Optical LO Clocking with Self-Injection Locking for Low Phase Noise
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Solution Overview
Problem
Electronic devices face challenges in supporting high data rates for wireless communications due to limitations in providing low jitter and low phase noise clocking at higher radio-frequency signals, particularly at frequencies above 100 GHz.
Innovation Solution
The implementation of clocking circuitry that includes a primary and secondary laser to generate optical local oscillator signals, coupled with a phase-locked loop and self-injection locking loop to minimize phase noise and jitter, while using optical components for efficient transmission and reception of wireless signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radio-frequency signals are used at higher frequencies to support higher data rates, then data rate capability is improved, but phase noise and jitter increase making low phase noise clocking difficult
Solution Approach 1:
The patent replaces traditional electrical RF clocking systems with an optical domain system. Optical local oscillator signals at frequencies greater than 100 GHz are generated using lasers and detected using photodiodes to produce RF clock signals. This substitution of the domain (from electrical to optical and back) enables achieving low phase noise and jitter at high frequencies where conventional electrical clocking becomes difficult.
2Reliability
If optical components are used to generate RF clock signals at frequencies greater than 100 GHz, then phase noise is minimized, but device complexity increases
Solution Approach 1:
The optical local oscillator signals generated by the lasers serve multiple functions: they directly clock the wireless circuitry for high-frequency operation and simultaneously serve as the basis for generating RF clock signals through photodetection. This multi-functionality reduces the need for separate clock generation paths and simplifies the overall system architecture despite using optical components.
Solution Approach 2:
The photodiode acts as an intermediary that converts optical local oscillator signals into RF clock signals. This intermediary component enables the transfer of the low phase noise characteristics from the optical domain to the RF domain, bridging the two domains and allowing the benefits of optical clocking to be applied to RF wireless circuitry.
3Device complexity
If traditional electrical clocking is used at high frequencies, then device complexity is reduced, but phase noise and jitter cannot be adequately controlled
Solution Approach 1:
The patent replaces traditional electrical clock distribution networks with optical clocking. By using optical local oscillator signals generated by lasers and distributed through optical paths, the system achieves superior phase noise performance. The optical signals are then converted back to RF using photodiodes, providing clean clock signals to the wireless circuitry without the phase noise limitations of electrical clocking at high frequencies.
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 minimizes phase noise and jitter, reduces power consumption, and optimizes chip area, enabling efficient wireless communication at frequencies greater than 100 GHz.
Implementation Method 1
a primary laser that emits a first optical local oscillator (LO) signal at a fixed first frequency
Implementation Method 2
a secondary laser that emits a second optical LO signal at an adjustable second frequency
Implementation Method 3
The photodiode may generate a photodiode signal based on the first and second optical LO signals
Implementation Method 4
A delay line or an optical resonator coupled between the second mixer and the secondary laser may de-correlate phase noise of the secondary laser by filtering the self-injection locking signal
Data Source
AI summary
An electronic device may include clocking circuitry with primary and secondary lasers that generate first and second optical local oscillator (LO) signals. A phase-locked loop (PLL) may tune the secondary laser based to phase lock the first and second optical LO signals. A self-injection locking loop path may couple an output of the secondary laser to its input. The self-injection locking loop path may include a first mixer and a second mixer. The first mixer may generate a beat signal using the first and second optical LO signals. The second mixer may generate a self-injection locking signal based on the first optical LO signal and the beat signal. A delay line or optical resonator may iteratively self-inject the self-injection locking signal onto the secondary laser. This may serve to minimize phase noise and jitter of the optical LO signals.