Biased Optical Microwave Phase Detector for Low-Noise Frequency Tuning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing systems for generating high-frequency signals are limited to integer multiples of the optical signal source's repetition rate, require complex designs, and are costly, with fiber-based Sagnac-loop intensity modulators occupying large space.
Innovation Solution
An adjustable signal source with a biased optical microwave phase detector using a series connection of photodiodes and controllable DC current/voltage sources to lock onto non-odd multiples of the optical pulse repetition rate, allowing for improved frequency resolution and reduced phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fiber-based Sagnac-loop intensity modulators are used, then low phase noise is achieved, but device complexity and space requirements increase
Solution Approach 1:
The patent extracts the essential function of the complex fiber-based Sagnac-loop intensity modulator and implements it using a simpler integrated photonic circuit. The intensity modulation capability is retained while removing the bulky fiber-based components, thereby reducing device complexity and space requirements while maintaining low phase noise performance.
Solution Approach 2:
The patent uses an integrated photonic circuit that copies the functional behavior of the fiber-based Sagnac-loop intensity modulator. By replicating the intensity modulation function in a compact integrated format rather than using the original fiber-based implementation, the system achieves the same phase noise performance with reduced complexity.
2Ease of operation
If symmetrical modulators are biased at odd symmetry points, then simple biasing is achieved, but frequency resolution is limited to integer multiples only
Solution Approach 1:
The patent introduces asymmetry in the modulator biasing by operating at even symmetry points rather than the conventional odd symmetry points. This asymmetric biasing approach enables the generation of non-integer frequency multiples, thereby improving frequency resolution while maintaining operational simplicity through controlled bias voltage application.
Solution Approach 2:
The patent dynamically adjusts the modulator bias voltage to switch between even and odd symmetry points, enabling flexible frequency tuning. This dynamic biasing control allows the system to achieve both simple operation and high frequency resolution by adapting the bias point according to the desired output frequency.
3Reliability
If microwave oscillators are locked to integer harmonics of optical clock, then phase noise is reduced, but frequency adaptability is limited
Solution Approach 1:
The patent implements dynamic frequency tuning by enabling the microwave oscillator to lock onto both integer and non-integer harmonics of the optical clock. This is achieved through dynamic control of the modulator bias voltage, which allows the system to adaptively select the appropriate locking point based on the desired output frequency, thereby expanding frequency adaptability while maintaining low phase noise.
Solution Approach 2:
The patent changes the operating parameters of the intensity modulator by adjusting the bias voltage to different symmetry points. This parameter change enables the system to generate frequencies that are not limited to integer multiples of the optical clock, thereby expanding the frequency range and adaptability while preserving the phase noise reduction benefits of harmonic locking.
4Reliability
If complex system designs are used, then low phase noise is achieved, but manufacturing cost and space requirements increase
Solution Approach 1:
The patent extracts the essential low phase noise function from the complex fiber-based Sagnac-loop intensity modulator and implements it using a simpler integrated photonic circuit. This extraction eliminates unnecessary complex components while retaining the core functionality, thereby reducing manufacturing cost and simplifying production without compromising phase noise performance.
Solution Approach 2:
The patent replaces the mechanical fiber-based optical system with an integrated photonic circuit implementation. This substitution eliminates the need for complex fiber alignment and assembly procedures, reducing manufacturing complexity and cost while maintaining the low phase noise performance through precise integrated circuit fabrication.
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
Enables a compact, low-phase-noise design capable of generating non-integer multiples of the optical clock frequency with enhanced frequency resolution and reduced complexity.
Implementation Method 1
a first photodiode PD1, which can be irradiated with light from the first output O1 during operation, and a second photodiode PD2, which can be irradiated with light from the second output O2 during operation
Data Source
Figure 1a
Figure 1b~3d
Figure 2
AI summary
The invention relates to an adjustable signal source with low phase noise, comprising • an optical microwave phase detector (BOMPD) comprising • an intensity modulator (BIM) having an optical signal input, a modulation input (I) and a first output (01) and a second output (02), • a first photodiode (PD1), which can be irradiated with light from the first output (01) during operation, • a second photodiode (PD2), which can be irradiated with light from the second output (02) during operation, • wherein the first photodiode (PD1) and the second photodiode (PD2) are connected in series in a biased configuration during operation, • wherein a tapping point for a tapped signal is arranged between the first photodiode (PD1) and the second photodiode (PD2), • furthermore comprising a controllable DC source (N4), • wherein an offset current can be set at the tapping point during operation by means of the first DC source (N4), whereby the symmetry of the optical microwave phase detector is eliminated during operation by way of an offset current, • wherein the tapping point with any offset current is conducted to a low-pass filter, • wherein the low-pass-filtered tapped signal is provided to an adjustable oscillator (OSZ).