Method and apparatus for evaluating transmitter performance capabilities in a passive optical network

A method of validating acceptable performance of an optical transmitter during transmission of a test signal operating a defined modulation rate, comprising:

• defining a target symbol error rate (SERtarget) and a maximum TDEC(T/2) value (TDEC(T/2)max) associated with acceptable performance of the optical transmitter;
• operating the optical transmitter under test to deliver the test signal to a test equipment apparatus emulating worst-case conditions at a reference receiver;
• generating an optical eye diagram based on reception at the reference receiver;
• defining a time-shifted sampling point ST/2 at a position one-half bit period away from a center of the optical eye diagram;
• performing a time-shifted TDEC (TDEC(T/2)) measurement at the time-shifted sampling point, based on the SERtarget;
• validating acceptable performance of the optical transmitter if the measured TDEC(T/2) is less than TDEC(T/2)max.

Apparatus for validating performance of an optical transmitter for use in a PON system, comprising:

• a test instrument for emulating performance of a reference optical receiver and generating as an output an eye diagram representative of a recovered test signal, the eye diagram defined as spanning a bit period T, with an original sampling point S at a mid-point of the eye diagram;
• an optical channel exhibiting a worst-case dispersion value, the optical channel used to support the propagation of a test optical signal from the optical transmitter to the test instrument;
• and
• an analysis component coupled to the test instrument, the analysis component including at least one processor and at least one memory including computer program code, the at least one memory storing a target bit error rate value (BERtarget), a target symbol error rate (SERtarget), a maximum TDEC value (TDECmax) and a maximum TDEC(T/2) value (TDEC(T/2)max), the at least one memory and the computer program code configured to, with the at least one processor, cause the analysis component to:
• perform a transmitter dispersion and eye closure (TDEC) measurement at a sampling point T at a mid-point of the optical eye diagram, based on the BERtarget;
• define a time-shifted sampling point ST/2 at a position one-half bit period away from the mid-point of the optical eye diagram;
• perform a time-shifted TDEC (TDEC(T/2)) measurement at the time-shifted sampling point, based on the SERtarget;
• and
• validating acceptable performance of the optical transmitter if the measured TDEC is less than TDECmax or if the measured TDEC(T/2) is less than TDEC(T/2)max.