"speed nonegotiate" command under SFP/GBIC port configuration

I have noticed that there is a "speed nonegotiate" command under SFP/GBIC port configuration in switches. I have seen this for example on Cisco 4506 WS-X4306-GB module, on Cisco 3750 series, WS-C2960G-24TC-L etc. However, it looks that "speed nonegotiate" is not available on fixed optics ports?.
Is the "speed nonegotiate" command for copper SFP's and GBIC's which support 10BASE-T and 100BASE-TX modes besides 1000BASE-T mode on certain platforms(for example Catalyst 3750 or 3560)? Or is it auto-negotiation in sense of IEEE 802.3af:

All 1000BASE-T PHYs shall provide support for Auto-Negotiation (Clause 2[IMG]https://us.v-cdn.net/6030959/uploads/images/smilies/icon_cool.gif[/IMG] and
shall be capable of operating as MASTER or SLAVE.

Auto-Negotiation is performed as
part of the initial set-up of the link, and allows the PHYs at each end to advertise their
capabilities (speed, PHY type, half or full duplex) and to automatically select the
operating mode for communication on the link. Auto-negotiation signaling is used for the
following two primary purposes for 1000BASE-T:

a) To negotiate that the PHY is capable of supporting 1000BASE-T half duplex or full
duplex transmission.

b) To determine the MASTER-SLAVE relationship between the PHYs at each end of the
link.

What affect has "speed nonegotiate" command in case of optical transceivers?