Capital University of science and Technology Islamabad

1. i
FIBER OPTIC COMMUNICATION LINK
DESIGN
By
Aamir Saleem
EE133013
A Project Report submitted to the
DEPARTMENT OF ELECTRONIC ENGINEERING
in partial fulfillment of the requirements for the degree of
BACHELORS OF SCIENCE IN ELECTRONIC ENGINEERING
Faculty of Engineering
Capital University of Science & Technology,
Islamabad
Jan , 2017

2. ii
DECLARATION
It is declared that this is an original piece of my own work, except where
otherwise acknowledged in text and references. This work has not been submitted in
any form for another degree or diploma at any university or other institution for
tertiary education and shall not be submitted by me in future for obtaining any degree
from this or any other University or Institution.
Aamir Saleem
EE133013
Jan , 2017

3. iii
CERTIFICATE OF APPROVAL
It is certified that the project titled “FIBER OPTIC COMMUNICATION LINK
DESIGN” carried out by Aamir Saleem, Reg. No. EE133013, under the supervision
of Dr. Imtiaz Ahmad Taj ,Capital University of Science & Technology, Islamabad,
is fully adequate, in scope and in quality, as a semester project for the degree of BS
.Electronic Engineering.
Instructor : -------------------------
Dr. Imtiaz Ahmad Taj
Department of Electrical Engineering
Faculty of Engineering
Capital University of Science & Technology, Islamabad
HOD: ----------------------------
Dr. Noor Mohammad Khan
Professor
Department of Electrical Engineering
Faculty of Engineering
Capital University of Science & Technology, Islamabad

4. iv
ACKNOWLEDGMENT
We forever owe utmost gratitude to Almighty-ALLAH whose divine light and
warmth provided me the inspiration, faith and strength to carry on my work. We
express my sincere and deep sense of gratitude to Dr. Imtiaz Ahmad Taj for his
guidance, valuable suggestions, immense help, encouragement and friendly behavior
throughout the working of this dissertation.
We are also grateful to all the members of evaluation committee for giving valuable
suggestions and advices for evaluating me from time to time. We humbly express
our sincere thanks to all the faculty members and the staff of ELECTRICAL
ENGINEERING Department for their constant assistance and providing the pleasant
working conditions in the complete duration of the dissertation work.
We are thankful to Dr. Imtiaz Ahmad Taj for his helping attitude and constant
encouragement. We cannot conclude this acknowledgement without mentioning my
parents. It would not be possible for me to complete this work without their love,
encouragement and support.

5. v
ABSTRACT
At present, all over the world, optical communication system have been seen
as one of the attractive solution to the increasing high data rate in telecommunication
systems. There also has been a tremendous increase in usage of transferring
information like Internet and multimedia applications. As this applications require
high gigabyte bandwidths over distances of hundreds of kilometers, larger bandwidth,
shorter interconnection delays, lower levels of power consumption and smaller
channel crosstalk compared to conventional electrical counter parts. For this reason, I
want to design an inexpensive low bit-rate digital link to provide 100Mbps to capital
University of Science and Technology and 3Mbps to each user in the path of optical
fiber link to different areas. The digital fiber optic link design has been done for long
distance about 22.6 km from transmitter to receiver. The data rate is 550Mbps at the
bit rate error of 10^-12. Four combinations of source, fiber and detector have been
compared.
.

6. vi
TABLE OF CONTENTS
DECLARATION........................................................................................................ ii
CERTIFICATE OF APPROVAL...............................................................................iii
ACKNOWLEDGMENT ........................................................................................... iv
ABSTRACT ...............................................................................................................v
TABLE OF CONTENTS .......................................................................................... vi
LIST OF FIGURES ...................................................................................................vii
LIST OF TABLES.....................................................................................................vii
Chapter 1................................................................... Error! Bookmark not defined.
INTRODUCTION .................................................... Error! Bookmark not defined.
1.1 Overview.................................................... Error! Bookmark not defined.
1.2 Project Objectives ...................................... Error! Bookmark not defined.
Chapter 2.....................................................................................................................2
REQUIREMENT SPACIFICATION.........................................................................2
2.1 Planning the Route.......................................................................................3
2.2 Fiber Rout Selection.....................................................................................3
2.3 Data Rate Requirement ................................................................................4
2.4 Summary of Requirements for Proposed System .....Error! Bookmark not
defined.
Chapter 3................................................................... Error! Bookmark not defined.
COMPONENTS SPACIFICATION ........................ Error! Bookmark not defined.
3.1 Selecting Optical Transmitter ......................................................................5
3.2 Selecting Optical Fiber.................................................................................6
3.2.1 Selection of Fiber..........................................................................6
3.2.2 Fiber Standards .............................................................................7
3.2.3 Optical Fiber Transmission System..............................................7
3.2 Selecting Optical Receiver...........................................................................8
Chapter 4.....................................................................................................................9
DESIGN OF OPTICAL FIBER LINK.......................................................................9
4.1 Wavelength Region......................................................................................9
4.2 Fiber Selction.............................................................................................10
4.3 Link budget Analysis .................................................................................11
4.3.1 Rise time Budget.........................................................................12

7. vii
4.3.2 Power Budget..............................................................................13
Chapter 5...............................................................................................................1414
CONCLUSION.........................................................................................................14
REFERENCES .........................................................................................................15
LIST OF FIGURES
Figure 1: Google Earth Map of Optical Fiber Link .......................................................2
LIST OF TABLES
Table 1:Distributions.................................................... Error! Bookmark not defined.
Table 2: Summary .........................................................................................................4
Table 3: Optical Transmitter Modules...........................................................................5
Table 4: Optical Fiber Comparison................................................................................6
Table 5: Optical Fiber Standards ...................................................................................7
Table 6: Optical Fiber Distance .....................................................................................8
Table 7: Optical Receiver Modules ...............................................................................8

8. 1
Chapter 1
INTRODUCTION
1.1 Overview
The Purpose of this project is to design the optical fiber link from Khayaban_e_sir
Syed Rawalpindi to Capital University of science and technology Islamabad. The first
step of this project is to calculate the distance from source to destination and select the
route for our optical fiber link in such a way that route selected must have minimum
distance from source to destination .Selection of route depends on factors such as road
crossing, rivers or lakes or it may cross long lengths of open fields etc. This Optical
fiber link provide the 100Mpbs to CUST and 3Mbps to each user in the path of optical
fiber link for different areas .Shared and dedicated bandwidth play important role in
our project , because from these parameters we can calculate the total bandwidth of
the optical fiber link. Optical fiber communication link provide the wide bandwidth,
low losses and security for our communication. The scope of this project is to
calculate the power budget and rise time budget for transmitting and receiving side.
1.2 Project objectives
In this project we are going to present an engineering approach to design the optical
fiber communication link in accordance to requirements.
Objectives of our project are to:
 Provide the 100Mbps data rate to Capital University of science and technology
Islamabad.
 To run Power loss budget & Rise time budget strategies to vindicate the link
design.
 Provide the 3Mbps data rate to each user living in different areas.
 Calculate the total bandwidth from dedicated and shared data rate.
 Increase the information carrying capacity of transmission line.
 Design the transmitter and receiver to reduce the dispersion in optical fiber
link.

9. 2
Chapter 2
REQUIREMENT SPACIFICATION
2.1 Planning the Route
Having decided to use fiber optics and chosen equipment appropriate for the
application, it’s important to select the Route of optical fiber link .Depending on the
distance of optical fiber link optical Transmitter and Receiver is used. In this link
design total distance is 22.6Km, and this distance is shortest possible distance from
Khayaban_e_sir Syed Rawalpindi to Capital University of science and technology
Islamabad. Route Map for this link design is created in Google Earth; all the
distributions are clearly shown in the Google earth.
Figure 1: Google Earth Map of Optical Fiber Link

10. 3
The following table summarizes the proposedservice distribution
and overallrequirement
No. Area Identification No of users provided
service
Data rate
(Mbps)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
New Katarian
Pendorha
Double road
Faizaabad
Sohan Highway
Dhoke kala khan
Zia masjid
Khana Bridge
Ghori town
Sawan Garden
Naval Anchrage
CUST
50
80
70
100
40
50
60
100
70
50
80
1
30
48
42
60
24
30
36
60
42
30
48
100
Total users 751
Total data rate Required 550Mbps
Table 1: Distributions
2.2 Route Selection
These are the points that are important while selecting route for optical fiber link:
 The route select must have shortest distance.
 Once you have marked up maps, the real “fun” begins: finding out whose
permission you need to run you’re cabling.
 Depending on the route it may cross long lengths of open fields, run along
paved rural or urban roads, cross roads, ravines, rivers or lakes, or, more
likely, some combination of all of these , so plane about these factors before
finalizing route.

11. 4
2.3 Data rate requirement
Total bandwidth of optical fiber communication system is obtained by adding
dedicated bandwidth of all the distributions or areas that are near to the path of optical
fiber communication link, and you want to give connections to that area. In our
project we give 3Mbps data rate to each user in each area. Shared bandwidth is
obtained using this formula:
Shared Data Rate =users*3Mbps
Dedicated Data Rate is equal to 20% of shared Data Rate because not all users active
at the same time [1][2]. Current estimates for the usage factor during peak usage
hours are around 5%, with the figure expected to grow to about 15% [3].Maximum
20% of users active at a time from 100% shared bandwidth so dedicated bandwidth is:
Dedicated data rate =20 * shared Data Rate /100
Data rate= (100+30+48+42+60+24+30+36+60+42+30+48) Mbps=550Mbps
 Greater Bandwidth better quality of the received signal.
2.4 Summary of Requirements for Proposed System
Table 2: Summary
Total users 751
Bandwidth 550Mbps
Bit error rate 10-12

12. 5
Chapter 3
COMPONENTS SPACIFICATION
In this chapter we will discuss the optical link components that can be used for our
link design .Different optical transmitter and receiver modules are used for different
requirement, so we have to choose suitable and cost effective optical source and
detector to meet our requirement.
This Fiber Optic Communication Link Design would consist of the following
Components:
 Photo Detector
 Optical Source
 Optical Fiber
3.1 Selecting Optical Transmitter
The basic requirement for the light source depends on the usage of the optical
communication systems (Long Distance communication or local area network).
[9].There is 2 types of light sources that can be used, Light Emitting Diodes (LEDs)
and Laser Diodes (LDs). Laser diodes have the advantage of high speeds, narrow
spectral width and high power. LEDs have the advantages of reliability, lower cost,
long lifetime and simplicity of design but they have a lower bandwidth compare to
Laser. Details of Transmitter Modules Are shown in Table-2. [3][4]
Optical
Source
Module Output
Power(dBm)
Wavelength
(nm)
Data
Rate
(Mbps)
Distance Rise
time
(ns)
LED
DLT1151A
HFBR-
1312TZ
-15
-11
650
1300
16
32
20m
5Km
40
3
LASER SPS-7110V
2TX1
TL 2063PT-
010
0
-8
1310
1310
50 to
1500
155
30km
50km
1
3
Table 3: Optical Transmitter Modules Comparison

13. 6
3.2 Selecting Optical Fiber
Light waves travels in the optic fiber in the form of modes, each with a distinct
Spatial distribution, propagation, velocity, attenuation coefficient and polarization.[5]
Hence the fiber chosen must meet the design goals after the consideration of:
 Single mode fiber, multimode step index or multimode graded index.
 Fiber core size
 Core refractive index
 Bandwidth
 Attenuation dB/km
 Numerical Aperture
3.1.1 SelectionofFiber
Table 4: Fiber Selection

14. 7
3.1.2 Fiber Standards
These are the Standards of Optical fiber Available in Market.
Table 5: Fiber Standards
3.1.3 Optical Fiber TransmissionSystem
Table 6: Transmission Distance
Fiber Attenuation Loss of Single mode Fiber is less for long distance as compare to
Multi mode Fiber, so Single mode Fiber is selected for our Link design. Single Mode
Fiber is used for long distance 10Km to 100Km due to only one light travel through
Long distance. Single Mode Fiber 9/125 is easily available in market .ITU-T G.652
Standard for single mode fiber[3].

15. 8
3.3 Selecting Optical Receiver
There are two types of the Photo detector avalanche photo detector (APD) and PIN
Photo detector. For the specific photo detector we must examine the responsively R at
the operating wavelength. Responsively of a photo detector is usually expressed in
amperes per watt, or volts per watt, of incident radiant power. Details of the Photo
detector modules are show in Table-7. [7][8]
Optical
Detector
Module Sensitivity
(dBm)
Wavelength(nm) Rise time
(ns)
PIN
SRD 00214X
HFBR-2316TZ
PINFETLDPA
0003R
ERM535A
-7
-11
-54
-34
1310
1300
1550
1300
0.5
0.3
0.05
0.5
APD ERM577
TOAD347-RXB
-32
-34
1550
1310
1.5
0.25
Table 7: Optical Receiver Modules
Table 3, 4 and 7 shows the details of possible optical fiber, transmitter, and detectors
that can be used for optical fiber link design .In the next chapter we will find the Rise
time and power budget of optical link using these components specifications then we
will choose the suitable optical fiber, source and detector which fulfil our design
requirements.

16. 9
Chapter 4
DESIGN OF OPTICAL FIBER LINK
4.1 Wavelength Region
We know for long distance communication attenuation should be minimum as a result
high wavelength region that is third optic region 1310nm has been considered.
4.2 Fiber Selection
As discussed in chapter 3 Table-6 single mode fiber 9/125 standard ITU-T G.652 is
used in our link design because it fulfils our distance and bandwidth requirement. It
has high bandwidth and narrow spectral width.Fiber Attenuation Loss of Single mode
Fiber is less for long distance as compare to Multi mode Fiber, so Single mode Fiber
is selected for our Link design. Single Mode Fiber is used for long distance 10Km to
100Km due to only one light travel through Long distance. Single Mode Fiber 9/125
is easily available in market.
4.3 Link Budget Analysis
Optical source and detector is selected after the power and rise time budget
calculation. For satisfactory operation optical source and detector must satisfy the
both conditions. In next section we will find the rise time and power budget for
different optical sources and detectors and better one will be selected for our link
design.
Four types of combination are considered.
1) LED -PIN
2) LED -APD
3) LD -PIN
4) LD -APD
Out of these four combinations one combination is selected on the basis of power and
rise time budget, also considers the cost of the design.

17. 10
4.3.1 Rise time Budget
LED-PIN combination
This is low end combination, let’s find the rise time budget of this combination decide
LED-PIN combination is suitable for this link design or not.
Tsys = [(tS) 2 + tR) 2 + (tmat)2 + (tmodal)2]1/2
ts =
𝟎.𝟕
𝑹𝒏𝒓𝒛
=0.7/550X10^6 = 1.27 ns
The material dispersion factor for ts = 1.75ns, is D = -20 ps/ (nm-km)
and the waveguide dispersion factor, [10] Dg = 4ps/ (nm-km)
The net dispersion factor, DT = 20-4
= 15 ps / (nm-km)
Now, L = Length between transmitter and Receiver = 22.5 km
∆λ = spectral width of LED = 50 nm
GVD rise time = Tgvd = D*L*∆λ =15*22.5*50=17.4ns
From Table-3 we have
LED’s rise time, tLS = 3ns
From Table-7 we have
PIN photo detector’s rise time [8] tPD = .3ns
Total Rise time = {(3) ^2+ (0.3) ^2+ (17.4) ^2} ^1/2 =17.659 ns
This exceeds the total system rise time budget. So, next higher cost combination will
have to be considered. This shows that LED_PIN combination is not suitable for this
link design, not fulfill the rise time budget condition.

18. 11
LED -APD combination
Let’s find rise time budget using second combination and selection is done according
to requirement.
Tsys = [(tS) 2 + tR) 2 + (tmat)2 + (tmodal)2]1/2
ts =
𝟎.𝟕
𝑹𝒏𝒓𝒛
=0.7/550X10^6 = 1.27 ns
The material dispersion factor for ts = 1.75ns, is D = -20 ps/ (nm-km)
and the waveguide dispersion factor, Dg = 4ps/ (nm-km)
The net dispersion factor, DT = 20-4
= 15 ps / (nm-km)
Now, L = Length between transmitter and Receiver = 22.5 km
∆λ = spectral width of LED = 50 nm
GVD rise time = Tgvd = D*L*∆λ =15*22.5*50=17.4ns
From Table-3
LED’s rise time, tLS = 3ns
From Table-7
APD photo detector’s rise time tPD = .25ns
Total Rise time = {(3) ^2+ (0.25) ^2+ (17.4) ^2} ^1/2 =17.3 ns
This combination also exceeds the total system rise time budget. So, next higher cost
combination will have to be considered. This combination is not suitable for our link
design because it does not satisfy the rise time budget condition that is must for link
design. For better results it must fulfill both rise time and power budget requirement.

19. 12
LD -PIN combination
Tsys = [(tS) 2 + tR) 2 + (tmat)2 + (tmodal)2]1/2
ts =
𝟎.𝟕
𝑹𝒏𝒓𝒛
=0.7/550X10^6 = 1.27 ns
The material dispersion factor for ts = 1.75ns, is D = -20 ps/ (nm-km)
and the waveguide dispersion factor, Dg = 4ps/ (nm-km)
The net dispersion factor, DT = 20-4
= 15 ps / (nm-km)
Now, L = Length between transmitter and Receiver = 22.5 km
∆λ = spectral width of Laser = 0.15 nm
GVD rise time = Tgvd = D*L*∆λ =15*22.5*0.15=0.05115ns
From Table-3
Laser’s rise time, tLS = 1ns
From Table-7
PIN detector’s rise time tPD = .3ns[8]
Total Rise time = {(1) ^2+ (0.3) ^2+ (0.05115) ^2} ^1/2 =1.0453 ns
This is less than the total system rise time budget. So, the power budget can be done
now. This combination satisfy the rise time condition so now we will find the power
budget and If it fulfill the power budget condition , this combination is selected for
our link design.

20. 13
4.3.2 PowerBudget
The purpose of the power budget is to ensure that enough power will reach the
receiver to maintain reliable performance during the entire system life time. In the
preparation of link power budget, certain parameters like required optical power level
pr at the receiver to meet the system requirements, coupling losses etc are required [9].
Bandwidth * length = 550 Mb/sec * 22.5 km = (12375 Mb/sec) km
From Table-3 we have
Laser Output power = 0 dBm = 1mw
From Table-4 we have
Sensitivity of PIN (ERM535A) =-34 dBm
Fiber Attenuation = a = 0.35dB/km
Connector loss = 0.75 dB
Splice loss = 0.1 dB
Maximum Allowable System loss:
Pmax = Optical Source power – Sensitivity
Pmax = 0+34 =34 db
Actual Total Loss:
Pt =# connectors *(0.75) + # splices *(0.1) + Fiber attenuation per km * L +PM
Pt =22*(0.75) *(0.75) + 6 *(0.1) + 0.35 * 22.5 +7
Pt=32.97 db
Pt >>> Pmax
Since the actual loss in the system is less than the allowable loss, hence the system is
functional.
LD-PIN combination is the one combination that satisfies both rise time
budget and power budget. So, LD- PIN is the correct design. The PIN is
cheaper, less sensitive to temperature, requires lower reverse bias voltage than the
APD, so this combination meet our requirement with minimum cost and our design is
completed.

21. 14
Chapter 5
CONCLUSION
Finally I may conclude that for this proposed link design lowest cost combination of
source-fiber and detector is LASER-SMF-PIN is used. The design of a fiber optic
communication system involves the optimization of a large number of parameters
associated with transmitters, optical fibers, and receivers. Attenuation Loss of Single
mode Fiber is less for long distance as compare to Multi mode Fiber, so Single mode
Fiber is used for this link design. It is a good learning experience for me.The
designing, developing and conducting of technical investigations of project was
tough but enjoyable as I have learn a lot more on fiber optics design.

22. 15
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http://www.datasheetarchive.co.uk/EPITAXX%20erm%20577-datasheet.html.
[Accessed at 1.1.2017]
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