Extinction Ratio (ER) is the ratio of the optical power when the transmitter is in the logic 1 state (P₁) to the optical power when it is in the logic 0 state (P₀): Higher ER: Stronger contrast between “on” and “off,” making signals easier to detect. Although specifications are defined by industry standards and test method-ologies loosely described, historically it has been. This white paper explains some of the benefits of highly accurate ER measurements in both 10 GbE (Ethernet), with its relatively low ER requirement, and in SONET/SDH, and the methodology that supports consistent, accurate ER result. However, the residual continuous wave (CW) component produced by modulation may considerably degrade the system sensitivity.
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