Result: standard mapping
How many STM-16s are in an OTU4?
An OTU4 carries 40 STM-16s, per ITU-T G.709. This is a client mapping of STM-16 into ODU1.
40
STM-16s in an OTU4
Working
OTU4 → 1 × ODU4 → 40 × ODU1 → 1 × STM-16
- 1 × ODU4 in each OTU4 ITU-T G.709The OTU4 frame carries exactly one ODU4.
- 40 × ODU1 in each ODU4 ITU-T G.70940 ODU1s, two slots each.
- 1 × STM-16 in each ODU1 ITU-T G.709Client mappingCBR STM-16 mapped into OPU1.
- 1 ODU4
- 1 × 40 = 40 ODU1s
- 1 × 40 × 1 = 40 STM-16s
Leftover capacity
12.277173568 Gbit/s of each OTU4 line rate (111.809973568 Gbit/s) sits outside 40 × 2.488320 Gbit/s of STM-16 line rate (99.532800 Gbit/s). That remainder is overhead, fixed stuff or justification. It is not another whole tributary.
By bit rate only
Dividing the line rates gives 44.93, which floors to 44 STM-16s by bit rate only. The standard mapping is 40. Use the mapping.