Extinction ratio, when used to describe the performance of an optical transmitter used in digital communications, is simply the ratio of the energy (power) used to transmit a logic level '1', to the energy used to transmit a logic level '0'. Please consult the ST297-2015 for information on all SDI optical signal parameters. P1 and P0 are represented by (binary 1) and (binary 0) respectively. In telecommunications, extinction ratio (re) is the ratio of two optical power levels of a digital. Extinction ratio is an important measurement for characterizing the performance of optical transmitters. As design/test margins get tighter, the challenges of making accurate and repeatable extinction ratio measurements become more apparent.