|can a telephone line Carrie a 6Mb/s ?|
Do you mean a telephone line or telephone cable.
If you mean telphone cable then Curt R's answer applies.
If you mean a telephone line with a telephone attached to it then the answer is only with DSL.
can Fiber opt. connection give you 6 Mb/s through your telephone line ?
You need to be a bit more specific as what you are actually referring to. A lot depends on how the fibre optic is connected to the telephone line. Probably involves DSL again.