I think you are right, According to my EFston source in Toronto fiber optics
go to 70 MHZ. We have 12 blades rotating at 2,500 RPS or 30,000 Hertz.
Ten times that is 300,000 Hertz. Well within the capabilities of fiber
optics. EFston assure me the cable is good to 125 C or about 275 F.
I should have a system  today or tomorrow to test.

Paul Lamar

Larry Hendrix wrote:

Paul,
Although the system may have the required bandwidth, the margin is not that great.  The 30,000 Hertz frequency response is only valid if the pulse has a 50% duty cycle.  Consider the frequency
response required to satisfactorily reproduce a 1 microsecond pulse repeated 30,000 times per second.  This is more like your example because the blade is narrow.  The required frequency response is
more likely 10 to 20 times that.

Larry Hendrix

70 MHZ ought to cover it.

Paul Lamar

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