A technique for measuring and optimizing modulator extinction ratio

Summary form only given. As global communication systems rapidly expand and high-speed optical TDM and WDM networks continue to mature, the performance of optical modulators becomes increasingly important. Accurate methods of characterizing and optimizing key parameters, such as the extinction ratio, to levels exceeding 40 dB become necessary. The modulator extinction ratio (ER), defined as the power off-to-on ratio, impacts on communication performance in many ways. It determines the initial distance between logical zero and one power levels. Incomplete ER degrades sensitivity in optically preamplified links and leads to multiple interferometric cross talk, which adversely impacts both TDM and WDM systems. Furthermore, the ER limits the dynamic range of data-rates for variable duty-cycle (VDC) multi-rate optical communications. The author describes a new method for accurately measuring ER using the properties of average power limited (APL) amplifiers that does not require high-speed detection equipment.