Exactly how does the WFM601M make jitter measurements?

Exactly how does the WFM601M make jitter measurements?

The WFM601M can measure jitter in two ways. The first is with the eye pattern, just as in the WFM601i and WFM601E. You can choose from three selectable clock recovery bandwidths: 10 Hz, 100 Hz, and 1 kHz. The second method is with the jitter demodulator, activated with the JITTER display button. The jitter demodulator recovers a clock from the digital signal including jitter and mixes it against a stable clock of the same frequency. This transfers the jitter spectrum down to DC. It is then applied to the selected high-pass filter and finally to a peak-to-peak detector, which creates the numeric readouts. The timing jitter bandwidth is 10 Hz to 5 MHz, the alignment jitter from the HPF (10, 1kHz, 10 kHz, or 100 kHz) to 5 MHz.

The jitter demodulator is a standard way to measure jitter in the telecom world.