Background Image
Table of Contents Table of Contents
Previous Page  50 / 80 Next Page
Information
Show Menu
Previous Page 50 / 80 Next Page
Page Background

Technical article

January 2017

48

www.read-eurowire.com

Investigating effects of

freezing conditions on

micro-duct air-blown cables

By Yunfang Ruan, Zhuang Xiong, Xiaoli Liu and Wenjing Ye, State Key Laboratory of Optical Fibre and Cable Manufacture Technology,

Yangtze Optical Fibre and Cable Joint Stock Co Ltd, and Huawei Technologies Co Ltd, Shenzhen, Guangdong, China

Figure 1

:

Micro-duct with cable soaked in water

Abstract

In some cold areas, freezing conditions are

a potential threat to micro-duct air-blown

cables. In order to study the effects of

freezing conditions on the transmission

performance of optical fibres in micro-

duct air-blown cables, two different

experiments were designed and carried

out in this paper.

The test results reveal that both freezing

in micro-ducts and that around end

caps have insignificant influence on

the transmission performance of the

fibres and no visual physical damage to

the cable has been detected after the

experiments.

1 Introduction

With the development of FTTx network

construction, micro-duct air-blown cables

are more frequently used due to the lack

of duct resources, even in some cold

regions. In this case, the water permeated

into the micro-duct will be frozen under

such low temperatures.

Some concern such as the cable

performance deterioration will discourage

the wide application of micro-duct

air-blown cables all over the world.

In order to study the effects of freezing

conditions

on

the

transmission

performance of optical fibres, freezing

tests were designed to simulate the cold

climate with the aid of a temperature

cycling chamber.

During the tests, the attenuation change

of the fibres was monitored, and the

appearance of the cable was checked.

The test procedures are described in detail

and the test results are carefully analysed.

2 Freezing test

conditions

Two experiments were designed to

simulate the conditions of water frozen in

the micro-duct and around the end caps

respectively with the aid of a temperature

cycling chamber.

The common test conditions in two

experiments are shown in

Table 1

.

3 Test for water frozen

in micro-duct

This experiment is designed to study the

impact of freezing conditions on fibre

attenuation while water is frozen in the

micro-duct, and performed in accordance

with IEC60794-1-22 Method F15: cable

external freezing test. A 1.8km-long

micro-duct air-blown cable and 80m-long

micro-duct are used in this experiment.

3.1 Test procedures

First, rewind the micro-duct onto a cable

drum and blow the cable into the duct.

Then, soak the 80m-long micro-duct (with

cable inside) in a pool for 24 hours to make

sure that the duct is completely filled with

water, as shown in

Figure 1

.

After that, seal the duct with end caps

before taking the cable drum out of the

pool. Finally, put the cable drum into the

temperature cycling chamber to perform

the temperature cycling test. Before that,

record the attenuation of each fibre at

room temperature (23°C).

3.2 Temperature cycling programme

The temperature cycling programme is set

as follows (one cycle):

1 Lower the temperature from 23°C to

3°C within 30 minutes and hold this

temperature for eight hours.

2 Then lower the temperature to -40°C

within 30 minutes and hold it until

the water is completely frozen and

the ice temperature is -10°C or lower

(by using a temperature monitoring

device).

Cable type

Stranded loose tube structure

with G.652D fibres

Fibre count

96

Cable OD

6.1mm

Micro-duct type

HDPE

OD/ID of micro-duct

10/8mm

TCT cycles

2

Table 1

:

Common test conditions