5. Assessing the quality of a component or complete optical system

5.1 Eye diagram

To evaluate the performance of a transmission system, it is necessary to have a quality criterion. In practice, this criterion is evaluated after the optical signal has been detected by the receiver. In traditional direct detection systems, the receiver contains a flip-flop designed to interpret the incoming symbol. This component compares the integrated energy in a fraction of the symbol duration, called the integration window, with a given threshold. Energy above the threshold means the symbol is a "1", otherwise it's a "0". Disturbances during propagation, whether due to amplifier...