How A Fiber-Optic Cable Transmission System Works - Siemens SIMATIC NET PROFIBUS Owner's Manual

Configuring Networks
3.2.1

How a Fiber-Optic Cable Transmission System Works

Introduction
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.
Transmission Path
An optical transmission path consists of a transmitter, the optical fiber, and a
receiver.
Power supply
E / O
Signal
converter
converter
Electr. signal
(digital/analog)
Figure 3-2 Structure of a Link
Transmitter
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.
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.
3-12
Optical fiber
Attenuation
transmission
path
E/O = Electro-optical converter
O/E = Optoelectrical converter
Power supply
O / E
Signal
converter
converter
Electr. signal
(digital/analog)
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000