# US 11,909,444 B2 · Method for an all fiber optic, polarization insensitive, etalon based optical receiver for coherent signals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,909,444 B2 - Document ID: US11909444B2 - Status: Granted - Kind: B2 - Application number: 17/670,119 - Filed: 2022-02-11 - Published: 2023-08-17 - Granted: 2024-02-20 - Earliest claimed: 2022-02-11 - Assignees: Raytheon Company - Applicants: Raytheon Company - Inventors: James Talamonti; Andrew Kowalevicz; Gary M. Graceffo; Benjamin P. Dolgin - Web page: https://patentgrep.com/patent/US11909444B2 ## CPC - H04B 10/2581: Multimode transmission - H04B 10/676: {for all-optical demodulation of the input optical signal} - H04B 10/071: using a reflected signal, e.g. using optical time domain reflectometers [OTDR] - H04B 10/615: {Arrangements affecting the optical part of the receiver} - H04B 10/67: Optical arrangements in the receiver - H04B: TRANSMISSION ## Abstract An optical signal receivers, systems including the optical signal receivers, and methods of operating the same include a multimode fiber circulator including a first port, a second port, and a third port, a first multimode fiber cable coupled to the first port and having an input configured to receive a complex modulated optical signal and provide the complex modulated optical signal to the first port of the multimode fiber circulator, a second multimode fiber cable including a low Q optical resonator coupled to the second port of the multimode fiber circulator that is configured to receive the complex modulated optical signal from the second port of the multimode circulator, and a third multimode fiber cable coupled to the third port of the multimode fiber circulator that is configured to receive a reflected optical signal from the third port of the multimode circulator, the reflected optical signal being reflected from the low Q optical resonator. ## Claims ### Claim 1 An optical signal receiver comprising: a multimode fiber circulator including a first port, a second port, and a third port; a first multimode fiber cable coupled to the first port and having an input configured to receive a complex modulated optical signal and provide the complex modulated optical signal to the first port of the multimode fiber circulator; a second multimode fiber cable including a low Quality (Q) factor optical resonator coupled to the second port of the multimode fiber circulator that is configured to receive the complex modulated optical signal from the second port of the multimode circulator; and a third multimode fiber cable coupled to the third port of the multimode fiber circulator that is configured to receive a reflected optical signal from the third port of the multimode circulator, the reflected optical signal being reflected from the low Q optical resonator; wherein the resonator of the receiver accounts for any wavefront distortion for detection without any adaptive optics and any local oscillators or mixers for measuring phase of the complex modulated optical signal. ### Claim 2 (depends on 1) The optical signal receiver of claim 1 wherein the low Q optical resonator is a Fabry-Perot interferometer. ### Claim 3 (depends on 2) The optical signal receiver of claim 2 wherein the Fabry-Perot interferometer is an in-line etalon. ### Claim 4 (depends on 3) The optical signal receiver of claim 3 wherein the in-line etalon is fabricated as part of the second multimode fiber cable. ### Claim 5 (depends on 3) The optical signal receiver of claim 3 wherein the in-line etalon is optically bonded to the second multimode fiber cable. ### Claim 6 (depends on 1) The optical signal receiver of claim 1 further comprising collimating optics coupled to the input of the first multimode fiber cable. ### Claim 7 (depends on 1) The optical signal receiver of claim 1 wherein the low Q optical resonator is configured to receive the complex modulated optical signal having a predetermined data rate and one or more symbols each having a predetermined length, wherein the predetermined length is larger than a decay time of the complex modulated optical signal in the low Q optical resonator. ### Claim 8 (depends on 1) The optical signal receiver of claim 1 wherein the low Q optical resonator is further configured to convert the complex modulated optical signal to an intensity modulated signal, and the optical signal receiver further comprises: a first detector coupled to an output of the low Q optical resonator via a multimode fiber cable, the first detector configured to convert the intensity modulated signal into an electrical signal, the electrical signal having an amplitude indicative of an intensity of the intensity modulated signal from the optical resonator, and that provides a detected signal; and/or a second detector coupled to an output of the third multimode fiber cable that is configured to convert the reflected optical signal into an electrical signal. ### Claim 9 (depends on 8) The optical signal receiver of claim 8, further comprising a processor coupled to an output of the first detector that receives and processes the electrical signal from the first detector to determine information encoded in the complex modulated optical signal. ### Claim 10 An optical system comprising: a transmitter that transmits a complex modulated optical signal; and an optical signal receiver that receives the complex modulated optical signal over the medium, the optical signal receiver including: a multimode fiber circulator including a first port, a second port, and a third port; a first multimode fiber cable coupled to the first port and having an input configured to receive the complex modulated optical signal and provide the complex modulated optical signal to the first port of the multimode fiber circulator; a second multimode fiber cable including a low Quality (Q) factor optical resonator coupled to the second port of the multimode fiber circulator that is configured to receive the complex modulated optical signal from the second port of the multimode circulator; and a third multimode fiber cable coupled to the third port of the multimode fiber circulator that is configured to receive a reflected optical signal from the third port of the multimode circulator, the reflected optical signal being reflected from the low Q optical resonator; wherein the resonator of the receiver accounts for any wavefront distortion for detection without any adaptive optics and any local oscillators or mixers for measuring phase of the complex modulated optical signal. ### Claim 11 (depends on 10) The optical system of claim 10 wherein the low Q optical resonator is a Fabry-Perot interferometer. ### Claim 12 (depends on 11) The optical system of claim 11 wherein the Fabry-Perot interferometer is an in-line etalon. ### Claim 13 (depends on 12) The optical system of claim 12 wherein the in-line etalon is fabricated as part of the second multimode fiber cable. ### Claim 14 (depends on 12) The optical system of claim 12 wherein the in-line etalon is optically bonded to the second multimode fiber cable. ### Claim 15 (depends on 10) The optical system of claim 10 wherein the optical receiver further comprises collimating optics coupled to the input of the first multimode fiber cable. ### Claim 16 (depends on 10) The optical system of claim 10 wherein the low Q optical resonator is configured to receive the complex modulated optical signal having a predetermined data rate and one or more symbols each having a predetermined length, wherein the predetermined length is larger than a decay time of the complex modulated optical signal in the low Q optical resonator. ### Claim 17 (depends on 10) The optical system of claim 10 wherein the low Q optical resonator is further configured to convert the complex modulated optical signal to an intensity modulated signal, and the optical signal receiver further comprises: a first detector coupled to an output of the low q optical resonator via a multimode fiber cable, the first detector configured to convert the intensity modulated signal into an electrical signal, the electrical signal having an amplitude indicative of an intensity of the intensity modulated signal from the optical resonator, and that provides a detected signal; and/or a second detector coupled to an output of the third multimode fiber cable that is configured to convert the reflected optical signal into an electrical signal. ### Claim 18 (depends on 17) The optical system of claim 17 further comprising a processor coupled to an output of the first detector that receives and processes the electrical signal from the first detector to determine information encoded in the complex modulated optical signal.