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Typically, most problems encountered with the TC3025 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 TC3025's optic receivers have a typical saturation level of -3 dBm. If the user's equipment's launch
power is higher than -3 dBm (i.e. -2 dBm or greater) and the fiber run is very short and has low signal loss,
it is likely to overdrive the TC3025'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 TC3025 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 (727) 547-8307. The part numbers are:
In-line attenuators are used to correct optic overdrive conditions that may exist on either side of the TC3025s.
The following is a typical diagram illustrating a TC3025 Mode Converter used to convert a 1300nm Single
Mode optical signal from a Single Mode Device into a 850nm Multimode optic signal to be received by a
Multimode Device.
MNL-30250-02-07
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