B-13
Cisco 7609 Internet Router Installation Guide
OL-5079-04
Appendix B Connector and Cable Specifications
Cable Specifications
Mode-Conditioning Patch Cord
When using the long wavelength/long-haul (LX/LH) GBIC with 62.5-micron
diameter MMF, you must install a mode-conditioning patch cord (Cisco
product number CAB-GELX-625 or equivalent) between the GBIC and the
multimode fiber (MMF) cable on both the transmit and receive ends of the link.
The patch cord is required for link distances greater than 984 feet (300 meters).
Note
We do not recommend using the LX/LH GBIC and MMF without the patch
cord for very short link distances of 33 to 328 feet (10 to 100 meters). The
result could be an elevated bit error rate (BER).
The patch cord is required to comply with IEEE standards. IEEE found that link
distances could not be met with certain types of fiber-optic cable due to a problem
in the center of some fiber-optic cable cores. The solution is to launch light from
the laser at a precise offset from the center by using the patch cord. At the output
of the patch cord, the LX/LH GBIC complies with the IEEE 802.3z standard for
1000BASE-LX.
Patch Cord Configuration Example
Figure B-7
shows a typical patch cord configuration.
Figure B-7
Patch Cord Configuration
1000BASE-LX/LH
port
Patch
panel
Link span greater than 984 ft
(300 m)
1000BASE-LX/LH
port
Rx
Tx
Patch
panel
Patch
cord
Building
cable plant
Tx
Rx
Patch
cord
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