US 11,855,754 B2
Subcarrier modulation with radio frequency (RF) IQ modulators
Kuang-Tsan Wu, San Jose, CA (US); Han Henry Sun, Ottawa (CA); Steven Joseph Hand, San Jose, CA (US); and David F. Welch, San Jose, CA (US)
Assigned to Infinera Corporation, San Jose, CA (US)
Filed by Infinera Corporation, Sunnyvale, CA (US)
Filed on Dec. 30, 2019, as Appl. No. 16/730,562.
Claims priority of provisional application 62/799,098, filed on Jan. 31, 2019.
Prior Publication US 2020/0252154 A1, Aug. 6, 2020
Int. Cl. H04J 14/02 (2006.01); H04B 10/25 (2013.01)
CPC H04J 14/02 (2013.01) [H04B 10/25 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A system, comprising:
a first digital signal processor operable to receive first input data and supply a first plurality of inphase signals and a first plurality of quadrature signals, collectively, the first plurality of inphase signals and the first plurality of quadrature signals being a first plurality of IQ signals;
a second digital processor operable to receive second input data and supply a second plurality of inphase signals and a second plurality of quadrature signals, collectively, the second plurality of inphase signals and the second plurality of quadrature signals being a second plurality of IQ signals;
a first plurality of inphase-quadrature (IQ) modulators, including first, second, third, and fourth IQ modulators, wherein the first IQ modulator and the third IQ modulator receive first selected IQ signals of the first plurality of IQ signals, and the second IQ modulator and the fourth IQ modulator receive first selected IQ signals of the second plurality of IQ signals;
a first adder to provide a first sum, the first sum being a sum of outputs of the first IQ modulator and the second IQ modulator;
a second adder operable to add outputs of the third IQ modulator and the fourth IQ modulator to provide a second sum;
a second plurality of inphase-quadrature (IQ) modulators, including fifth, sixth, seventh, and eighth IQ modulators, wherein the fifth IQ modulator and the seventh IQ modulator receive second selected IQ signals of the first plurality of IQ signals, and the sixth IQ modulator and the eighth IQ modulator receive second selected IQ signals of the second plurality of IQ signals;
a third adder to provide a third sum, the third sum being a sum of outputs of the fifth IQ modulator and the sixth IQ modulator;
a fourth adder operable to add outputs of the seventh IQ modulator and the eighth IQ modulator to provide a fourth sum;
a modulator circuit configured to receive a carrier optical signal, the carrier optical signal being operable to receive the first, second, third and fourth sums, such that:
an X polarization of a modulated optical signal output from the modulator circuit includes:
a modulated inphase component based on the first sum associated with the first and second IQ modulators, and
a modulated quadrature component based on the second sum associated with the third and fourth IQ modulators, and a Y polarization of the modulated optical signal includes:
a modulated inphase component based on the third sum associated with the fifth and sixth IQ modulators, and
a modulated quadrature component based on the fourth sum associated with the seventh and eighth IQ modulators, wherein:
the modulated optical signal is centered at frequency ωc;
the modulated optical signal comprises a plurality of subcarriers; and
a center frequency of each of the plurality of subcarriers is offset from ωc by a frequency of said one of the plurality of local oscillator signals.