Optical OFDM Sub-Channel Generation for 100 Gbit/s Transmission
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Solution Overview
Problem
Current methods for generating 100 Gbit/s OFDM signals for optical transmission face limitations due to high-speed electronic device bandwidth constraints, making real-time 100 Gbit/s OFDM transmission unachievable, and existing optical components suffer from significant penalties from residual chromatic dispersion and polarization mode dispersion.
Innovation Solution
The method involves generating multiple orthogonal optical sub-channels from a single lightwave source using carrier-suppressed up-converted OFDM signals, reducing the bandwidth requirement for each sub-channel to 1/n, allowing for 100 Gbit/s or higher transmission with improved dispersion and PMD tolerance by using optical carrier suppression and external modulation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electrical OFDM signal generation is used for 100 Gbit/s optical transmission, then spectral efficiency is improved, but electronic device bandwidth limitations prevent real-time transmission
Solution Approach 1:
The patent replaces the electrical domain OFDM signal generation system with an optical domain system. Instead of using high-speed electronic devices (A/D and D/A converters) to generate OFDM signals, the invention uses optical frequency combs and optical modulators to directly generate optical OFDM signals, thereby avoiding the bandwidth limitations of electronic devices and enabling real-time 100 Gbit/s transmission.
2Length of stationary object
If 100 Gbit/s signals are transmitted over wide-area network, then transmission distance is improved, but chromatic dispersion and polarization mode dispersion cause strong penalties
Solution Approach 1:
The patent segments the 100 Gbit/s signal into multiple lower-rate sub-channels (e.g., four 25 Gbit/s sub-channels) using orthogonal frequency division multiplexing. Each sub-channel experiences reduced dispersion effects due to its narrower bandwidth, allowing transmission over longer distances without severe penalties from chromatic dispersion and polarization mode dispersion.
Solution Approach 2:
The patent changes the spectral parameters of the transmission signal by using optical frequency combs with specific spacing and applying carrier-suppressed modulation. This creates sub-channels with optimized spectral characteristics that are more tolerant to dispersion effects, enabling extended transmission distances.
3Productivity
If multiple optical sub-channels are combined for 100 Gbit/s transmission, then spectral efficiency is improved, but device complexity increases
Solution Approach 1:
The patent uses a single optical frequency comb source that simultaneously generates multiple optical carriers for multiple sub-channels. This single source performs the function of multiple individual laser sources, reducing system complexity while maintaining high spectral efficiency through parallel sub-channel transmission.
Solution Approach 2:
The patent combines multiple sub-channels into a single optical spectrum using wavelength division multiplexing. The optical modulators and combiners are designed to efficiently merge the sub-channels, achieving high spectral efficiency while keeping the overall device structure manageable through integrated optical 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
This approach enables high-speed, long-distance optical transmission with increased spectral efficiency and tolerance to polarization mode dispersion and chromatic dispersion, facilitating longer transmission distances and higher capacity optical communication networks.
Implementation Method 1
generating at least two lightwave carriers from a lightwave source, the carriers having a wavelength spacing
Implementation Method 2
creating an up-subchannel and a down-subchannel orthogonal to one another and spaced apart based on the wavelength spacing from modulations of the lightwave carriers according to respective up-converted OFDM signals
Implementation Method 3
combining one lightwave from the up-subchannel and one lightwave from the down-subchannel into an optical channel for transmission over an optical fiber
Data Source
AI summary
A method includes generating at least two lightwave carriers from a lightwave source, the carriers having a wavelength spacing, creating an up-subchannel and a down-subchannel orthogonal to one another and spaced apart based on the fixed wavelength spacing from modulations of the lightwave carriers according to respective up-converted OFDM signals that are carrier suppressed, and combining one lightwave from the up-subchannel and one lightwave from the down-subchannel into an optical channel for transmission over an optical fiber.