Keysight Technologies N4917BSCB 400G User Manual

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Keysight Technologies N4917BSCB 400G User Manual Manual pdf 42 page image

42 Keysight N4917BSCB 400G Optical Receiver Test Application User Guide3 Concepts and Features of N4917BSCB SoftwareAutomated CalibrationOne of the main features of the N4917BSCB solution software is theautomated calibration of stressed receiver conformance test signal asspecified in the IEEE specification.The signal metrics and the calibration procedure is very similar to those ofNRZ-based 100GBASE transmission standards (as defined in IEEE802.3ba) but there are noticeable differences:• A new TDECQ/SECQ metric is employed to characterize the quality of atransmitted/received signal instead of the traditional eye maskanalysis.• A digital reference equalizer is required to compute various signalmetrics during transmitter performance testing or during stress signalcalibration for receiver stress testing.Therefore, achieving accurate, stable and repeatable stress signalcalibration, to ensure reliable transceiver performance test andqualification, has become even more challenging. Optical receiver stresstest procedures, defined by the IEEE, are performed using severalinstruments such as a bit error ratio tester, digital sampling oscilloscope,optical reference transmitter and tunable laser source. The purpose of thetest is to generate a stable and repeatable stressed optical signal withspecific characteristics, and send it to the receiver under test to measurethe resulting bit error ratio. However, achieving this is not a trivial task asthe combination of different stress factors (inter symbol interference, jitter,sinusoidal interferences, Gaussian noise, optical power level) gives rise tocomplex dependencies on the target metrics.Composition of IEEE 802.3bs Stressed Receiver Conformance Test SignalThe N4917BSCB software calibrates the stressed receiver conformancetest signal according to the definitions in the IEEE 802.3bs clauses 120,121, 122, and 124 (for 400GBASE and 200GBASE). Note that you canchange the target values of the metrics to be optimized (select Debug inthe Configure tab).The M8045A BERT pattern generator generates a test pattern with thesignal parameters listed in the following table. The calibration procedurethen performs the following steps to create an impaired signal using thespecified stress components and measuring the stress signal calibrationmetrics listed in the following table.