Coherent optical receiver
AssigneeElenion Technologies, LLC
InventorThomas Wetteland Baehr-Jones
Life of this patent
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Abstract
An optical IQ demodulator that does not require a power-consuming DSP is disclosed. A DC offset is added to one of the I and Q optical signal components at an IQ transmitter. After mixing with an LO signal and differential detection at the receiver, this DC offset results in a heterodyne-frequency tone in each of the quadrature detection channels of the receiver. The phase of this oscillation is recovered using a PLL circuit, which output is used to separate the transmitter I and Q channels for decoding thereof using conventional electronics.
Claims14
A method for coherent demodulation of quadrature-modulated (QM) light comprising two transmitter signals optically combined in quadrature, the method comprising:
- performing optical quadrature heterodyne detection of the QM light to obtain two electrical signals;
- detecting a heterodyne frequency (HF) tone in each of the two electrical signals so as to preserve a relative phase therebetween;
- and,
- decomposing the two transmitter signals from the two electrical signals based at least in part on the HF tones to obtain two decomposed transmitter signals.
A method for coherent demodulation of quadrature-modulated (QM) light comprising two transmitter signals optically combined in quadrature, the method comprising:
- at a transmitter site, adding a DC amplitude offset to an optical modulator driven by one of the two transmitter signals;
- performing optical quadrature heterodyne detection of the QM light to obtain two electrical signals;
- detecting a heterodyne frequency (HF) tone in each of the two electrical signals so as to preserve a relative phase therebetween;
- and,
- decomposing the two transmitter signals from the two electrical signals based at least in part on the HF tones to obtain two decomposed transmitter signals.
A method for coherent demodulation of quadrature-modulated (QM) light comprising two transmitter signals optically combined in quadrature, the method comprising:
- performing optical quadrature heterodyne detection of the QM light to obtain two electrical signals;
- detecting a heterodyne frequency (HF) tone in each of the two electrical signals so as to preserve a relative phase therebetween;
- and,
- decomposing the two transmitter signals from the two electrical signals based at least in part on the HF tones to obtain two decomposed transmitter signals;
- wherein the QM light is polarization multiplexed using a dither signal in one polarization thereof, the method further comprising:
- splitting received QM light into two light signals of orthogonal polarizations,
- detecting the dither signal in at least one of the two light signals, and
- using the dither signal detected in the at least one of the two light signals to control the splitting of the received QM light.
Dependencies are inferred from the claim text.