# US 11,444,694 B2 · Optical transmission system

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,444,694 B2
- Document ID: US11444694B2
- Status: Granted
- Kind: B2
- Application number: 17/291,228
- Filed: 2019-11-06
- Published: 2021-11-25
- Granted: 2022-09-13
- Earliest claimed: 2018-11-06
- Assignees: Nippon Telegraph and Telephone Corporation
- Applicants: Nippon Telegraph and Telephone Corporation
- Inventors: Shuto Yamamoto; Akira Masuda; Hiroki Taniguchi; Yoshiaki Kisaka
- Web page: https://patentgrep.com/patent/US11444694B2

## CPC

- H04B 10/2507: for the reduction or elimination of distortion or dispersion
- H04L 25/4917: {using multilevel codes}
- H03M 13/41: using the Viterbi algorithm or Viterbi processors
- H04B 10/516: Details of coding or modulation
- H04B 10/524: Pulse modulation
- H04B 10/61: Coherent receivers
- H04L 25/49: using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels {; Baseband coding techniques specific to data transmission systems (spectral shaping H04L25/03828)}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)

## Abstract

Provided is an optical transmission system that includes an optical transmitter, and an optical receiver. The optical transmitter includes: a signal coding unit configured to perform nonlinear trellis coding, which corresponds to nonlinear calculation, on a symbol sequence; and a modulator configured to modulate the symbol sequence subjected to the nonlinear trellis coding by the signal coding unit, and transmit the modulated symbol sequence to the optical receiver. The optical receiver includes: a light receiving unit configured to receive an optical signal transmitted from the optical transmitter, and convert the received optical signal into an electrical signal; and a digital signal processing unit configured to perform digital signal processing on the electrical signal to reconstruct the symbol sequence.

## Claims

### Claim 1

An optical transmission system comprising:
an optical transmitter, the optical transmitter including:
a signal generation unit configured to generate, using input information data, an N-value symbol that is Gray-coded, the N being an integer of 2 or greater;
a signal coding unit configured to perform nonlinear trellis coding, which corresponds to nonlinear calculation, on the N-value symbol to generate an N+2-value symbol; and
a modulator configured to modulate the N+2-value symbol and transmit an optical signal corresponding to the N+2-value symbol to an optical receiver, and
the optical receiver, the optical receiver including:
a light receiving unit configured to receive the optical signal and convert the received optical signal into an electrical signal; and
a digital signal processing unit configured to perform digital signal processing on the electrical signal to reconstruct the N+2-value symbol.

### Claim 2 (depends on 1)

The optical transmission system according to claim 1, wherein the optical receiver further includes a Viterbi decoding unit configured to perform symbol determination based on sequence estimation using Viterbi decoding when the electrical signal is demodulated.

### Claim 3 (depends on 1)

The optical transmission system according to claim 1,
wherein the signal coding unit is configured to perform the nonlinear trellis coding given by Expressions 1 to 3 below to generate the N+2-value symbol,
the digital signal processing unit is configured to perform predetermined determination on the electrical signal to reconstruct the N+2-value symbol, and
the digital signal processing unit is configured to reconstruct the N-value symbol before the nonlinear trellis coding, based on Expressions 4 to 6 below, using the reconstructed N+2-value symbol and an already determined N+2-value symbol in a previous time slot, wherein the Expressions 1 to 6 are defined as:
the Expression 1 is vn=un(vn-1<N/2);
the Expression 2 is vn=un+1(N/2≤vn-1<(N/2)+2);
the Expression 3 is vn=un+2((N/2)+2≤vn-1);
the Expression 4 is un=vn(vn-1<N/2);
the Expression 5 is un=vn−1(N/2≤vn-1<(N/2)+2);
and
the Expression 6 is un=vn−2((N/2)+2≤vn-1).

### Claim 4 (depends on 3)

The optical transmission system according to claim 3,
wherein the digital signal processing unit is configured to perform symbol determination based on sequence estimation using Viterbi decoding as the predetermined determination on the electrical signal.

### Claim 5 (depends on 1)

The optical transmission system according to claim 1,
wherein the signal generation unit is configured to generate two systems of the N-value symbols,
the signal coding unit is configured to perform the nonlinear trellis coding given by Expressions 7 to 9 below to generate two systems of the N+2-value symbols,
the digital signal processing unit is configured to perform predetermined determination on the electrical signal to reconstruct the two systems of the N+2-value symbols, and
the digital signal processing unit is configured to reconstruct the N-value symbols before the nonlinear trellis coding, based on Expressions 10 to 12 below, using a plurality of reconstructed N+2-value symbols and a plurality of already determined N+2-value symbols in a previous time slot, wherein the Expressions 7 to 12 are defined as:
the Expression 7 is vn=un(vn-1<N/2);
the Expression 8 is vn=un+1(N/2≤vn-1<(N/2)+2);
the Expression 9 is vn=un+2((N/2)+2≤vn-1);
the Expression 10 is un=vn(vn-1<N/2);
the Expression 11 is un=vn−1(N/2≤vn-1<(N/2)+2);
and
the Expression 12 is un=vn−2((N/2)+2≤vn-1).

### Claim 6 (depends on 5)

The optical transmission system according to claim 5,
wherein the digital signal processing unit is configured to perform symbol determination based on sequence estimation using Viterbi decoding as the predetermined determination on the electrical signal.