SLK2501

OC48/24/12/3 SONET/SDH MULTIRATE TRANSCEIVER

SLLS502A – OCTOBER 2001 – REVISED NOVEMBER 2001

9

POST OFFICE BOX 655303

detailed description (continued)

clock and data recovery

The CDR unit of SLK2501 recovers the clock and data from the incoming data streams.

In the event of receive data loss, the PLL automatically locks to the local REFCLK to maintain frequency stability.

If the frequency of the data differs by more that 100 ppm with respect to the REFCLK frequency, the LOL pin

is asserted as a warning. Actual loss of lock occurs if the data frequency differs by more than 170 ppm.

minimum transition density

The loop filter transfer function is optimized to enable the CDR to track ppm difference in the clocking and

tolerate the minimum transition density that can be received in a SONET data signal (

±20 ppm). The transfer

function yields a typical capture time of 3500 bit times for random incoming NRZ data after the device is powered

up and achieves frequency locking.

The device tolerates up to 72 consecutive digits (CID) without sustaining an error.

jitter transfer

The jitter transfer is less than the mask shown in Figure 2 (GR-253 Figure 5-27). Jitter transfer function is defined

as the ratio of jitter on the output signal to the jitter applied on the input signal versus frequency. The input

sinusoidal jitter amplitude is applied up to the mask level in the jitter tolerance requirement (see Figure 3).

OC-N/STS-N

LEVEL

fc

(kHz)

P

(dB)

3

12

24

48

130

500

2000

0.1

0.1

0.1

Not Specified

Slop = –20 dB / Decade

Frequency – kHz

fc

P

Figure 2. Jitter Transfer

jitter tolerance

Input jitter tolerance is defined as the peak to peak amplitude of sinusoidal jitter applied on the input signal that

causes the equivalent 1 dB optical/electrical power penalty. This refers to the ability of the device to withstand

input jitter without causing a recovered data error. The device has a jitter tolerance that exceeds the mask shown

in Figure 3 (GR-253 Figure 5-28). This jitter tolerance is specified using a pseudorandom data pattern of