Mode-Locked Laser Clock Circuit for Jitter and Phase Noise Reduction
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Solution Overview
Problem
Existing clock generation circuits fail to effectively reduce jitter in clock signals due to the presence of phase noise components, particularly DC and harmonic components, which degrade the signal-to-noise ratio and affect circuit operation.
Innovation Solution
A clock generation circuit configuration that includes a mode-locked laser, a photodetector, and a filter that attenuates at least one of the DC and harmonic components, along with an amplifier and matching circuits to further reduce jitter by selectively amplifying and matching impedance at specific frequencies, thereby improving the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pulse width of light is made narrow to reduce jitter, then the peak intensity becomes stronger, but it becomes difficult for the photodetector to receive the light
Solution Approach 1:
The patent changes the temporal parameter (pulse width) of the optical signal to be narrow for jitter reduction, while compensating for the energy loss through amplification of the electrical signal after photodetection, thus maintaining photodetector reception capability
2Use of energy by moving object
If the pulse width of light is made wide to ensure photodetector reception, then the light can be received properly, but phase noise components are generated in the spectrum
Solution Approach 1:
The patent extracts and removes the harmful phase noise components (DC component and harmonic components) from the electrical signal spectrum after photodetection, while preserving the useful signal components through selective filtering
Solution Approach 2:
The patent converts the harmful phase noise components into removable spectral components by using a filter to attenuate specific frequency ranges, thereby transforming the noise problem into a solvable filtering problem that improves overall signal quality
3Object-generated harmful factors
If a filter is added to attenuate DC and harmonic components, then phase noise is reduced, but device complexity increases
Solution Approach 1:
The patent introduces a filter as an intermediary component between the photodetector and the output, which mediates the signal by selectively attenuating harmful frequency components while passing the useful signal, thus reducing phase noise with minimal complexity addition
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 proposed configuration significantly reduces jitter in the clock signal by effectively removing or attenuating unwanted frequency components, leading to improved signal quality and reduced noise interference.
Implementation Method 1
The MLL outputs an optical pulse by a nonlinear optical effect
Implementation Method 2
a PD (Photo-Diode) 201 serving as a photodetector... the broadband PD 201 converts an optical pulse from the MLL 200 into an electric pulse
Data Source
AI summary
A clock generation circuit includes a mode-locked laser that generates an optical pulse, a photodiode that photoelectrically converts the optical pulse generated by the mode-locked laser, and a filter that attenuates at least one of a DC component and a harmonic component of the mode-locked laser included in an electric signal output from the photodiode.