What is the difference between a low order and a high order Path delay tester?
The high order Path Delay Emulator (PD) analyzes the incoming signal, down to the STS1 level. The low order Path Delay Emulator (LOPD) is capable of further analyzing an STS1/STM0 or STM-1 path for VT1.5, VT2 or VT6 (SDH equivalents are VC11, VC12 and VC2) rates. (Note that VC-3 support will be available in a future release of the LOPD.) The LOPD is then capable of differentially delaying the low order paths. Note that the PD unit does not re-compute the B3 bytes of its paths. However, since the LOPD delays its constituent low order paths, it requires the B3 to be recomputed, if that path is setup to do low order delay, as the outgoing V1/V2/V3’s will be recomputed.
