Look, I understand what you meant I converted their two images to the jpeg format, and in it I saw what you meant “i used both ODA & PIN … but sometimes i am getting Amplitude Modulated Waveforms too”. At 165-GHz and 15GHz, I would say to you see the global parameters as it was not offered more details of your project or you’re working I created a transceiver (+ external modulation laser + receiver) connected the photodio PIN and APD, and then bessel filter and low was stirring in the cutoff frequency, the here what will change is the value that is being in its cutting frequency, in versions greater than there are optisystem 7 ‘s a variable in the global paramatros called symbol rate, this variable was created specifically for to set the cutoff frequency of electrical filters, there you will vary the value of it, to arrive at a value in a waveform is acceptable in your oscilocospio. If you are using optisystem 7, created a new variable in global parameters then goes in the properties of the photodiodo and in the script of “custom frequency” place 0.75 * (name of the variable that you created) I hope this helps
my compliments