The extinction ratio is the ratio of the average optical power for transmitting signals 1 to the average optical power for transmitting signals 0 under the worst transmission conditions. The larger the extinction ratio, the better the logical discrimination. In fiber-optic communication, designers and system engineers confront many performance metrics—optical power, extinction ratio, receiver sensitivity, jitter, etc. Among them, Optical Modulation Amplitude (OMA) is a central figure of merit for digital (on-off) modulation schemes. The OMA directly influences the system bit error ratio (BER). With an appropriate point of reference (such as average. For a given OMA, a power meter can read a range of Pavg values, depending on ER of a PMD. This uncertainty is a function of “Minimum ER” spec of PMD. By specifying Minimum ER of a PMD, we limit the uncertainty. Although specifications are defined by industry standards and test method-ologies loosely described, historically it has been. Eye diagram showing an example of two power levels in an OOK modulation scheme, which can be used to calculate extinction ratio. P1 and P0 are represented by (binary 1) and (binary 0) respectively.