Siemens S7-400 Cable Lengths, Mixed Use of Plastic Fiber-Optic and PCF Fiber-Optic Cable

Networking

5.8.3Connecting a Fiber-Optic Cable to the PROFIBUS Device

Cable Lengths

With fiber-optic cables, the length of the cable segment does not depend on the transmission rate.

Each bus node in the optical PROFIBUS-DP network has repeater functionality. The distances specified below are the distances between two neighboring PROFIBUS nodes in the partyline topology.

The maximum cable length between two PROFIBUS nodes depends on the type of the fiber-optic cable used.

Table 5-7 Permissible Cable Lengths on the Optical PROFIBUS-DP Network (Partyline Topology)

SIMATIC NET	Maximum cable	Projected for 1 Network
PROFIBUS	Lengths Between Two	(= 32 nodes) (in m)
Fiber-Optic Cable	Nodes (in m)
Plastic fiber-optic	50	1.550
duplex conductor
Plastic fiber-optic	50	1.550
standard cable
PCF fiber-optic	300	9.300
standard cable

Mixed Use of Plastic Fiber-Optic and PCF Fiber-Optic Cable

To gain the maximum benefit from the different cable lengths you can mix the plastic and PCF fiber-optic cables.

For example, you can use plastic fiber-optic cable for connections between DP slaves locally (distances <50 m) and PCF fiber-optic cable for the connection between the DP master and the first DP slave in the partyline topology (distance >50 m).

Laying PCF Fiber-Optic Cable

You can order PCF fiber-optic cables fitted with 2x2 connectors in specific lengths from Siemens.

Lengths and order numbers: See Table 5-5

Laying Plastic Fiber-Optic Cable

You can easily fit connectors to and install plastic fiber-optic cables yourself. Please read the following information on how to do this and on the rules for laying the cable.

5-28	Automation System S7-400	Hardware and Installation
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