Optical Frequency Comb Phase Noise Detection System
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Solution Overview
Problem
Current phase noise measurement techniques are inadequate for detecting ultra-low phase noise in high-stability oscillators, as they are either insensitive, require high-quality local oscillator sources, or suffer from electromagnetic interference and signal loss.
Innovation Solution
An ultra-low phase noise detection system utilizing an optical frequency comb (OFC) generator, optical couplers, microwave mixers, and optical fiber delay lines to generate millimeter wave signals, which reduces dependence on local oscillator sources and minimizes noise interference, enabling accurate measurement of phase noise in high-frequency signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If direct spectrum analyzer measurement method is used, then measurement simplicity is improved, but measurement precision deteriorates because phase noise is submerged in local oscillator noise
Solution Approach 1:
The patent introduces an optical frequency comb as an intermediary between the oscillator under test and the spectrum analyzer. The optical frequency comb acts as a mediator that transfers phase noise information from the microwave oscillator to the optical domain, where it can be measured with high precision without being contaminated by the spectrum analyzer's local oscillator noise. This resolves the contradiction by enabling both operational simplicity and high measurement precision through the optical intermediary.
2Measurement precision
If beat frequency domain method is used, then measurement precision is improved, but device complexity increases due to frequency multipliers and high requirements on reference sources
Solution Approach 1:
The patent replaces the traditional microwave-frequency multiplication mechanism with an optical frequency multiplication approach. Instead of using complex microwave frequency multipliers and stringent reference source requirements, the system uses the optical frequency comb's inherent equidistant frequency lines to achieve frequency multiplication in the optical domain. This substitution dramatically simplifies the system structure while maintaining or improving measurement precision.
3Measurement precision
If delayed self-homodyne measurement method is used, then measurement precision is improved, but loss of energy increases due to high loss of long electrical delay line
Solution Approach 1:
The patent substitutes the electrical delay line with an optical delay line implemented through the optical frequency comb. Instead of using long electrical cables that incur significant signal loss, the system employs optical propagation in the frequency comb, which experiences minimal loss. This substitution maintains the necessary time delay for self-homodyne measurement while dramatically reducing energy loss.
4Measurement precision
If phase detection method is used, then measurement precision is improved, but object-generated harmful factors increase due to local oscillator phase noise contamination
Solution Approach 1:
The patent introduces the optical frequency comb as an intermediary that isolates the measurement system from local oscillator noise contamination. The optical frequency comb serves as a buffer that transfers phase noise information from the microwave oscillator to the optical domain, where the measurement is performed using a low-noise optical local oscillator. This intermediary approach enables high-precision phase noise detection without the harmful effects of microwave local oscillator noise contamination.
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 effectively calculates and measures ultra-low phase noise levels in millimeter wave signals by eliminating local oscillator noise interference and providing a low-noise floor for high-quality oscillation sources, such as photoelectric oscillators and optical frequency clocks.
Implementation Method 1
an optical frequency comb (OFC) generator (1), wherein the OFC generator (1) is divided into two paths through an optical coupler (2)
Implementation Method 2
the OFC generator (1) is divided into two paths through an optical coupler (2)
Implementation Method 3
The electro-optical modulator is configured to modulate a n-multiplied OFC signal with the local oscillator signal and output an intensity-modulated optical signal
Implementation Method 4
The first photodetector is configured to receive the intensity-modulated optical signal and beat the intensity-modulated optical signal to obtain an electrical signal
Implementation Method 5
after passing the delay compensation link, the local oscillator signal is down-converted with the intermediate frequency signal in the first microwave mixer; a first output signal of the first microwave mixer is down-converted with the millimeter wave signal in the second microwave mixer
Data Source
AI summary
The device of the disclosure provides an optical frequency comb frequency multiplication link to generate millimeter wave signals. The device of the disclosure also provides a local oscillator and a delay compensation link to eliminate the influence of the phase noise of the local oscillator on the test system. The local oscillator signal is down-converted in the optical carrier radio frequency link to obtain an intermediate frequency signal. The intermediate frequency signal is then down-converted with the local oscillator signal and the millimeter wave signal twice to cancel the influence of the microwave mixer noise on the test system. At last, by detecting the output low-frequency signal noise, the ultra-low phase noise level of the millimeter wave signal can be accurately obtained.