I am modulating an OOK signal(square wave) of 100 MHz. The electrical signal after photodetection shows a frequency of 20 MHz. The amplifiers used in my system are capable of handling 100 MHz.
Can someone help me understand this difference ? Is this due to LED non-linearity or does the ratio 1:5 has some significance?
This must be a measurement error, possibly an aliasing error. Do you use a sampling oscilloscope?
Ok, it's a sampling scope. Build two crystal oscillators, one with 100 MHz and another with 20 MHz, connect them to the scope. Any difference?
Hi, I started the experiment from low frequency square wave (5 MHz) and obtained the following result(green-direct signal from AWG) and (pink-Signal after photodetection). It shows that there is some phase shift(delay) and also distortion. But I do not understand why the peaks are not uniform in their amplitude?
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