OFDMA overlay on legacy passive optical networks using optical nyquist filtering
View Patent ↗Methods and systems for combining signals include modulating data onto a first signal at a first frequency and wavelength; modulating data onto a second signal at a second wavelength using a modulation scheme that produces spectral components at the first frequency; filtering the second signal using an optical filter to suppress spectral components that would cause interference to the first signal; and combining the first signal and the second signal onto a transmission medium.
1. A method for combining signals, comprising:
modulating data onto a first signal at a first frequency and wavelength using an orthogonal frequency division multiple access modulation scheme;
modulating data onto a second signal at a second wavelength using an on-off keying modulation scheme that produces spectral components at the first frequency;
filtering the second signal using an optical filter to suppress spectral components that would cause interference to the first signal; and
combining the first signal and the second signal onto a transmission medium after filtering the second signal.
2. The method of claim 1 , wherein filtering comprises applying a Nyquist-shape optical filter to the second signal.
3. The method of claim 1 , wherein said steps of modulating comprise modulating data onto respective laser beams.
4. The method of claim 1 , further comprising jointly receiving the first and second signals without receiver-side optical filtering or coherent detection.
5. A system for combining signals, comprising:
a first transmitter configured to modulating data onto a first signal at a first frequency and wavelength using an orthogonal frequency division multiple access modulation scheme;
a second transmitter configured to modulate data onto a second signal at a second wavelength using an on-off-keying modulation scheme that produces spectral components at the first frequency;
a filter configured to suppress the spectral components in the second signal that would cause interference to the first signal; and
a combiner configured to combine the first signal and the second signal onto a transmission medium after filtering the second signal.
6. The system of claim 5 , wherein the filter is an optical Nyquist-shape filter.
7. The system of claim 5 , wherein said first and second transmitters are configured to modulate data onto respective laser beams.
8. The system of claim 5 , further comprising a splitter configured to jointly receive the first and second signals without receiver-side optical filtering or coherent detection.