Apparatuses and methods for testing the integrity of high speed optical
fiber transmission networks are presented. Data from an optical network,
for example, NRZ formatted data at forty gigabits per second and higher
may be reliably recovered using embodiments of the invention. The
invention employs hybrid microwave and high speed processing technology
to reliably measure the phase shift of the data transmitted over a high
speed optical transmission network by comparing the incoming data to a
super-stable clock/frequency reference. The clock/frequency reference is
intentionally offset by fractional frequency resulting in a beat
frequency when compared to the incoming data. The beat frequency provides
the ability for automatic calibration of the phase measurements because
the period of the full 360 degrees phase is known. Also, the invention
provides reliable means for measuring jitter and for generating
Eye-pattern diagrams by eliminating issues associated with oscilloscope
loop bandwidth limitations. Additionally, the phase of an incoming data
and the time of the phase are available from measurements using high
speed samplers.