# US 12,184,333 B2 · Optical multiple-input-multiple-output (MIMO) demultiplexers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,184,333 B2 - Document ID: US12184333B2 - Status: Granted - Kind: B2 - Application number: 17/485,215 - Filed: 2021-09-24 - Published: 2023-03-30 - Granted: 2024-12-31 - Earliest claimed: 2021-09-24 - Assignees: Aloe Semiconductor Inc. - Applicants: Aloe Semiconductor Inc. - Inventors: Christopher R. Doerr - Web page: https://patentgrep.com/patent/US12184333B2 ## CPC - H04B 10/5053: {using a parallel, i.e. shunt, combination of modulators} - H04J 14/06: Polarisation multiplex systems - H04B 10/505: {using external modulation} - H04B 10/556: Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK] - H04B 10/614: {comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers (H04J14/06 takes precedence)} - H04B 10/6166: {Polarisation demultiplexing, tracking or alignment of orthogonal polarisation components} - H04J 14/0307: {Multiplexers; Demultiplexers} - 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 A 2×2 optical multi-input-multi-output (MIMO) demultiplexer is disclosed. A first optical phase shifter applies a first relative phase shift between a first pair of optical transmission paths that are received from MIMO inputs, and a first 2×2 optical coupler combines the first pair of optical transmission paths and outputs a second pair of optical transmission paths. A second optical phase shifter applies a second relative phase shift between the second pair of optical transmission paths, and a second 2×2 optical coupler combines the second pair of optical transmission paths and outputs a third pair of optical transmission paths. A third optical phase shifter applies a third relative phase shift between the third pair of optical transmission paths, and a third 2×2 optical coupler combines the third pair of optical transmission paths and outputs a fourth pair of optical transmission paths, which are output by a pair of MIMO outputs. ## Claims ### Claim 1 A 2×2 optical multi-input-multi-output (MIMO) demultiplexer, comprising: a pair of MIMO inputs configured to input light into a first pair of optical transmission paths; a first optical phase shifter configured to apply a first relative phase shift between the first pair of optical transmission paths; a first 2×2 optical coupler configured to combine the first pair of optical transmission paths and output a second pair of optical transmission paths; a second optical phase shifter configured to apply a second relative phase shift between the second pair of optical transmission paths; a second 2×2 optical coupler configured to combine the second pair of optical transmission paths and output a third pair of optical transmission paths; a third optical phase shifter configured to apply a third relative phase shift between the third pair of optical transmission paths; a third 2×2 optical coupler configured to combine the third pair of optical transmission paths and output a fourth pair of optical transmission paths; a pair of MIMO outputs configured to output the fourth pair of optical transmission paths, which are output from the third 2×2 optical coupler, as a pair of demultiplexed output light signals; and a controller configured to control the first optical phase shifter to apply a value of the first relative phase shift that varies in a discontinuous manner, control the second optical phase shifter to apply a value of the second relative phase shift that varies in a continuous manner, and control the third optical phase shifter to apply a value of the third relative phase shift that varies in a continuous manner. ### Claim 2 (depends on 1) The 2×2 optical MIMO demultiplexer of claim 1, wherein the controller is configured to control the first optical phase shifter such that the value of the first relative phase shift varies in a binary manner. ### Claim 3 (depends on 2) The 2×2 optical MIMO demultiplexer of claim 2, wherein the value of the first relative phase shift is binary between c+π/2 and c−π/2, where c is a real number. ### Claim 4 (depends on 1) The 2×2 optical MIMO demultiplexer of claim 1, wherein the controller is configured to control the second optical phase shifter such that the value of the second relative phase shift is continuous within a finite range that includes −nπ and +nπ, where n is an integer. ### Claim 5 (depends on 4) The 2×2 optical MIMO demultiplexer of claim 4, wherein the controller is configured to control the second optical phase shifter in an analog manner such that the value of the second relative phase shift various continuously within a range (−nπ, +nπ). ### Claim 6 (depends on 1) The 2×2 optical MIMO demultiplexer of claim 1, wherein the controller is configured to control the third optical phase shifter such that the value of the third relative phase shift varies within a finite range that depends on the value of the first relative phase shift. ### Claim 7 (depends on 6) The 2×2 optical MIMO demultiplexer of claim 6, wherein the controller is configured to control the third optical phase shifter such that the value of the third relative phase shift is between 0 and +nπ, based on the value of the first relative phase shift being c−π/2, and such that the value of the third relative phase shift is between −nπ and 0, based on the value of the first relative phase shift being c+π/2, where n is an integer and where c is a real number. ### Claim 8 (depends on 6) The 2×2 optical MIMO demultiplexer of claim 6, wherein the controller is configured to control the third optical phase shifter in an analog manner such that the value of the third relative phase shift various continuously within a range (0, +nπ) or within a range (−nπ, 0). ### Claim 9 (depends on 1) The 2×2 optical MIMO demultiplexer of claim 1, wherein the controller comprises: at least one processor; and at least one memory storing instructions that, based on being executed by the at least one processor, cause the at least one processor to control the first optical phase shifter, the second optical phase shifter, and the third optical phase shifter. ### Claim 10 (depends on 1) The 2×2 optical MIMO demultiplexer of claim 1, further comprising a first optical attenuator configured to apply a first relative attenuation between the first pair of optical transmission paths. ### Claim 11 (depends on 10) The 2×2 optical MIMO demultiplexer of claim 10, further comprising a second optical attenuator configured to apply a second relative attenuation between the third pair of optical transmission paths. ### Claim 12 (depends on 1) The 2×2 optical MIMO demultiplexer of claim 1, wherein each of the first optical phase shifter, the second optical phase shifter, and the third optical phase shifter have a phase shifting range that is less than or equal to 2π. ### Claim 13 An optical multi-input-multi-output (MIMO) receiver, comprising: an input port configured to receive input light; means for performing adaptive 2×2 optical MIMO polarization demultiplexing on the input light using 3-stage optical phase-shifting to output a first optical signal and a second optical signal, the means comprising a first optical phase shifter controlled to apply a first relative phase shift that varies in a discontinuous manner, a second optical phase shifter controlled to apply a second relative phase shift that varies in a continuous manner, and a third optical phase shifter controlled to apply a third relative phase shift that varies in a continuous manner; and at least one photodetector configured to detect the first optical signal and the second optical signal. ### Claim 14 A method of performing 2×2 optical multi-input-multi-output (MIMO) demultiplexing, the method comprising: receiving light through a pair of MIMO inputs into a first pair of optical transmission paths; controlling a first optical phase shifter to apply a first relative phase shift between the first pair of optical transmission paths, the first relative phase shift varying in a discontinuous manner; combining the first pair of optical transmission paths with a first 2×2 optical coupler to output a second pair of optical transmission paths; controlling a second optical phase shifter to apply a second relative phase shift between the second pair of optical transmission paths, the second relative phase shift varying in a continuous manner; combining the second pair of optical transmission paths with a second 2×2 optical coupler to output a third pair of optical transmission paths; controlling a third optical phase shifter to apply a third relative phase shift between the third pair of optical transmission paths, the third relative phase shift varying in a continuous manner; combining the third pair of optical transmission paths with a third 2×2 optical coupler to output a fourth pair of optical transmission paths; and outputting the fourth pair of optical transmission paths through a pair of MIMO outputs, which are output from the third 2×2 optical coupler, as a pair of demultiplexed output light signals. ### Claim 15 (depends on 14) The method of claim 14, wherein controlling the first optical phase shifter comprises applying a value of the first relative phase shift that various discontinuously between binary values. ### Claim 16 (depends on 15) The method of claim 15, wherein the value of the first relative phase shift is binary between c+π/2 and c−π/2, where c is a real number. ### Claim 17 (depends on 14) The method of claim 14, wherein controlling the second optical phase shifter comprises applying a value of the second relative phase shift that is continuous within a finite range that includes −nπ and +nπ, where n is an integer. ### Claim 18 (depends on 17) The method of claim 17, wherein controlling the second optical phase shifter is performed by analog operation within a range (−nπ, +nπ). ### Claim 19 (depends on 14) The method of claim 14, wherein controlling the third optical phase shifter comprises applying a value of the third relative phase shift that varies within a finite range that depends on a value of the first relative phase shift. ### Claim 20 (depends on 19) The method of claim 19, wherein controlling the third optical phase shifter further comprises: controlling the third optical phase shifter to operate between 0 and +nπ, based on the value of the first relative phase shift being c−π/2, and to operate between −nπ and 0, based on the value of the first relative phase shift being c+π/2, where n is an integer and where c is a real number. ### Claim 21 (depends on 19) The method of claim 19, wherein controlling the third optical phase shifter is performed by analog operation within a range (0, +nπ) or within a range (−nπ, 0), depending on the value of the first relative phase shift. ### Claim 22 (depends on 14) The method of claim 14, further comprising: detecting a first reference signal on a first polarization channel in a first MIMO output of the pair of MIMO outputs, detecting a second reference signal on a second polarization channel in a second MIMO output of the pair of MIMO outputs, determining an amount of error in demultiplexing measured from the first reference signal and the second reference signal; and controlling at least one of the first optical phase shifter, the second optical phase shifter, or the third optical phase shifter based on the amount of error measured from the first reference signal and the second reference signal. ### Claim 23 (depends on 14) The method of claim 14, wherein the 2×2 optical MIMO demultiplexing is performed in an endless manner without resetting any of the first optical phase shifter, the second optical phase shifter, or the third optical phase shifter during operation.