|
|
|
|
Group: Forum Members
Last Login: Yesterday @ 14:12:24
Posts: 25,
Visits: 135
|
I'm trying to understand some measurement I have made. I have a laser source and a relatively flat broadband source coupled with a 3dB coupler. I also have a variable optical attenuator to control the relative level of the broadband optical "noise". I have the OSA resolution bandwidth set to 0.1 nm.
First, I measure the FWHM maximum of the laser source by itself. Next, I turn on the broadband source and adjust the VOA to get close an OSNR of about 10dB. Now, when I measure the FWHM of the spectrum, it is wider than when I measured the laser by itself.
I can't think of a reason why adding a constant noise level would affect the measured bandwidth of the signal. Comparing my two measurements without and with noise, shouldn't each measurement point in the former case simply have a constant level added to it in the latter case? Why does the bandwidth broaden? Can anybody explain why this happens?
|