# US 2021/0240050 A1 · Integrated Modulator Structure for In-situ Power Balancing in Photonic Fiber Optic Gyroscopes > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0240050 A1 - Document ID: US20210240050A1 - Status: Published application - Kind: A1 - Application number: 17/161,064 - Filed: 2021-01-28 - Published: 2021-08-05 - Earliest claimed: 2020-01-30 - Assignees: KVH Industries, Inc. - Applicants: KVH Industries, Inc. - Inventors: Jan Amir Khan - Web page: https://patentgrep.com/patent/US20210240050A1 ## CPC - G02F 1/212: {Mach-Zehnder type} - G01C 19/721: {Details, e.g. optical or electronical details} - G01C 19/725: {using nxn optical couplers, e.g. 3x3 couplers} - G02F 1/2252: {in optical fibres} - 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 - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) ## Abstract A light amplitude balancing system for use in a photonic integrated circuit (PIC)-based fiber optic gyroscope (FOG) may comprise one or more 2×2 PIC-based FOG optical circuits and a PIC-based modulator assembly. The modulator assembly may be configured to receive one or more input light signals, and to produce one or more output light signals that (i) correspond to the input light signals and (ii) are conveyed to the one or more FOG optical circuits. Each of the one or more output light signals may have an amplitude that is a modified version of an amplitude of the corresponding input signal. The one or more FOG optical circuits and the PIC-based modulator assembly may be disposed on a common PIC substrate. Alternatively, the one or more FOG optical circuits may be disposed on a first PIC substrate, and the PIC-based modulator assembly may be disposed on a second PIC substrate. ## Claims ### Claim 1 A light amplitude control system for use in a photonic integrated circuit (PIC)-based fiber optic gyroscope (FOG), comprising: one or more 2×2 PIC-based FOG optical circuits; a PIC-based modulator assembly configured to receive one or more input light signals, and to produce one or more output light signals that (i) correspond to the one or more input light signals and (ii) are conveyed to the one or more 2×2 PIC-based FOG optical circuits, each of the one or more output light signals having an amplitude that is a modified version of an amplitude of the corresponding input signal. ### Claim 2 (depends on 1) The light amplitude control system of claim 1, wherein the one or more 2×2 PIC-based FOG optical circuits and the PIC-based modulator assembly are disposed on a common PIC substrate. ### Claim 3 (depends on 1) The light amplitude control system of claim 1, wherein the one or more 2×2 PIC-based FOG optical circuits are disposed on a first PIC substrate, and the PIC-based modulator assembly is disposed on a second PIC substrate. ### Claim 4 (depends on 1) The light amplitude control system of claim 1, further comprising a one port to three port (1:3) coupler configured to receive a source light signal from a light source, to split the source light signal into two or more substantially equal composite light signals, and to provide the two or more composite light signals to the PIC-based modulator assembly as the one or more input light signals. ### Claim 5 (depends on 1) The light amplitude control system of claim 1, wherein the light source is super luminescent diode (SLD). ### Claim 6 (depends on 1) The light amplitude control system of claim 1, wherein the PIC-based modulator assembly comprises an optical modulator associated with each of the one or more output light signals, and wherein each optical modulator is configured to modify the amplitude of the corresponding input signal to produce the associated output light signal. ### Claim 7 (depends on 6) The light amplitude control system of claim 6, wherein each optical modulator comprises a Mach-Zehnder Interferometer (MZI) configuration modulator. ### Claim 8 (depends on 7) The light amplitude control system of claim 7, wherein the MZI configuration modulator comprises at least one of (i) a cascade MZI, (ii) a parallel MZI, (iii) an MZI-based ring resonator cavity, and/or combinations thereof. ### Claim 9 (depends on 7) The light amplitude control system of claim 7, wherein the MZI configuration modulator is based on at least one of (i) thermo-optic phase shifter-based modulation, PN junction-based modulation, or absorption-based modulation. ### Claim 10 (depends on 7) The light amplitude control system of claim 7, wherein the MZI configuration modulator comprises a first optical path and a second optical path, wherein the first optical path is effectively within a decoherence length of the second optical path. ### Claim 11 (depends on 10) The light amplitude control system of claim 10, wherein an integrated refractive index-based modulator is associated with the first optical path and no optical modulator is associated with the second optical path. ### Claim 12 (depends on 10) The light amplitude control system of claim 10, wherein a first integrated refractive index-based modulator is associated with the first optical path and a second integrated refractive index-based modulator is associated with the second optical path. ### Claim 13 (depends on 7) The light amplitude control system of claim 7, wherein an integrated refractive index-based modulator that is associated with the MZI configuration modulator is constructed as one of (i) an in-plane structure or (ii) an overlay structure. ### Claim 14 (depends on 7) The light amplitude control system of claim 7, wherein an electro-absorptive modulator is associated with at least one optical path of the MZI configuration modulator. ### Claim 15 (depends on 6) The light amplitude control system of claim 6, wherein each optical modulator comprises at least one of an electro-absorptive modulator and/or an electro-refractive modulator. ### Claim 16 (depends on 6) The light amplitude control system of claim 6, further comprising a controller configured (i) to receive information about amplitude of light along an optical path associated with each optical modulator, and (ii) to send a control signal to each optical modulator, wherein each optical modulator is configured to modify the amplitude of the corresponding input signal based on the control signal. ### Claim 17 (depends on 16) The light amplitude control system of claim 16, wherein the controller is configured to generate the respective control signal to each optical modulator to balance optical power across the optical paths associated with the one or more output light signals. ### Claim 18 (depends on 16) The light amplitude control system of claim 16, wherein each optical modulator controls the amplitude of light propagating in its respective optical path independent of optical paths associated with other optical modulators. ### Claim 19 (depends on 6) The light amplitude control system of claim 6, wherein the optical modulator is an electro-absorptive modulator implemented directly in an optical path between one of the one or more input light signals and one of the one or more output light signals. ### Claim 20 A PIC-based modulator assembly, comprising: an optical splitter configured to receive an input light signal and to produce one or more output light signals therefrom; an optical path module configured to receive the one or more output light signals from the optical splitter, and to produce one or more output light signals that (i) correspond to the one or more input light signals and (ii) are conveyed to the one or more 2×2 PIC-based FOG optical circuits, each of the one or more output light signals having an amplitude that is a modified version of an amplitude of the corresponding input signal.