How to compare RF-LO dBc/Hz values with my optical LO

Discussion in 'Wireless & RF Design' started by sohagiut, Nov 11, 2010.

  1. sohagiut

    Thread Starter New Member

    May 5, 2008
    i have a RF-LO specification
    -50dBc/Hz @ 1KHz
    -70dBc/Hz @ 10KHz
    -90dBc/Hz @ 100KHz
    -110dBc/Hz @1MHz

    now i like to compare this with an optically generated LO whose PSD is

    where, A=is the amplitude;
    f0=carrier frequency;
    w=LO linewidth;
    i have calculated the LO power (carrier) and plot this PSD of the phase noise S(f) as dBc/Hz.
    Then varies the w to know on which linewidth (FWHM) of the beat signal it fits to the RF-LO and it comes as 30Hz. This means the laser linewidth (FWHM) is 15 Hz.

    what i am doing wrong? can anyone plz help?

    thanks a lot