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Configuring Networks

3-2

SIMATIC NET Twisted-Pair and Fiber-Optic Networks

C79000-G8976-C125-02

3.1 Shared LANs (CSMA/CD Networks)

Shared LAN

The main feature of shared LANs is that all attached components share the

bandwidth of the transmission medium. At any one time, there can only be one

data packet in transit through the network. All data packets pass through all

segments. One station sends while all others receive. The station obtains the right

to send according to the CSMA/CD medium access method. The products that

operate according to the CSMA/CD medium access method and therefore form

shared LANs include the OLM/ELM, Mini UTDE, Mini OTDE, ASGE star coupler.

Using these components, it is possible to create bus, star and ring structures. The

rules for the network configuration are explained in this chapter. In this respect, it is

advisable to make a distinction between the length restrictions of individual

fiber-optic, twisted pair or AUI links dictated by attenuation characteristics and the

limits of the entire network span (collision domain) as dictated by the Ethernet

principle.

Note

For detailed information about configuring, installing, and operating components of

the SIMATIC NET triaxial network, refer to the manual for triaxial networks

(German/English, order number 6GK1 970-1AA20-0AA0)

3.1.1 Fiber-Optic Links

The optical ports of the OLM, Mini OTDE, ECFL2, and ECFL4 (interface cards for

the ASGE) comply with the IEEE 802.3j: 10BASE-FL standard. This means that

these ports can be linked in any combination.

The ideal media for these links are multimode glass fibers of the type 50/125 µm or

62.5/125 µm.

The length of the FO link that can be inserted depends on the optical power budget

available and the optical power loss at a wavelength of 850 nm.

FO Link Power Budget

A fiber-optic link power budget is available between the transmitter and receiver on

a fiber-optic link.

This represents the difference between the optical power coupled into a particular

fiber by an optical transmitter and the input power required by an optical receiver

for problem-free signal recognition.

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Siemens SIMATIC NET Betriebsanleitung Seite 28