Integrated Opto-Electronic Oscillator Chip With Self-Injection Locking
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Solution Overview
Problem
Existing RF signal generation techniques at microwave and millimeter-wave frequencies face challenges in achieving short-term stability (close-in to carrier phase noise and timing jitter) and long-term frequency stability due to reduced quality factors of resonators, leading to degraded timing jitter and optical side-bands, which are not adequately addressed by electronic techniques.
Innovation Solution
A compact opto-electronic oscillator chip (IOEC) integrates a mutually-coupled multi-mode laser (MML) with self-mode locking and self-injection locking techniques, using passive optical components and electrical control functions to stabilize RF signals, employing self-forced oscillation and external feedback for improved frequency synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard OEO uses long optical delay to achieve high Q factor for frequency stability, then frequency stability is improved, but timing jitter is degraded
Solution Approach 1:
The patent changes the fundamental parameter from long optical delay to short optical delay combined with self-injection locking feedback. This parameter transformation allows achieving high Q factor (frequency stability) without the harmful side effect of long delays, thereby resolving the contradiction between frequency stability and timing jitter performance
Solution Approach 2:
The patent introduces self-injection locking feedback mechanism where a portion of the laser output is fed back to the laser input through an optical delay line. This feedback loop enables the system to achieve stable oscillation and high Q factor with much shorter delay times, thus improving frequency stability while maintaining low timing jitter
2Volume of moving object
If multi-mode laser uses large number of modes for compact OEO realization, then device size is reduced, but frequency stability deteriorates
Solution Approach 1:
The self-injection locking feedback mechanism selectively stabilizes specific longitudinal modes of the multi-mode laser while suppressing others. This feedback control allows the compact multi-mode laser structure to achieve high frequency stability by locking onto well-defined spectral lines, resolving the contradiction between compact size and frequency stability
Solution Approach 2:
The patent applies local quality by selecting specific longitudinal modes from the multi-mode laser spectrum for stabilization. Instead of treating all modes equally, the self-injection locking mechanism provides selective feedback to specific modes, creating localized stability in the frequency domain while maintaining the compact multi-mode structure
3Device complexity
If electronic techniques are used for RF signal generation at microwave and millimeter-wave frequencies, then device integration is improved, but short-term stability (phase noise and timing jitter) deteriorates
Solution Approach 1:
The patent replaces purely electronic oscillation mechanisms with an opto-electronic hybrid system. The optical domain provides the stable oscillation foundation through self-injection locking, while electronic components handle signal processing. This substitution leverages the high stability of optical oscillators to overcome the phase noise and timing jitter limitations of electronic techniques, while maintaining integration benefits
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 IOEC achieves high stability and tunability with low environmental sensitivity, suitable for coherent communication systems, radar, and remote sensing, with phase noise and timing jitter significantly reduced, making it suitable for analog-to-digital and digital-to-analog converters.
Implementation Method 1
stabilized using self-forced and self-mode locking processes
Implementation Method 2
self-injection locking (SIL), self-phase lock loop (SPLL), and self-injection locked phase locked loop (SILPLL)
Implementation Method 3
either phase or intensity modulator
Implementation Method 4
optical detectors
Data Source
AI summary
In absence of electrical approaches for realization of highly stable RF oscillator, opto-electronic oscillators (OEO) techniques are provided, where self-forced oscillation techniques using long optical delays demonstrate significant short-term and long-term frequency stability. Fully integrated opto-electronic oscillator chip (IOEC) may be the most efficient realization of an RF frequency synthesizer in terms of operation frequency (covering microwave and millimeter wave), size (<10 cm3), ruggedness to environmental effects of temperature (−40 to 80 C), vibration (up to 40 g), low timing jitter (<5 fs for 40 GHz carrier), and wall-plug efficiency (output power >10 dBm from under 1 W power). A free-running III-V (primarily InP) based multi-mode laser (MML) diodes is designed with large mode number (e.g., over 60 modes) and intermodal oscillation frequency compatible with desired RF carrier signal (e.g., 1-40 GHz).