every sfp with a twi?

hi,

do all SFPs have a Two wire interface?
Also DACs?
I saw some with i2c in some shops...


In SFF 8431 is a description of twi:

CHAPTER 4 SFP+ 2- WIRE INTERFACE

But it doesn't describe the information which can be read right?
It referres to:

"SFP+ management memory map is specified by SFF-8472."

And it sais:

"this document defines an enhanced memory map with a digital diagnostic 
monitoring interface for optical
transceivers that allows pseudo real time access to device operating 
parameters."

* So is it only a must-have for optical SFPs?

* Or a must-have for all SFPs?

* Do I need to configure it always first? (with my NIC it works fine I 
guess. but another devices doesnt connect..)


Thank you :D