- This topic has 9 replies, 3 voices, and was last updated 10 years ago by boldoo.
-
AuthorPosts
-
-
November 6, 2014 at 6:06 am #14986boldooParticipant
how to draw pure constellation in I-Q modulator. Mine is always so many spots.
-
November 6, 2014 at 11:50 am #15022Damian MarekParticipant
Make sure your oscillator (CW Laser ) has a small linewidth. For a perfect system set it to 0, realistically I think nowadays a linewidth of 0.1 MHz is not unreasonable.
Good luck!
-
November 6, 2014 at 9:38 pm #15058boldooParticipant
Hi Damian,
you mean we should keep 0.1MHz at CW laser?
my schema has CW laser with 0.1MHz. I will add fiber and receiver to my schema.
-
November 7, 2014 at 9:54 am #15077Damian MarekParticipant
Phase noise is what causes that wander of the constellation diagram, so using a laser with a smaller line width will eliminate that problem. Try a linewidth of 0 and you will get “perfect” results, although physically it might not be accurate.
-
-
November 11, 2014 at 2:43 am #15177Alessandro FestaParticipant
Is you constellation after the signal passes in an optical system?
-
November 11, 2014 at 4:19 am #15180boldooParticipant
No, just after modulation. I didn’t add amplifier and fiber.
But actually after added fiber(50km), my constellation became to just crowded thing in central. how to fix it?
-
November 11, 2014 at 5:39 am #15183Alessandro FestaParticipant
What kind of modulation are you applying?
-
-
November 11, 2014 at 6:08 am #15184boldooParticipant
I’m trying to apply 16QAM.
after transmitter, connected to amplifier and Gaussian filter then 50km fiber, then amplifier and filter.
After second filter, I checked 16QAM coherent Receiver and Constellation Visulaizer.
but result is like attached.
-
November 11, 2014 at 2:30 pm #15210Damian MarekParticipant
It should be possible to transmit the signal over 50 km of fiber with low distortion of the constellation. Maybe you have a filter or component that is set to the wrong values. Can you attach your project file?
-
-
November 13, 2014 at 9:54 am #15339boldooParticipant
Hi Damian,
please check attached project. i created 16APSK signal after modulator. But After fiber and amplifier, constellation is very bad. is there any way to keep constellation as possible? what components was wrong ?
-
-
AuthorPosts
- You must be logged in to reply to this topic.