Aim

To Study the 8051 Serial Communication using Fiber optics

Apparatus Required

• Fiber Optics Digital Transmitter Module– 01
• Fiber Optics Digital Receiver Module– 01
• Plastic Fiber cable 1 meter – 01
• 8051 kit – 02
• Adapter +15V/ DC – 02
• Patch Chords – 04
• PC to PC cable – 02

Theory

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.

Transmitter

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.

Receiver

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

Procedure

• ☞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 Address	Opcode	Mnemonics
8500	75,89,21	MOV TMOD,#21
8503	75 8D FD	MOV TH1,#FD
8506	75 98 52	MOV SCON,#52
8509	D2 8E	SETB TR1
850B	74 41	H:MOV A,#41
850D	B1 00	ACALL TXMT
850F	74 42	MOV A,#42
8511	D1 00	ACALL TXMT
8513	80 FE	SJMP 8517
8600	F5 99	MOV 99,A
8602	30 99 FD	JNB 99,8602
8605	C2 99	CLR 99
8607	22	RET

8051 Receiver Program

Memory Address	Opcode	Mnemonics
8500	90 87 00	MOV DPTR,#8700
8503	75,89,21	MOV TMOD,#21
8506	75 8D FD	MOV TH1,#FD
8509	75 98 52	MOV SCON,#52
850C	D2 8E	SETB TR1
850E	30 98 FB	JNB RI,850C
8511	E5 99	MOV A,99
8513	F0	MOVX @DPTR,A
8514	A3	INC DPTR
8515	80 F5	SJMP 850C
8516	F5 99	MOV SBUF,A
8518	22	RET

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