Kerr Effect Compensation in Optical Ring Resonators
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Solution Overview
Problem
The non-linear Kerr effect in fiber optical resonator gyros causes a phase shift difference between clockwise and counterclockwise light waves, leading to erroneous rotation rate measurements due to unequal intensities in the resonator, resulting in inaccurate rotation rate indication.
Innovation Solution
Compensating for the non-linear phase shift accumulation by using a compensating device such as a second harmonic generating (SHG) optical crystal, phase conjugating element, or semiconductor waveguide to create a negative Kerr effect, effectively reversing the sign of the non-linear phase shift accumulation, thereby reducing or eliminating the net total non-linear phase shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light propagates through the optical fiber resonator in both clockwise and counterclockwise directions, then the fiber optical resonator gyro can measure rotation rate, but the non-linear Kerr effect causes non-reciprocal phase shifts that lead to measurement errors
Solution Approach 1:
The patent applies the counterweight principle by introducing a compensating medium with negative Kerr coefficient that generates an equal and opposite non-reciprocal phase shift to cancel the harmful phase shift accumulated in the optical fiber. The compensating medium acts as a counterbalance, producing a phase shift of opposite sign that neutralizes the measurement error caused by the Kerr effect in the fiber.
Solution Approach 2:
The patent converts the harmful non-linear Kerr effect into a beneficial compensation mechanism. By utilizing a medium with negative Kerr coefficient, the system transforms the problematic non-reciprocal phase shift into a useful compensating effect that actively corrects the measurement error, turning the harmful non-linearity into a solution for improving measurement accuracy.
2Productivity
If the intensities of clockwise and counterclockwise light waves are unequal in the resonator, then the system can operate, but non-reciprocal phase shifts accumulate leading to erroneous rotation rate indication
Solution Approach 1:
The compensating medium provides a counterbalancing non-reciprocal phase shift that is equal in magnitude but opposite in sign to the phase shift caused by unequal intensities in the optical fiber. This counterweight approach ensures that even when intensities are unequal during operation, the net non-reciprocal phase shift is canceled, maintaining accurate rotation rate indication.
3Measurement precision
If a compensating device with negative Kerr effect is introduced to reduce non-linear phase shift accumulation, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent introduces a compensating medium as an intermediary element between the light source and the detection system. This mediator provides the necessary negative Kerr effect compensation without requiring fundamental changes to the overall gyro architecture, allowing the system to maintain its basic operational structure while improving measurement accuracy through the added compensating component.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces or eliminates the non-reciprocal phase shifts and errors in the fiber optic resonator gyro, providing accurate rotation rate measurements by ensuring equal phase shifts for both light waves.
Implementation Method 1
The non-linear Kerr effect, for a light wave propagating in a single direction, gives an effective index of refraction coefficient of a material that changes with the intensity of the light wave: n=n0+K|E|2
Implementation Method 2
Compensating is performed by a compensating device, suggested by Malomed et al. in U.S. Pat. No. 6,591,047 for communication systems, such as a second harmonic generating (SHG) optical crystal
Implementation Method 3
The compensating device may also be a phase conjugating element (PCE)
Data Source
AI summary
Systems and methods for compensating for nonlinear phase shift accumulation in an optical ring resonator. An example method includes sending a first beam in a clockwise direction around the optical ring resonator and sending a second beam in a counterclockwise direction around the optical ring resonator. Then, nonlinear phase shift accumulation of the first and second beams is compensated for within the optical ring resonator. Compensating includes creating a negative Kerr effect phase shift for each beam based on an estimate of accumulated positive Kerr effect.