT is designed to organize and administer fiber optic cables and passive optical splitters.

FDT serves all the user inside a particular geographical area (called FDT boundary) and, ideally, the FDT should be positioned in the middle of this area, as close to users as possible, reducing subsequent distribution cable lengths and thus minimizing additional construction costs. However, the location of the FDT may be determined by other factors such as the location of available ducts. The FDT location is under the responsibility of the OSP designers as it is also related to permits.

Two construction alternatives are possible:

Indoor The indoor FDT is designed to organize and administer fiber optic cables and passive optical splitters in an indoor environment. That solution is typically suitable for high rise buildings (with more than 128 Dwelling Units) wherein the FDT is placed in the telecom room.

Outdoor. The outdoor FDT is designed to organize and administer fiber optic cables and passive optical splitters in an outdoor environment. Installed strategically in a street cabinet. This is the most common way to install the FDT for FTTH deployment.

In the most common topology, feeder fibers are split towards the distribution network. However pass-through fiber ports are also possible, wherein feeder fibers are directly interconnected to distribution fibers.

FDT Connectivity

FDT Connectivity with Feeder cable

The main features of FDT

➥Provides heavy-duty protection from wind, rain, and other contaminants.

➥Lightweight structure for easy installation.

➥Complete fiber management allows for flexible rearrangement.

➥Identification and labelling assure product traceability and ease of identification.

➥Cable management and routing limits radius and adds strain relief.

➥Provides an easier testing point for operation and maintenance purposes.

DISTRIBUTION NETWORK

DISTRIBUTION CABLE

Distribution Network runs from the FDT to the FATs. Distribution Network is served by the Distribution Fiber Optic Cables (FOC).Each Distribution Cable connects a number of FATs in his path. The number of FATs connected by cable depends on the typology of the residential market.

FIBER ACCESS TERMINAL (FAT)

Fibers need to be separated within the network before being connected to the subscriber. This second point of flexibility is called Fiber Access Terminal (FAT).The FAT is positioned at an optimum point within the network, enabling the drop cabling to be split out as close as possible to the majority of users to be served.

A FAT should normally be found very close physically to a number of customers (approximately in the range of 50-250m). FAT’s are typically an underground fiber optic joint closure designed to handle a relatively small number of fibers and splices with the capacity being determined by either the number of connections available or the number of drop cables, or a culmination of both.

The main features of FAT

➥A weather proof outside plant enclosure either aerial mounted or ground fixed.

➥A storage facility for slack drop fiber cable length.

DROP CABLE

Drop cabling forms the final OSP link, running from the closest FAT to the user. Drop cables are used to connect the user end-service points. Drop cables may include additional fibers for extra capacity.The drop cabling is deployed within small ducts or within micro-ducts and can be terminated in the following devices:

➥Optical Splitter Box (OSB)

➥Optical Distribution Box (ODB)

➥Fiber Termination Box (FTB)

OPTICAL SPLITTER BOX-INDOOR (OSB)

The Optical Splitter Box aims to extend splitters near to customer for high density parcels. For MDUs a wall mounted unit is suitable for in-building installation where the number of tenancies is from 16 and up to 128.

OSB can host internally 1 or 2 Passive Optical Splitters 2:32. Those users served by splitter ports in the OSB bypass the splitter at the FDT.

OPTICAL DISTRIBUTION BOX (ODB)

The Optical Distribution Box is being used for lower density MDUs. The capacity of each box ranges from 12/24/48/96 fibers and It aims for medium density parcels by utilizing FDT Splitters.

FIBER TERMINATION BOX (FTB)

The Fiber Termination Box is installed at the entrance of each SFU. It provides the test point for customer connection without entering the premises.