Page 88 - Optical Switching And Networking Handbook

04_200023_CH03/Batesx 1/17/01 9:42 AM Page 73

SONET 73

1
Figure 3-15
The multiplexing
function of SONET STS-1s 2 STS-3 Number 1

3

4
STS-1s 5 STS-3 Number 2 STS-9 Number 1

6

7
STS-1s 8 STS-3 Number 3

9

multiplexing function from an STS-1 to an STS-3 and then to an
STS-9. This interleaving is what SONET is designed to perform.
Another alternative to this multistep process is to use a single
multiplexer to handle an STS-12 output with 12 individual STS-1
signals inserted directly into it, as shown in Figure 3-16.This single-
stage interleaving process directly byte-interleaves the n STS-1 sig-
nals into the STS-12 signal shown. However, the numbers can vary,
but the outcome is the same; it is a matter of equipment selection
and processing.

Concatenation

Concatenation provides SONET with the flexibility to carry digital
signals that are larger than the payload described earlier (49.536
Mbps). A designator of a concatenated signal occurs when a small c
appears after the number of the STS-n (that is, STS-3c). The c indi-