A method and apparatus for polarization-independent RF spectrum analysis
of an optical source, the apparatus including a coupler for coupling the
light from an optical source under test with light from a continuous-wave
(CW) laser. A nonlinear apparatus is coupled to the coupler for
modulating the electric field of the light from the CW laser using the
temporal intensity of the light from the source under test to generate a
modulated signal. The nonlinear apparatus is adapted to mitigate or
compensate for any phase difference between polarization components of
signals propagated through the nonlinear apparatus. A polarizer is
coupled to the nonlinear apparatus for generating a linearly polarized
signal from the modulated signal. An optical spectrum analyzer is coupled
to the polarizer for measuring the optical spectrum of the linearly
polarized signal to determine an RF spectrum of the optical source under
test.