Method and apparatus for testing network integrity
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.
1. A method for testing network integrity of test equipment by generating jittered data, comprising:
determining a desired phase jitter to be used for a data stream used to test test equipment;
generating a sine of phase angle and a cosine of phase angle with respect to the desired phase jitter;
inputting the sine of phase angle and the cosine of phase angle with respect to the desired phase jitter to a quadrature mixer, for which a reference clock waveform is also inputted thereto, and obtaining a phase modulated clock signal as a result thereof;
inputting the phase modulated clock signal to a clock input of a flip-flop;
dividing the phase modulated clock and providing the divided phase modulated clock to a select port of a multiplexer which receives an NRZ data stream on its input port;
providing the multiplexed NRZ data stream obtained at an output port of the multiplexer to a data input of the flip-flop; and
testing integrity of the test equipment by providing a jittered NRZ data stream to the test equipment as obtained from an output port of the flip-flop.