Photonic System Carrier Extraction for Signal Integrity
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Solution Overview
Problem
Microwave-photonic optical links face signal degradation due to dispersion and Stimulated Brillouin Scattering in optical fibers, and existing RF photonic devices using Mach-Zehnder modulators have limitations in operating point control and flexibility.
Innovation Solution
A photonic system that includes an optical source, a modulator, an optical filter, and a wavelength controller module to generate and filter vestigial sideband signals, allowing for flexible use of Mach-Zehnder or phase modulators, and includes a balanced optical detector for heterodyning to reduce signal saturation and scattering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large carrier signal level is used for RF transmission, then the signal strength is improved, but the receive detector saturation level is exceeded and Stimulated Brillouin Scattering occurs
Solution Approach 1:
The patent extracts and removes the carrier signal from the modulated optical signal before detection. By using optical filtering to eliminate the carrier component, the system can transmit with high power without the carrier causing detector saturation or Stimulated Brillouin Scattering, while still recovering the RF signal through detection of the sidebands alone
Solution Approach 2:
The patent converts the potentially harmful large carrier signal into a beneficial high-power transmission capability. By removing the carrier before detection, the system can utilize high optical power to overcome fiber losses and improve signal-to-noise ratio without suffering from carrier-induced saturation or scattering effects
2Adaptability or versatility
If a Mach-Zehnder modulator is used for signal modulation, then the modulation capability is improved, but the operating point control complexity increases
Solution Approach 1:
The patent removes the need for complex operating point control circuits by extracting and eliminating the carrier signal. Since the carrier is removed, the modulator no longer requires precise bias control to maintain a specific operating point, simplifying the overall system while retaining modulation capability through sideband generation
3Reliability
If vestigial sideband filtering is applied, then the bandwidth is reduced and signal degradation is minimized, but the system complexity increases
Solution Approach 1:
The patent combines the vestigial sideband filtering function with the carrier removal function into a single optical filtering stage. This integrated approach achieves both bandwidth reduction for improved signal quality and carrier elimination for reduced complexity, rather than requiring separate filtering and carrier suppression components
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 reduces signal degradation by controlling carrier power and bandwidth, enabling efficient transmission and demodulation of RF signals while minimizing Stimulated Brillouin Scattering, and allows for simplified system design using single phase modulators.
Implementation Method 1
an optical filter configured to filter the modulated signal to generate a vestigial sideband signal
Implementation Method 2
a balanced optical detector configured for heterodyning the coupled vestigial sideband signal plus a coupled carrier signal to generate an RF output signal
Implementation Method 3
This phenomenon is known as Stimulated Brillouin Scattering
Implementation Method 4
The electromagnetic optical field is coupled to acoustic waves through the process of electrostriction, which sets up an index grating that scatters the incoming optical signal in the backwards direction through Bragg diffraction
Data Source
AI summary
A photonic system and method are provided. The system includes an optical source configured to generate a carrier signal; and a modulator configured to modulate the carrier signal with a radio frequency, (“RF”) input signal to generate a modulated signal. The system also includes an optical filter configured to filter the modulated signal to generate a vestigial sideband modulated signal; and an optical detector configured to demodulate the vestigial sideband signal to generate an RF output signal. The system further includes a wavelength controller module configured to set an operating parameter of the optical source.