# US 2017/0285373 A1 · Automatic Endless Polarization Controller For A Silicon-On-Insulator Platform > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0285373 A1 - Document ID: US20170285373A1 - Status: Published application - Kind: A1 - Application number: 15/087,449 - Filed: 2016-03-31 - Published: 2017-10-05 - Earliest claimed: 2016-03-31 - Assignees: Huawei Technologies Co., Ltd. - Inventors: Chunshu Zhang; Jia Jiang; Dominic John Goodwill; Patrick Dumais - Web page: https://patentgrep.com/patent/US20170285373A1 ## CPC - G02F 1/0136: {for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation (G02F1/0353 takes precedence)} - G02B 6/2773: {Polarisation splitting or combining} - G02B 6/29302: {based on birefringence or polarisation, e.g. wavelength dependent birefringence, polarisation interferometers} - G02B 6/29344: {operating by modal interference or beating, i.e. of transverse modes, e.g. zero-gap directional coupler, MMI} - G02F 1/0121: {Operation of devices; Circuit arrangements, not otherwise provided for in this subclass} - G02F 1/2257: {the optical waveguides being made of semiconducting material} - G02F 1/0142: {TE-TM mode conversion} - G02F 1/212: {Mach-Zehnder type} - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A photonic platform based polarization controller providing a fixed target polarization is disclosed. The polarization controller has a polarization rotator splitter splitting the beam into first and second feeds corresponding to first and second orthogonal polarization components. A first Mach-Zehnder interferometer (MZI) stage provides a first phase delay between the first and second feeds based on a first control signal, and a first mixer mixes the first and second feeds to provide third and fourth feeds. A second MZI stage provides a second phase delay between the third and fourth feeds based on a second control signal, and a second mixer mixes the third and fourth feeds to provide fifth and sixth feeds. A third MZI stage provides a third phase delay between the fifth and sixth feeds based on a third control signal, and a third mixer mixes the fifth and sixth feeds to provide the fixed target polarization. An optical tap splits a portion of the beam. ## Claims ### Claim 1 A photonic platform based polarization controller for providing a fixed target polarization of an optical beam having first and second orthogonal polarization components, the polarization controller comprising: a polarization rotator splitter (PRS) for splitting the optical beam into first and second feeds corresponding to the first and second orthogonal polarization components, respectively, wherein the first and second feeds have a same fixed state of polarization; a first Mach-Zehnder interferometer (MZI) stage coupled to the PRS and comprising a first phase shifter for providing a first optical phase delay between the first and second feeds based on a first control signal, and a first mixer for mixing the first and second feeds having the first optical phase delay therebetween, to provide third and fourth feeds; a second MZI stage coupled to the first MZI stage and comprising a second phase shifter for providing a second optical phase delay between the third and fourth feeds based on a second control signal, and a second mixer for mixing the third and fourth feeds having the second optical phase delay therebetween, to provide fifth and sixth feeds; a third MZI stage coupled to the second MZI stage and comprising a third phase shifter for providing a third optical phase delay between the fifth and sixth feeds based on a third control signal, and a third mixer for mixing the fifth and sixth feeds having the third optical phase delay therebetween, to provide the optical beam having the fixed target polarization; and an optical tap optically coupled to the third mixer for splitting a portion of the optical beam. ### Claim 2 (depends on 1) The polarization controller of claim 1 wherein the first and second mixers each comprise a 2×2 optical coupler, and the third mixer comprises a 2×1 optical coupler. ### Claim 3 (depends on 2) The polarization controller of claim 2, wherein the 2×2 and 2×1 optical couplers each comprise a multimode interference optical coupler. ### Claim 4 (depends on 1) The polarization controller of claim 1, further comprising a photodetector optically coupled to the optical tap for providing a photodetector signal based on the portion of the optical beam. ### Claim 5 (depends on 4) The polarization controller of claim 4, further comprising a control module coupled to the photodetector and the first to third phase shifters and configured for providing the first to third control signals to the first to third phase shifters, respectively, for increasing optical power of the optical beam based on the photodetector signal. ### Claim 6 (depends on 5) The polarization controller of claim 5, wherein the control module is configured for gradually lessening a selected one of the first to third control signals when the selected control signal reaches a pre-defined threshold, while adjusting at least another one of the first to third control signals so as to maintain the fixed polarization and optical power level of the optical beam provided by the third mixer. ### Claim 7 (depends on 1) The polarization controller of claim 1, wherein the first to third MZI stages form a three-stage cascaded MZI. ### Claim 8 (depends on 7) The polarization controller of claim 7, absent a four-stage cascaded MZI. ### Claim 9 (depends on 1) The polarization controller of claim 1, wherein the photonic platform comprises silicon on insulator. ### Claim 10 (depends on 9) The polarization controller of claim 9, wherein the target fixed polarization is a transverse electric polarization. ### Claim 11 A photonic platform based polarization controller for providing a fixed target polarization of an input optical beam having first and second orthogonal polarization components, the polarization controller comprising: a polarization rotator splitter (PRS) for splitting the input optical beam into first and second feeds corresponding to the first and second orthogonal polarization components, respectively, wherein the first and second feeds have a same fixed state of polarization; a first phase shifter coupled to the PRS for providing a first optical phase delay between the first and second feeds based on a first control signal, and a first 2×2 optical coupler coupled to the first phase shifter for mixing the first and second feeds having the first optical phase delay therebetween, to provide third and fourth feeds; a second phase shifter coupled to the first 2×2 optical coupler for providing a second optical phase delay between the third and fourth feeds based on a second control signal, and a second 2×2 optical coupler coupled to the second phase shifter for mixing the third and fourth feeds having the second optical phase delay therebetween, to provide fifth and sixth feeds; a third phase shifter coupled to the second 2×2 optical coupler for providing a third optical phase delay between the fifth and sixth feeds based on a third control signal, and an output optical coupler coupled to the third phase shifter for mixing the fifth and sixth feeds having the third optical phase delay therebetween, to provide an output optical beam having the fixed target polarization; and an optical tap optically coupled to the output optical coupler for splitting a portion of the output optical beam. ### Claim 12 (depends on 11) The polarization controller of claim 11, further comprising: a photodetector optically coupled to the optical tap for providing a photodetector signal based on the portion of the optical beam; a control module coupled to the photodetector and the first to third phase shifters and configured for providing the first to third control signals to the first to third phase shifters, respectively, for increasing optical power of the optical beam based on the photodetector signal, wherein the control module is configured for gradually lessening a selected one of the first to third control signals when the selected control signal reaches a pre-defined threshold, while adjusting at least another one of the first to third control signals so as to maintain the fixed polarization and optical power level of the optical beam provided by the third mixer. ### Claim 13 (depends on 12) The polarization controller of claim 12, wherein the target fixed polarization is a transverse electric polarization. ### Claim 14 A method of providing a fixed target polarization of an optical beam having first and second orthogonal polarization components, the method comprising: splitting the optical beam into first and second feeds corresponding to the first and second orthogonal polarization components, respectively, such that the first and second feeds have a same fixed state of polarization; adjusting a first optical phase delay between the first and second feeds based on a first control signal; mixing the first and second feeds having the first optical phase delay therebetween to provide third and fourth feeds; adjusting a second optical phase delay between the third and fourth feeds based on a second control signal; mixing the third and fourth feeds having the second optical phase delay therebetween to provide fifth and sixth feeds; adjusting a third optical phase delay between the fifth and sixth feeds based on a third control signal; mixing the fifth and sixth feeds having the third optical phase delay therebetween to provide the optical beam having the fixed target polarization; and splitting a portion of the optical beam using an optical tap. ### Claim 15 (depends on 14) The method of claim 14 further comprising providing a photodetector signal based on the portion of the optical beam using a photodetector optically coupled to the optical tap. ### Claim 16 (depends on 15) The method of claim 15 further comprising: receiving the photodetector signal at a control module coupled to the photodetector; and providing the first to third control signals to the first to third phase shifters, respectively, for increasing optical power of the optical beam based on the photodetector signal. ### Claim 17 (depends on 16) The method of claim 16 comprising gradually lessening a selected one of the first to third control signals when the selected control signal reaches a pre-defined threshold, while adjusting at least another one of the first to third control signals so as to maintain the fixed polarization and optical power level of the optical beam. ### Claim 18 (depends on 17) The method of claim 17 wherein the target fixed polarization is a transverse electric polarization. ### Claim 19 (depends on 16) The method of claim 16 further comprising determining coarse setting parameters for the first, second and third control signals by scanning using a coarse step size. ### Claim 20 (depends on 19) The method of claim 19 wherein determining the first, second and third control signals comprises scanning using a fine step near the coarse setting parameters.