Optical Comb Synchronization for Low Relative Phase Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical comb distance meters face challenges in achieving high accuracy and stability due to relative phase noise and phase fluctuations in the driving signals of optical comb generators, leading to variations in measurement results, especially when measuring long distances in short times.
Innovation Solution
A low relative phase noise optical comb generation device is developed, utilizing at least three oscillators and two frequency converters to generate modulation signals with reduced relative phase noise, which are then supplied to optical comb generators, stabilizing the repetitive frequency of the interference signal and reducing measurement variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical comb generators are driven by multiple oscillators with different frequencies, then the optical comb distance meter can perform distance measurements, but relative phase noise between the oscillators causes measurement variations and reduces accuracy
Solution Approach 1:
The patent merges multiple oscillators into a unified frequency management system where all oscillators are phase-locked to a single reference oscillator. This combining approach ensures that while multiple frequency signals are generated for different optical comb generators, they all share a common phase reference, thereby eliminating relative phase noise between oscillators and improving both measurement accuracy and stability.
Solution Approach 2:
The patent implements feedback control through phase-locked loops (PLL) that continuously monitor and adjust the phase and frequency of each oscillator based on the reference oscillator. This feedback mechanism ensures that any phase deviations are corrected in real-time, maintaining coherent relationships between multiple oscillators and preventing measurement variations caused by relative phase noise.
2Productivity
If the measurement time is shortened to accelerate distance measurement, then productivity improves, but phase fluctuations have greater impact causing measurement variations
Solution Approach 1:
The patent applies preliminary action by pre-establishing phase-locked relationships between all oscillators before measurements begin. The reference oscillator and all frequency converters are synchronized in advance, creating a stable phase framework that remains valid throughout the measurement process. This preliminary synchronization ensures that even short-duration measurements are not affected by phase fluctuations, allowing high productivity without sacrificing accuracy.
3Adaptability or versatility
If multiple oscillators with different frequencies are used to drive optical comb generators, then the device can generate reference light and measuring light with different modulation cycles, but phase noise between oscillators creates variations in interference signals
Solution Approach 1:
The patent segments the frequency generation function across multiple independent oscillators, each capable of operating at different frequencies for different modulation requirements. However, each segmented oscillator is individually phase-locked to the reference oscillator, maintaining phase coherence despite frequency differences. This segmentation approach enables versatile modulation frequency selection while preserving phase stability through distributed phase-locking.
Solution Approach 2:
The reference oscillator serves as an intermediary that mediates the phase relationships between multiple frequency converters and oscillators. By using this common reference as an intermediary, the system achieves both frequency diversity (through different oscillation frequencies) and phase coherence (through shared reference), resolving the contradiction between adaptability and reliability.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A purpose of the present invention is to provide a low relative phase noise optical comb generation device in which a repetitive frequency of an interference signal of an optical comb is stabilized by reducing a relative phase noise of driving signals with different frequencies for driving multiple optical comb generators in an optical comb distance meter. A low relative phase noise optical comb generation device, comprising: at least three oscillators 13, 13A, 13B for generating frequency signals with mutually different frequencies phase locked to a reference frequency signal FREF given by a reference oscillator 11; and at least two frequency converters 14A, 14B to which a frequency signal obtained by one oscillator 13 of the at least three oscillators and respective frequency signals obtained by respective oscillators 13A, 13B other than the one oscillator are input; wherein the at least two frequency converters 14A, 14B supply the at least two types of modulation signals, in which a relative phase noise is reduced respectively as a sum frequency signal or a difference frequency signal of the frequency signal by the one oscillator and a frequency signal by other oscillator with a lower phase noise, to at least two optical comb generators 15A, 15B as driving signals.