Distribution matching for probabilistic constellation shaping with an arbitrary input/output alphabet

Patent metadata

Field	Value
Publication number	US-2022303166-A1
Application number	US-202117473537-A
Country	US
Kind code	A1
Filing date	Sep 13, 2021
Priority date	Oct 4, 2017
Publication date	Sep 22, 2022
Grant date	—

Abstract

Consistent with the present disclosure, an encoder circuit is provided at a transmit side of an optical fiber link that maps an input sequence of bits of fixed length k a sequence of symbols of a codeword of length n, such that the symbols of the codeword define a predetermined transmission probability distribution. Preferably, each symbol of the codeword is generated during a corresponding clock cycle, such that after n clock cycles, a complete codeword corresponding to the input bit sequence is output. On a receive end of the link, a decoder is provided that outputs the k-bit sequence every n clock cycles. Accordingly, buffers need not be provided at the output of the encoder and the input of the decoder, such that processing of the input sequence, codewords, and output sequence may be achieved efficiently without large buffers and complicated circuitry. Moreover, the input sequence, with any binary alphabet may be matched to a desired output distribution with any arbitrary alphabet. Accordingly, probabilistic constellation shaping may be achieved over constellations of arbitrary size. In addition, relatively long codewords, may be encoded and decoded with the apparatus and method disclosed herein. Accordingly, for a fixed SNR a higher SE (more bits per symbol) can be achieved. Alternatively, for a fixed SE, a lower SNR may be sufficient. Moreover, the resulting SE may be finely tailored to a particular optical link SNR to provide data transmission rates that are higher than the low order modulation formats that would otherwise be employed for optical signals carried by such links.

First claim

1 - 33 . (canceled)

34 . A transmitter, comprising:
a laser; and a modulator, the receives light output from the laser and a drive signal, such that, based on the drive signal, the modulator supplies a modulated optical signal that includes a plurality of subcarriers, wherein each of the plurality of subcarriers is a Nyquist subcarrier, and each of the plurality of subcarriers carries a corresponding one of a plurality of sequences of modulation symbols in accordance with a respective one of a plurality transmission probability distributions, wherein a first one of the plurality of subcarriers carries a first one of the plurality of sequences of modulation symbols, the first one of the plurality of sequences of modulation symbols includes first modulation symbols and second modulation symbols, the first modulation symbols being transmitted more frequently than the second modulation symbols in accordance with a first one of the plurality of transmission probability distributions, and wherein a second one of the plurality of the plurality of subcarriers carries a second one of the plurality of sequences of modulation symbols, the second one of the plurality of sequences of modulation symbols includes third modulation symbols and fourth modulation symbols, the third modulation symbols being transmitted more frequently than the fourth modulation symbols in accordance with a second one of the plurality of transmission probability distributions, which is different than the first one of the plurality of transmission probability distributions.

35 . A transmitter in accordance with claim 34 , wherein the first one of the plurality of subcarriers is attenuated relative to the second one of the plurality of subcarriers, the first one of the plurality of subcarriers having a lower spectral efficiency than the second one of the plurality of subcarriers.

36 . A transmitter in accordance with claim 34 , wherein the first one of the plurality of subcarriers has a bit error rate that is higher than a bit error rate of the second one of the plurality of subcarriers, the first one of the plurality of subcarriers having a lower spectral efficiency than the second one of the plurality of subcarriers.

37 . A transmitter in accordance with claim 34 , further including:
an encoder that outputs a plurality of codewords; and a demultiplexer that provides a plurality of outputs, each of the outputs being indicative of a corresponding one of the plurality of codewords.

38 . A transmitter in accordance with claim 37 , further including a forward error correction encoder that receives an input indicative of the plurality of codewords and supplies an encoded output, the encoded output being provided to the demultiplexer.

39 . A transmitter in accordance with claim 34 , wherein the first modulation points correspond to first constellation points having a first amplitude and the second modulation points correspond to second constellation points having a second amplitude, the second amplitude being greater than the first amplitude.

40 . A transmitter in accordance with claim 34 , wherein the first modulation points correspond to first constellation points having a first amplitude and the second modulation points correspond to second constellation points having a second amplitude, the second amplitude being less than the first amplitude.

41 . An apparatus, comprising:
a first laser; a second laser; a first modulator that receives light output from the first laser and a first drive signal, such that, based on the drive signal, the modulator supplies a first modulated optical signal; a second modulator that receives light from the second modulator and a second drive signal, such that, based on the second drive signal, the modulator supplies a second modulated optical signal, wherein the first modulated optical signal carries a first plurality of sequences of modulation symbols, the first plurality of sequences of modulation symbols includes first modulation symbols and second modulation symbols, the first modulation symbols being transmitted more frequently than the second modulation symbols in accordance with a first transmission probability distribution, and the second modulated optical signal carries a second plurality of sequences of modulation symbols, the second plurality of sequences of modulation symbols includes third modulation symbols and fourth modulation symbols, the third modulation symbols being transmitted more frequently than the fourth modulation symbols in accordance with a second transmission probability distribution, which is different than the first transmission probability distribution.

42 . An apparatus in accordance with claim 41 , wherein the first channel is attenuated relative to the second channel, the first channel having a lower spectral efficiency than the first channel.

43 . An apparatus in accordance with claim 41 , wherein the first channel has a first bit error rat and the second channel has a second bit error rate that is less than the first bit error rate, the first channel having a lower spectral efficiency than the first channel.

44 . A system, comprising:
a first transmitter including a first laser and a first modulator, the first modulator receiving light output from the first laser and a first drive signal, such that, based on the drive signal, the modulator supplies a first modulated optical signal; a second transmitter laser including a second laser and a second modulator, the second modulator receiving light from the second modulator and a second drive signal, such that, based on the second drive signal, the modulator supplies a second modulated optical signal, wherein the first modulated optical signal carries a first plurality of sequences of modulation symbols, the first plurality of sequences of modulation symbols includes first modulation symbols and second modulation symbols, the first modulation symbols being transmitted more frequently than the second modulation symbols in accordance with a first transmission probability distribution, and the second modulated optical signal carries a second plurality of sequences of modulation symbols, the second plurality of sequences of modulation symbols includes third modulation symbols and fourth modulation symbols, the third modulation symbols being transmitted more frequently than the fourth modulation symbols in accordance with a second transmission probability distribution, which is different than the first transmission probability distribution; and an optical combiner that combines the first and second modulated optical signals onto an optical communication path

45 . A system in accordance with claim 44 , further including a first receiver and a second receiver, the first receiver and the second receiver being coupled to the optical communication path and receiving first and second received signals corresponding the first and second modulated optical signals, respectively.

46 . A transmitter in accordance with claim 44 , wherein the first channel is attenuated relative to the second channel, the first channel having a lower spectral efficiency than the first channel.

47 . A transmitter in accordance with claim 44 , wherein the first channel has a first bit error rat and the second channel has a second bit error rate that is less than the first bit error rate, the first channel having a lower spectral efficiency than the first channel.

48 . A system, comprising:
a transmitter including a laser and a modulator, the receives light output from the laser and a drive signal, such that, based on the drive signal, the m

Assignees

• Infinera Corp

Inventors

• Torbatian Mehdi
• Chan Deyuan
• Sun Han Henry
• Thomson Sandy
• Wu Kuang-Tsan

Classifications

• H04L1/0041

  Arrangements at the transmitter end · CPC title

• H04L27/362 Primary

  Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated (H04L27/366 takes precedence) · CPC title

• H04L1/0057

  Block codes (H04L1/0061, H04L1/0064 take precedence) · CPC title

• H04L27/3433

  using an underlying square constellation · CPC title

• H04L2025/03611

  Iterative algorithms · CPC title