Download - Optical Fiber

Shri Shankaracharya Institute of

Professional Management & Technology

Laboratory Manual

Optical Fiber Communications

For

Final Year Students

Manual made by

Asst. Prof. Piyush Mishra

©Author SSIPMT, Raipur

Dept. of Electronics & Telecommunication

Technical Document

This technical document is a series of Laboratory manuals of Electronics and Telecommunication Department and is a certified of Shri Shankaracharya Institute of Professional Management & Technology. The care has been taken to make the document error free. But still if any error is found, kindly bring it to the notice of subject teacher and HOD.

Recommended by

HOD

Approved by,Principal

Copies:

1. Departmental Library2. Laboratory3. HOD4. Principal


FOREWARD

It is my great pleasure to present this laboratory manual for final year students for the subject of Microwave Communications keeping in view the vast coverage required for visualization of concept of Microwave Communications.

As a student, many of you may be wondering with some of the questions in your mind regarding the subject and exactly what has been tried to answer through this manual.

Faculty members are also advised that covering these aspects in initial stage itself will greatly relieve them in future as much of the load will be taken care by the enthusiasm energies of the students once they are conceptually clear.

H.O.D


LABORATORY MANUAL CONTENTS

This manual is intended for the Final Year students of Engineering in the subject of Microwave Communication. This manual typically contains practical/Lab sessions related Microwave Communication covering various aspects of the subject to enhance understanding.

Students are advised to go thoroughly through this manual rather than only topics mentioned in the syllabus as practical aspects are the key to understand and conceptual visualization of theoretical aspects covered in the books

Good Luck for your enjoyable Laboratory sessions.

Asst. Prof.

Piyush Mishra


DO’s and Don’ts in Laboratory :

1. Do not handle the equipment without reading the instructions/Instruction manuals.

2. Read carefully the power ratings of the equipment before it is switched on. For

3. Indian equipments, the power ratings are normally230V/50Hz.If you have equipment with115V/60Hz ratings do not insert power plug, as our normal power supply is 230V/50Hz,Which will damage the equipment.

4. Observe the type of sockets to avoid mechanical damage.5. Do not forcefully place the connectors.6. Strictly observe the instructions given by the teacher/lab

instructor.

Instruction for Laboratory Teachers :

1. Lab work completed during prior session should be corrected during the next lab session.

2. Students should be guided and helped whenever they face difficulties.

3. The promptness of submission should be encouraged by way of marking and evaluation patterns that will benefit the sincere students.


Subject Index

Lab Experiment

1. To setting up a fiber optic analog link.

2. To setting up a fiber optic digital link.

3. To study of pulse width modulation and demodulation.

4. To study of Pulse Position modulation and demodulation.

5. To study of numerical aperture of optical fiber.

6. To study of losses in optical fiber.

7. To study of pulse amplitude modulation & demodulation.

8. To study of frequency division multiplexing & demultiplexing.

9. To study of characteristics of fiber optic LED.

10. To study Amplitude modulation & demodulation.

11. To connect the RS – 232 of two computers using Optical Fiber

Digital Link.


Shri Shankaracharya Institute of ProfessionalManagement & Technology, Raipur

DEPARMENT OF ELECTRONICS & TELECOMMUNICATION

Subject Name & Code : Optical Fiber Communication Lab 328821(28)

Branch: ET&T Semester: 8 th

EXPERIMENT NO. 1

AIM: - Setting up a fiber optic analog link.

APPARATUS REQUIRED: - Fiber optic Trainer kit, function generator, fiber cable, C.R.O., patch cords.

THEORY:- Fiber optic links can be used for transmission of digital as well as analog signals. Basically, a fiber optic link contains three main elements, a transmitter, an optical fiber& a receiver. The transmitter module takes the input signal in electrical form& then transforms it into optical (light) energy containing the same information. The optical fiber is the medium, which carries this energy to the receiver. At the receiver, light is converted back into electrical form with the same pattern as originally fed to the transmitter.

PROCEDURE: -1. Keep all the switch faults in off position.2. Make connections as shown in fig. While connecting this ensures that

the power supply is off.3. Connect function generator to trainer kit.4. Keep the jumpers JP2 &JP3 on FCL-03 as shown in fig. Switch on the

power supply.5. Connect the 2 KHz, 2Vpp Signal from FG. As a constant signal to the

IN post of the Analog Buffer on FCL-03. 6. Connect the output of Analog Buffer post OUT to post TX IN.


7. Slightly unscrew the cap of LED SFH756V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back.

8. Slightly unscrew the cap of RX2 Photo DiodeSFH250V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back.

9. Observe the output signal from the detector at ANALOG OUT post on Oscilloscope by adjusting Optical power control Pot 3 in clockwise direction and you should get the reproduction of the original transmitted signal.

10. To measure the analog band width of the link, keep the same connection and vary the frequency of the input signal from 100 Hz onwards. Measure the amplitude of the received signal for each frequency reading.

11. Plot a graph of Gain/Frequency. Measure the frequency range for which the response is flat.

PRECAUTIONS: -1. Slightly unscrew the cap of LED. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 2. You have to prepare each end of the fiber cable very carefully so it transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle.4. Permissible ambient temperature range for CRO during operation is 0- 40c the Ventilation holes should not be covered.


EXPERIMENTAL SET UP: -


RESULT:-

CONCLUSION:-

EXPERIMENT RELATED QUESTION:-

1. Give the name of fabrication method of optical fiber?

2. What are the applications of optical fiber?

3. What are step index fiber & Graded index fiber?

4. What are single mode fiber &Multimode fiber?






EXPERIMENT NO. 2

AIM: - Setting up a fiber optic Digital link

APPARATUS REQUIRED : - Fiber optic trainer kit, CRO, Function generator, Patch cords .

THEORY:- Fiber optic links can be used for transmission of digital as well as analog signals. Basically, a fiber optic link contains three main elements, a transmitter, an optical fiber& a receiver. The transmitter module takes the input signal in electrical form& then transforms it into optical (light) energy containing the same information. The optical fiber is the medium, which carries this energy to the receiver. At the receiver, light is converted back into electrical form with the same pattern as originally fed to the transmitter.


PROCEDURE: - 1. Keep all the switch faults in off position

2. Make connections as shown in fig. While connecting this ensure that the power supply is Off.

3 .Connect function generator to trainer kit. 4. Keep the jumpers JP2 &JP3 on FCL-03 as shown in fig. Switch on the power supply. 5. Connect the 2 KHz, 2Vpp Signal from FG. As a constant signal to the

IN post of the Digital Buffer on FCL-03. 6 .Connect the output of Analog Buffer post OUT to post TX IN. 7. Slightly unscrew the cap of LED SFH756V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into

the cap. Now tighten the cap by screwing it back. 8. Slightly unscrew the cap of RX2 Photo DiodeSFH250V. Do not remove the cap from the connector. Once the cap is loosened, insert

the fiber into the cap. Now tighten the cap by screwing it back.9. Observe the output signal from the detector at DIGITAL OUT post on Oscilloscope by adjusting Optical power control Pot 3 in clockwise direction and you should get the direction and you should get the reproduction of the original transmitted signal.

10. To measure the analog band width of the link, keep the same connection and vary the frequency of the input signal from 100 Hz

onwards. Measure the amplitude of the received signal for each frequency reading.

11. Plot a graph of Gain/Frequency. Measure the frequency range for which the response is flat.

Precautions: - 1. Slightly unscrew the cap of LED. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 2. You have to prepare each end of the fiber cable very carefully so it

transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle. 4. Permissible ambient temperature range for CRO during operation is 0-40c the Ventilation holes should not be covered.


(V) Experimental set up: -


RESULT:-

CONCLUSION:-


1. Explain the basic block diagram of optical fiber communication? 2. What does u mean by splices & connectors? 3. Give the name of different type of splices & connectors? 4. Mention three specific communication based advantages of optical fiber communication?






EXPERIMENT NO. 3

AIM: - Study of pulse width modulation and demodulation.

APPARATUS REQUIRED:- Fiber optic trainer kit, CRO, Function generator, Patch cords.

THEORY:-

PULSE WIDTH MODULATION:

This technique of modulation controls the variation of duty cycle of the square wave according to the input modulating signal. Here the amplitude variation of the modulating signal is reflected in to on period variation of square wave. Hence, it is also called as technique of V to T conversion.

PULSE WIDTH DEMODULATION:

The input signal is pulse width modulated, so the on time of the signal is changing according to the modulating signal. In this demodulation technique during the on time of PWM signal is changing according to the modulating signal. In this demodulation technique, the PWM signal is applied to an Integrator, whose output is then filtered to obtain original signal. Thus at the output we get the original modulating signal extracted from PWM wave. Fiber optic transmitter (SFH756V) & receiver (SFH551V) are used to transmit and receive PWM signal respectively.


PROCEDURE: - 1. Keep all the switch faults in off position.

2. Make connections as shown in fig. While connecting this3. Connect function generator to trainer kit.4. Keep the jumpers JP1, JP2& JP3 on FCL-3 as shown in fig.5. Connect the out signal from FG. To the PWM in post of PWM

modulator on FCl - 3 and keep the signal frequency at 1 KHz & Amplitude at 1Vpp.

6. Connect the PWM OUT Signal from PWM Modulator to the IN postof digital buffer on kit.7. Connect the output of digital buffer post out to post TX IN. 8. Slightly unscrew the cap of LED SFH756V. Do not remove the cap

from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back.9. Slightly unscrew the cap of RX1 Photo transistor with TTL logic output SFH551V. Do not remove the cap from the connector. Once

the cap is loosened, insert the fiber Into the cap. Now tighten the cap by screwing it back.

10. Connect the output of detector post TTL OUT to post PWM DEMOD IN of PWM.

DEMODULATOR. 1. Keep Switch SW1 in PWM position.

2. Connect the output of PWM Demodulator post DEMOD OUT to post IN of filter 1.

3. Observe the PWM signal at PWM out post. 4. Observed the received signal at filter O/p post OUT Demodulated signal represents original signal.

PRECAUTIONS: - 1. Slightly unscrew the cap of LED. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 2. You have to prepare each end of the fiber cable very carefully so it

transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp

knife. Try to obtain a precise 90 degree angle. 4. Permissible ambient temperature range for CRO during operation is

0 -40c the Ventilation holes should not be covered.


(V) Experimental set up: -


RESULT:-

CONCLUSION:-


1. What are the SNR's of PWM system?

2. Explain how a PWM signal can be generated/detected?






EXPERIMENT NO.4

AIM: - Study of Pulse Position modulation and demodulation.


THEORY:- The position of the TTL pulses is changed on time scale according to

the variation of input modulating signal amplitude. Now pulse width modulated signal is fed as input to this circuit. Please note that input modulating signal must be converted into pulse width modulated from before applying to pulse position modulator. As the signal is PWM, naturally, according to the input signal, the pulse duration is changing and this change in pulse duration causes for the delay in triggering. The input is given to trailing edge trigger input of monoshot. So finally we get the pulses at the output, which are shifted on the time slot. This is nothing but pulse position modulation.

Thus Pulse Position is directly proportional to the instantaneous values of modulating signal. This PPM signal is then transmitted through transmitter (SFH756V) and received at detector output (SFH551V).


PROCEDURE: - 1. Keep all the switch faults in off position.2. Make connections as shown in fig. While connecting this3. Connect function generator to trainer kit.4. Keep the jumpers JP1,JP2& JP3 on FCL-3 as shown in fig.5. Connect the out signal from FG. To the PWM in post of PWM modulator on FCl 3 and keep the signal frequency at 1 KHz &

Amplitude at 1Vpp. 6. Connect the PPM OUT Signal from PPM Modulator to the IN post of digital buffer on kit.

7. Connect the output of digital buffer post out to post TX IN. 8. Slightly unscrew the cap of LED SFH756V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 9. Slightly unscrew the cap of RX1 Photo transistor with TTL logic output SFH551V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by

screwing it back. 10. Connect the output of detector post TTL OUT to post PPM DEMOD

IN of PPM Demodulator. 11. Keep Switch SW1 in PPM position. 12. Connect the output of PPM Demodulator post DEMOD OUT to post IN of filter 1. 13. Observe the PPM signal at PPM out post. 14. Observed the received signal at filter O/p post OUT Demodulated signal represents original signal.


transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle. 4. Permissible ambient temperature range for CRO during operation is

0-40c the Ventilation holes should not be covered.


RESULT:-

CONCLUSION:-


1. What are the SNR's of PPM.

2. Explain how a PPM signal can be generated/detected?






EXPERIMENT NO.5

AIM: - Study of numerical aperture of optical fiber.

APPARATUS REQUIRED:- Fiber optic trainer kit, CRO, Function generator, Patch cords .

THEORY:- Numerical aperture refers to the maximum angle at which the light incident on the fiber end is totally internally reflected and is transmitted properly along the fiber. The cone formed by the rotation of this angle along the axis of the fiber is the cone of acceptance, of the fiber. The light ray should strike the fiber end within its cone of acceptance; else it is reflected out of the fiber core.


PROCEDURE: - 1. Make connection as shown in fig. Keep all switches faults in off

position.2. While connecting this, ensure that the power supply is OFF.3. Slightly unscrew the cap of LED SFH756V. Do not remove the

cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back

4. Keep the jumpers JP1, JP2&JP4 on FCL-1 as shown in fig.5. Keep switch S2 in VI position on FCL-01.6. Insert the other end of the fiber into the numerical aperture

measurement Jig Hold the white sheet facing the fiber. Adjust the fiber such that its cut face is perpendicular to the axis of the fiber.

7. Keep the distance of about 10 mm between the fiber tip and the screen. Gently tighten the screw and thus fix the fiber in the place.

8. Observe the bright red light spot on the screen by varying intensity pot 3 & bias pot P4.

9. Measure exactly the distance d and also the vertical and horizontal diameters MR and PN as indicated in the fig.

10. Mean radius is calculated using the following formula.r = (MR +PN)/ 4

11. Find the numerical aperture of the fiber using the formula

NA = sinmax = r d2 +r2

Where max is the maximum angle at which the light incident is properly transmitted through the fiber.

Precautions: - 1. Slightly unscrew the cap of LED. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back . 2. You have to prepare each end of the fiber cable very carefully so it.

transmits light effectively3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle.4. Permissible ambient temperature range for CRO during operation

is 0-40c the Ventilation holes should not be covered.


RESULT:-

CONCLUSION:-

EXPERIMENT RELATED QUESTION:

1. Define numerical aperture of the optical fiber? 2. Define acceptance angle of the optical fiber? 3. What are the conditions for total internal reflection? 4. What are the basic principles of fiber?






EXPERIMENT NO.6

AIM: - To study of losses in optical fiber.

APPARATUS REQUIRED:-

Fiber optic trainer kit, CRO, Function generator, Patch cords .

THEORY:-

Optical fibers are available in different variety of materials. These

materials are usually selected by taking into account their absorption

characteristics for different wavelengths of light. In case of optical fiber,

since the signal is transmitted in the form of light, which is completely

different in nature as that of electrons, one has to consider the interaction of

matter with the radiation to study the losses in fiber. Losses are introduced in

fiber due to various reasons. As light propagates from one end of fiber to

another end, part of it is absorbed in the material exhibiting absorption loss.

Also part of the light is reflected back or in some other direction from the

impurity particles present in the material contributing to the loss of the


signal at the other end of the fiber. In general terms it is known as

propagation loss. Plastic fibers have higher loss of the order of 180 db/Km.

whenever the condition for angle of incidence of the incident light is

violated the losses are introduced due to refraction of light. This occurs

when fiber is subjected to bending. Lower the radius of curvature more is the

loss. Another loss is due to the coupling of fiber at LED & photo detector

ends.

When light travels down optical fibers, some of the light is

absorbed by the glass or plastic. This means the light coming out of the end

of the fiber is not as strong as the light going in to the fiber. When designing

a fiber communications system, you need to know the size of this loss to

calculate the maximum distance the signal will travel. In this experiment you

will try one way of measuring the loss in the fiber.

PROCEDURE: -

MEASUREMENT OF PROPAGATION LOSS:1. Make connection as shown in fig. While connecting this, ensure that the

power supply is off.2. Keep all switch faults in off position.3. Keep the jumpers JP1, JP2, JP3 & JP4 on FCL-01 as shown in fig.4. Keep the jumpers JP1, JP2 on FCL-02 as shown in fig.5. Keep switch S2 in VI position on FCL-01.6. Slightly unscrew the cap of LED SFH756V. Do not remove the cap

from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back

7. Slightly unscrew the cap of LED SFH250V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back

8. Keep Switch SW1 to Signal Strength position in FCL-02.9. Connect the output of photo diode detector post out to post IN of signal

strength indicator block.


10.Observe the signal strength LED’s, adjust the TRANSMITTER LEVEL using intensity control pot3 until you get the reading of all LED’s glow.

11.We will measure the light output using the signal strength section of the kit. The loss will be larger for a longer piece of fiber, so you will measure the loss of long piece of fiber. In order to measure the loss in the fiber you first need a reference of how much light goes in to the piece of fiber from the LIGHT TRANSMITTER. You will use the short piece of fiber to measure this reference.

12.Now remove the 1meter fiber and insert 3 meter fiber.13.Then take the signal strength reading you obtained for the long fiber

and convert it to db using the Equ.

14.Power = 10 log (P2/P1) db

i. = 10 log (8/6) db

ii. = 1.25 db

15.P2: Reference reading by 1 meter.

16.P1: Reading obtained after replacing 3 meter fiber.

A. MEASUREMENTOF BENDING LOSS:1. Keep the connection with 1 meter fiber as per the above procedure.2. Adjust the transmitter power so that the signal strength reading is 8. Now take the portion of the fiber and loop it to match bends. As you match each bends write down the reading from signal strength indicator.3. Observe the loss of signal strength.B. MEASUREMENTOF CONNECTOR LOSS1. Keep the connection with 1 meter fiber as per the above procedure.2. Adjust the transmitter power so that the signal strength reading is 8.3. Remove the 1 meter fiber and insert 0.5 meter connectorized fibers through connecting sleeve. Note the reading of signal stength. 4. Now take connector loss and subtract it from 8db. This is connector loss.



transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle. 4. Permissible ambient temperature range for CRO during operation is

0-40c the Ventilation holes should not be covered.


RESULT:-

CONCLUSION:-


1. Describe the major losses in optical fiber?

2. What does u mean by Bending Losses? What are macroscopic?

Bending loss& microscopic bending loss?

3. What are intramural dispersion & intermodal dispersion?

4. What is pulse dispersion?






EXPERIMENT NO.7

AIM: - To study of pulse amplitude modulation & demodulation.


THEORY:-Pulse amplitude modulation is a technique of communication in which

the high frequency square wave is modulated by the low frequency signal. The modulating signal is sampled by the pulses.

The PAM signal is nothing but the high frequency square wave in which the amplitude of each pulse is equal to that of the information signal at the respective sampling instant.

PROCEDURE: - 1. Make the connection as shown in fig.2. Keep all the switch faults in off position. Connect the power supply.3. Connect F.G. to FCL-01 kit4. Keep the jumpers JP1, JP2, JP3&JP4 on FCL-01 as shown in fig.5. Keep the jumpers JP1, JP2 on FCL-02as shown in fig.6. Keep S1 at 16 KHz position on FCL-01.7. Keep S2 in TX IN position on FCL-01.


8. Connect the 1 KHz, 2Vpp signal from F.G. as a constant signal to the IN post of PAM section on FCL-01.

9. Connect the output of PAM section post to post IN of Analog Buffer on FCL-01.

10. Connect the output of Analog Buffer post OUT to post TX IN.

11. Slightly unscrew the cap of LED SFH756V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 12. Slightly unscrew the cap of LED SFH250V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 13. Keep SW2 in ANALOG OUT position on FCL-02. 14. Connect the out put of photo diode detector post out to post in of PAM Demodulator section. 15. Observe the output in FCL-02, we will receive the same sine wave at the output. 16. Observe the effect of sampling rate by changing the sampling clock from 16KHz to 32KHz. 17. Observe the effect of varying signal frequency.

PRECAUTIONS: - 1. Slightly unscrew the cap of LED. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 2. You have to prepare each end of the fiber cable very carefully so it transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle. 4. Permissible ambient temperature range for CRO during operation is 0- 40c the Ventilation holes should not be covered.


RESULT:-

CONCLUSION:-


1. What are the SNR’S of PAM system?

2. Explain how a PAM signal can be generated/detected?






EXPERIMENT NO.8

AIM: - Study of frequency division multiplexing & de-multiplexing.


THEORY:- Multiplexing is a signal processing operation by which a number of independent. Messages can be combined into a composite suitable for transmission over common channel. The incoming signal is first passed through a low pass filter to remove high frequency components that do not contribute significantly to signal representation but disturb other messages. The filtered signal is then applied to modulators that shifts the frequency ranges of the signals so as the occupy mutually exclusive frequency intervals. The necessary carrier frequencies needed to perform these frequency translations are obtained from a carrier supply. Then input signal is modulated with respect to carrier signal. Modulation technique used here is frequency modulation technique. The band pass filters following the modulators are used to respect the band of each modulated wave to its prescribed range. The resulting band pass filter outputs are combined in parallel to form the input to the common channels.

The received signal is applied to bank of band pass filters with their input connected in a parallel. This technique is used to separate message


signals on frequency occupancy basis. Finally the original message signals are recovered by individual’s demodulators. PROCEDURE: - 1. Make connection as shown in fig. Ensure that the power supply is OFF. 2. Connect function generator & keep the jumpers JP2&JP3 as shown in fig. 3. Switch on the power supply. 4. Connect the out signal from function generator to the CH1 post of FDM transmitter & keep the signal frequency at 1 KHz & Amplitude at 0.5 Vpp. 5. Connect the 2 KHz, 0.5Vpp signal from function generator to the CH2 post of FDM transmitter. 6. Connect the OUT post of FDM transmitter to the IN post of Analog Buffer on kit. do not remove the cap from the connector. Once the cap

is loosened, insert the other end of fiber into the cap. Now tighten the cap by screwing it back.

7. Observe the output signal from the detector at ANALOG OUT then set carrier frequency of mod 1of about 10KHz with the help of P1 and z carrier freq. Of mod 2 of about 20 KHz with the help of pot P2. 8. Then observe the signal at Band Pass filter 1 out it should be maximum signal transmission at center freq. Of 10 KHz. 9. Then observe the signal at Band Pass filter 2 out it should be maximum signal transmission at center freq. Of 20 KHz. 10. Then observe signal at the out post of summation block as shown in waveform .11. Connect the output of Analog Buffer post OUT to post TX IN.

12. Slightly unscrew the cap of LED SFH756V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back.

13. Now rotate the optical power control pot P3 in kit anticlockwise direction. This ensures minimum current flow through LED.

14. Slightly unscrew the cap of RX2 PHOTO DIODE sfh250Vpost on Oscilloscope by adjusting optical power control pot P3.

15. Connect the output of detector post ANALOG OUT to post IN of FDM Receiver.

16. Observe the demultiplexed &demodulated signal at CH1 &CH2 output posts of FDM Receiver, fine tune carrier frequency of modulator so as it will give clear reproduction of input signal as shown in fig.


17. Connect CH1&CH2 post to IN post of filter 1&2 respectively. 18. Observe the signal at OUT post of filter 1&filter 2 as a reproduction of

original signal.



RESULT:-

CONCLUSION:-


1. What is multiplexing/demultiplexing?

2. Compare FDM/TDM.

3. What are the disadvantages of FDM?






EXPERIMENT NO.9

AIM:- Study of characteristics of fiber optic LED.


THEORY:-In optical fiber communication system, electrical signal is first

converted into optical signal with the help of E/O conversion as LED.

After this optical signal is transmitted through optical fiber, it is retrieved in

its original electrical from with the help O/E conversion device as photo

detector.

Data sheets for LED’s usually specify electrical and optical

characteristics, out of which are important peak wavelength of emission,

conversion efficiency, optical rise and fall times which put the limitation on

operating frequency, maximum forward current through LED and typical

forward voltage across LED.


Photo detectors usually come in variety of forms like

photoconductive, photovoltaic, transistor type output and diode type output.

Here also characteristics to be taken into account are response time of the

detector, which puts the limitation on the operating frequency, wavelength

sensitivity and responsivity.

PROCEDURE: - Confirm that the power switch is in OFF position.

1. Make the jumper setting as shown in the jumper diagram.

2. Then short AMP O/P post to TX I/P post with help of patch chord.

3. Insert the jumper connecting wires in JP2 and JP3 at positions

shown in the diagram.

4. Connect the ammeter and voltmeter with the jumper wires

connected to JP2 andJP3 as shown in the diagram.

5. Switch on the power supply. Keep the potentiometer Pr6 in its

maximum position. P6 is used to control current flowing through

the LED to get the IV characteristics of LED, rotate P6 slowly and

measure forward current and corresponding forward voltage, Take

number of such readings for various current values and plot IV

characteristics graph for the LED.

6. For each reading taken above, find out the power, which is the

product of I&V. this is the electrical power supplied to the LED.

Data sheets for the LED specify optical power coupled into plastic

fiber when forward current was 10 mA as 200mW. this means that

the electrical power at 10mA, current is converted into 200mW of

optical energy. Hence the efficiency of the LED comes out to be

approx. 1.15%.


7. With the efficiency assumed find out optical power coupled into

plastic optical fiber for each of the readings in step 7. Plot the

graph of forward current verses output optical power of the LED.

8. Repeat the above procedure by SFH 450V.



RESULT:-

CONCLUSION:-


1. what is the basic principle of LASER &LED?

2. Give the name of different type of lasers?

3. Write down the application of LED & LASER?

4. What are the characteristics of LED?

5. Distinction between Spontaneous & stimulated emission processes?






EXPERIMENT NO.10

AIM: - The objective of this experiment is to study Amplitude modulation & demodulation through fiber optic analog link.


THEORY:- In amplitude modulation, the modulating voltage, whose frequency is invariably lower than that of the carrier, varies the amplitude of a carrier signal. The amplitude of the carrier is made proportional to the instantaneous amplitude of the modulating voltage.

Let carrier voltage- ec = Ec cos (ct +)and modulating voltage - em = Em cos mt

The instantaneous amplitude of the modulated wave can be expressed as,e = ( Ec + K em) cos ct

= ( Ec + K em cos mt) cosct = Ec cos ct + Ecm cos mt . cos ct

Ec cos ct + mEc/2 x cos (fc+fm)t + mEc/2 x cos (fc-fm)tModulation Index: Modulation index m = Em/Ec Modulation index is also expressed in terms of maximum & minimum amplitude of the modulated carrier wave.

Emax - Emin

ma = -----------------Emax + Emin


Procedure: -1. Make the connection as shown in fig.

2. Keep all the switch faults in off position. Connect the power supply.

3. Connect F.G. to FCL-01 kit

4. Keep the jumpers JP1, JP2, JP3&JP4 on FCL-01 as shown in fig.

5. Keep the jumpers JP1, JP2 on FCL-02as shown in fig.

6. Keep S1 at 16 KHz position on FCL-01.

7. Keep S2 in TX IN position on FCL-01.

8. Connect the 1 KHz, 2Vpp signal from F.G. as a constant signal to the

IN post of AM section on FCL-01.

9. Connect the sine out of F.G. to post carrier IN of Amplitude modulator

section. On FCL-01.

10. Connect the output of Amplitude Modulator section post AM OUT to

post IN of Analog Buffer.

11. Connect the output of Analog Buffer post OUT to post TX IN.

12. Slightly unscrew the cap of LED SFH756V. Do not remove the cap

from the connector. Once the cap is loosened, insert the fiber into the

cap. Now tighten the cap by screwing it back.

13. Slightly unscrew the cap of LED SFH250V. Do not remove the cap

from the connector. Once the cap is loosened, insert the fiber into the

cap. Now tighten the cap by screwing it back.

14. Keep SW2 in ANALOG OUT position on FCL-02

15. Connect the out put of photo diode detector post out to post IN of AM

Demodulator section.

16. Observe the output in FCL-02; we will receive the same sine wave at

the output.

17. Observe the effect of varying signal frequency.


OBSERVATION & CALCULATION:-

Frequency of RF oscillator = ---------------------- KHz.Modulation Frequency Input Em Emax Emin


Precautions: - 1. Slightly unscrew the cap of LED. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 2. You have to prepare each end of the fiber cable very carefully so it transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle. 4. Permissible ambient temperature range for CRO during operation is 0- 40c the Ventilation holes should not be covered.



RESULT:-

1. The modulation index ma =_______________________

2. Waveform =

CONCLUSION :-


1. Explain where am used in daily life.

2. How many types of am are there.

3. Explain low level and high level am modulation.

4. Define modulation index or depth of modulation.






EXPERIMENT NO.11

AIM: - The objective of this experiment is to connect the RS – 232 of two computers using Optical Fiber Digital Link.


THEORY:- The computer communicates from serial com port which is at RS232 level i.e. at 12v. transceiver MAX232 performs the function of converting RS232 signals to TTL levels & vice versa.

Very important advantage of serial mode of data transfer is that it is inexpensive. Also the data is accurately transferred and received in the link. Uncorrupted data transfer is greatest advantage of serial mode, and exactly this is the reason behind the fact that serial mode is preferred in many applications.

PROCEDURE: - 1. Keep all the switch faults in off position.2. Make connections as shown in fig. 3. Connect COM 1 post in RS-232 section to IN post of Digital Buffer Section.4. Connect the output of Digital Buffer post OUT to post TX IN.5. Slightly unscrew the cap of RX1 Photo transistor with TTL logic output SFH551V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber. into the cap. Now tighten the cap by screwing it back.


6. Slightly unscrew the cap of RX1 Photo transistor with TTL logic output SFH551V. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back.7. Connect the output of detector post TTL OUT to post COM 2 in RS- 232 section.8. Connect one end of the 9 to 9 pin cable to Computer COM 1 port and other end to CN2 connector on FCL- 03 then connect second 9 to 9 pin cable one end to second Computer COM1 port and other end to CN3 connector on FCL-03.9. Switch on the computers.10. After putting ON one of the PC, go to START MENU, PROGRAMS, ACCESSORIES, COMMUNICATION and then Click on HYPER TERMINAL.11. A new Window will open, where in you double Click on

HYPERTRM, Two Windows will open , one at the background and another (small

window) with title Connection Description which will be Active. 12. Enter the name in the box by which you would like to store your connection, 13. Then specify connect using by selecting Direct to COM 1 or port

where your cable is connected and then click on OK. Now Window with Title COM 1 Properties will appear, where Port Setting

should be done as shown below and click on OK.

Bits Per Second Up to 115200Data Bits 8

Parity NoneStop Bits 1

Flow Control Xon/Xoff

14. After the above Settings you click OK. The Background window will become Active.

15. Click on file, Save As, and save it in Directory, which you want.16. Perform the same procedure from 10 to 15 on the computer to with

whom you want to communicate.17. To start communicating between the two PCs click on the Transfer

Menu and click on Send file. 18. Select Browse for the file, which you would like to send to PC

connected, select the file and click on OPEN, the file name and


address will be displayed in the small window. Then select the Kermit Protocol.

19. To receive the file on the PC click on the Transfer Menu and again click on Receive File. A window will be prompted having title Receive File with Location at which you want to store the Received file and Receiving Protocol.

20. Select Browse for the location where you would like to store the received file, select the folder and click OK, the folder name and address will be displayed in the small window. Protocol to be selected should be Kermit and same as file transmitting PC.

21. On the PC from which the selected file to be transmitted, click on SEND. A window will open showing file transfer status. Immediately at the Receiving PC Click Receive. You will see a window showing file is being received in the form of packets.

22. After file is transferred both the windows in the (transmitting & receiving PCs) will close. Check for the received file in the folder where the file is stored.

PRECAUTIONS: - 1. Slightly unscrew the cap of LED. Do not remove the cap from the connector. Once the cap is loosened, insert the fiber into the cap. Now tighten the cap by screwing it back. 2. You have to prepare each end of the fiber cable very carefully so it transmits light effectively. 3. Cut of the ends of the cable with a single-edge razor blade or sharp knife. Try to obtain a precise 90 degree angle. 4. Permissible ambient temperature range for CRO during operation is 0-40c the Ventilation holes should not be covered.



RESULT:-


CONCLUSION:-


1. Explain the functional description of RS-232?

2. Difference between OSI & TCP/ IP model?

3. Explain the types of Data transmission mode?

4. Define point to point and multipoint communication.
