EXFO PSO-200 Optical Modulation Analyzer - Manual (Page 96)

Bit Pattern Analysis and the Gearbox
88 PSO-200
Performing Detailed Bit Pattern Analysis with the Gearbox
Gearbox Streaming Types
Depending on how the bit pattern is sent to your transmitter, the Gearbox
can be configured as follows:

One global stream – a single known encoded data stream is
demultiplexed inside the transmitter into several parallel sub-streams
sent to the modulator, with delays and inversions (if any).

N individual streams – as many encoded data streams as there are bits
per symbol (four in the example diagram) are sent with known delays
and inversions, if any, to the same number of modulators.

Dual X-Y streams (dual-polarization modulations only) – two known
encoded data streams corresponding to the X and Y states of
polarization are demultiplexed inside the transmitter into parallel
streams sent to the modulators.
Note: If the transmitter has an internal encoder, it is the encoded data that must
be input to the Gearbox.