Result: standard mapping
How many STM-4s are in an OTU1?
An OTU1 carries 4 STM-4s, per ITU-T G.709 and ITU-T G.707. This path maps STM-16 into ODU1 as a client, then follows that client's tributaries.
4
STM-4s in an OTU1
Working
OTU1 → 1 × ODU1 → 1 × STM-16 → 4 × STM-4
- 1 × ODU1 in each OTU1 ITU-T G.709The OTU1 frame carries exactly one ODU1. The line-rate gap is OTU overhead and FEC.
- 1 × STM-16 in each ODU1 ITU-T G.709Client mappingCBR STM-16 mapped into OPU1.
- 4 × STM-4 in each STM-16 ITU-T G.7074 × STM-4.
- 1 ODU1
- 1 × 1 = 1 STM-16
- 1 × 1 × 4 = 4 STM-4s
Leftover capacity
177.737143 Mbit/s of each OTU1 line rate (2.666057143 Gbit/s) sits outside 4 × 622.080 Mbit/s of STM-4 line rate (2.488320 Gbit/s). That remainder is overhead, fixed stuff or justification. It is not another whole tributary.