The invention relates to a control system (100) for a fiber optic gryoscope, comprising a phase modulator (110) for modulating a phase of a light signal (115) and a control unit (120) for producing a control signal (125), by the value of which the phase is modulated and which is fed to the phase modulator (110). The control signal changes statistically and does not have an average value.

A photonics gyroscope comprises a laser and a common intensity modulation unit that outputs an intensity modulated beam, split into a CCW beam having a first power level and a CW beam having a second power level. A first phase modulator (PA) receives the CCW beam, and a second PA receives the CW beam. A variable optical attenuator (VOA) is coupled to the first or second PA. The CCW beam is coupled into a resonator and the CW beam is coupled into the resonator. A first detector receives the CCW beam and a second detector receives the CW beam from the resonator. A CCW control loop locks the CCW beam, and a CW control loop locks the CW beam, to resonance peaks. The VOA receives a feedback loop signal to aid in balancing power levels between CCW and CW beams to eliminate a rate signal at an intensity modulation frequency.

The described embodiments relate to a photonic integrated circuit (PIC) for use in a fiber optic gyroscope (FOG). Some embodiments describe a PIC with connectors for coupling to external components such as a light source, a photodetector and a fiber coil, with beamsplitting devices (e.g., couplers), waveguide and other photonic components integrated on the PIC. Some embodiments describe a hybrid PIC (HPIC) with the PIC, light source and photodetector attached to a common submount, and with connectors for coupling to a fiber coil. Other embodiments describe an extended PIC (EPIC) that integrates the PIC components, the light source, the photodetector, and other components (e.g., a wavemeter) on a common substrate. The described embodiments may also include a detection/feedback circuit that provides control signals and other parameters to the PIC, HPIC, or EPIC, and receives output signals from the PIC, HPIC, or EPIC.

A method for a resonant fiber optic gyroscope is provided. The method includes locking a frequency of a light wave from a master laser to a resonant frequency of a fiber optic resonator; phase locking a first slave laser to the frequency of the master laser at a first offset frequency; combining the light wave from the master laser with a light wave from the first slave laser; launching the combined light wave in the clockwise (CW) direction in the fiber optic resonator; and prior to combining the light wave from the master laser and the light wave from the first slave laser, shifting the frequency of the light wave from the master laser to avoid interference with a signal produced by pick-up in the first slave laser, that includes a light wave at the frequency of the light wave from the master laser.

Interferometric measurement device includes a light source emitting a source signal and optical coupling elements receiving the source signal, directing part of the latter towards a measurement pathway including a Sagnac ring interferometer, of frequency f.sub.p, producing a power output signal P.sub.OUT polarized according to a first polarization direction, tapping off another part of the source signal towards a compensation pathway producing a return power compensation signal P.sub.RET, and directing the output and compensation signals towards detection elements. The compensation pathway includes polarization rotation elements producing the compensation signal according to a second cross-direction of polarization, and optical looping elements redirecting part of the compensation signal towards the measurement pathway; the detection elements include a single detector connected to the coupling elements for receiving the output signal and the compensation signal; the device further includes power equilibration elements equalizing the output power and/or return power are routed towards the detector.

A gyroscope comprises a source emitting a broadband beam, and a first waveguide arrangement that splits the beam into CCW and CW beams. First and second phase modulators are coupled to the waveguide arrangement and provide phase modulations or frequency shifts to the CCW and CW beams. An optical resonator is in communication with the phase modulators such that the CCW and CW beams are optically coupled into the resonator. A second waveguide arrangement receives the CCW and CW beams transmitted from the resonator. First and second RIN detectors are coupled to the second waveguide arrangement and respectively receive the CCW and CW beams. A rate detector receives the CCW and CW beams. A rate calculation unit receives intensity noise signals from the RIN detectors, and rate and intensity noise signals from the rate detector. The rate calculation unit performs a RIN subtraction technique to reduce intensity noise limited ARW.

The invention relates to a control system (100) for a fiber optic gryoscope, comprising a phase modulator (110) for modulating a phase of a light signal (115) and a control unit (120) for producing a control signal (125), by the value of which the phase is modulated and which is fed to the phase modulator (110). The control signal changes statistically and does not have an average value.

A RFOG, comprising: a master laser emitting a reference optical signal; first and second slave lasers emitting first and second optical signals; an optical resonator ring cavity coupled to the lasers, the first and second optical signals propagating in first and second directions through the optical resonator ring cavity; one or more signal generators to inject first and second modulation signals at first and second frequencies on both optical signals; first and second photodetectors that generate first and second signals; first and second demodulators to demodulate the first and second signals using first and second reference signals and the first and second frequencies; a differencing function to output the difference between resonance frequencies of the first and second signals; at least a third demodulator to detect reference phase errors; and at least one phase servo to adjust the phase of at least one of the first and second reference signals.

A RFOG, comprising: a master laser emitting a reference optical signal; first and second slave lasers emitting first and second optical signals; an optical resonator ring cavity coupled to the lasers, the first and second optical signals propagating in first and second directions through the optical resonator ring cavity; one or more signal generators to inject first and second modulation signals at first and second frequencies on both optical signals; first and second photodetectors that generate first and second signals; first and second demodulators to demodulate the first and second signals using first and second reference signals and the first and second frequencies; a differencing function to output the difference between resonance frequencies of the first and second signals; at least a third demodulator to detect reference phase errors; and at least one phase servo to adjust the phase of at least one of the first and second reference signals.

A directional coupler with reduced phase deviation is provided. The directional coupler includes a first coupler waveguide and second coupler waveguide. At least one of a spaced distance between the first coupler waveguide and the second coupler waveguide and a length of the first coupler waveguide and the second coupler waveguide selected to achieve an acceptable phase deviation and a set coupling ratio. The phase deviation is caused by a difference in loss coefficients between a first optical mode in the first coupler waveguide and a second optical mode in the second coupler waveguide.