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Technical Specifications
10-20 Issue 1 December 1997
Table 10-11 details the maximum link budgets for each pairing of OC-3 rate OLIUs when
operating on multimode (MM) fiber. These numbers give the maximum attenuation
acceptable for proper operation of each transmitter/receiver pair. The link must have no more
than this much attenuation either from fiber loss, splice loss, connector loss, external
attenuators or a combination of these or the link will not operate properly. The maximum link
budgets for MM fiber were calculated using the following margins. The first column of
margins applies to any link where there is at least one OC-3 OLIU (21G/21G-U, 22F or
22G-U/22G2-U). The second column of margins applies to links having two IS-3 (21D/21D-U
or 22D-U) OLIUs.
NOTE:
The maximum link budget is not always symmetrical. A transmitter/receiver
pair may have one maximum link budget in one direction and another in the
opposite direction. For example, a 21G/21G-U (low power) transmitting to a
22F has a maximum MM link budget of 15.6 dB. In the opposite direction,
though, a 22F transmitting to a 21G/21G-U (low power) has a maximum SM
link budget of 12.0 dB. Be careful of this asymmetry when planning and
engineering a link having mixed OLIUs.
At Least One
OC-3 OLIU
IS-3 OLIUs
Only
MM Optical Path Penalty (dB)
Connector Loss (dB)
Unallocated Margin (dB)
4.0
1.5
1.5
1.6
1.5
2.0
Table 10-11. OC-3 Rate OLIU Mixes—Maximum Link Budgets for MM Fiber (dB)
Transmitter
Receiver
21G/
21G-U 21G2-U 22F
22G-U∗/
22G2-U
21D/21D-U/
22D-U
(Ctrld. Env.)
21D/21D-U/
22D-U
(Unctrld. Env.)
21G/21G-U
(high power)
22.0 22.0 22.0 22.0 21.8 19.8
21G/21G-U
(low power)
15.6 15.6 15.6 15.6 15.4 13.4
21G2-U 22.0 22.0 22.0 22.0 21.8 19.8
22F 12.0 12.0 12.0 12.0 11.8 9.8
22G-U∗/22G2-U 20.0 20.0 20.0 20.0 19.8 17.8
21D/21D-U/22D-U
(ctrld. env.)
8.2 8.2 8.2 8.2 9.9 7.9
21D/21D-U/22D-U
(unctrld. env.)
5.2 5.2 5.2 5.2 6.9 4.9
* 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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