XRT75R12D_07 Datasheet, PDF (127/133 Pages) Exar Corporation – TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET

XRT75R12D
REV. 1.0.3 TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER
output a DS3 line signal (to the DS3 facility) that complies with the "Category I Intrinsic Jitter Requirements -
per Telcordia GR-253-CORE (for DS3 applications). This scheme is illustrated below in Figure 71.
FIGURE 71. SIMPLE ILLUSTRATION OF THE LIU BEING USED IN A SONET DE-SYNCHRONIZER" APPLICATION
STS-N Signal
De-Mapped (Gapped)
DS3 Data and Clock
DDSS33ttooSSTTSS--NN
MMaappppeerr//
DDeemmaappppeerr
IICC
TPDATA_n input pin
LLIIUU
TCLK_n input
8.8.3 How does the LIU permit the user to comply with the SONET APS Recovery Time
requirements of 50ms (per Telcordia GR-253-CORE)?
Telcordia GR-253-CORE, Section 5.3.3.3 mandates that the "APS Completion" (or Recovery) time be 50ms or
less. Many of our customers interpret this particular requirement as follows.
"From the instant that an APS is initiated on a high-speed SONET signal, all lower-speed SONET traffic (which
is being transported via this "high-speed" SONET signal) must be fully restored within 50ms. Similarly, if the
"high-speed" SONET signal is transporting some PDH signals (such as DS1 or DS3, etc.), then those entities
that are responsible for acquiring and maintaining DS1 or DS3 frame synchronization (with these DS1 or DS3
data-streams that have been de-mapped from SONET) must have re-acquired DS1 or DS3 frame
synchronization within 50ms" after APS has been initiated."
The LIU was designed such that the DS3 signals that it receives from a SONET Mapper device and processes
will comply with the Category I Intrinsic Jitter requirements per Telcordia GR-253-CORE.
Reference 1 documents some APS Recovery Time testing, which was performed to verify that the Jitter
Attenuator blocks (within the LIU) device that permit it to comply with the Category I Intrinsic Jitter
Requirements (for DS3 Applications) per Telcordia GR-253-CORE, do not cause it to fail to comply with the
"APS Completion Time" requirements per Section 5.3.3.3 of Telcordia GR-253-CORE. However, Table 50
presents a summary of some APS Recovery Time requirements that were documented within this test report.
TABLE 50: MEASURED APS RECOVERY TIME AS A FUNCTION OF DS3 PPM OFFSET
DS3 PPM OFFSET (PER W&G ANT-20SE)
MEASURED APS RECOVERY TIME (PER LOGIC ANALYZER)
-99 ppm
1.25ms
-40ppm
1.54ms
-30 ppm
1.34ms
-20 ppm
1.49ms
-10 ppm
1.30ms
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