Siemens SIMATIC NET PROFIBUS Benutzerhandbuch

3-12

PROFIBUS Networks SIMATIC NET

6GK1970-5CA20-0AA1 Release 2 05/2000

This section describes the structure and functions of an optical transmission
system. The information here will help you to understand the rules for calculating
the optical power budget in the next section.

An optical transmission path consists of a transmitter, the optical fiber, and a
receiver.

Signal
converter

E / O
converter

Electr. signal
(digital/analog)

E/O = Electro-optical converter
O/E = Optoelectrical converter

Signal
converter

O / E
converter

Power supply

Electr. signal
(digital/analog)

Optical fiber

Power supply

Attenuation
transmission
      path

Figure 3-2

Structure of a Link

The transmitter in an optical digital transmission system consists of a signal
converter that converts the digital signals from the electronics in to a pulse type
suitable for the electro-optical converter, and an electro-optical converter (E/O
converter) that converts the electric pulses to optical signals. In SIMATIC NET
PROFIBUS, LEDs (LED = Light Emitting Diode) are used as E/O converters. The
LEDs are specially adapted to the various transmission media.

The transmission media used in SIMATIC NET PROFIBUS are as follows:

S

Plastic fiber-optic cables

S

PCF fiber-optic cables (polymer cladded fiber)

S

Glass fiber-optic cables

For more detailed information about the various fiber-optic cables for SIMATIC
NET PROFIBUS, refer to Chapter 7.