In order to meet the constantly increasing need for bandwidth, more and more telecommunications operators are now deploying 40G or 100G coherent systems on long-haul dense wavelength-division multiplexing (DWDM) networks. These new technologies are certainly beneficial, but they also bring about new test and measurement challenges, in particular for optical spectrum analyzers (OSAs), versatile test instruments that are key to successful DWDM system commissioning and troubleshooting. Indeed, recent 40G/100G coherent systems featuring polarization multiplexing have made some traditional OSA measurements, such as optical signal-to-noise ratio (OSNR), impossible to carry out. This white paper first establishes why an OSA is a fundamental test instrument in DWDM networks. Next, it identifies common OSA measurements being performed in the field, and then explains why a Pol-Mux OSA is required to perform OSNR measurements of 40G/100G coherent networks. Lastly, it presents EXFO’s Pol-Mux OSA, the first third-party test instrument on the market that allows accurate OSNR measurement of Pol-Mux systems.
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