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8. Troubleshooting
Typically, most problems encountered with the TC3020R/S are related to optic receiver overdrive. The
maximum optic power that can be received without distortion is referred to as the optic receiver's
"saturation level." When the incoming optic power is greater than the saturation level of the receiver, optic
"overdrive" can occur.
The TC3020R/S optic receivers have a typical saturation level of -14 dBm. If the user's equipment's launch
power is higher than -14dBm (i.e. -13dBm or greater) and the fiber run is very short and has low signal loss,
it is likely to overdrive the TC3020R/S Multimode receiver. The consequences of overdrive can be high
error rates or the device's failure to recognize the incoming optic signal at all.
The TC3020R/S has been adjusted at the factory so that the Single Mode transmitter will not overdrive the
Single Mode receiver even when short cables are used to connect them; hence, the overdrive condition
happens most frequently at the Multimode receiver optic.
If you suspect the Multimode receiver has an optic overdrive condition, a simple test will help verify it. At
the receiving optic in question, simply disconnect the optic connector and back it out of the receptacle
(about 1/8 of an inch), creating a gap between the fiber connector and the receiver. Verify that the
equipment is still in "sync" with the optic signal and that the overdrive condition has been corrected. To
resolve the overdrive condition permanently, insert a 5dB or 10dB in-line attenuator into the problem link.
In-line attenuators can be purchased from Metrotek* at (914) 347-4112. The part numbers are:
Description:
ST@5dB
Part Number:
68-JJ-7-0513
The following diagram illustrates a TC3020R/S Mode Converter used to convert a 1300nm Single Mode
optical signal from a customer's device (5 Mbps) into a 1300nm Multimode optic signal to be received by
a remote device. In the reverse direction, the remote device's Multimode optic signal is converted to Single
Mode format to be received by the local device. In-line attenuators are used to correct optic overdrive
conditions that exist on either side of the TC3020R/S.
Note: Launch power measurements may vary due to the actual optic signal's duty cycle variation.
9. Further Troubleshooting & Assessment Tests on your TC3020 Unit(s).
If you are having trouble establishing communication with your equipment and the TC3020 unit(s), you can test the
unit(s) by performing the following simple assessment tests. If your application requires the use of one or two
TC3020 unit(s), then the following procedures will apply to your system. You will need to perform a Single Mode
Loopback test and a Multimode Loopback test on your TC3020 unit(s). These tests should be done using your
PC's hyperterminal.
Note: Make sure that your equipment's wavelengths match with that of the TC3020's. The 1310nm wavelength is
shown as a reference only on the following figures.
*Metrotek is not affiliated with TC Communications, Inc.
ST@10dB
68-JJ-7-1013
Figure 4. In-line Attenuator Placement Diagram
FC@5dB
68-FF-0513
−4−
TC3020R/S
User's Manual
Rev. 1.7
FC@10dB
68-FF-1013
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