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www.sigmatrainers.com

SIGMA TRAINERS

AHMEDABAD (INDIA)

DIGITAL TRANSMISSION

RECEIVER

FIBER OPTIC TRAINER

MODEL-FOT102

More

than2000

Trainers

Since

23

Years

TRAINERS

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INTRODUCTION

This trainer has been designed with a view to provide practical and experimental knowledge of a general

circuit of Digital Transmission Receiver fiber optics on a SINGLE P.C.B.

SPECIFICATIONS

1. Power supply requirement : 230V AC, 50 Hz.

2. Built in IC based power supply.

3. On Digital Data generator.

Bits : 8 bits, NRZ

4. Transmission Source : Fiber Optic LED - 660 nm

5. Receiver Source : Fiber Optic Avalanche Photo diode (APD).

1. All parts are soldered on single pin TAGS on single PCB of size 12" x 9" with complete circuit diagram

screen printed.

7. Standard Accessories : 1. A Training Manual.

2. Connecting Patch cords.

3. Fiber Optic Cable - 1 mtr

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CHAPTER-2

THEORY & CIRCUIT DETAILS FIBER OPTIC

DIGITAL TRANSMITTER/RECEIVER

The Analog Transmitter/Receiver System consists of following sections.

1. Digital Da ta ge nerator2. Digital Data transmitter

3. Digital Da ta rec eiver

4. Power supply.

(2) Digital data G enerator section:

To generate 8 bit digital data several digital ICs are used in this section. IC 7404 is used to generate bit clockof 8 Khz by using its two NOT gates. This bit clock is then divided by factor of eight to generate word clock.

During one word (Byte) period 8 bits are decided by data switch positions. Here eight data switches are used.Any random data can be set by making this switch in ON and off conditions i.e in Low and High positions. This

8 bit data is then loaded in two shift registers made of two 7495 Ics. Then this data is serially outputted as digital

data at "Digital Data" output terminal of this section. The frequency of data transmission can be selected byswitch S1 in two range 10 to 100 Hz and 100 Hz to 1Khz. Pot P1 is fine frequency variation pot.

(4) Digital Transmitter section:

Here digital data is given to source Fiber LED of 660 nm. This LED converts electrical signal into light signal

and is then transmitted in fiber optic cable. External digital input can be given by selecting switch.

(6). Digital signal receiver section:

The received light signal is converted into electrical signal by receiving Photo diode. Then it is given to IC 741and 311 which are used to amplify input analog signal. The amplified signal is available at output terminal.

(4) Power supply section:

The regulated power supply is used for different supply voltages.

Following output D.C. Voltages are required to operate PSK Modulation demodulation system.

+15V, 250mA,

-15V, 250mA,

+ 5V, 250mA,- 5V, 500mA.

Three terminal regulators are used for different output voltages i.e. IC 7805 for + 5V, IC 7815 for +15V, IC

7915 for -15V,IC 7905 for -5V.

These ICs are supplied different dc input voltages by two Half wave rectifiers consisting of D1-D4 and D5-D8

and C1, C2, C3, C3. The capacitors at each input and each output are for filtering purpose. SW 301 is main AC

ON/OFF Switch.

**************

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EXPERIMENT-1

Aim: To transmit and receive Digital signal using fiber optic cable.

Procedure:

1. Connect CRO channel-1 at the output of digital data transmitter.

1. Now Apply in digital word using given on/off switch. 00001111 etc.

2. Now connect the output of digital data generator to the input of the digital data transmitter.

3. Now connect the fiber optic link between input and output terminal.

4. Keep the CRO channel 2 at the output of the digital data receiver and check if it is same as input or not

If not than vary the 10k 10turn port and check if output is same as input or not.

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