What an OTU1 contains

An OTU1 carries 32,256 DS0s, per ITU-T G.709, ITU-T G.707 and ANSI T1.107. This path maps STM-16 into ODU1 as a client, then follows that client's tributaries.

OTU1 → 1 × ODU1 → 1 × STM-16 → 16 × STM-1 → 84 × DS1 → 24 × DS0

1 ODU1
1 × 1 = 1 STM-16
1 × 1 × 16 = 16 STM-1s
1 × 1 × 16 × 84 = 1,344 DS1s
1 × 1 × 16 × 84 × 24 = 32,256 DS0s

E1 mapping: 1,008 E1s, which is 30,240 voice channels at 30 per E1. E1s in an OTU1.

Down to DS0

OTU1

1 × ODU1 ITU-T G.709The OTU1 frame carries exactly one ODU1. The line-rate gap is OTU overhead and FEC.
1. 1 × STM-16 ITU-T G.709Client mappingCBR STM-16 mapped into OPU1.
  1. 16 × STM-1 ITU-T G.70716 × 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-4 ITU-T G.7074 × STM-4.
2. 2 × ODU0 ITU-T G.709Two 1.25 Gbit/s tributary slots, one ODU0 each.
3. 1 × OC-48 ITU-T G.709Client mappingCBR OC-48, the same client rate as STM-16, mapped into OPU1.

OTU1 rates and aliases