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Technical Specifications
Issue 1 December 1997 10-17
OC-3 Optical Interface Mixing 10
Mixing different OC-3 rate OLIUs at opposite ends of an optical link is often
necessary for technical reasons or for convenience. The following information will
aid in planning and engineering optical links having different types of OC-3 rate
OLIUs at each end of the fiber. Table 10-9 details the minimum link budget
necessary for each pairing of OC-3 rate OLIUs.
To use Table 10-9, locate the number at the intersection of the transmitter/receiver
pair of interest. This number is the minimum attenuation necessary for proper
operation of that transmitter/receiver pair. The link must have at least this much
attenuation either from fiber loss, splice loss, connector loss, external attenuators,
or a combination of these, or the receiver will be overdriven and the link will not
operate properly.
Note that the minimum link budget is not always symmetrical. A transmitter/
receiver pair may have one minimum link budget in one direction and another in
the opposite direction. For example, a 21G/21G-U (low power) OLIU transmitting
to a 21D/21D-U (controlled environment) OLIU has a minimum link budget of 6.5
dB. In the opposite direction, though, a 21D/21D-U (controlled environment) OLIU
transmitting to a 21G/21G-U (low power) OLIU has a minimum link budget of 0.0
dB. Be careful of this asymmetry when planning and engineering a link having
mixed OLIUs.
Table 10-9. OC-3 Rate OLIU Mixes - Minimum Link Budgets (dB)
Transmitter
Receiver
21G/21G-U 21G2-U
22F/
22F-U 22G-U∗ 22G2-U
21D/21D-U/
22D-U 22F2-U
21G/21G-U
(high power)
4.5 0.0 4.5 4.5 0.0 11.5 0.0
21G/21G-U
(low power)
0.0 0.0 0.0 0.0 0.0 6.5 0.0
21G2-U 7.0 0.0 7.0 7.0 0.0 14.0 0.0
22F/22F-U/
22F2-U
22G-U∗
22G2-U
0.0
7.0
7.0
0.0
0.0
0.0
0.0
7.0
7.0
0.0
7.0
7.0
0.0
0.0
0.0
6.0
14.0
14.0
0.0
0.0
0.0
21D/21D-U/
22D-U
0.0 0.0 0.0 0.0 0.0 0.0 0.0
*
The LAA10 FT-2000 OC-3 Optical Interface has the same optical loss budget as the 22G-U and
therefore should follow the same optical mixing rules.
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