Siemens SIMATIC 500 Series Description And Operating Instructions page 37

5 LED Indicators and Troubleshooting
2. Define the optical receiving level (see 4.4.7 "Defining the receiving level of the optical ports", p. 26 and
8.8 "Measuring sockets", p. 38):
– Level is in the range "Function is not guaranteed".
Check the optical fiber absorption using an optical level measuring device.
too high:
in valid range:
– Level is in the range "Optical system reserves reduced" or "Normal mode".
As described above, check the optical receiving level of the other OLM in the disturbed optical fiber
segment at the appropriate port.
– The levels at both OLMs of the disturbed optical fiber segments are in the range "Optical system reserves
reduced" or "Normal mode": one of the two OLMs in the disturbed optical fiber segments is defective.
First replace one of the OLMs in the disturbed optical fiber segment. If the fault still persists, replace the
other OLM instead.
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replace the optical fiber
one of the two OLMs of the disturbed optical fiber segments is defective.
First replace the other OLM of the disturbed optical fiber segments (i.e. the OLM, which
supplies the send signal for the measurement described above). If the fault still persists,
replace the other OLM instead.
5.2 Troubleshooting
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