"Sorry in delay to talk you again"

When you start a thread, it would be polite if you could say, "I'm sorry, but I won't be around for the next n days..."

"the output pin varyes according to the barcodes"

But what does that mean???

How does the output pin vary according to the barcode?
What is the relationship between the '1's and '0's in the bitstream, and the thick & thin, wide & narrow bars & spaces of the barcode?

* Does it output a '1' for the same time duration that a "white" portion of the code is passing the sensor, and a '0' for the same time duration that a "black" portion is passing the sensor?

* Does it output a '1' on a "black-to-white" and a '0' on a "white-to-black" transition?

Or what???

"producing an "pulse train" exactaly as the serial port"

What serial port?

"so can be called a bit-stream"

Yes, of course it can be called a bit-stream; I've never queried your calling it a bit stream; what you still haven't said is what the bits in that bit-stream represent - that is the essential & fundamental piece of missing information!!
You can't process (decode) the bits until you know what they mean!!!