6

Optical Modules for General-Purpose Use

Application circuits

Receiving module with analog output for an optical flux monitor (TORX198 and TODX298)

There are two series in the TOSLINK family which are designed or

general-purpose use. One is the TOSLINK 170 Series which was the

first generation of TOSLINK. The other is the TOSLINK 190 Series,

which is part of the new generation. The main technical features of

modules for general-purpose use in the TOSLINK 190 Series are as

follows:

Data transmission rate:Up to 6 Mb/s or 8 Mb/s.

Transmission distance: Up to 1000 m with PCF.

Up to 40 m with APF.

Wider dynamic range: 6 dB wider than the

TOSLINK 170 Series.

Constant external resistor value irrespective of transmission

distance.

There are two connector types, the F05 (simplex) and F07 (duplex),

which are available for both the TOSLINK 170 and 190 Series devices.

Application circuits for the TOTX197 and TORX196, a pair of transmitting and

receiving modules for general-purpose use, are shown in the figure on the

right. For the TOTX197 transmission module, an external resistor is required to

supply current to the LED.

For the TORX196 receiving module, a noise filter must be placed on the power

line. The module case is made of conductive resin in order to have a shielding

effect against noise. All case pins must be securely grounded.

There are also duplex modules in the general-purpose TOSLINK series devices,

but application circuits for these are generally the same as for simplex modules.

Interfaces in these modules are all at the transistor-transistor logic (TTL) level;

hence it is easy to connect them with other circuits.

The general-purpose modules described above provide digital output. In

addition there is also one receiving module (TORX198) with an analog output

for amplifier.

The analog output voltage (output voltage of the amplifier in the receiving

circuit) depends on the optical power input into the receiving module.

Hence, it is possible to measure optical flux without an optical power meter,

by monitoring this analog output terminal.

When an optical flux-monitoring function is not required, this receiving module

is used for digital data transmission, like the other TOSLINK receiving

modules. In this case this analog output pin should be kept open.

There is also the optical module product having flux-monitoring functions

such the duplex type TODX298 (for PCF cables).

Dynamic range of devices for general-purpose use

Application circuits for

TOTX197 and TORX196 devices

Receiving module with analog output

for optical flux monitoring

0.5

1

2

3 4

6

10

20 30

50

100

—4

—6

—8

—10

—12

—14

—16

—18

—20

—22

—24

—26

—28

—30

—32

—34

—36

Ta = 25

:190series

:170series

NRZ random pattern

PCF

Data transmission rate (Mb/s)

TODX270

TODX296

GND

4.3 k

Ω

Input

4

56

321

Optical

Transmitting Module

Fiber-optic connector

insertion side

Soldered to

PC board

Soldered to

PC board

(View from below)

TOTX197

GND

GND

GND

47

µH

0.1

µF

Output

4

56

321

Optical

Receiving Module

Fiber-optic connector

insertion side

(View from below)

TORX196

Analog output

Digital output

GND

GND

GND

GND

4

3

2

1

Amplifier

ATC circut

Voltage

Generator

Pin-PD

Comparator

—

Received optical power (dBm)

—

5

4

3

2

1

0

Ta = 25

With APF