# US 10,871,662 B2 · Linearization and reduction of modulated optical insertion loss for quadrature optical modulator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,871,662 B2 - Document ID: US10871662B2 - Status: Granted - Kind: B2 - Application number: 16/559,962 - Filed: 2019-09-04 - Published: 2020-03-12 - Granted: 2020-12-22 - Earliest claimed: 2018-09-06 - Assignees: II-Vi Delaware, Inc. - Applicants: Finisar Corporation - Inventors: Suhas P. Bhandare; Daniel Mahgerefteh - Web page: https://patentgrep.com/patent/US10871662B2 ## CPC - G02F 1/0123: {Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops} - 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)} - G02F 1/21: by interference - 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 ## Abstract An optical Mach-Zehnder superstructure modulator and method that can simultaneously linearize in-phase and quadrature components of optically modulated optical signals and reduce the modulated optical insertion loss (MOIL) by in-phase addition of the in-phase and quadrature components of an amplitude and/or phase modulated optical signal using two high-speed phase modulators embedded in the optical Mach-Zehnder superstructure modulator. ## Claims ### Claim 1 A method of modulating an optical Mach-Zehnder superstructure modulator, the method comprising: a) applying a first modulation signal to a first child Mach-Zehnder interferometric modulator positioned in a first arm of the optical Mach-Zehnder superstructure modulator to impart a first modulation phase on a first optical signal; b) applying a second modulation signal to a second child Mach-Zehnder interferometric modulator positioned in a second arm of the optical Mach-Zehnder superstructure modulator to impart a second modulation phase on a second optical signal; c) phase shifting the first optical signal by applying a first AC bias signal to the first arm of the optical Mach-Zehnder superstructure; d) phase shifting the second optical signal by applying a second AC bias signal to the second arm of the optical Mach-Zehnder superstructure; and e) interferometically combining the first optical signal and the second optical signal to generate an output optical signal at an output, wherein at least one of the first and second AC bias signal is a function of at least one of the first and second modulation signal. ### Claim 2 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein an angle of a phase shift on the first optical signal and an angle of a phase shift on the second optical signal are complementary angles. ### Claim 3 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 further comprising biasing the optical Mach-Zehnder superstructure modulator to a quadrature bias point. ### Claim 4 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein applying the first modulation signal to the first child Mach-Zehnder interferometric modulator comprises applying a phase shift keying modulation signal. ### Claim 5 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein applying the first modulation signal to the first child Mach-Zehnder interferometric modulator comprises applying an in-phase phase shift keying modulation signal. ### Claim 6 (depends on 5) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 5 wherein applying the second modulation signal to the second child Mach-Zehnder interferometric modulator comprises applying a quadrature phase shift keying modulation signal. ### Claim 7 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein applying the first modulation signal to the first child Mach-Zehnder interferometric modulator comprises applying an amplitude modulation signal. ### Claim 8 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein applying the first modulation signal to the first child Mach-Zehnder interferometric modulator comprises applying an in-phase amplitude modulation signal. ### Claim 9 (depends on 8) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 8 wherein applying the second modulation signal to the second child Mach-Zehnder interferometric modulator comprises applying a quadrature amplitude modulation signal. ### Claim 10 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein applying the first modulation signal to the first child Mach-Zehnder interferometric modulator comprises applying a Vπ peak-to-peak voltage swing. ### Claim 11 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein applying the first modulation signal to the first child Mach-Zehnder interferometric modulator comprises applying a 2Vπ peak-to-peak voltage swing. ### Claim 12 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein at least one of the first and second AC bias signal changes based on a particular symbol encoded in at least one of the first and second modulation signal. ### Claim 13 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein at least one of the first and second AC bias signals are chosen to provide a desired modulated optical insertion loss (MOIL) of the optical Mach-Zehnder superstructure modulator. ### Claim 14 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein at least one of the first and second AC bias signals are chosen to provide a reduction of a modulated optical insertion loss (MOIL) of the optical Mach-Zehnder superstructure modulator. ### Claim 15 (depends on 14) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 14 wherein the reduction of the modulated optical insertion loss (MOIL) of the optical Mach-Zehnder superstructure modulator comprises a 3 dB reduction of the modulated optical insertion loss (MOIL). ### Claim 16 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein at least one of the first and second AC bias signals are chosen to provide a desired linearity of the output optical signal. ### Claim 17 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein at least one of the first and second AC bias signals are chosen to provide a desired Hamming distance of the output optical signal. ### Claim 18 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein phase shifting the first optical signal by applying the first AC bias signal to the first arm of the optical Mach-Zehnder superstructure comprises consulting a look-up table that stores data-dependent phase angles. ### Claim 19 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein the optical Mach-Zehnder superstructure modulator is constructed using at least one of Lithium Niobate, Indium Phosphide, Gallium Arsenide, and/or Silicon Photonics technology. ### Claim 20 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 wherein the output optical signal comprises at least one of a DPSK, QPSK, 8QAM, 16 QAM, and 64 QAM optical signal. ### Claim 21 (depends on 1) The method of modulating an optical Mach-Zehnder superstructure modulator of claim 1 further comprising polarization multiplexing the output optical signal.