Modulation systems and methods in optical transceivers
AssigneeAcacia Communications, Inc.
InventorsHongbin Zhang, Mehmet Aydinlik
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Abstract
Quadrature amplitude modulation (QAM) techniques for use in optical systems are described. An optical transceiver may include a modulator configured to modulate data according to a scaled set-partitioning QAM (SP-QAM) scheme. The modulator may be configured to receive a plurality of bits, associate the plurality of bits with a plurality of symbols according to the scaled (SP-QAM) scheme; and transmit the plurality of symbols over an optical channel. A demodulator in an optical receiver may receive the plurality of symbols transmitted over the optical channel and associate the received symbols with a plurality of bits according to the scaled (SP-QAM) scheme; and provide the plurality of bits to a forward error correction decoder.
Claims21
An optical transmitter, comprising:
- a modulator configured to:
- receive a plurality of bits;
- associate the plurality of bits with a plurality of symbols using a scaled set-partitioning quadrature amplitude modulation (SP-QAM) constellation, the SP-QAM constellation comprising a set of points arranged along a first direction and a second direction orthogonal to the first direction, the set of points including:
- a first point having a same location as a corresponding first point in an unscaled SP-QAM constellation, and
- a second point spaced a first distance away from the first point along the first direction, the second point having a non-zero offset relative to a corresponding point in the unscaled SP-QAM constellation;
- and
- transmit the plurality of symbols;
- wherein a scaling factor S of the SP-QAM constellation is chosen based on a signal to noise ratio (SNR).
An optical receiver, comprising:
- a demodulator configured to:
- receive a plurality of symbols;
- associate the plurality of symbols with a plurality of bits or soft metrics according to a scaled set-partitioning quadrature amplitude modulation (SP-QAM) constellation, wherein the demodulator stores constellation information indicating locations of points in a scaled SP-QAM constellation, the SP-QAM constellation comprising a set of points arranged along a first direction and a second direction orthogonal to the first direction, the set of points including:
- a first point having a same location as a corresponding first point in an unscaled SP-QAM constellation, and
- a second point spaced a first distance away from the first point along the first direction, the second point having a non-zero offset relative to a corresponding point in the unscaled SP-QAM constellation;
- and
- provide the plurality of bits to a forward error correction decoder.
A method, comprising:
- using an optical transmitter to perform:
- receiving a plurality of bits;
- associating the plurality of bits with a plurality of symbols using a scaled set-partitioning quadrature amplitude modulation (SP-QAM) constellation, the SP-QAM constellation comprising a set of points arranged along a first direction and a second direction orthogonal to the first direction, the set of points including:
- a first point having a same location as a corresponding first point in an unscaled SP-QAM constellation, and
- a second point spaced a first distance away from the first point along the first direction, the second point having a non-zero offset relative to a corresponding point in the unscaled SP-QAM constellation;
- and
- transmitting the plurality of symbols over an optical channel;
- wherein a scaling factor S of the SP-QAM constellation is chosen based on a signal to noise ratio (SNR).
Dependencies are inferred from the claim text.