# US 8,543,882 B2 · Joint carrier phase estimation and forward error correction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,543,882 B2 - Document ID: US8543882B2 - Status: Granted - Kind: B2 - Application number: 12/905,652 - Filed: 2010-10-15 - Published: 2012-04-19 - Granted: 2013-09-24 - Earliest claimed: 2010-10-15 - Assignees: Tyco Electronics Subsea Communications LLC - Applicants: Yi Cai - Inventors: Yi Cai - Web page: https://patentgrep.com/patent/US8543882B2 ## CPC - H04L 1/0047: {Decoding adapted to other signal detection operation (in conjunction with sequence estimation or equalization H04L25/03286)} - H03M 13/3746: {with iterative decoding} - H03M 13/6325: {Error control coding in combination with demodulation} - H04B 10/6165: {Estimation of the phase of the received optical signal, phase error estimation or phase error correction} - H04B 10/695: {Arrangements for optimizing the decision element in the receiver, e.g. by using automatic threshold control} - H03M 13/1102: {Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes} - H03M 13/152: {Bose-Chaudhuri-Hocquenghem [BCH] codes} - H03M 13/17: Burst error correction, e.g. error trapping, Fire codes - H03M 13/19: Single error correction without using particular properties of the cyclic codes, e.g. Hamming codes, extended or generalised Hamming codes - H03M 13/23: using convolutional codes, e.g. unit memory codes - H03M 13/2957: {Turbo codes and decoding} - H03M 13/2963: {Turbo-block codes, i.e. turbo codes based on block codes, e.g. turbo decoding of product codes} - 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) - H04B: TRANSMISSION ## Abstract Methods and systems for processing an optical signal in a communication system are disclosed. The disclosed methods yield benefits for estimation and tracking of carrier phase of received signals at a digital coherent receiver without the use of differential coding. Specifically, phase ambiguity is removed by calculating the slope of the CPE at a location where the CPE begins to lose track of the received carrier phase signal. As such, a CPE offset adjustment may be applied in accordance with the calculated slope to reduce the number of ones and zeros corrected by a FEC decoder. Thus, the FEC aided CPE scheme may be a feed forward scheme that requires no training. ## Claims ### Claim 1 A receiver utilized in an optical communication system comprising: a decision circuit for receiving an input signal and providing an output signal representing logic ones and zeros in response to a comparison of said input signal with a Carrier Phase Estimation (CPE) of said input signal; a forward error correction (FEC) decoder configured to decode said output signal and to provide feedback representative of the number of errors corrected by said FEC decoder and indicating a polarity of said input signal; and a CPE offset adjuster configured to adjust said CPE in response to said feedback to reduce a number of said ones and zeros corrected by said FEC decoder. ### Claim 2 (depends on 1) The apparatus according to claim 1, wherein said CPE offset adjuster is configured to adjust said CPE by an offset in a direction determined by the polarity of said input signal. ### Claim 3 (depends on 1) The apparatus according to claim 1, wherein said CPE offset adjuster is configured to adjust said CPE by an offset in a direction determined by a slope of the CPE at a location where the CPE offset begins. ### Claim 4 (depends on 1) The apparatus according to claim 1, wherein said input signal is a modulated signal using a quadrature phase shift keying (QPSK) format. ### Claim 5 (depends on 1) The apparatus according to claim 1, wherein said CPE offset adjuster is configured to add said number errors corrected by said FEC decoder over one or more sampling periods to determine a total number of said errors corrected by said FEC decoder over said one or more sampling periods, and wherein said CPE offset adjuster is configured to adjust said CPE when said total number of said errors exceeds a predetermined error threshold. ### Claim 6 (depends on 1) The apparatus according to claim 1, wherein said CPE offset adjuster is configured to add said number errors corrected by said FEC decoder over one or more frame alignment words to determine a total number of said errors corrected by said FEC decoder over said one or more frame alignment words, and wherein said CPE offset adjuster is configured to adjust said CPE when said total number of said errors exceeds a predetermined error threshold. ### Claim 7 An optical communication system comprising: an optical signal transmitter comprising an encoder for encoding a binary data stream and a modulator for modulating said encoded binary data stream to produce an encoded optical signal; and an optical signal receiver for receiving said encoded optical signal, said optical signal receiver comprising: a demodulator for demodulating said encoded optical signal to provide an input signal; a decision circuit for receiving said input signal and providing an output signal representing logic ones and zeros in response to comparison of said input signal with a Carrier Phase Estimation (CPE) of said input signal; a Forward Error Correction (FEC) decoder configured to decode said output signal and to provide feedback representative of a number of errors corrected by said FEC decoder and indicating a polarity of said input signal; and a CPE offset adjuster configured to adjust said CPE in response to said feedback to reduce the number of said ones and zeros corrected by said FEC decoder. ### Claim 8 (depends on 7) The system according to claim 7, wherein said CPE offset adjuster is configured to adjust said CPE by an offset in a direction determined by the polarity of said input signal. ### Claim 9 (depends on 7) The system according to claim 7, wherein said CPE offset adjuster is configured to adjust said CPE by an offset in a direction determined by a slope of the CPE at a location where the CPE offset begins. ### Claim 10 (depends on 7) The system according to claim 7, wherein said input signal is a modulated signal using a Quadrature Phase Shift Keying (QPSK) format. ### Claim 11 (depends on 7) The system according to claim 7, wherein said CPE offset adjuster is configured to add said number errors corrected by said FEC decoder over one or more sampling periods to determine a total number of said errors corrected by said FEC decoder over said one or more sampling periods, and wherein said CPE offset adjuster is configured to adjust said CPE when said total number of said errors exceeds a predetermined error threshold. ### Claim 12 (depends on 7) The system according to claim 7, wherein said CPE offset adjuster is configured to add said number errors corrected by said FEC decoder over one or more frame alignment words to determine a total number of said errors corrected by said FEC decoder over said one or more frame alignment words, and wherein said CPE offset adjuster is configured to adjust said CPE when said total number of said errors exceeds a predetermined error threshold. ### Claim 13 A method for processing a received optical communication signal, comprising: receiving an input signal and providing an output signal representing logic ones and zeros in response to comparing said input signal with a Carrier Phase Estimation (CPE) of said input signal; decoding said output signal and providing a feedback representative of a number of errors corrected by a Forward error Correction (FEC) decoder and indicating a polarity of said input signal; and adjusting said CPE in response to said feedback to reduce the number of said ones and zeros corrected by said FEC decoder. ### Claim 14 (depends on 13) The method of claim 13 further comprising, adjusting said CPE by an offset in a direction determined by the polarity of said input signal. ### Claim 15 (depends on 13) The method of claim 13 further comprising, adjusting said CPE by an offset in a direction determined by a slope of the CPE at a location where the CPE offset begins. ### Claim 16 (depends on 13) The method of claim 13 further comprising, modulating the input signal using a QPSK format. ### Claim 17 (depends on 13) The method of claim 13 wherein providing a feedback representative of a number of errors corrected by a FEC decoder, further comprising adding said number errors corrected by said FEC decoder over one or more sampling periods to determine a total number of said errors corrected by said FEC decoder over said one or more sampling periods, and wherein said CPE offset adjuster is configured to adjust said CPE when said total number of said errors exceeds a predetermined error threshold. ### Claim 18 (depends on 13) The method of claim 13 wherein providing a feedback representative of a number of errors corrected by a FEC decoder, further comprising adding said number errors corrected by said FEC decoder over one or more frame alignment words to determine a total number of said errors corrected by said FEC decoder over said one or more frame alignment words, and wherein said CPE offset adjuster is configured to adjust said CPE when said total number of said errors exceeds a predetermined error threshold.