Chapter 3 - Troubleshooting; General; All Leds Are "Off; Alarm Led - TC Communications TC2100 User Manual

Rack mount/stand alone multi-drop (dual master self healing ring) fiber optic modem

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Table Of Contents

Table of Contents

General

Alarm conditions occur whenever an optical problem or "fault" is detected by the TC2100. Under normal

operation, all LEDs should be "On" (either solid or blinking), with the exception of the "ALARM" LED.

All LEDs are "Off"

If no LEDs are lit on the unit, check the DC power supply, terminal block connector plug, and/or power

source.

Alarm LED

When there is an alarm condition, the Alarm LED should be on solidly and at least one additional LED will

flash. The following fault conditions will cause the Alarm to be triggered:

1. Optic signal lost from "RxA" or "RxB." "Sync-A" or "Sync-B" LED will be flashing.

2. Optic signal is marginal, which causes invalid data packets to be received. The "Sync-A" or "Sync-B"

LED will also be "Off."

3. Optic overdrive can cause the "Sync-A" or "Sync-B" LED to turn "Off," although optic "A" or "B" still

receives a valid signal.

4. One (or more) of the external DIP switches is in the "On" position.

5. The Anti-Streaming function has been activated.

6. On the Master unit, the "A-Ring" or "B-Ring" is incomplete.

7. On the Slave units, a data wrap condition exists. The "A2B" or "B2A" LED is flashing, indicating the

wrap condition, and the "LPA" or "LPB" LED will also be blinking.

Optic Cable Types

Conventionally, fiber optic cable with yellow-colored insulation is used for single mode applications; gray or

orange-colored insulated cable is for multimode use. If multimode cable is used in a single mode application,

the test results could be erroneous and confusing.

Calculating the Loss on the Fiber

The fiber optic link and/or the connectors are frequently the source of communication problems. If problems

are present, check the optic connectors and the integrity of the link first. Ideally, the link should be calibrated

for total loss after the installation has been completed. This will accomplish two things: (1) it will verify that

the total loss of the link is within the loss budget of the device and (2) it will provide a benchmark for future

testing. For example, a system that has been tested as having 6dB of signal loss when installed should not

suddenly test out as having a loss of 10dB. If this were the case, however, the fiber link or connector would

probably be the source of the problem.

These are the reference values we use to calculate the loss on the fiber:

Multimode 850nm

Multimode 1300nm

Single Mode 1300nm

Single Mode 1550nm

*These numbers are listed for reference only. We recommend an OTDR reading be used to determine actual link loss.