ABSTRACT

Fiber optic communication systems have revolutionized the telecommunications industry, because it is used for faster transmitting of telephone signals, internet communication and cable television signal due to such lower attenuation and interference. The optical fibers are buried deep in the ground (1.2-1.5 meters) away from human activities. However, these fibers are been cut on frequently, the minute a fiber is cut, there is a halt in the smooth transition of signal.

 To prevent this occurrence, we designed and constructed underground cable cut detection system. The underground monitoring system comprises of two parts, the Fm transmitter and distance to fault measurement system. FM transmitter was design to broadcasts radio signals of frequency 73.4 MHz with the aid of a trimmer accompanied by an antenna. An interrupt signal was generated when there is a cut on power cable joining the transmitter circuit and the power supply. To find the exact position where an intruder is working we employed the distance to fault measurement system. Resistors where fixed parallel across a copper wire at an interval of 1m at a distance of 10m and the total resistor value was measured with a fixed multimeter. A cut on the wire indicated a change in the resistor value on the multimeter reading and hence the distance was figured from the distance to fault document drafted. This project was designed to provide a quick respond system to the network operator of intruders attempting to destroy underground fiber cables during signal transmission.

TABLE OF CONTENT

DEDICATION ___________________________________________ I

ACKNOWLEDGEMENT___________________________________V

ABSTRACT ___________________________________________________________ vi

CHAPTER ONE ________________________________________________________ 1

INTRODUCTION _______________________________________________________ 1

1.1PROBLEM STATEMENT___________________ 4

1.2 AIMS/ OBJECTIVES ____________________________________________ 4

1.3 SCOPE AND LIMITATIONS4

CHAPTER TWO ________________________________________________________ 6

THEORY______________________________________________________________ 6

2.1 UNDERGROUND MONITORY SYSTEM_________________________6

2.1.1 FM TRANSMITTER______________________________________ 6

2.1.1.1 PRE-AMPLIFIER_______________________________________ 7

2.1.1.2 LC OSCILLATOR______________________________ 8

2.1.1.3 FMMODULATOR__________________________10

2.1.2 LAID CABLES SYSTEM_________________________________________________ 11

2.1.2.1 MONITORY CABLE SYSTEM______________________________12

2.1.2.2 RESISTORS MULTIMETER CABLE_________________________12

2.1.3 RECEIVING UNIT ________________________________________13

2.2 OUTPUT SIGNAL_____________________________________14

2.2.1 ELECTROMAGNETIC WAVE

2.2.2 RADIOWAVE

2.2.3 FREQUENCY MODULATION

CHAPTER THREE _____________________________________________________15

METHODOLOGY______________________________________________________15

3.1 INTRODUCTION__________________________________________15

3.2 PLANNING_________________________________________________ 15

3.2.1 DATA COLLECTION______________________________________________________ 15

3.3 IMPLEMENTING___________________________________ 17

3.3.1CONSTRUCTION________________________________________________________ 20

3.3.2 CHECKING_____________________________ 22

3.4 ANALYSIS________________________22

3.4.2 CIRCUIT DESCRIPTION _____________________________________________ 22

3.5 APPLICATIONS________________________________________________ 24 viii

3.5.1 FM TRANSMITTER________________________27

3.5.2 DISTANCE TO FAULT                                                       

CHAPTER FOUR ______________________________________________________ 30

RESULTS AND DISCUSSION ___________________________________________ 30

4.1 DISTANCE TO FAULT DOCUMENT _______________________30

4.1.1 RESISTANCES AND LENGTH READINGS _______ _______ 33

4.4 SYSTEM TEST RESULTS AND ERRORS________________________ 35

CHAPTER FIVE _______________________________________________________36

CONCLUSION AND RECOMMENDATION ________________________________36

5.1 CONCLUSION ___________________________________________ 36

5.2 RECOMMENDATIONS _____________________________________ 36

REFERENCES ________________________________________________________ 38

APPENDIX ___________________________________________________________ 40

APPENDIX A ______________________________________________ 40           

RESISTOR MULTIMETER CABLE SYSTEM _____________________40

APPENDIX B _______________________________________________45          

SPEED OF ELECTROMAGNETIC WAVE DERIVATION________________________45

APPENDIX C _______________________________________________49

WAVELENGTH- FREQUENCY RELATION FORMULAR DERIVATION_______ 49

APPENDIX D _______________________________________________49

HARDWARE REQUIREMENT _______ 50