A Construction Support System for Optical Fiber Networksby Tetsuhiro Yamashita* and Akio Hasemi*

The expansion of optical fiber networks has created an increasing demand for greater

ABSTRACT efficiency and higher quality in cable laying and repair work. This paper reports on
the development of a compact, simple system for the support of optical fiber testing and measuring
work in the course of construction. In this system a small, lightweight portable terminal is used tooperate an Optical Time Domain Reflectometer and Optical Fiber Selector that are installed at aconsiderable distance from the work-site, allowing the results of measurement to be referred to aswork proceeds.

1. INTRODUCTION
As with wide use of the terminology "Multimedia", recent
development of the telecommunication industry has resulted to produce higher levels of various services, bymeans of construction of wide area optical communication networks with high quality, large capacity data communication through the employment of optical fibers.
Optical fibers, for mass information transfer media, havehigher reliability than conventional metal cables. However,work failure due to improper installation or road repair work(causing damage on buried cables) seriously affects theService center

reliability of optical networks.
Supporting systems performing inspection of cable
network installation, track maintenance for informationtransfer quality, and urgent recovery from troubles are essential to the optical fiber networks; the development of a
network maintenance then becomes necessary for assuring effectiveness of the networks.
To comply with the requirement, we have developed arecovery support system for optical fiber installation
troubles or accidents that may happen in the network laying-out and maintenance work. Our recovery support system has a feature of smaller size/space saving, and simple

Public lines

Measurement unit
Optical Time Domain
Reflectometer (OTDR)
Controlunit

Connecting workshop

Optical Fiber Selector(FS)Portable terminal

Optical fiber cable
Optical fiber
termination frame

Figure 1 System configuration* Optical Cable System Sec., Optical Line Development
Dept., Opto-Technology Lab., R&D Div.

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operation through portable terminals to correspond various optical networks operated by different carriers.

cables, and control terminal connectors (D-sub 9 pin andmodular jack) are provided on the front right side. Table 3shows the specifications of the control unit (FS included).

2. SYSTEM CONFIGURATION
2.1 System Outline
Figure 1 shows the outline of our optical cable installation
support system. The system consists of such measuring
equipment to be installed near the optical fiber termination frame in the service center as an Optical Time Domain Reflectometer (OTDR), an Optical Fiber Selector(FS), measuring equipment having a control unit, and aportable input / output terminal carried by cable installation operators. The control unit of the measuring equipment is connected to the portable terminal through thepublic lines; therefore, the operators are able to run various meters and watch data from a remote work-site. The
testing light generated from the OTDR passes through FS
and is connected to an optical fiber cable in the opticalfiber termination frame. The FS automatically switches thetest light into a designated optical fiber in optical cables.
The purpose of our system developed is to support thework of connecting or transferring optical fiber cables, andto search for trouble points in optical cables, therefore,
one operator can perform his/her entire inspection workfrom a distant service-center room achieving the above
connection and trouble seeking procedures.
2.2 Measuring Equipment
The measuring equipment consists of an Optical Time
Domain Reflectometer (OTDR), an Optical Fiber Selector(FS) and a control unit.
2.2.1 OTDRThis system uses a Hewlett-Packard made mini-OTDR.
Table 1 shows the specifications of OTDR. The mini-OTDR
is small-sized and lightweight, exhibiting the same performance as the conventional types of OTDR. In addition,
the mini-OTDR acts as a light source for fiber identification and loss measurement. Other maker's OTDRs arealso available by changing the control commands between
the control unit and the OTDR.
2.2.2 Optical Fiber Selector
Figure 2 shows the structure of the Fiber Selector (FS). In
the FS, an optical fiber on the measuring equipment side(Master) and an optical fiber for connecting (Slave) are
jointed through the V grooves. FS is filled with matching
oil to reduce the connection loss and the reflection on thejointed portion. Table 2 shows the characteristics of theFS.
2.2.3 Control Unit
The control unit is accommodated with the FS, and Photo
1 shows its appearance. It can connect a maximum of
144 connectors of optical fibers; SC connectors are aligned
in front of the unit. SC connectors for connecting OTDR
optical cords, connectors (D-sub 9 pin) for OTDR control

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Table 1

Specifications of OTDR

Items

Specification

Span
1km~200km(full width of transverse axis)
Horizontal Reading resolution
0.1m (10cm)
axis
Precision of distance reading ±0.1m±Sampling interval×0.5±Measured distance×10-4

Verticalaxis

Lightsource
outputPulselightsource

Vertical axis scale

0.1~10.0dB/div

Reading resolution

0.001dBLinearity

0.05dB/dB

Reflection measurement
range

20dB~>60dB

CW mode output power-3dBm

CW mode stability±0.1dB/15 minutes,
After 10 minutes warming-up
at constant temperature

Modulation

270Hz, 1kHz, 2kHz,
Square wave

Modulation mode output
power

-6dBm

Wavelength

1310/1550nm

Test fiber

Single mode

Dynamic range

10ns 24/22
1µs 35/34

Dead zone

5m

Auto-analysis

Built-inType of event

Reflective,
Non-reflective event

Maximum event No.

100

Non-reflective event
detection value

0.0~5.0dB
Setting in 0.01dB step

Reflective event detectionvalue-14.0~65.0dB
Setting in 0.1dB step

Detection value of broken
point analysis

0.1~10dB
Setting in 0.01dB step

100ns 29/27
10µs 40/39

Function

Optical fiber(measurementequipment side)
V groove base

Optical fiber (cable side)

Figure 2 Structure of fiber selector

Furukawa Review, No. 18. 1999

an RS232-C, it can transmit and receive data; and controlling of communication devices having RS232C interface such as optical talk sets can be made, in addition todirect connection.

3. FUNCTIONSPhoto 1 Control unit

Table 2 Performance of Fiber SelectorItems

Specification

Optical properties
Insertion loss

Less than 0.5dB

Reflection attenuation quantity

More than 40dB

3.1 Support for Connecting WorkIn the connecting work support mode, the connection loss
at the joints is measured in order to confirm whether theconnection is correctly made in optical fiber extension jointing work. Figure 3 shows a flow chart of the support forconnecting work.
In order to measure the characteristics of jointed section, several data, such as types of connections (fusion,MT, single connector), connection loss threshold, reflection threshold, connected positions, and position errors
are to be input (refer to Figure 4). Based on the input data,
cable conditions before connection are measured by theOTDR and the connecting point is confirmed by measuring the position of the cable termination. Figure 5 shows
an example of measurement trace data.

FunctionTransfer port No.

Less than 400 cores

Transfer work time (second)

Less than 10 seconds

Connecting work support
Transmission line connectionMore than 1 million cycles

Durability

OTDR setting
Connecting loss reproducibilityLess than 0.1dB

Connecting point information input

Table 3 Specifications of control unit
Items

Specifications

Size

W300×H250×D380 mm

Weight12kg

Interface

D-sub 9pin×2
Modular jack×1

Port No.

144 ports

Power source

AC100VFS setting
Confirmation of connecting point
Connecting work
Connecting loss measurement
at connecting point
Transmission line cutting
EndFigure 3 Flow chart for connecting work
Table 4 Specifications of Zaurus
Items

Specifications

Information on connecting point
Size

W161×H90×D23 mm

Weight320g

Display

320×240 dots
65536 color

Power source

Lithium ion battery
AC adopter with charging function

Type of connecting method Fusion
Connecting loss threshold
Reflection threshold
Connecting point
Tolerance ofposition measurement

2.3 Portable Terminals
SHARP's PDA, named as "ZAURUS" is used for the portable terminal. Table 4 shows the specifications of ZAURUS.
The portable terminal can transmit and receive data byusing a control unit and a portable phone. Also, throughClick OK button after setting each item
OKEndFigure 4 Information page of connecting point

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After the connection work, the optical loss of the opticalfiber at the confirmed point is measured (refer to Figure 6
Measurement trace data), then judgement for right connection is done by comparing the measured data with thepre-input connection loss threshold. Another judgement
is also required if connectors are used. Figure 7 shows apage for the optical cable connecting work.

Measurement trace data
Event Type

Location Reflect Loss

Atten. Total Loss

3.2 Support for Cable Transfer WorkIn this work, in order to confirm completion of proper cabletransfer work made with another optical cable at a certain
service field, the optical loss of the optical fiber in the transferred section is to be measured. Figure 8 shows a flow
chart of the support for cable transfer work.
In order to measure the optical loss in the transferred
section, transferring information, such as: the type of transferring point, the optical loss threshold after transferring,
positions of two replacement end points must be input(Figure 9). Firstly, to identify the transferring optical fiber,
by applying a light source emitting menu (Figure 10), anOTDR is used as the identification test light source (270Hz modulation light).The operator confirms the optical fiber in which the identification testing light is in by meansof the optical fiber identifier.
After the completion of the optical cable transfer work,
the optical loss of the transfer section (designated on theinformation input page) are to be measured to confirm theoptical loss whether the data measured is within the range

Distance
EndCable transfer work

Figure 5 Measurement trace data (before connecting)Transmission line connection
OTDR setting

Measurement trace data
Event Type

Location Reflect Loss

Atten. Total Loss

Transfer point information input
FS setting
Confirmation of transferring
optical fiber
Transfer work
Connecting loss measurement
at transfer point
Transmission line cutting

DistanceEndEnd

Figure 6 Measurement trace data

Figure 8 Flow chart for cable transfer work

Transfer point informationConnecting work supportOperator
Port No.

Date 24 Jul.1998
Location

Fiber length LossCheck

Type of cable transfer pointFusion

Connecting loss threshold
between two points

dB

Transfer point 1m

Transfer point 2m

Click OK button after setting each item
OKOTDR setting

FS setting

Information

Start

Figure 7 Page of optical cable connecting work88EndEndFigure 9 Information page of cable transfer point

Furukawa Review, No. 18. 1999

OTDR light source mode

Searching trouble point
Wavelength

Transmission line connection
OTDR setting

Modulation

FS setting
Searching trouble point
Click light emission button after setting each item

Light onLight offEnd

Figure 10 Page of light source mode

Point 1Figure 12 Flow chart for searching trouble point

Operator

Date 24 Jul.1998

Port No.

End

Support of searching trouble points

Optical cable transfer
Operator

Transmission line cutting

Point 2Loss(1-2)

CheckOTDR set

FS setPoint info.

LS mode

Start

End

Figure 11 Page of optical cable transferof pre-input threshold value. Figure 11 shows a page forthe work of optical cable transfer.
3.3 Locating Trouble Points in Optical Cables
Locating troubled points is carried out by measuring theoptical fiber with the OTDR. Figure 12 shows a flow chart
for searching trouble points.
Location of troubled points is searched through the automatic function of the OTDR by analyzing mismatching
points against the event judgement value pre-determined
as OTDR measuring conditions. The operator can designate a fiber cable to be checked, as required, and uses
the automatic analyzing function of the OTDR for the evaluation. Figure 13 shows a page for locating work of troubledpoints in optical cables.

Date 24 Jul.1998
Port No.

OTDR set

FS setTrouble check

StartEnd

Figure 13 Page of searching trouble point in optical cable

4. In Conclusion
We have made a success in the development of the support system for the installation of optical fiber cables withhigh efficiency and quality. We are going to continuously
pay the efforts to develop much smaller-sized and lightweight, portable terminals with improved functions
matched to the user's needs.
Manuscript received on November 3, 1998.

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