Fiber SFP Gigabit Ethernet

Most of the vendors won't allow auto-negotiation. If there is mismatch, the Interface will become down/down.

Cisco Switch (C4900)
For fiber Gigabit Ethernet interfaces, the default is no speed nonegotiate, which sets the speed to 1000 Mbps and enables link negotiation for flow-control parameters and remote fault information. The speed nonegotiatecommand disables link negotiation.

Router:

no negotiation auto

show interface

Full Duplex, 1000Mbps, link type is force-up, media type is LX  (when nonegotiate)

Full Duplex, 1000Mbps, link type is auto, media type is LX  (when auto negotiate)