Fiber Optic Gyroscope Clock System Asynchronous Demodulation
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Solution Overview
Problem
Existing fiber optic gyroscope systems face challenges in generating a highly tunable clock for bias modulation and a high-speed clock for photodetector sampling, particularly in applications requiring radiation-hardened components where such devices are limited or unavailable.
Innovation Solution
A clock system is developed that separates the bias modulation clock and photodetector sampling clock, using a direct digital synthesis (DDS) circuit for the bias modulation clock and dividing down a fixed-frequency high-speed clock for the sampling clock, allowing for tunability and high-speed operation with readily available, lower performance radiation-hardened electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single tunable high-frequency clock is used for both bias modulation and photodetector sampling, then device complexity is reduced, but the ability to achieve both high tunability and high-speed operation is compromised
Solution Approach 1:
The patent divides the single clock system into two separate clock generators: a tunable bias modulation clock generator and a fixed-frequency sampling clock generator. This segmentation allows each clock to be optimized independently - the bias modulation clock can be highly tunable for proper frequency adjustment, while the sampling clock maintains high-speed operation at a fixed frequency, resolving the contradiction between complexity reduction and performance optimization.
2Reliability
If high-speed, radiation-hardened devices are used for both clock generation, then reliability is improved, but availability and cost are reduced
Solution Approach 1:
The patent applies different quality levels to different parts of the system based on their specific requirements. The bias modulation clock generator uses lower-performance, more available radiation-hardened components since it requires tunability rather than extreme speed. The sampling clock generator uses fixed-frequency high-speed components. This local differentiation allows the system to achieve necessary reliability where required while using components that are actually available and cost-effective.
3Ease of operation
If the bias modulation frequency is not set to the proper frequency, then ease of operation is improved, but quadrature errors increase
Solution Approach 1:
The patent implements a dynamic, tunable bias modulation clock generator that can adjust its frequency to match the proper frequency for the specific optical fiber length and refractive index. This dynamic adjustment capability allows the system to maintain measurement precision by eliminating quadrature errors through proper frequency matching, while the tunability feature makes the operation easier by allowing frequency adaptation rather than requiring fixed, complex calibration procedures.
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 enables both tunability of the bias modulation clock and high-speed sampling clock performance, improving noise performance and reducing the need for high-speed, radiation-hardened devices, while using lower performance components that are more readily available.
Implementation Method 1
the phase modulation is achieved by applying a mediating signal across the electrodes of the optical phase modulator
Implementation Method 2
waves propagating in opposite directions interfere when recombined and impinge upon photodetector, which measure the intensity of the combined wave
Implementation Method 3
impinge upon photodetector, which measure the intensity of the combined wave
Implementation Method 4
a rotation about the sensing axis of the core provides an effective optical path length increase in one rotational direction, and an optical path length decrease in the other rotational direction. The resulting path length difference results in a phase shift between the waves propagating in opposite directions. This result is generally referred to as the Sagnac effect.
Data Source
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AI summary
A clock system for a fiber optic gyroscope is provided that includes a highly-tunable clock for the bias modulation and a separate asynchronous high-speed clock for the photodetector sampling. By separating the two clocks rather than using two derivatives of the same clock, the clock system and method can Provide both the tunability objective of the bias modulation clock and the high-speed objective of the sampling clock, while using readily available, lower performance, radiation-hardened electronics parts.