Atomic Clock Laser Stabilization for Fiber Noise Across Long Links
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Solution Overview
Problem
Conventional fiber noise cancellation methods are ineffective in removing high-frequency noise components when laser light with a narrow line width is transmitted over long distances through optical fibers, leading to unsuitable time observation in systems using multiple atomic clocks connected by optical fibers.
Innovation Solution
An atomic clock system with frequency stabilization devices at both local and remote sites, where the local site removes low-frequency fiber noise using Fiber Noise Cancellation (FNC) and the remote site removes high-frequency noise using a Pound-Drever-Hall (PDH) method, ensuring synchronized and stable laser light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser light is transmitted through optical fiber over long distance, then the atomic clock system can compare time at distant locations, but fiber noise superimposes on the laser light causing frequency instability
Solution Approach 1:
The patent implements fiber noise cancellation by feeding back a portion of the laser light that has traveled through the optical fiber to the source location. This feedback signal contains the accumulated fiber noise, which is then used to generate a correction signal that cancels the noise when applied to the laser light before transmission. This feedback mechanism resolves the contradiction by actively compensating for the fiber noise that degrades frequency stability while maintaining the long-distance time comparison capability.
Solution Approach 2:
The patent combines two different frequency stabilization techniques into a composite stabilization system: phase modulation technique for removing low-frequency noise components and Pound-Drever-Hall technique for removing high-frequency noise components. This composite approach addresses the full spectrum of fiber noise, resolving the contradiction between maintaining frequency stability and enabling long-distance transmission by handling different noise frequency ranges with specialized methods.
2Reliability
If conventional fiber noise cancellation is used, then low-frequency noise can be removed, but high-frequency noise components remain uncanceled
Solution Approach 1:
The patent segments the noise removal task into two distinct frequency ranges: low-frequency noise is handled by the phase modulation technique, and high-frequency noise is handled by the Pound-Drever-Hall technique. This segmentation allows each technique to be optimized for its specific frequency range, resolving the contradiction by ensuring comprehensive noise removal across the entire spectrum rather than attempting a single technique to handle all frequencies.
Solution Approach 2:
The patent changes the stabilization parameters by employing two different stabilization techniques with different operational characteristics. The phase modulation technique targets low-frequency deviations, while the Pound-Drever-Hall technique targets high-frequency deviations. By adjusting which technique handles which frequency range, the system achieves complete noise removal, resolving the contradiction between partial and complete noise cancellation.
3Measurement precision
If a single frequency stabilization device is used, then the device complexity is low, but it cannot remove both low-frequency and high-frequency noise components
Solution Approach 1:
The patent segments the frequency stabilization function into two separate devices: one dedicated to low-frequency noise removal via phase modulation, and another dedicated to high-frequency noise removal via Pound-Drever-Hall technique. This segmentation allows each device to be simpler and more specialized, while together they achieve comprehensive noise removal, resolving the contradiction by distributing complexity across multiple specialized components rather than requiring one complex universal device.
Solution Approach 2:
The patent creates a universal frequency stabilization system that handles both low-frequency and high-frequency noise by combining two stabilization techniques. While implemented as separate devices, the system as a whole provides multi-functional capability, resolving the contradiction by achieving comprehensive noise removal through a modular universal system rather than requiring a single complex device.
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
The system stabilizes laser light frequency at both local and remote sites, enabling precise time observation and synchronization between multiple atomic clocks connected by optical fibers.
Implementation Method 1
a reflection mechanism that is disposed on an optical path between the optical fiber and the second optical modulator, and reflects a portion of laser light traveling through the optical fiber toward the second optical modulator to return the portion of the laser light to the optical fiber as feedback light
Implementation Method 2
a first frequency stabilization device disposed to configure a negative feedback circuit on an optical path between the laser light source and the first optical modulator, wherein the first frequency stabilization device uses the first laser light and the feedback light to remove fiber noise superimposed on the first laser light
Implementation Method 3
a second frequency stabilization device disposed to configure a negative feedback circuit on an optical path between the second optical modulator and the second atomic clock, wherein the second frequency stabilization device removes a noise of a high-frequency component superimposed on the second laser light
Data Source
AI summary
An atomic clock system comprises: a laser light source that outputs first laser light; a first atomic clock; a first optical modulator; a second optical modulator that receives laser light from the first optical modulator through an optical fiber, a reflection mechanism; a second atomic clock; a first frequency stabilization device; and a second frequency stabilization device.