An integrated photonics optical gyroscope fabricated on a silicon nitride (SiN) waveguide platform comprises a first straight waveguide to receive incoming light and to output outgoing light to be coupled to a photodetector to provide an optical signal for rotational sensing. The gyroscope comprises a first microresonator ring proximate to the first straight waveguide. Light evanescently couples from the first straight waveguide to the first microresonator ring and experiences propagation loss while circulating as a guided beam within the first microresonator ring. The guided beam evanescently couples back from the first microresonator ring to the first straight waveguide to provide the optical signal for rotational sensing after optical gain is imparted to guided beam to counter the propagation loss. In a coupled-ring configurations, the first microresonator ring acts as a loss ring, and optical gain is imparted to a second microresonator ring which acts as a gain ring.

Techniques are provided for correcting for time varying changes to a gyroscope incorporating a resonator and/or to an environment in which the gyroscope is located, and which affect the resonator. Free spectral range of the gyroscope, which varies with such changes, is determined and is used to correct at least one of gyroscope bias and scale factor.

The present disclosure relates to system-level integration of lasers, electronics, integrated photonics-based optical components and a sensing chip. Novel waveguide design on the integrated photonics chip, acting as a front-end chip, ensures precise detection of phase change in a fiber coil or a sensing chip having a waveguide coil or ring resonator, where the sending chip is coupled to the front end chip. Strip waveguides are designed to primarily select TE mode over TM mode when laser light is coupled into the integrated photonics chip. A plurality of mode-selective filters, based on multi-mode interference (MMI) filter, a serpentine structure, or other types of waveguide-based mode-selective structure, are introduced in the system architecture. Additionally, implant regions are introduced around the waveguides and other optical components to block unwanted/stray light into the waveguides and optical signal leaking out of the waveguide.

A passive ring interferometer sensor includes an electromagnetic ring path configured to receive a pair of electromagnetic waves from an electromagnetic radiation source and to direct the waves to be counter-propagating within the ring path toward respective ends of the path. A combination junction receives the waves from the respective ends and combines the waves to be co-propagating within a coupling path. Polarization elements are configured to set the waves to be mutually co-polarized within the electromagnetic ring path and to be mutually cross-polarized within the coupling path. A detector is configured to receive the mutually cross-polarized waves from the coupling path and to detect second-order coherence. Embodiments can sense rotation rate as fiber-optic gyroscopes or serve as other types of sensors such as gravitational wave sensors. Embodiments may have greatly increased unambiguous range and decreased sensitivity to any centroid wavelength shift.

A method comprises receiving a first optical signal and a second optical signal at or near an optical resonator, where the first optical signal includes a clockwise (CW) optical signal and the second optical signal includes a counter clockwise optical signal; injecting the first optical signal and the second optical signal into a resonator loop closure optics system of the optical resonator; sampling a portion of the first optical signal and a portion of the second optical signal; combining the portion of the first optical signal and the second optical signal; converting the combined optical signals to an analog electrical signal; digitizing the analog electrical signal; storing an estimated frequency of a beat signal created by a combination of the CW optical signal and the CCW optical signal; and using the stored estimated beat signal frequency, digitally phase lock to a frequency of the beat signal.

A ring-laser gyroscope which generates in an optical ring resonator and in response to a first pump beam, a first back-scattered beam propagating in a direction; generates in the optical ring resonator and in response to a second pumped beam, a second back-scattered beam propagating in an opposite direction; determines a first difference between the frequencies of the first and second back-scattered beams; reverses the directions of the first and second back-scattered beams; determines a second difference between the frequencies of the first and second back-scattered beams; determines a third difference between the first and second differences; and determines a rotation of the optical ring resonator in response to the third difference.

An optical gyroscope assembly for measuring a rotation rate. The optical gyroscope assembly includes a first multimode interferometer with an input for receiving light and two outputs, each connected to a second light guide; a ring resonator on each of the second light guides; a second multimode interferometer with two inputs, each connected to one of the second light guides, and two outputs, each connected to a third light guide; and a third multimode interferometer with two inputs, each connected to one of the third light guides, and two outputs, each connected to a fourth light guide.

A hyperbolic modulation offset reducer circuit for a resonator fiber optic gyro (RFOG) is provided. The circuit includes a first demodulation circuit that is configured to demodulate a received transmission signal from a resonator at twice a sideband heterodyne detection modulation frequency to reject signals due to backscatter. A slave resonance tracking loop of the circuit is coupled to an output of the first demodulation circuit. The slave resonance tracking loop is configured to create an offset frequency signal from the transmission signal that is applied to an optical phase lock loop of a RFOG. A hyperbolic modulator offset control loop is also coupled to the output of the first demodulation circuit. The hyperbolic modulator offset control loop is configured to create a subharmonic common modulation signal from the transmission signal that is coupled to a common phase module in a silicon photonics chip of the RFOG.

An optical gyroscope includes, in part, an optical switch, a pair of optical rings and a pair of photodetectors. The optical switch supplies a laser beam. The first optical ring delivers a first portion of the beam in a clockwise direction during the first half of a period, and a first portion of the beam in a counter clockwise direction during the second half of the period. The second optical ring delivers a second portion of the beam in a counter clockwise direction during the first half of the period, and a second portion of the beam in a clockwise direction during the second half of the period. The first photodetector receives the beams delivered by the first and second optical rings during the first half of the period. The second photodetector receives the beams delivered by the first and second optical rings during the second half of the period.

A resonance fiber-optic gyro (RFOG) with quadrature error reducer is provided. The RFOG with quadrature error reducer includes a laser assembly, a fiber resonator assembly, a resonance tracking loop and a quadrature error reducer circuit. The resonance tracking loop, coupled to an output of the finder resonator assembly, is used to generate a resonance frequency signal that is coupled to an OPLL mixer in one of a CCW OPLL or the CW OPLL of the laser assembly. The quadrature error reducer circuit includes an amplitude control loop and a second harmonic phase control loop. The amplitude control loop is used to generate a common modulation signal. An output of the amplitude control loop is coupled to a common phase modulator in the laser assembly. The second harmonic phase control loop is used to selectively adjust a phase of a second harmonic modulation signal in the amplitude control loop at startup.