Three-Pump SBS Gyroscope Resolving Bias and Dead-Time
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Solution Overview
Problem
Conventional SBS gyroscopes on chips face limitations due to the pump laser being used as a readout frequency, which restricts the linewidth of the measured signal and results in bias and noise, as well as dead-time in data acquisition.
Innovation Solution
A three-pump SBS gyroscope configuration where three laser pumps are locked to adjacent resonances, generating distinct SBS lines that are combined to eliminate the pump signals from readout and reduce angular random walk, enabling real-time data acquisition by encoding rotational rate information in the frequencies of electrical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pump laser is used as one of the readout frequencies in conventional SBS gyroscope configurations, then the system can operate with fewer laser devices, but the linewidth of the measured signal is limited and bias and noise are introduced
Solution Approach 1:
The patent divides the readout function into separate components by using three distinct laser devices: one for pumping and two for readout. This segmentation allows the readout lasers to operate at frequencies optimized for measurement precision without being constrained by pump laser requirements, thereby achieving narrower linewidths and reduced bias while maintaining manageable system complexity
Solution Approach 2:
The patent extracts the pump laser function from the readout function by using separate laser devices for each purpose. The pump laser is dedicated to generating SBS signals, while two separate readout lasers are used for measuring rotation, eliminating the limitation where the pump laser's frequency and linewidth constraints directly affect measurement precision
2Device complexity
If the pump laser is used as a readout frequency, then the system structure is simplified, but dead-time is introduced in data acquisition
Solution Approach 1:
By segmenting the functional roles of different laser devices, the patent enables continuous data acquisition. The pump laser continuously generates SBS signals while the two readout lasers continuously monitor rotation, eliminating the need to switch between pump and readout modes that would create dead-time in the data acquisition process
Solution Approach 2:
The patent implements continuous useful action by having the pump laser and readout lasers operate simultaneously and continuously. The pump laser continuously generates the necessary SBS signals while the readout lasers continuously measure rotation, ensuring uninterrupted data acquisition without dead-time
3Device complexity
If conventional SBS gyroscope configurations are used, then the system is simpler to implement, but angular random walk is increased
Solution Approach 1:
The patent applies local quality by optimizing each laser device for its specific function: the pump laser is optimized for generating strong SBS signals, while the two readout lasers are optimized for precise frequency measurement. This functional specialization allows each component to operate at its optimal performance point, reducing overall system noise and angular random walk
Solution Approach 2:
The patent introduces an intermediary approach by using two separate readout lasers that beat against the SBS signals generated by the pump laser. This intermediary measurement method allows for more precise rotation detection by measuring the frequency difference between the readout lasers and SBS signals, thereby reducing angular random walk
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 reduces bias and noise, eliminates dead-time, and enhances navigation-grade accuracy by providing rotation-sensitive outputs with improved sensitivity and reduced angular random walk, allowing for real-time data acquisition.
Implementation Method 1
an optical resonator; a first laser device in optical communication with the optical resonator, the first laser device configured to emit a first optical signal that propagates in a first direction in the optical resonator, wherein the first optical signal produces a first SBS signal in the optical resonator that counter-propagates in a second direction opposite from the first direction
Implementation Method 2
A conventional SBS gyroscope on a chip is an optical waveguide ring resonator that operates based on the Sagnac effect. The SBS tones are then directed onto high-speed photodetectors and their beat frequency, which is rotation-sensitive due to their counter-propagating nature, is monitored over time.
Data Source
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AI summary
A stimulated Brillouin scattering (SBS) gyroscope comprises a resonator; a first laser in communication with the resonator and configured to emit a first optical signal propagating in a first direction, the first optical signal producing a first SBS signal counter-propagating in a second direction; a second laser in communication with the resonator and configured to emit a second optical signal propagating in the first direction, the second optical signal producing a second SBS signal counter-propagating in the second direction; a third laser in communication with the resonator and configured to emit a third optical signal propagating in the second direction, the third optical signal producing a third SBS signal counter-propagating in the first direction. At least one photodetector is coupled to the resonator and receives the SBS signals, which are combined in the photodetector to produce electrical signals that include rotational rate information encoded in frequencies of the electrical signals.