# US 12,224,803 B2 · Control module, optical signal generator module, and RF-over-fiber system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,224,803 B2 - Document ID: US12224803B2 - Status: Granted - Kind: B2 - Application number: 18/074,324 - Filed: 2022-12-02 - Published: 2024-06-13 - Granted: 2025-02-11 - Earliest claimed: 2022-12-02 - Assignees: Rohde & Schwarz GmbH & Co. KG - Applicants: Rohde & Schwarz GmbH & Co. KG - Inventors: Julius Seeger - Web page: https://patentgrep.com/patent/US12224803B2 ## CPC - H04B 10/516: Details of coding or modulation - G02F 1/0118: {by controlling the evanescent coupling of light from a fibre into an active, e.g. electro-optic, overlay} - G02F 1/0123: {Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops} - G02F 1/2255: {controlled by a high-frequency electromagnetic component in an electric waveguide structure} - H04B 10/2575: Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier - H04B 2210/006: Devices for generating or processing an RF signal by optical means - H04B: TRANSMISSION - 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 A control apparatus for generating a control signal for an electro-optic modulator is described. The control apparatus includes an RF signal source being configured to generate a radio frequency (RF) signal. The control apparatus further includes an amplitude adjustment circuit being configured to adjust an amplitude of the RF signal, thereby obtaining an adjusted RF signal. The control apparatus further includes a DC signal source being configured to generate a direct current (DC) signal. The control apparatus further includes a superposition circuit being configured to superimpose the adjusted RF signal and the DC signal, thereby obtaining the control signal for the electro-optic modulator. The control apparatus further includes a control circuit, wherein the control circuit is configured to receive at least one frequency parameter associated with the electro-optic modulator. The at least one frequency parameter includes a frequency multiplication factor and/or a target modulation frequency. The control circuit is configured to control the DC signal source to adapt a voltage of the DC signal based on the at least one frequency parameter received. Further, an optical signal generator apparatus and an RF-over-fiber system are described. ## Claims ### Claim 1 A control apparatus for generating a control signal for an electro-optic modulator, the control apparatus comprising: an RF signal source being configured to generate a radio frequency (RF) signal; an amplitude adjustment circuit being configured to adjust an amplitude of the RF signal, thereby obtaining an adjusted RF signal, wherein the RF signal is at least one of a periodic signal, a non-modulated signal, or a monochromatic signal; a DC signal source being configured to generate a direct current (DC) signal; a superposition circuit being configured to superimpose the adjusted RF signal and the DC signal, thereby obtaining the control signal for the electro-optic modulator; and a control circuit, wherein the control circuit is configured to receive at least one frequency parameter associated with the electro-optic modulator, wherein the at least one frequency parameter comprises a frequency multiplication factor and/or a target modulation frequency, and wherein the control circuit is configured to control the DC signal source to adapt a voltage of the DC signal based on the at least one frequency parameter received. ### Claim 2 (depends on 1) The control apparatus of claim 1, wherein the control circuit is configured to determine an allowable voltage range for the DC signal based on the at least one frequency parameter received. ### Claim 3 (depends on 2) The control apparatus of claim 2, wherein the control circuit is configured to determine the allowable voltage range based on the amplitude of the adjusted RF signal. ### Claim 4 (depends on 2) The control apparatus of claim 2, wherein the allowable voltage range is configured such that a phase of an output signal of the electro-optic modulator is stable over the allowable voltage range. ### Claim 5 (depends on 2) The control apparatus of claim 2, wherein the allowable voltage range is configured such that a power of an output signal of the electro-optic modulator is larger than a predefined threshold over the allowable voltage range. ### Claim 6 (depends on 1) The control apparatus of claim 1, wherein the frequency multiplication factor is an integer. ### Claim 7 (depends on 1) The control apparatus of claim 1, wherein the control circuit is configured to control the RF signal source to adapt a frequency of the RF signal such that a frequency of the control signal multiplied by the multiplication factor is equal to the target modulation frequency. ### Claim 8 (depends on 1) The control apparatus of claim 1, wherein the control circuit is configured to control the amplitude adjustment circuit based on the at least one frequency parameter received. ### Claim 9 (depends on 8) The control apparatus of claim 8, wherein the control circuit is configured to determine an allowable amplitude range for the RF signal based on the at least one frequency parameter received. ### Claim 10 (depends on 9) The control apparatus of claim 9, wherein the allowable amplitude range is configured such that a resulting amplitude of an output signal of the electro-optic modulator is equal to at least 75% of a maximum possible amplitude of the output signal. ### Claim 11 (depends on 1) The control apparatus of claim 1, wherein the RF signal source is established as a voltage controlled oscillator. ### Claim 12 (depends on 1) The control apparatus of claim 1, wherein the amplitude adjustment circuit comprises at least one of a VVA, a VGA, an attenuator, or an amplifier. ### Claim 13 (depends on 1) The control apparatus of claim 1, wherein the RF signal source is integrated in a direct signal synthesizer (DDS) circuit. ### Claim 14 (depends on 1) The control apparatus of claim 1, wherein the superposition circuit comprises a capacitance that is connected with the amplitude adjustment circuit so as to receive the adjusted RF signal. ### Claim 15 (depends on 1) The control apparatus of claim 1, wherein the superposition circuit comprises an inductance that is connected with the DC signal source so as to receive the DC signal. ### Claim 16 (depends on 1) The control apparatus of claim 1, further comprising a control loop for setting the voltage of the DC signal. ### Claim 17 (depends on 1) An optical signal generator apparatus, comprising a control apparatus according to claim 1, a light source, and an electro-optic modulator, wherein the light source is configured to generate an optical signal, and wherein the electro-optic modulator is configured to modulate the optical signal based on the control signal provided by the control apparatus, thereby obtaining a modulated optical signal. ### Claim 18 (depends on 17) The optical signal generator apparatus of claim 17, wherein the electro-optic modulator is a Mach-Zehnder modulator (MZM). ### Claim 19 (depends on 17) An RF-over-fiber system, the RF over fiber system comprising an optical signal generator apparatus according to claim 17. ### Claim 20 A control apparatus for generating a control signal for an electro-optic modulator, the control apparatus comprising: an RF signal source being configured to generate a radio frequency (RF) signal; an amplitude adjustment circuit being configured to adjust an amplitude of the RF signal, thereby obtaining an adjusted RF signal; a DC signal source being configured to generate a direct current (DC) signal; a superposition circuit being configured to superimpose the adjusted RF signal and the DC signal, thereby obtaining the control signal for the electro-optic modulator; and a control circuit, wherein the control circuit is configured to receive at least one frequency parameter associated with the electro-optic modulator, wherein the at least one frequency parameter comprises a frequency multiplication factor and/or a target modulation frequency, and wherein the control circuit is configured to control the DC signal source to adapt a voltage of the DC signal based on the at least one frequency parameter received, wherein the control circuit is configured to control the RF signal source to adapt a frequency of the RF signal such that a frequency of the control signal multiplied by the multiplication factor is equal to the target modulation frequency.