Multi-Mode Optical Fiber RF Link With Optical Frequency Conversion
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Solution Overview
Problem
High-frequency wireless communication systems face challenges such as signal attenuation in coaxial cables, increased size, weight, and power consumption of RF devices, and limitations due to nonlinear optical effects like stimulated Brillouin scattering in optical systems.
Innovation Solution
A communications device utilizing a local and remote device connected by a multi-mode optical fiber, with spatial optical multiplexers/demultiplexers, opto-electric converters, and electro-optic modulators, enabling efficient transmission and processing of RF signals by generating and modulating optical carrier signals, and using fiber Bragg gratings for band pass filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical power is increased to improve system performance, then signal quality improves, but nonlinear optical effects such as stimulated Brillouin scattering limit the amount of optical power that can be utilized
Solution Approach 1:
The patent introduces an optical frequency converter as an intermediary device between the optical fiber transmission medium and the EHF signal processing components. This converter translates EHF signals to optical frequencies for transmission and back to EHF frequencies at the receiving end, enabling the system to operate at lower optical power levels while maintaining signal integrity and avoiding nonlinear optical effects.
Solution Approach 2:
The patent replaces traditional RF/electrical signal transmission through coaxial cables with optical signal transmission through optical fibers. This substitution eliminates the signal attenuation problems associated with coaxial cables at EHF frequencies and allows for long-distance transmission with lower power levels, avoiding the harmful nonlinear optical effects that occur at high power levels.
2Ease of operation
If RF devices are used in EHF communication systems, then signal transmission is enabled, but the size, weight, and power consumption of components increase to undesirable levels
Solution Approach 1:
The patent substitutes heavy RF/electrical components with lightweight optical components. By using optical fibers for signal transmission and optical frequency converters for signal processing, the system eliminates bulky RF amplifiers, mixers, and other heavy EHF components, thereby significantly reducing the size, weight, and power consumption of the communication system.
3Ease of operation
If coaxial cable is used for signal transmission, then connection between components is established, but large attenuation effects occur
Solution Approach 1:
The patent replaces coaxial cable transmission with optical fiber transmission. Optical fibers have significantly lower attenuation characteristics compared to coaxial cables, especially at EHF frequencies. This substitution enables long-distance signal transmission with minimal loss, eliminating the need for frequent signal regeneration and maintaining signal quality over extended distances.
4Ease of operation
If downstream receiver processing such as downconverting is performed, then signal reception is enabled, but the processing becomes difficult
Solution Approach 1:
The patent uses optical frequency converters as intermediary devices that perform the downconversion function in a simplified manner. These converters directly translate optical signals back to EHF frequencies at the receiving end, eliminating the need for complex multi-stage downconversion processes and signal processing chains, thereby reducing device complexity while maintaining reception capability.
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 solution allows for robust and efficient communication systems that mitigate signal degradation and nonlinear effects, reducing the size, weight, and power requirements while maintaining high signal quality over long distances.
Implementation Method 1
an electro-optic (E/O) modulator configured to generate a modulated signal onto a first remote optical output based upon modulating the first optical carrier signal from the first remote optical input
Implementation Method 2
an O/E converter coupled to the OIL source and to generate an output signal including a replica of the input signal at a second frequency based upon the reference signal
Implementation Method 3
a first band pass filter coupled downstream from the local E/O modulator and configured to pass a reference signal frequency sideband, and a second band pass filter coupled downstream from the remote E/O modulator and configured to pass a carrier frequency sideband
Data Source
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AI summary
A communications device may include a local device, a remote device, and a multi-mode optical fiber coupled between the local device and the remote device. The local device may include a local spatial optical mux/demux coupled to the multi-mode optical fiber and having first and second local optical outputs and first and second local optical inputs, and a local electro-optic E/O modulator coupled to the second local optical input. The remote device may include a remote spatial optical mux/demux coupled to the multi-mode optical fiber, and a remote E/O modulator configured to generate a modulated signal onto a first remote optical output based upon modulating the first optical carrier signal from a first remote optical input responsive to a radio frequency (RF) electrical input signal.