G52154-0, Rev 4.2

© VITESSE SEMICONDUCTOR CORPORATION

Page 9

3/19/99

741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896

VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC8113

ATM/SONET/SDH 622 Mb/s Transceiver Mux/Demux

with Integrated Clock Generation and Clock Recovery

Jitter Tolerance

Jitter Tolerance is the ability of the Clock Recovery Unit to track timing variation in the received data

stream. The bellcore and ITU specifications allow the received optical data to contain jitter. The amount that

must be tolerated is a function of the frequency of the jitter. At high frequencies the specifications do not require

the CRU to tolerate large amounts, whereas at low frequencies many unit intervals (bit times) of jitter have to be

tolerated. The CRU is designed to tolerate this jitter with margin over the specification limits, see Figure 7. The

CRU obtains and maintains lock based on the data transition information. When there is no transition on the

data stream, the recovered clock frequency can drift. The VSC8113 can maintain lock over 100 bits of no

switching on data stream.

Figure 7: Jitter Tolerance

10

30

300

15

1.5

0.15

2.5M

150

60

6

0.6

Bellcore Requirement

VSC8113 Guaranteed

Jitter Tolerance