Probabilistic constellation shaping of multi-dimensional symbols for improved tolerance to nonlinear impairments

Patent metadata

Field	Value
Publication number	US-10848269-B2
Application number	US-201916599157-A
Country	US
Kind code	B2
Filing date	Oct 11, 2019
Priority date	Oct 12, 2018
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

An optical transmitter device includes a digital signal processor (DSP) having digital hardware. The DSP is operative to generate shaped bits from a first set of information bits, and to apply a systematic forward error correction (FEC) scheme to encode the shaped bits and a second set of information bits, where the first set of information bits and the second set of information bits are disjoint sets. Unshaped bits and the shaped bits are mapped to selected symbols or are used to select symbols from one or more constellations. The selected symbols are mapped to physical dimensions. Each unshaped bit is either one of the second set of information bits or one of multiple parity bits resulting from the FEC encoding. In this manner, a target spectral efficiency is achieved.

First claim

What is claimed is:

1. An optical transmitter device comprising:
a digital signal processor (DSP) comprising digital hardware, the DSP operative
to generate shaped bits from a first set of information bits;
to apply a systematic forward error correction (FEC) scheme to encode the shaped bits and a second set of information bits, where the first set of information bits and the second set of information bits are disjoint sets; and
for multiple pairs of groups, each pair consisting of a first group and a second group, each first group consisting of a first unshaped bit and a first shaped bit and each second group consisting of a second unshaped bit and second shaped bit
to map the first unshaped bit and the first shaped bit to a first quadrature phase shift keying (QPSK) symbol according to a labeling scheme;
to map the second unshaped bit and the second one of the shaped bits to a second QPSK symbol according to the labeling scheme; and
to map the first QPSK symbol and the second QPSK symbol to four physical dimensions,

wherein each unshaped bit is either one of the second set of information bits or one of multiple parity bits resulting from the FEC encoding; and
wherein either the least significant bit in all groups is always one of the shaped bits or the most significant bit in all groups is always one of the shaped bits.

2. The optical transmitter device recited in claim 1 , further comprising
a first modulator operative to modulate a first component of an optical carrier to convey the first QPSK symbol, the first component polarized in a first polarization; and
a second modulator operative to modulate a second component of the optical carrier to convey the second QPSK symbol, the second component polarized in a second polarization that is orthogonal to the first polarization.

3. The optical transmitter device recited in claim 1 , wherein the DSP is operative to apply any arbitrary shaping algorithm to the first set of information bits to generate the shaped bits.

4. The optical transmitter device recited in claim 1 , wherein the DSP is operative to apply a tree encoding structure to the first set of information bits to generate the shaped bits, the tree encoding structure having look-up tables that were programmed according to different pseudo-energies that were assigned to points of a two-point constellation.

5. An optical transmitter device comprising:
a digital signal processor (DSP) comprising digital hardware, the DSP operative
to generate shaped bits from a first set of information bits;
to apply a systematic forward error correction (FEC) scheme to encode the shaped bits and a second set of information bits, where the first set of information bits and the second set of information bits are disjoint sets; and
for multiple groups, each group consisting of K unshaped bits and one shaped bit,
to select one of two constellations based on a value of the shaped bit, where all symbols of one of the two constellations have an amplitude A, all symbols of the other of the two constellations have an amplitude B, A and B are real positive numbers, B<A, and a sum of squares of the amplitudes A 2 +B 2 is equal to 1 or differs slightly from 1,
to use the K unshaped bits to select a first symbol from a first of the two constellations and a second symbol from a second of the two constellations;
where the first of the two constellations is selected, to map the first symbol to two physical dimensions of an optical carrier component that is polarized in a first polarization and to map the second symbol to two physical dimensions of an optical carrier component that is polarized in a second polarization that is orthogonal to the first polarization; and
where the second of the two constellations is selected, to map the second symbol to the two physical dimensions of the optical carrier component that is polarized in the first polarization and to map the first symbol to the two physical dimensions of the optical carrier component that is polarized in the second polarization,

wherein each of the K unshaped bits is either one of the second set of information bits or one of multiple parity bits resulting from the FEC encoding, and K is a positive integer greater than three.

6. The optical transmitter device recited in claim 5 , where K equals 5, the constellation whose symbols have the amplitude A is an 8 phase shift keying (8PSK) constellation, and the constellation whose symbols have the amplitude B is a QPSK constellation.

7. The optical transmitter device recited in claim 5 , where K equals 4, and the two constellations are QPSK constellations.

8. The optical transmitter device recited in claim 5 , wherein the DSP is operative to apply any arbitrary shaping algorithm to the first set of information bits to generate the shaped bits.

9. The optical transmitter device recited in claim 5 , wherein the DSP is operative to apply a tree encoding structure to the first set of information bits to generate the shaped bits, the tree encoding structure having look-up tables that were programmed according to different pseudo-energies that were assigned to points of a two-point constellation.

10. An optical transmitter device comprising:
a digital signal processor (DSP) comprising digital hardware, the DSP operative
to generate shaped bits from a first set of information bits;
to apply a systematic forward error correction (FEC) scheme to encode the shaped bits and a second set of information bits, where the first set of information bits and the second set of information bits are disjoint sets; and
for multiple groups, each group consisting of seven unshaped bits and one of the shaped bits
to select one of two collections based on a value of the one of the shaped bits;
to use the seven unshaped bits to select an ordered quadruplet of QPSK symbols from the selected collection; and
to map the four QPSK symbols of the selected ordered quadruplet to eight physical dimensions,

wherein each of the seven unshaped bits is either one of the second set of information bits or one of multiple parity bits resulting from the FEC encoding, and
wherein a labeling scheme uses eight bits to label all 256 possible ordered quadruplets of QPSK symbols, one of the two collections consists of all 128 ordered quadruplets of QPSK symbols whose 8-bit label according to the labeling scheme has even parity, and the other of the two collections consists of all 128 ordered quadruplets of QPSK symbols whose 8-bit label according to the labeling scheme has odd parity.

11. The optical transmitter device recited in claim 10 , further comprising
a first modulator operative to modulate, in a first time slot, a first component of an optical carrier according to a first of the four QPSK symbols or a processed version thereof, the first component polarized in a first polarization, and to modulate, in a second time slot, the first component of the optical carrier according to a third of the four QPSK symbols or a processed version thereof; and
a second modulator operative to modulate, in the first time slot, a second component of the optical carrier according to a second of the four QPSK symbols or a processed version thereof, the second component polarized in a second polarization that is orthogonal to the first polarization, and to modulate, in the second time slot, the second component of the optical carrier according to a fourth of the four QPSK symbols or a processed version thereof.

12. The optical transmitter device recited in claim 10 , wherein the DSP is operative to apply any arbitrary shaping algorithm to the first set of information bits to generate the shaped bits.

13. Th

Assignees

• Ciena Corp

Inventors

• Ebrahimzad Hamid
• Reimer Michael Andrew
• Grigoryan Vladimir S
• Oveis Gharan Shahab

Classifications

• H04L27/34 Primary

  Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems · CPC title

• H04L27/20

  Modulator circuits; Transmitter circuits · CPC title

• H04L1/0041

  Arrangements at the transmitter end · CPC title

• H04B10/5561

  Digital phase modulation · CPC title

• H03M13/11

  using multiple parity bits · CPC title