The OC hierarchy in Optical world

The OC hierarchy goes as follows, starting with a T3/DS3 electrical carrier and then on to an OC-1:

DS3 (Electrical) = 44.736mbits/sec = 28 T1s/DS1s

STS1 (Electrical) = (1) DS3 @ 44.736mbits/sec with SONET (Synchronous Optical NET) overhead = 51.840mbits/sec

OC-1 (Optical) = (1) STS1 on Optical facilities

OC-3 = (3) OC-1s = 155.52mbits/sec

OC-9 = (9) OC-1s (not commonly used) = 466.56mbits/sec

OC-12 = (12) OC-1s or (4) OC-3s = 622.08mbits/sec

OC-18 = (18) OC-1s (not commonly used) = 933.12mbits/sec

OC-24 = (24) OC-1s (not commonly used) = 1.244gbits/sec

OC-36 = (36) OC-1s (not commonly used) = 1.866gbits/sec

OC-48 = (48) OC-1s or (4) OC-12s or (16) OC-3s = 2.488gbits/sec

OC-192= (192) OC-1s or (4) OC-48s or (16) OC-12s or (64) OC-3s = 9.953gbits/sec

The reason for the stair-stepping of the OC Hierarchy is due to the fact that the next available level of multiplexing ('muxing") of lower-level circuits is usually 4: (4) OC-3s = (1) OC-12, and (4) OC-48s = (1) OC-192.

This muxing scheme is usually dictated by the equipment manufacturers and is pretty much an adopted standard in the Telecom industry - hence the lack of the lesser-common bandwidth aggregations like OC-9, OC-18, etc. The only exception is the OC-3, which was needed to allow the upper-level hierarchy to work. Hope this tidbit of info helps in the future!

Compiled by Scott Kindorf, Network Technician, as quoted in Sunbelt W2K News of June 6, 2001.

references

http://www.techtransform.com/id147.htm