The measurement range can be specif

The measurement range can be specified up to 75 nm anywhere from600 to 1700 nm. To insure that noise peaks are not confused withtrue signals, the application provides for the definition of signal peakswith “peak excursion” and “peak threshold” parameters.The user selects the resolution bandwidth for each of the two sweeps.The first sweep measures the signal amplitude and requires a wideresolution bandwidth. The second sweep measures the noise andrequires a narrow resolution. The resolution bandwidth settings willdepend on how tightly spaced the channels are and the modulationrate. The 8614xB is optimized for 50 GHz channel spacing.The sensitivity is user-specified to ensure that the true noise floor isbeing measured while optimizing the sweep time. Additionally, theWDM application can be set to run either a single measurement orcontinually sweep to observe how the signal parameters are changingin time.5Filter ModeThe heart of Agilent’s grating based optical spectrum analyzer is themonochromator. The monochromator spreads the input light spectrum so that a selected band of the spectrum can be analyzed. Thetime it takes to analyze the entirespectrum is referred to as thesweep time. When in filter mode,the monochromator stops sweeping and analyzes only one selectedportion of the input spectrum.The signal is then diverted by aninternal flexure from a 50 µmmulti-mode internal fiber into a9 µm single-mode internal fiberthat leads to the front panel. Atthe front panel the user has theoption of routing the light backinto the OSA via a front paneljumper, or to couple the output toanother instrument for furthertesting. This filter mode featureis only available on the Agilent86144B and 86146B models.