What an OTU3 contains

An OTU3 carries 516,096 DS0s, per ITU-T G.709, ITU-T G.707 and ANSI T1.107. This path maps STM-256 into ODU3 as a client, then follows that client's tributaries.

OTU3 → 1 × ODU3 → 1 × STM-256 → 256 × STM-1 → 84 × DS1 → 24 × DS0

1 ODU3
1 × 1 = 1 STM-256
1 × 1 × 256 = 256 STM-1s
1 × 1 × 256 × 84 = 21,504 DS1s
1 × 1 × 256 × 84 × 24 = 516,096 DS0s

E1 mapping: 16,128 E1s, which is 483,840 voice channels at 30 per E1. E1s in an OTU3.

Down to DS0

OTU3

1 × ODU3 ITU-T G.709The OTU3 frame carries exactly one ODU3.
1. 1 × STM-256 ITU-T G.709Client mappingCBR STM-256 mapped into OPU3.
  1. 256 × STM-1 ITU-T G.707256 × STM-1.
    1. 84 × DS1 ITU-T G.70784 VC-11 tributaries: 3 TUG-3 × 7 TUG-2 × 4 TU-11.
      1. 24 × DS0 ANSI T1.10724 payload timeslots. The framing bit adds 8 kbit/s and brings the line rate to 1.544 Mbit/s.
    2. 1 × E4 ITU-T G.707Client mappingAsynchronous E4 mapped into the C-4 / VC-4. This client holds 64 E1s internally; the VC-12 tributary count of an STM-1 is 63.
    3. 3 × E3 ITU-T G.707Three VC-3s, each carrying an E3.
    4. 3 × DS3 ITU-T G.707Three VC-3s, each able to carry a DS3.
    5. 63 × E1 ITU-T G.70763 VC-12 tributaries: 3 TUG-3 × 7 TUG-2 × 3 TU-12.
  2. 4 × STM-64 ITU-T G.7074 × STM-64.
  3. 16 × STM-16 ITU-T G.70716 × STM-16.
  4. 64 × STM-4 ITU-T G.70764 × STM-4.
2. 4 × ODU2 ITU-T G.709Four ODU2s fill the 32 tributary slots of 1.25 Gbit/s.
3. 16 × ODU1 ITU-T G.70916 ODU1s, two slots each.
4. 32 × ODU0 ITU-T G.70932 ODU0s, one slot each.
5. 1 × OC-768 ITU-T G.709Client mappingCBR OC-768, the same client rate as STM-256, mapped into OPU3.

OTU3 rates and aliases