# US 10,484,123 B2 · Apparatus and method for distributed compensation of narrow optical filtering effects in an optical network > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,123 B2 - Document ID: US10484123B2 - Status: Granted - Kind: B2 - Application number: 16/138,353 - Filed: 2018-09-21 - Published: 2019-01-24 - Granted: 2019-11-19 - Earliest claimed: 2011-12-02 - Assignees: AT&T Intellectual Property I, L.P. - Applicants: AT&T Intellectual Property I, L.P. - Inventors: Xiang Zhou - Web page: https://patentgrep.com/patent/US10484123B2 ## CPC - H04J 14/0212: {using optical switches or wavelength selective switches [WSS]} - 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 The present disclosure describes a reconfigurable optical add-drop multiplexer including a wavelength selective switch configured to filter wavelengths of an optical signal; and an optical equalizer, coupled to the wavelength selective switch, configured to equalize the optical signal to mitigate optical filtering effects caused by the wavelength selective switch. ## Claims ### Claim 1 A method comprising: receiving an optical signal at an optical equalizer; equalizing a spectral shape of a signal of each channel of the optical signal by adjusting a frequency strength of each channel based on optical filtering effects caused by a first wavelength selective switch to mitigate the optical filtering effects and reduce noise degradation of the optical equalizer, the equalizing producing an equalized optical signal; and transmitting the equalized optical signal to a sole input of the first wavelength selective switch. ### Claim 2 (depends on 1) The method of claim 1, wherein the equalizing the spectral shape of the signal of each channel of the optical signal further comprises: mitigating distributed optical filtering effects of a plurality of wavelength routing devices along a transmission link. ### Claim 3 (depends on 2) The method of claim 2, wherein one of the plurality of wavelength routing devices comprises a second wavelength selective switch. ### Claim 4 (depends on 2) The method of claim 2, wherein the plurality of wavelength routing devices along the transmission link are downstream of the optical equalizer. ### Claim 5 (depends on 4) The method of claim 4, wherein the optical equalizer precompensates the optical signal based on the distributed optical filtering effects of the plurality of wavelength routing devices. ### Claim 6 (depends on 1) The method of claim 1, wherein the optical equalizer is a liquid crystal on silicon based optical equalizer having a loss of less than 7 dB. ### Claim 7 (depends on 1) The method of claim 1, wherein the equalizing the spectral shape of the signal of each channel of the optical signal is further based on optical filtering effects caused by wavelength routing devices upstream of the optical equalizer. ### Claim 8 A reconfigurable optical add-drop multiplexer comprising: a first wavelength selective switch having an input; and an optical equalizer, coupled to the input of the first wavelength selective switch, to equalize a spectral shape of a signal of each channel of an optical signal by adjusting a frequency strength of each channel based on optical filtering effects caused by the first wavelength selective switch to mitigate the optical filtering effects and reduce noise degradation of the optical equalizer. ### Claim 9 (depends on 8) The reconfigurable optical add-drop multiplexer of claim 8, wherein the spectral shape of the signal of each channel of the optical signal is equalized by mitigating distributed optical filtering effects of a plurality of wavelength routing devices along a transmission link. ### Claim 10 (depends on 9) The reconfigurable optical add-drop multiplexer of claim 9, wherein one of the plurality of wavelength routing devices comprises a second wavelength selective switch. ### Claim 11 (depends on 9) The reconfigurable optical add-drop multiplexer of claim 9, wherein the plurality of wavelength routing devices along the transmission link are downstream of the optical equalizer. ### Claim 12 (depends on 11) The reconfigurable optical add-drop multiplexer of claim 11, wherein the optical equalizer precompensates the optical signal based on the distributed optical filtering effects of the plurality of wavelength routing devices. ### Claim 13 (depends on 8) The reconfigurable optical add-drop multiplexer of claim 8, wherein the optical equalizer is a liquid crystal on silicon based optical equalizer having a loss of less than 7 dB. ### Claim 14 (depends on 8) The reconfigurable optical add-drop multiplexer of claim 8, wherein the spectral shape of the signal of each channel of the optical signal is equalized by mitigating optical filtering effects caused by wavelength routing devices upstream of the optical equalizer. ### Claim 15 A method comprising: receiving an optical signal at an optical equalizer from a wavelength routing device; equalizing a spectral shape of a signal of each channel of the optical signal by adjusting a frequency strength of each channel based on optical filtering effects caused by a first wavelength selective switch to mitigate the optical filtering effects and reduce noise degradation of the optical equalizer, the equalizing producing an equalized optical signal; and transmitting the equalized optical signal to a sole input of the first wavelength selective switch. ### Claim 16 (depends on 15) The method of claim 15, wherein the equalizing the spectral shape of the signal of each channel of the optical signal further comprises: mitigating distributed optical filtering effects of a plurality of wavelength routing devices along a transmission link. ### Claim 17 (depends on 16) The method of claim 16, wherein one of the plurality of wavelength routing devices comprises a second wavelength selective switch. ### Claim 18 (depends on 16) The method of claim 16, wherein the plurality of wavelength routing devices along the transmission link are downstream of the optical equalizer. ### Claim 19 (depends on 18) The method of claim 18, wherein the optical equalizer precompensates the optical signal based on the distributed optical filtering effects of the plurality of wavelength routing devices. ### Claim 20 (depends on 15) The method of claim 15, wherein the optical equalizer is a liquid crystal on silicon based optical equalizer having a loss of less than 7 dB.