NBN fiber optic modulation scheme

[merseyless]

Hi All,

Does anyone know what kind of modulation scheme is currently used in PON networks such as EPON or GPON?

I'm doing an assignment for university on the different types of modulation schemes used in fiber optics and am having one hell of a time trying to find out what is being commonly used in these systems. It's easy enough to write about the advantages and disadvantages of the various different modulation types, but one hell of a mission to find out what is actually in use as I'm trying to link it all back to current systems and the hardware limitations.