2

Note: TOSLINK is a trademark of Toshiba Corp.

Raytela is a trademark of Toray Industries Inc.

Eska Premier is a trademark of Mitubishi Rayon Co. Ltd.

Sumiguide is a trademark of Sumitomo Electronic Industries Ltd.

signals instead of electrical signals.

Its principal features are as follows:

Electromagnetic noise has no effect on the transmission line.

The transmission line does not radiate any electromagnetic

noise.

The device is as easy to handle as like a digital IC, and

connector assembly is easy.

Comparison of TOSLINK and photocoupler

The function ability of TOSLINK is similar to that of a photocoupler.

A photocoupler has light-emitting and light-receiving devices in one package.

It is used to transmit electrical signals in a circuit, for a very short distane.

TOSLINK can be imagined as follows: separate the emitting device from the

receiving device in the center of a photocoupler, then re-connect the two

devices using a long optical fiber cable.

Because optical fiber is used as the transmission line, it is possible to transmit

signals over long distances while isolating them using TOSLINK.

As a result, TOSLINK is also sometimes referred to as a long-distance

photocoupler.

Comparison of TOSLINK and photocoupler

Electrical and optical transmission system

Electrical data transmission systems consist of the following devices: a line driver

and line receiver to amplify electrical signals, a twisted-pair (or coaxial) cable as

the transmission line and electrical connectors linking the line driver and line

receiver to the electrical cable.

By contrast, TOSLINK consist of the following devices: a transmitting module

which converts electrical signals into optical ones, a receiving module which

reconverts optical signals into electrical ones, optical fiber cable as the

transmission line and optical connectors to link the transmitting and receiving

modules to the optical fiber cable.

In TOSLINK, a transmitting IC (LED driver) and LED are included in the

transmitting module, and a receiving IC (waveform-reshaping circuit) and

photodiode are included in the receiving module. The interface between

transmitting and receiving ICs is at the transistor-transistor logic (TTL) or emitter

coupled logic (ECL) levels. Because of this it is easy to make connections with

the other circuits.

Data transmission system

(a) Data transmission by electrical wire

Electrical input signal

Line

Driver

Twisted

pair

or coaxial

cable

Electrical

connector

Electrical output signal

Line

Receiver

Electrical

connector

(b) Data transmission using fiber-optic cables

Electrical input signal

Transmitting

Module

Transmitting

Circuit

Optical fiber

E/O converter

LED

Receiving

Circuit

Photodiode

O/E converter

Fiber-optic link

Fiber-optic

connector

Electrical output signal

Receiving

Module

Fiber-optic

connector

Output

Input

(a)Photocoupler

Output

Input

(b)TOSLINK

Optical fiber

Optical transmitting module

Optical receiving module