Active Bidirectional Mode-Locked Lasers for Navigation
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Solution Overview
Problem
Current guidance, navigation, and control systems rely on outdated technologies such as ring He—Ne lasers, which have high power consumption, limited lifetime, nonlinearity, and dead bands, making them inefficient for precise attitude measurements in vehicles like satellites and aircraft.
Innovation Solution
The development of an active bidirectional mode-locked fiber ring laser system that uses a combination of passive and active mechanisms for intracavity phase interferometry, enabling simultaneous measurement of rotation and position with improved sensitivity and accuracy, eliminating dead bands and nonlinearity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ring He-Ne lasers are used for inertial measurements, then attitude sensing capability is provided, but power consumption is high and efficiency is low
Solution Approach 1:
The patent transitions from conventional ring He-Ne laser technology to a mode-locked laser system operating at 1550 nm wavelength, representing a fundamental parameter change in the light source characteristics. This enables higher efficiency operation while maintaining precise attitude sensing capability through intracavity interferometric detection
Solution Approach 2:
The invention replaces the mechanical vacuum tube technology of traditional He-Ne lasers with a solid-state mode-locked laser system. This substitution eliminates the need for vacuum tubes and associated mechanical components, resulting in lower power consumption and higher operational efficiency while preserving the inertial measurement function
2Measurement precision
If ring He-Ne lasers are used for inertial measurements, then attitude sensing is achieved, but lifetime is limited by vacuum tube technology
Solution Approach 1:
The patent replaces the vacuum tube-based He-Ne laser with a solid-state mode-locked laser system. This substitution eliminates the limited lifetime associated with vacuum tube degradation, providing a more durable and long-lived inertial sensing platform while maintaining attitude sensing precision
Solution Approach 2:
The invention adopts solid-state laser components that are more reliable and have extended operational lifetimes compared to vacuum tube technology. The mode-locked laser system with intracavity interferometric detection provides a sustainable solution without the lifetime constraints of conventional vacuum tube-based systems
3Measurement precision
If ring He-Ne lasers are used for inertial measurements, then rotation detection is provided, but nonlinearity and zero response at low rotation rate occur
Solution Approach 1:
The patent employs mode-locking to generate periodic ultrashort pulses within the laser cavity. This periodic action creates a stable interference pattern that linearly responds to rotation rates, eliminating the nonlinearity and dead band problems of continuous-wave He-Ne lasers. The pulsed operation enables accurate detection even at very low rotation rates
Solution Approach 2:
The intracavity interferometric detection system provides continuous feedback on the phase difference between counter-propagating pulses. This feedback mechanism ensures linear response across the full range of rotation rates, including low rates, by dynamically adjusting to maintain measurement accuracy and eliminate zero response conditions
4Measurement precision
If ring He-Ne lasers are used for inertial measurements, then attitude monitoring is enabled, but device volume is large
Solution Approach 1:
The patent combines the laser oscillator and the interferometric detector into a single integrated intracavity system. By merging these functions within the same optical cavity, the device volume is significantly reduced while maintaining precise attitude monitoring capability. The mode-locked laser structure inherently provides both the light source and the interference detection mechanism
Solution Approach 2:
The mode-locked laser system performs multiple functions simultaneously: it generates the coherent light source, creates the interferometric measurement signal, and detects rotation and acceleration. This multi-functionality eliminates the need for separate components, reducing overall device volume while maintaining comprehensive attitude monitoring capabilities
5Volume of moving object
If fiber optic gyro is used for attitude sensing, then device compactness is improved, but signal to noise ratio and sensitivity are reduced
Solution Approach 1:
The patent uses mode-locked pulsed operation to concentrate the optical energy into short, intense bursts. This periodic action significantly enhances the signal-to-noise ratio by increasing peak power while maintaining compact device size. The ultrashort pulses create stronger interference signals that are more sensitive to rotation and acceleration inputs
Solution Approach 2:
The invention operates at 1550 nm wavelength with mode-locked pulses, representing a parameter change from conventional fiber optic gyro operations. This enables higher sensitivity and better signal-to-noise ratio while maintaining the compactness advantage of fiber-based systems through intracavity interferometric detection
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 system provides highly accurate and efficient measurements of attitude, including pitch, yaw, and roll, with reduced power consumption and no moving parts, offering a compact, cost-effective solution for navigation systems.
Implementation Method 1
uses a combination of passive and active mechanisms for intracavity phase interferometry, enabling simultaneous measurement of rotation and position with improved sensitivity and accuracy
Implementation Method 2
a FOG, the difference in phase induced by rotation (Sagnac effect) is translated into a difference in intensity
Implementation Method 3
The frequency difference between the two output trains of pulses emitted by the laser can be picked-up as a beat note on a detector
Data Source
AI summary
In various embodiments, systems and methods can be structured to provide efficient active bidirectional mode-locked lasers, which can be used as intracavity phase interferometer (IPI) sensors. Stable bidirectional mode-locking can be achieved by a combination of a passive mechanism, a passively driven active mechanism, and a beat note detection system. Such systems can be used in guidance, navigation, and control systems, where attitude control of a vehicle relies on accurate measurements of its position and motion. In various embodiments, a detection system can be based on an all fiber intracavity phase interferometer (IPI) active laser capable of delivering accurate simultaneous measurements of all three degrees of rotation and position in a single, compact, cost effective unit. A variation of the same system can include a linear cavity laser for accurate measurements of acceleration without the use of any inertial masses. Additional apparatus, systems, and methods are disclosed.