Fiber Optic Gyroscope Polarization Control for Stable Interference
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Solution Overview
Problem
The increased polarization extinction ratio of linearly polarized light beams in fiber optic gyroscopes leads to fluctuations in light intensity, deteriorating the signal-to-noise ratio and performance due to polarization rotation during propagation through single-mode optical fibers.
Innovation Solution
Incorporating an additional polarization-maintaining optical fiber connected to the light source, ensuring each of the six polarization-maintaining optical fibers has a length greater than the coherent length of the light source, and aligning principal axes to maintain equal intensity and depolarize light, preventing polarization mode correlation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the polarization extinction ratio of the light source is increased to improve signal quality, then the light intensity becomes more sensitive to polarization rotation, but this causes fluctuations in light intensity passing through the single-mode optical fiber coil, deteriorating the signal-to-noise ratio
Solution Approach 1:
The patent applies preliminary action by introducing polarization-maintaining optical fibers before the light enters the single-mode optical fiber coil. These fibers prepare the light's polarization state in advance, ensuring that the polarization modes remain stable and uncorrelated during propagation through the coil, thus preventing intensity fluctuations before they occur
Solution Approach 2:
The patent uses polarization-maintaining optical fibers as intermediary components between the light source and the single-mode optical fiber coil. These intermediary fibers act as a buffer that maintains polarization integrity and prevents direct interaction between the light source's polarization properties and the coil's polarization rotation effects
2Reliability
If polarization-maintaining optical fibers are used to maintain polarization state, then polarization mode correlation is prevented, but this increases the device complexity and number of components
Solution Approach 1:
The patent applies parameter changes by carefully controlling the lengths of the polarization-maintaining optical fibers relative to the coherent length of the light source. By setting specific length relationships (L1 > Lc and L2 > Lc), the system achieves reliable polarization mode decorrelation while minimizing the number of fibers needed
Solution Approach 2:
The patent applies local quality by using polarization-maintaining optical fibers only in specific locations where polarization control is critical (at the light source input and at the coil output), while using ordinary single-mode fibers in other sections. This localized application maintains reliability while reducing overall device complexity
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
Stabilizes light intensity through the single-mode optical fiber coil, ensuring consistent interference and improved performance by maintaining equal light intensity and preventing polarization mode correlation.
Implementation Method 1
Each of the six polarization-maintaining optical fibers has the same beat length... the optical length of each of the six polarization-maintaining optical fibers is larger than the coherent length of the linearly polarized light from the light source
Implementation Method 2
stabilizes light intensity through the single-mode optical fiber coil, ensuring consistent interference and improved performance
Implementation Method 3
Fiber optic gyroscope... angular velocity detection, etc. on the basis of an electrical signal from the photoelectric converter
Data Source
Figure 1~2
AI summary
Totally six polarization-maintaining optical fibers having the same beat length are arranged at both ends of a single-mode optical fiber and both ends of a single-mode optical fiber coil, respectively. An angle between a principal axis of polarization in a first polarization-maintaining optical fiber and a plane of polarization of linearly polarized light from a light source is 45 degrees. The optical length of each of the six polarization-maintaining optical fibers is larger than a coherent length of the linearly polarized light from the light source. The total of the optical lengths of the six polarization-maintaining optical fibers into which polarization rotation in the process of passing through the single-mode optical fibers is factored is larger than the coherent length of the linearly polarized light from the light source.