Overview
When using an LX/LH GBIC with a 62.5-micron diameter MMF, you must install a mode-conditioning patch cord (CAB-GELX-625 or equivalent) between the GBIC and the MMF cable on both the transmit and receive ends of the link in the following situations:
•Less than 328 feet (100 meters). When illuminating short lengths of MMF with an LX/LH GBIC, the mode-conditioning patch cord reduces the amount of optical power coupled into the MMF. Excessive power can saturate the LX/LH receiver causing an elevated bit error rate (BER).
•Greater than 984 feet (300 meters). When illuminating long lengths of MMF with an LX/LH GBIC, the mode-conditioning patch cord offsets the laser light to reduce the possibility of differential mode delay.
WS-G5487
The WS-G5487 GBIC (1000BASE-ZX) operates on ordinary SMF link spans of up to 70 km in length. Link spans of up to 100 km are possible using premium SMF or dispersion-shifted SMF (premium SMF has a lower attenuation per unit length than ordinary SMF; dispersion-shifted SMF has both lower attenuation per unit length and less dispersion).
The WS-G5487 GBIC must be coupled to SMF cable, which is the cable type typically used in long-haul telecommunications applications. The WS-G5487 GBIC will not operate correctly when coupled to MMF cable, and it is not intended to be used in application environments (e.g., building backbones or horizontal cabling) where MMF is frequently used.
The WS-G5487 GBIC is intended to be used as a physical medium dependent (PMD) component for Gigabit Ethernet interfaces. This GBIC operates at a signaling rate of 1250 MBaud, transmitting and receiving 8B/10B encoded data.
When you have shorter distances of SMF, you might need to insert an in-line optical attenuator in the link to avoid overloading the receiver:
•Insert a 10-dB in-line optical attenuator between the fiber-optic cable plant and the receiving port on the WS-G5487 GBIC at each end of the link whenever the fiber-optic cable span is less than 15.5 miles (25 km).
•Insert a 5-dB in-line optical attenuator between the fiber-optic cable plant and the receiving port on the WS-G5487 GBIC at each end of the link whenever the fiber-optic cable span is equal to or greater than 15.5 miles (25 km) and less than 31 miles (50 km).
Note The maximum number of installed 1000BASE-ZX GBICs is limited in each Catalyst chassis. These limits fall within the emission specifications for these products. Table 2 lists the 1000BASE-ZX GBIC limits for the different Catalyst systems.
Table 2 Maximum Number of 1000BASE-ZX (WS-G5487) GBICs Per Platform
Platform | Maximum number of 1000BASE-ZX GBICs |
| |
Catalyst 4000 family | 12 to comply with EN55022 Class B and FCC Class A |
| |
Catalyst 5000 family | 12 to comply with FCC Class A |
| |
Catalyst 6000 family | 12 to comply with EN55022 Class B |
| 24 to comply with FCC Class A |
| |
| | Gigabit Interface Converter Installation Note | | | |
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| 78-5399-03 Rev. A0 | | | 3 | |
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