Analysis of jitter peaking effects in digital long-haul transmission systems using SAW-filter retiming.
01 January 1985
The new lightwave long-haul transmission systems typically use Surface-Acoustic-Wave (SAW) filters for timing recovery, in place of the phaselocked loops favored in slower systems. We report here analytical studies of jitter phenomena allowed by two kinds of filter ripple. The ripple is capable of causing jitter to accumulate exponentially with the number of regenerators, N, in a repeatered line. Such behavior is well known in the case of phaselocked-loop retiming, where the "jitter-peaking" that usually appears in the loop response must be carefully limited to avoid exponential jitter growth. We show that equivalent phenomena can appear when the SAW filters exhibit passband ripple, or, as previously reported in condensed form, when ripple-free filters are detuned by approximately one-half the full 3dB bandwidth.