# US 10,374,709 B2 · Chromatic dispersion management > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,374,709 B2 - Document ID: US10374709B2 - Status: Granted - Kind: B2 - Application number: 15/655,795 - Filed: 2017-07-20 - Published: 2019-01-24 - Granted: 2019-08-06 - Earliest claimed: 2017-07-20 - Assignees: Facebook, Inc. - Applicants: Facebook, Inc. - Inventors: Ilya Lyubomirsky - Web page: https://patentgrep.com/patent/US10374709B2 ## CPC - H04B 10/2513: due to chromatic dispersion - H04B 10/07951: {Monitoring or measuring chromatic dispersion or PMD} - H04B 10/25133: {including a lumped electrical or optical dispersion compensator (H04B10/2519, H04B10/2525 takes precedence)} - H04B 10/5161: {Combination of different modulation schemes} - H04B 10/612: {for optical signals modulated with a format different from binary or higher-order PSK [X-PSK], e.g. QAM, DPSK, FSK, MSK, ASK} - H04B 10/6161: {Compensation of chromatic dispersion} - H04J 14/0201: {Add-and-drop multiplexing} - H04J 14/0256: {at the optical channel layer} - H04B: TRANSMISSION - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) ## Abstract Optical fiber data communications are described. A controller can determine chromatic dispersion of an optical signal that is to be demodulated using coherent detection. The controller can then determine the chromatic dispersion of another optical signal that is to be demodulated using direct detection. The chromatic dispersion of the other optical signal can then be adjusted to account for chromatic dispersion experienced by the other optical signal when it propagated through an optical fiber. ## Claims ### Claim 1 An optical fiber data communications system, comprising: a chromatic dispersion determining circuit configured to determine chromatic dispersion of a first optical signal to be demodulated using direct detection, the determination of the chromatic dispersion of the first optical signal based on information indicative of chromatic dispersion of a second optical signal to be demodulated using coherent detection, wherein the chromatic dispersion determining circuit is configured to determine phase information of the second optical signal and further configured to determine the information indicative of chromatic dispersion of the second optical signal based on the determined phase information; and a chromatic dispersion reversing module configured to apply a chromatic dispersion adjustment to adjust the chromatic dispersion of the first optical signal based on the determination of the chromatic dispersion of the first optical signal, wherein the chromatic dispersion reversing module is further configured to determine the chromatic dispersion adjustment that reverses at least a portion of the chromatic dispersion of the first optical signal. ### Claim 2 (depends on 1) The optical fiber data communications system of claim 1, wherein the first optical signal provides information based on intensity modulation, and the second optical signal provides information based on phase modulation. ### Claim 3 (depends on 1) The optical fiber data communications system of claim 1, wherein the information indicative of the chromatic dispersion of the second optical signal is a phase of the second optical signal. ### Claim 4 (depends on 1) The optical fiber data communications system of claim 1, wherein the chromatic dispersion adjustment applied to the first optical signal is based on chromatic dispersion associated with an optical fiber that the first optical signal and the second optical signal propagate through. ### Claim 5 (depends on 1) The optical fiber data communications system of claim 1, wherein determining the chromatic dispersion of the first optical signal is based on extrapolating the chromatic dispersion of the second optical signal to the first optical signal, the first optical signal and the second optical signal being at different wavelengths. ### Claim 6 (depends on 1) The optical fiber data communications system of claim 1, further comprising: a first transponder to receive the first optical signal and configured to demodulate the first optical signal using direct detection; and a second transponder to receive the second optical signal and configured to demodulate the second optical signal using coherent detection. ### Claim 7 (depends on 6) The optical fiber data communications system of claim 6, wherein the information indicative of chromatic dispersion of the second optical signal is based on a phase of the second optical signal determined using coherent detection. ### Claim 8 An optical fiber data communications system managing chromatic dispersion configured to determine characteristics of a first optical signal corresponding with coherent detection, and configured to reverse at least a portion of dispersion of a second optical signal corresponding with direct detection based on the characteristics of the first optical signal corresponding with coherent detection. ### Claim 9 (depends on 8) The optical fiber data communications system managing chromatic dispersion of claim 8, wherein the characteristics of the first optical signal include dispersion of the first optical signal. ### Claim 10 (depends on 8) The optical fiber data communications system managing chromatic dispersion of claim 8, wherein the characteristics of the first optical signal include a phase of the first optical signal. ### Claim 11 (depends on 8) The optical fiber data communications system managing chromatic dispersion of claim 8, wherein the first optical signal provides information based on phase modulation, and the second optical signal provides information based on intensity modulation. ### Claim 12 (depends on 8) The optical fiber data communications system managing chromatic dispersion of claim 8, wherein the characteristics of the first optical signal are indicative of dispersion of the first optical signal. ### Claim 13 (depends on 12) The optical fiber data communications system managing chromatic dispersion of claim 12, further configured to determine dispersion of the second optical signal based on the characteristics of the first optical signal that are indicative of the dispersion of the first optical signal. ### Claim 14 (depends on 13) The optical fiber data communications system managing chromatic dispersion of claim 13, wherein the dispersion of the second optical signal is determined based on an extrapolation of the dispersion of the first optical signal. ### Claim 15 (depends on 8) The optical fiber data communications system managing chromatic dispersion of claim 8, wherein the first optical signal and the second optical signal are at different wavelengths. ### Claim 16 A method, comprising: determining characteristics of a first optical signal corresponding to coherent detection; determining chromatic dispersion of a second optical signal corresponding to direct detection based on the characteristics of the first optical signal; and reversing at least a portion of the chromatic dispersion of the second optical signal based on the determination of the chromatic dispersion of the second optical signal. ### Claim 17 (depends on 16) The method of claim 16, wherein the characteristics of the first optical signal are indicative of chromatic dispersion of the first optical signal. ### Claim 18 (depends on 16) The method of claim 16, wherein the characteristics of the first optical signal include a phase of the first optical signal. ### Claim 19 (depends on 16) The method of claim 16, wherein the chromatic dispersion of the second optical signal is adjusted to account for chromatic dispersion experienced by the second optical signal as it propagated through an optical fiber. ### Claim 20 (depends on 16) The method of claim 16, wherein the first optical signal provides information based on phase modulation, and the second optical signal provides information based on intensity modulation.