EXFO FTB/IQS-85100G Packet Blazer for FTB-500/IQS-600 - Manual (Page 376)

Glossary
366 FTB/IQS-85100G
G.709 Optical Transport Network (OTN)
The OTU, ODU (including the ODU tandem connection) and OPU layers
can all be analyzed and monitored. As per ITU G.709, current test solutions
offer these possibilities using the following line rates:

OTU1 (255/238 x 2.488 320 Gbit/s ≈ 2.666057143 Gbit/s) also referred to
as 2.7 Gbit/s

OTU2 (255/237 x 9.953280 Gbit/s ≈ 10.709225316 Gbit/s) also referred
to as 10.7 Gbit/s

OTU3 (255/236 x 39.813120 Gbit/s ≈ 43.018413559 Gbit/s) also referred
as to 43 Gbit/s

OTU4 (255/227 x 99. 532 800 Gbit/s ≈ 111.809973568 Gbit/s) also
referred to as 112 Gbit/s.
The following non standard rates are also defined:

OTU3e1 (255/236 x 4 x 10.3125 Gbit/s ≈ 44.570974576 Gbit/s)

OTU3e2 (243/217 x 16 x 2.488320 Gbit/s ≈ 44.583355576 Gbit/s)
Each line rate is adapted to service different client signals:

OC-48/STM-16 is transported via OTU1

OC-192/STM-64 is transported via OTU2

OC-768/STM-256 is transported via OTU3

Null Client (All 0s) is transported via OTUk (k = 3, 3e1, 3e2, 4)

PRBS31 is transported via OTUk (k = 3, 3e1, 3e2, 4)
In order to map client signals via ITU G.709, they are encapsulated using
the structure illustrated in the following figure.