Photonic integrated circuit for an interference fiber optic gyroscope (IFOG)
View Patent ↗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.
1. A photonic integrated circuit (PIC) for use in a fiber optic gyroscope (FOG), comprising:
a first connector configured to be connected to a light source;
a second connector configured to be connected to a photodetector;
a third connector configured to be connected to a first port of a fiber coil;
a fourth connector configured to be connected to a second port of the fiber coil;
a first coupler having a first branch port, a second branch port and a common base port;
a waveguide polarizer having a first polarizer port and a second polarizer port;
a second coupler having a first branch port, a second branch port and a common base port;
the first branch port of the first coupler coupled to the first connector through a first waveguide, the second branch port of the first coupler coupled to the second connector through a second waveguide, and the common base port of the first coupler coupled to the first polarizer port through a third waveguide;
the first branch port of the second coupler coupled to the third connector through a fourth waveguide, the second branch port of the second coupler connected to the fourth connector through a fifth waveguide, and the common base port of the second coupler coupled to the second polarizer port through a sixth waveguide;
at least one of an isolator, an absorber, a filter, and a deflector disposed proximate to the one or more of the fifth waveguide, the polarizer, and the sixth waveguide; and
the first through sixth waveguides are optic waveguides configured to be single-mode and polarization-maintaining.
2. The PIC of claim 1 , further comprising:
a light source coupled to the first connector;
a photodetector coupled to the second connector;
a fiber coil having a first fiber coil port coupled to the third connector and a second fiber coil port coupled to the fourth connector; and
a phase modulator associated with the fiber coil, the phase modulator configured to modulate, based on a modulating signal, light that propagates through the fiber coil,
thereby forming an optic system for use in a FOG.
3. The PIC of claim 2 , further comprising:
a detection/feedback circuit, comprising:
a local oscillator configured to provide a reference signal from which the modulating signal is derived; and
a phase sensing detector configured to receive an output from the photodetector and produce a rotation measurement signal therefrom,
thereby forming the FOG.
4. The PIC of claim 1 , wherein the first through sixth waveguides are configured to support only a single spatial mode.
5. The PIC of claim 1 , wherein the first through sixth waveguides are configured to be birefringent.
6. The PIC of claim 5 , wherein the first through sixth waveguides are configured to support only a single linear polarization mode.
7. The PIC of claim 1 , wherein the light source is a broadband, semiconductor-based light source.
8. The PIC of claim 1 , further comprising an inline optic isolator disposed in the first waveguide, between the first connector and the first coupler.
9. An extended photonic integrated circuit (EPIC) for use in a fiber optic gyroscope (FOG), comprising:
a light source;
a photodetector;
a first connector configured to be connected to a first port of a fiber coil;
a second connector configured to be connected to a second port of the fiber coil;
a first coupler having a first branch port, a second branch port and a common base port;
a waveguide polarizer having a first polarizer port and a second polarizer port;
a second coupler having a first branch port, a second branch port and a common base port;
the first branch port of the first coupler coupled to the light source through a first waveguide, the second branch port of the first coupler coupled to the photodetector through a second waveguide, and the common base port of the first coupler coupled to the first polarizer port through a third waveguide;
the first branch port of the second coupler coupled to the first connector through a fourth waveguide, the second branch port of the second coupler connected to the second connector through a fifth waveguide, and the common base port of the second coupler coupled to the second polarizer port through a sixth waveguide;
at least one of an isolator, an absorber, a filter and a deflector, disposed proximate to the fifth waveguide, the polarizer, and the sixth waveguide;
an optic wavemeter that uses at least a portion of an optical signal that is (i) derived from the light source and (ii) returned from the fiber coil, and produces a signal that represents an effective interferometric wavelength of the optical signal;
the first through sixth waveguides configured to be single-mode and polarization-maintaining.
10. The EPIC of claim 9 , further comprising:
a fiber coil having a first fiber coil port coupled to the first connector and a second fiber coil port coupled to the second connector; and
a phase modulator associated with the fiber coil, the phase modulator configured to modulate, based on a modulating signal, light that propagates through the fiber coil,
thereby forming an optic system for use in the FOG.
11. The EPIC of claim 10 , further comprising:
a detection/feedback circuit module, comprising:
a local oscillator configured to provide a reference signal from which the modulating signal is derived;
a phase sensing detector configured to receive an output from the photodetector and produce a rotation measurement signal therefrom; and
a scale factor correction mechanism that corrects a FOG scale factor based on the effective interferometric wavelength of the optical signal,
thereby forming the FOG.
12. The EPIC of claim 9 , wherein the first through sixth waveguides are configured to support only a single spatial mode.
13. The EPIC of claim 9 , wherein the first through sixth waveguides are configured to be birefringent.
14. The PIC of claim 13 , wherein the first through sixth waveguides are configured to support only a single linear polarization mode.
15. The EPIC of claim 11 , wherein the phase sensing detector removes a modulation frequency component from the output of the photodetector to produce the rotation measurement signal.
16. The EPIC of claim 9 , wherein the light source is a broadband, semiconductor-based light source.
17. The EPIC of claim 9 , further comprising an inline optic isolator disposed in the first waveguide, between the light source and the first coupler.
18. An hybrid photonic integrated circuit (HPIC) for use in a fiber optic gyroscope (FOG), comprising:
a submount;
a semiconductor-based light source fixedly attached to the submount;
a photodetector fixedly attached to the submount;
a first connector, fixedly attached to the submount, the first connector configured to be connected to a first port of a fiber coil;
a second connector, fixedly attached to the submount, the second connector configured to be connected to a second port of the fiber coil;
a photonic integrated circuit, fixedly attached to the submount, comprising:
a first coupler having a first branch port, a second branch port and a common base port;
a waveguide polarizer having a first polarizer port and a second polarizer port;
a second coupler having a first branch port, a second branch port and a common base port;
the first branch port of the first coupler coupled to the light source through a first waveguide, the second branch port of the first coupler coupled to the photodetector through a second waveguide, and the common base port of the first coupler coupled to the first polarizer port through a third waveguide;
the first branch port of the second coupler coupled to the first connector through a fourth waveguide, the second branch port of the second coupler connected to the second connector through a fifth waveguide, and the common base port of the second coupler coupled to the second polarizer port through a sixth waveguide; and
at least one of an isolator, an absorber, a filter and a deflector, disposed proximate to the fifth waveguide, the polarizer, and the sixth waveguide;
the first through sixth waveguides configured to be single-mode and polarization-maintaining.
19. The HPIC of claim 18 , further comprising:
a fiber coil having a first fiber coil port coupled to the first connector and a second fiber coil port coupled to the second connector; and
a phase modulator associated with the fiber coil, the phase modulator configured to modulate, based on a modulating signal, light that propagates through the fiber coil,
thereby forming an optic system for use in a FOG.
20. The HPIC of claim 19 , further comprising:
a detection/feedback circuit, comprising:
a local oscillator configured to provide a reference signal from which the modulating signal is derived; and
a phase sensing detector configured to receive an output signal produced by the photodetector, and produce a rotation measurement signal therefrom,
thereby forming the FOG.
21. The HPIC of claim 20 , further comprising:
an optic wavemeter, formed on the photonic integrated circuit, which uses at least a portion of an optical signal that is (i) derived from the light source and (ii) returned from the fiber coil, and produces a signal that represents an effective interferometric wavelength of the optical signal; and
a scale factor correction mechanism, included with the detection/feedback circuit, that corrects a FOG scale factor based on the effective interferometric wavelength of the optical signal.
22. The HPIC of claim 21 , wherein the phase sensing detector removes the modulating signal from the output signal produced by the photodetector.
23. The HPIC of claim 18 , further comprising an inline optic isolator disposed in the first waveguide, between the semiconductor-based light source and the first coupler.
24. The HPIC of claim 18 , wherein the first through sixth waveguides are configured to support only a single spatial mode.
25. The HPIC of claim 18 , wherein the first through sixth waveguides are configured to be birefringent.
26. The HPIC of claim 25 , wherein the first through sixth waveguides are configured to support only a single linear polarization mode.
27. The HPIC of claim 18 , wherein the semiconductor light source is a broadband light source.