A very accurate frequency demodulator

I am working on a biomedical engineering research project. It involves investigating the possible techniques of measuring mean light pathways variations of the light propagating through a vascular tissue.
One of the theoretically predicted ways of conducting such a measurement requires a very accurate frequency demodulator.
The predicted signal frequency modulation ranges are as following:
- f = 500 MHz, Δf = 5 μHz
- f = 1 GHz, Δf = 10 μHz
- f = 10 GHz, Δf = 100 μHz
- … (and so on – the relation is linear)
f is the base harmonic signal frequency, Δf is the expected frequency modulation range (μ - micro).
I have zero experience in both high frequency and FM techniques.
Can you advise please if it is at all possible, what devices/techniques might be used to demodulate the described above signal.
Thank you,
Victor.

Short correction: replace homodyne with heterodyne...
and here is the link to Polytec
http://www.polytec.com
Greetings from Germany
Henrik
LV since v3.1
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