and receiving the upstream frame receives an additional delimiter it shall remove it from the data flow in a way that corresponds with the delimiter insertion method implemented in the onu further the olt operation may be dynamically adjustable to properly handle upstream frames from different onus using different delimiter insertion methods whereas the implementation of olt functionality per conventions 1 and 2 is straightforward and independent of the way the delimiter is inserted in the frame the implementation of convention 3 varies depending on the insertion type the frame structure and specific onu and olt operation associated with delimiter insertion at each insertion point of fig6 will now be described insertion point a as shown in fig1 a delimiter inserted at this point 61 bypasses the onu scrambler 32 fec encoder 33 and gem framer 34 implying that the additional delimiters 71 are transmitted unscrambled and outside of the fec blocks and gem frames as shown in fig7 a and 8 a such delimiter insertion does not interfere with the operation of the onu upstream pipeline which is operating as if no insertion is taking place during the transmission of the additional delimiter the output of this pipeline is stored in a mini buffer 67 as also shown in fig1 this way the continuity of the scrambling pattern fec blocks and gem frames is preserved the corresponding frame structure is shown in fig7 a and 8 a for the cases when upstream fec is used and not used respectively if the olt compatible with insertion at point a is already synchronized to a previously detected delimiter its control logic shall stop the descrambler for the duration of the reception of each additional delimiter as determined by.