Cisco EF4116 Hardware Installation And Maintenance Manual page 50

Network Connection Considerations
Figure 2-29
Multimode port
Alignment groove
Optical Bypass Switch Connections
Both the dual-attachment and single-attachment FDDI modules have an optical bypass switch
connector. An optical bypass switch is a passive optical device powered by the FDDI module. If a
fault in the router occurs, or if power is lost, the optical bypass switch is enabled, and the ring will
be unaffected. The optical bypass switch is automatically enabled if power is lost. In addition, the
system software can enable the optical bypass switch if a problem is detected or if the operator
chooses to take the router out of the ring.
2-28 Cisco 4000 Series Hardware Installation and Maintenance
Single-Attachment Multimode FDDI Module—End View
PHY-S
LED
FDDI
OPT-BYPASS
PHY-S
PHY-S
RING OPT
Mounting
screw locations
Optical bypass
switch connector
Alignment groove