Ducts type used in FTTH Network

Ducts type used in FTTH Network : In this article, I will cover the ducts type used in FTTH network and standard ducts specifications and configuration. Standard ducts are used in small trenches and can support cable pulling installations, as well as blowing methods. By default, unless there is an official direction to change, standard ducts must be used to design civil infrastructure for fiber installation.

Specified ducts configuration is to be used inside cities between exchanges, between an exchange and access sites, and in distribution networks between the FDT and Manholes/Handholes. We all know that Underground duct is one of the major cost items of the network. It is important -that new duct or duct additions be well planned. Insufficient duct will result in early additional cost; too large a duct structure will represent uneconomical investment of money and material.

Ducts in FTTH Network from Exchange to Customer

It is important to know how to use the ducts from Exchange to Customer in FTTH Network. In the FTTH network it is divided into three parts-
1. Feeder Network
2. Distribution Network
3. Drop Network

1. Feeder Network : Network that connects FDT to exchange. Feeder connection can also connect key account customers, FTTM, or any access site. 

2. Distribution Network : Network between FDT and MH\HH within the FDT boundary.

3. Drop Network : Duct or cable that connects MH\HH to customer.

In feeder network, distribution network and drop network different type of ducts are required. These ducts can be different in shape and size, ducts color can be also different its depend upon the telecom industry specification. To understand this, see the image below.

Ducts from Exchange to Customer in FTTH

FTTH network from exchange to customer

Ducts Configuration for Feeder and Distribution

For feeder and distribution used 20 ducts (32/26mm), generally ducts shall be used with the following colors (Its not universal standard,it also depend upon the telecom industry specification).

10 black only, 

5 Black with orange stripes.

5 Orange only

Ducts must be arranged in a matrix shape with 5 rows and 4 columns. Like below arrangement of ducts-

32/26 mm 20 ducts arrangement in feeder and distribution 

Standard Feeder and Distribution Ducts

Ducts Configuration for Drop

Drop ducts are used in distribution networks between last MH/HH and customers. Two 20/16mm ducts to be used between the last MH/HH and each customer building. 

Drop ducts in FTTH network

Standard Drop Ducts

Ducts type used in FTTH Network

Generally below type of ducts used in Access Network or FTTH Network-

➤Steel Ducts.
➤Fiber Reinforced Epoxy (FRE).
➤Polyvinyl Chloride (PVC)
➤Polyethylene (PE).
➤Polyethylene Corrugated (PEC).
➤Sub-Ducts & Mini Ducts.

Steel and PVC ducts are supplied in pieces 6 meters long, while PE & PEC ducts are supplied in rolls of (100 – 300) meters long. The ducts are in different sizes.

Definitions of Polyethylene Corrugated (PEC Duct or PECD) ducts mentioned below-

PECD, Type 1: 110 mm OD x 90 mm ID, W/ 5-33 mm OD Sub-ducts, Generally Orange color, one sub-duct black, 300 m reel length. Used for fiber optical cable..

PECD, Type 2: 110 mm OD x 90 mm ID, W/ 3-42 mm OD Sub-ducts, Orange co lour, one sub-duct black, reel length 300 m. Used for fiber optical cable..

PECD, Type 3: 110 mm OD x 90 mm ID, Without Sub-ducts, Orange, reel length 300 m. Used for copper cables.

PECD, Type 4: 77mm OD x 58 mm ID, W/ 3-27.2 mm OD Sub-ducts, Orange color, one sub-duct black, reel length 1200 m. Used for fiber optical cable.

PECD, Type 5: 77mm OD x 58 mm ID, without Sub-ducts, Orange, reel length 1200 m. Used for fiber optical cable, BSWs & small copper cables.

Types of PEC Ducts

Types of Ducts used in FTTH Network

Important Point About Ducts Planning

For identification of ducts number and dimensions, the primary network cables maximum requirements should be taken into consideration beside the usage of the new technologies to reduce the ducts size.

If the route including copper cables then the maximum duct length between tow manholes in the same route is 295m. If the route including only fiber cables then the maximum duct length is 500m. It is based on road crosses that the duct or its branch outs pass through, or curves impacting cable tension.

The main factor affecting the identification of the ducts number is the ducts annual usage rate derived from the cables forecasted requirements.

The economies of alternate locations must be compared relative to permanence, safety and utilization. The routes should be selected to avoid any future relocation. Locations should be chosen that are free of danger and also provide a safe working environment. There will be times when the safety aspect alone will have the greatest bearing upon the selection of one route over another.

Advantages of the triangular design from the Exchange to the subscriber are:

- Short cable lengths
- Smallest cable conductor gauge
- Least money per cable pair invested.

Locate the trench line so that it agrees with the government office . Agreement. If that location is already occupied by another utility locate the trench line so that the duct structure will be free as possible from disturbance of other underground users. In so doing the following should be considered.

In Cities For FTTH Network

Under the sidewalk, especially if the construction precedes the laying of the sidewalk, is usually an excellent location.

Between the sidewalk and the building line usually provides an undisturbed location. Between the sidewalk and the curb is not the best location because of tree planting or possible street widening.

In the street near the curb; if this location is used every effort should be made to locate the manholes under the sidewalk. In parkways, duct may be placed along the edge of the park if permission can be obtained.

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