HP HP-Bench-Briefs-1994-01-03 free download

File name HP-Bench-Briefs-1994-01-03.pdf

SERVICE INFORMATION FROM HEWLET-PACKARD 1st Quarter 1994 The Optical Spectrum Analyzer = Part 3 ; ' Sensitivity Mike LevernierlHmlett-Packard tical spectrum analyzers, see the pre- sitivity. Sensitivity is coupled directly vious issue of Bench Briefs.) Figure 1 to video bandwidth, as shown in shows the display of a signal that has Figure 2. As the sensitivity level is an amplitude equal to the sensitivity lowered, the video bandwidth is de- setting of the optical spectrumanalyzer. creased (or the transimpedance amplifier gain is increased), which re- Single monochromators typically sults in a longer sweep time, since the have sensitivity about 10 to 15 dB bet- sweep time is inversely proportional ter than that of double monochroma- to the video bandwidth. The sweep Introduction tors due to the additional loss of the time can be optimized because the r In the previous issue of Bench Briefs Richard Ogg explained the optical spectrum analyzer in terms of signal second diffraction grating in double monochromators. The double-pass monochromator has the same high video bandwidth is continuously vari- able and just enough video filtering can be performed. This avoids the sensitivity of single monochromators problem of small increases in sensitiv- processing, various operating modes, even though the light strikes the dif- ity causing large increases in sweep noise generation, and the control of fraction grating twice. The hig