System and method for multimodulation in a passive optical network

Patent metadata

Field	Value
Publication number	US-12244348-B2
Application number	US-202217714959-A
Country	US
Kind code	B2
Filing date	Apr 6, 2022
Priority date	Apr 6, 2022
Publication date	Mar 4, 2025
Grant date	Mar 4, 2025

Abstract

An optical line terminal (OLT) in flexible passive optical network (PON) transmits a downstream signal with two or more modulation formats, wherein at least one of the modulation formats is a modified PAMx modulation format and wherein x is greater than 2. The modified PAMx modulation encodes data bits such that the probability of at least one predetermined transition between amplitude levels is modified. Furthermore, an optical network unit (ONU) in the flexible PON is assigned to one of the plurality of modulation formats based on one or more parameters, such as configuration of the ONU and line conditions.

First claim

The invention claimed is:

1. An optical device, comprising:
a signal encoder configured to generate a digital encoding signal using a first modulation format and a different, second modulation format, wherein the second modulation format is a modified pulse amplitude modulation having x amplitude levels (PAMx), wherein x is greater than 2; and
a modulator for modulating a first wavelength of an optical signal using the digital encoding signal, by modulating a first portion of the optical signal with the first modulation format and modulating a second portion of the optical signal with the second modulation format, wherein the modulator modulates the second portion of the optical signal modulated with the modified PAMx format by selecting consecutive symbol patterns to generate a first adapted probability of a first transition between a first pair of amplitude levels that is greater than a second adapted probability of a second transition between a different second pair of amplitude levels.

2. The optical device of claim 1 , wherein the optical device is configured to broadcast the modulated optical signal to a plurality of optical network units (ONUs) in a point to multipoint optical network.

3. The optical device of claim 2 , wherein the optical device includes:
at least one processor and at least one memory, wherein the at least one memory stores instructions that, when executed by the at least one processor, causes the optical device to:
assign the first modulation to a first ONU of the plurality of ONUs; and
assign the second modulation to a second ONU of the plurality of ONUs.

4. The optical device of claim 3 , wherein the at least one memory stores instructions that when executed by the at least one processor, cause the optical device to:
obtain one or more parameters associated with at least the first ONU and the second ONU, wherein the parameters include one or more of: configuration information; signal quality of the optical signal; link budget; or subscriber status information.

5. The optical device of claim 4 , wherein the at least one memory stores instructions that when executed by the at least one processor, cause the optical device to:
assign the first modulation to the first ONU in response to the one or more parameters associated with the first ONU; and
assign the second modulation to the second ONU in response to the one or more parameters associated with the second ONU.

6. The optical device of claim 1 , wherein the first modulation format includes a non-return to zero (NRZ) format and wherein the second modulation format includes a modified 4-level pulse amplitude modulation (PAM4), wherein the NRZ format has a lower bit rate than the modified PAM4 format.

7. The optical device of claim 1 , wherein the signal encoder is configured to generate the digital encoding signal using the PAMx format by at least one of:
encoding blocks of N data bits to a set of symbol patterns of L symbols using one or more codebooks, wherein the set of symbol patterns includes the first adapted probability of the first transition between the first pair of amplitude levels that is greater than the second adapted probability of the second transition between the different second pair of amplitude levels; or
encoding, using at least one state machine with a plurality of states, the blocks of N data bits to the set of symbol patterns of L symbols, wherein the mapped constellation patterns have the first adapted probability of the first transition between the first pair of amplitude levels that is greater than the second adapted probability of the second transition between the different second pair of amplitude levels.

8. The optical device of claim 1 ,
wherein the first transition between the first pair of amplitude levels includes a transition between a first amplitude level and the same first amplitude level and the second transition between the different second pair of amplitude levels includes a transition between the first amplitude level and a different, second amplitude level.

9. The device of claim 8 , wherein the signal encoder is configured to select the consecutive first and second symbol patterns to generate the first adapted probability of the first transition between the first pair of amplitude levels by:
selecting the first symbol pattern having a terminating symbol S T ; and
selecting the second symbol pattern having an initial symbol S I , wherein an amplitude level of S T and S I is the same.

10. A method of an optical device, comprising:
generating by a signal encoder a digital encoding signal using a first modulation format and a different, second modulation format, wherein the second modulation format is a modified pulse amplitude modulation having x amplitude levels (PAMx), wherein x is greater than 2; and
modulating by a modulator a first wavelength of an optical signal using the digital encoding signal, wherein the modulator modulates a first portion of the optical signal with the first modulation format and the modulator modulates a second portion of the optical signal with the second modulation format, wherein the modulator modulates the second portion of the optical signal with the modified PAMx format by selecting consecutive symbol patterns to generate a first adapted probability of a first transition between a predetermined first pair of amplitude levels that is greater than a second adapted probability of a second transition between a predetermined different pair of amplitude levels.

11. The method of claim 10 , further comprising:
broadcasting by the optical device the modulated optical signal to a plurality of optical network units (ONUs) in a point to multipoint optical network.

12. The method of claim 11 , further comprising:
assigning by the optical device the first modulation to a first ONU of the plurality of ONUs; and
assigning by the optical device the second modulation to a second ONU of the plurality of ONUs.

13. The method of claim 12 , further comprising:
obtaining by the optical device one or more parameters associated with at least the first ONU and the second ONU, wherein the parameters include one or more of: configuration information; signal quality of the optical signal; link budget; or subscriber status information.

14. The method of claim 13 , further comprising:
assigning by the optical device the first modulation to the first ONU in response to the one or more parameters associated with the first ONU; and
assigning by the optical device the second modulation to the second ONU in response to the one or more parameters associated with the second ONU.

15. The method of claim 10 , wherein the first modulation format includes a non-return to zero (NRZ) format and wherein the second modulation format includes a 4-level pulse amplitude modulation (PAM4), wherein the NRZ format has a lower bit rate than the modified PAM4 format.

16. The method of claim 10 , wherein generating by the signal encoder the digital encoding signal using the different, second modulation format, wherein the second modulation format is the modified PAMx, wherein x is greater than 2, comprises at least one of:
encoding by the signal encoder blocks of N data bits to a set of symbol patterns of L symbols using one or more codebooks, wherein the mapped constellation points exhibit the first adapted probability of the first transition between the predetermined first pair of amplitude levels that is greater than the second adapted probability of the second transition between the predetermined different pair of amplitude levels; or
encoding by the signal encoder, u

Assignees

• Nokia Solutions & Networks Oy

Inventors

• Van Veen Doutje
• Mahadevan Amitkumar
• Houtsma Vincent

Classifications

• H04L27/2626

  Arrangements specific to the transmitter only · CPC title

• H04B10/272

  Star-type networks {or tree-type networks} · CPC title

• H04B10/541 Primary

  Digital intensity or amplitude modulation · CPC title

• H04B10/5161

  Combination of different modulation schemes · CPC title

• H04B14/023

  using pulse amplitude modulation · CPC title