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.

The present disclosure relates to integrated photonics-based optical gyroscopes with silicon nitride (SiN) waveguide-based microresonators. SiN microresonators are fabricated either on a fused silica platform or on a silicon substrate with oxide cladding. A narrow linewidth high-Q laser is hybridly integrated on a silicon photonics platform. The laser is tuned with a first SiN microresonator, and the rotational sensing component of the gyroscope comprises another SiN microresonator. The silicon photonics front-end chip has components for a balanced detection scheme to cancel noise in the optical signal coming back from the rotational sensing component.

Novel small-footprint integrated photonics optical gyroscopes disclosed herein can provide ARW in the range of 0.05°/√Hr or below (e.g. as low as 0.02°/√Hr), which makes them comparable to fiber optic gyroscopes (FOGs) in terms of performance, at a much lower cost. The low bias stability value in the integrated photonics optical gyroscope corresponds to a low bias estimation error (in the range of 1.5°/Hr or even lower) that is crucial for safety-critical applications, such as calculating heading for autonomous vehicles, drones, aircrafts etc. The integrated photonics optical gyroscopes may be co-packaged with mechanical gyroscopes into a hybrid inertial measurement unit (IMU) to provide high-precision angular measurement for one or more axes.

Novel small-footprint integrated photonics optical gyroscopes disclosed herein can provide ARW in the range of 0.05°/√Hr or below (e.g. as low as 0.02°/√Hr), which makes them comparable to fiber optic gyroscopes (FOGs) in terms of performance, at a much lower cost. The low bias stability value in the integrated photonics optical gyroscope corresponds to a low bias estimation error (in the range of 1.5°/Hr or even lower) that is crucial for safety-critical applications, such as calculating heading for autonomous vehicles, drones, aircrafts etc. The integrated photonics optical gyroscopes may be co-packaged with mechanical gyroscopes into a hybrid inertial measurement unit (IMU) to provide high-precision angular measurement for one or more axes.

An interferometric optical fibre sensor comprises optical fibre defining an optical circuit configured to propagate a first optical wave via an environment in which the optical fibre can be exposed to a stimulus that modifies the first optical wave, and a second optical wave, and to combine the first optical wave and the second optical wave to create an interference signal containing information about the stimulus, wherein optical fibre propagating either or both of the first optical wave and the second optical wave comprises hollow core optical fibre configured to propagate the optical wave or waves by an antiresonant optical guidance effect.

In an aspect, a pressure sensor for determining pressure in an environment comprises: a source for emitting a coherent reference light characterized by a reference light frequency; a first lock-in mechanism configured to send an electrical signal to the source based on a reference resonance frequency; a reference cavity; wherein the reference cavity is characterized by the reference resonance frequency; a modulator configured a reference light to generate at least a first sideband frequency such that an output of said modulator is a measurement light characterized by at least the first sideband frequency; a frequency synthesizer configured to drive the modulator; a second lock-in mechanism configured to send an electrical signal to the frequency synthesizer based on a measurement resonance frequency; and a measurement cavity configured to receive at least a portion of the measurement light; wherein the measurement cavity is characterized by the measurement resonance frequency; and wherein the pressure of the environment is determined based on the reference resonant frequency and the measurement resonance frequency.

A polarization-maintaining fully-reciprocal bi-directional optical carrier microwave resonance system and an angular velocity measurement method thereof. In the system, highly stable optical carrier microwaves are generated in a clockwise direction and a counterclockwise direction in the same resonant cavity, and are used to measure the angular velocity of rotation of a carrier apparatus. A fully reciprocal ring-shaped resonant cavity structure is used to achieve a fully reciprocal bi-directional optical resonance system. A polarization state separation technique is used to separate an optical signal into two wavelengths, and optical signals with perpendicular polarization states are transmitted in opposite directions in a sensing ring, thereby improving the measurement capability of the sensing ring. Bi-directional optical carrier microwave resonance is achieved by using a phase tracking structure and a regenerative mode locking technique. A cavity length control technique is used to lock the oscillation frequency of microwaves in one of the directions to a highly stable standard time reference source, thereby achieving a stable relative cavity length of an optical resonant cavity. The described key techniques greatly improve the signal-to-noise ratio of bi-directional oscillation difference frequency signals caused by the Sagnac effect. The system and the method are practical and have high measurement precision.

Improvements to optical power regulation in a gyroscopic system are described. The system can include an optical assembly (e.g., optical bench) which couples opposing optical signals to a resonator coil. The system can monitor the power of the optical signals through the resonator coil by including signal extraction optics in the optical assembly which are configured to extract a portion of the optical signals. The portions can be extracted via a single beamsplitter, wherein the beamsplitter reflects the portions at a single common surface, and can also reflect the portions to a respective photodetector in free space free from intervening optical components, such as polarizers or beamsplitters. One or more processors can be coupled to the optical assembly, wherein the processor(s) are configured to adjust the power of the optical signals in response to detecting a power difference between the optical signals.

The present disclosure relates to system-level integration of lasers, electronics, integrated photonics-based optical components and a rotation sensing element, which can be a fiber coil or a sensing coil/micro-resonator ring on a sensing chip. Novel waveguide design on the integrated photonics chip, acting as a front-end chip, ensures precise detection of phase change in the fiber coil or the sensing chip, where the sending chip is coupled to the front end chip. Electrical and/or thermal phase modulators are integrated with the integrated photonics chip. 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.

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.