You are currently viewing 8051 to 8051  Serial Communication using Optical Digital Link -Fiber optic communication Project

8051 to 8051 Serial Communication using Optical Digital Link -Fiber optic communication Project

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To Study the 8051 Serial Communication using Fiber optics

Apparatus Required


Kit to Kit communication

Fiber optic digital link was used to transmit and receive the data from one place another place .In this digital link will be supporting 1Mbd speed data communication. It will be act as an optical data modem. So we can use this digital link system in various sectors. And this digital link was used RS 232 serial port for communication.


The heart of the transmitter is a light source. The major function of a light source is to convert an information signal from its electrical form into light. Today’s fiber-optic communications systems use, as a light source, either light-emitting diodes (LEDs) or laser diodes (LDS). Both are miniature semiconductor devices that effectively convert electrical signals into light. They need power-supply connections and modulation circuitry. All these components are usually fabricated in one integrated package.

Transmitting LED HFBR 1251

This type LEDs needs external Driver circuits. Here we used IC 75451 for drive the LED.

Optical fiber

The transmission medium in fiber-optic communications systems is an optical fiber. The optical fiber is the transparent flexible filament that guides light from a transmitter to a receiver. An optical information signal entered at the transmitter end of a fiber – optic communications system is delivered to the receiver end by the optical fiber.

Model Diagram for Plastic Fiber cable

This is multi mode plastic fiber cable, in this fiber cable core diameter 1000 micron and fiber cladding index 1.402.


The key component of an optical receiver is its photo detector. The major function of a photo detector is to convert an optical information signal back into an electrical signal (Photocurrent). The photo detector in today’s fiber – optic communications systems is a semiconductor photodiode (PD). This miniature device is usually fabricated together with its electrical circuitry to from an integrated package that provides power-supply connections and signal amplification.

Receiving Photo Diode HFBR 2521

In this type Photo Diode have internal driver circuits. So no need any external driver.

Fiber Optics Digital Transmitter

Fiber Optics Digital Receiver


  • ☞Connect +15V adapter to both transmitter and receiver module.
  • ☞Switch (sw1) ON the transmitter Module,  8051 kits and receiver module (sw1).
  • ☞Connect PC to PC cable between 8051 kit 1 to transmitter module P5 connector and receiver module P8 connecter to 8051 kit 2.
  • ☞Connect the 1 m Plastic fiber cable between transmitter modules LED to receiver module Photo Diode.
  • ☞Connect P7 and P9 using patch chord at transmitter module.
  • ☞Connect P3 and P7 using patch chord at receiver module.
  • ☞Now type the transmitter program in transmitter side kit and receiver program in receiver side8051 Kit.

8051 Transmitter Program

Memory AddressOpcodeMnemonics
850075,89,21MOV TMOD,#21
850375 8D FDMOV TH1,#FD
850675 98 52MOV SCON,#52
8509D2 8ESETB TR1
850B74 41H:MOV A,#41
850F74 42MOV A,#42
851380 FESJMP 8517
8600F5 99MOV 99,A
860230 99 FDJNB 99,8602
8605C2 99CLR 99

8051 Receiver Program

Memory AddressOpcodeMnemonics
850090 87 00MOV DPTR,#8700
850375,89,21MOV TMOD,#21
850675 8D FDMOV TH1,#FD
850975 98 52MOV SCON,#52
850E30 98 FBJNB RI,850C
8511E5 99MOV A,99
851580 F5SJMP 850C
8516F5 99MOV SBUF,A

First execute the receiver side 8051 Kit, then transmitter side 8051 Kit.

☞Now received data verified from 8700 address in receiver side 8051 kit.

Note: You can also write c program to transmit and receive data through fiber optics digital link

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