Optical Transmitter Adaptive Frequency Comb and Modulation
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Solution Overview
Problem
Conventional optical communication systems face challenges in maintaining signal quality at high transmission capacities due to OSNR degradation, waveform distortions, and varying network conditions, requiring flexible modulation schemes and Baud Rates to adapt to changing traffic volumes and transmission distances.
Innovation Solution
An optical transmitter with a multi-frequency phase-synchronized light source, frequency selection demultiplexer, and optical modulators that vary modulation rates and frequencies in response to dynamic network conditions, using a reference clock for synchronization and control, enabling flexible modulation and Baud Rate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmission capacity per single wavelength is increased, then communication capacity is improved, but signal quality deteriorates due to lowered OSNR and waveform distortions
Solution Approach 1:
The patent divides a high-capacity signal into multiple lower-capacity sub-wavelength signals that can be transmitted simultaneously. By segmenting the total communication capacity into multiple sub-channels, each sub-signal experiences less distortion and maintains better signal quality, while the aggregate capacity meets the high throughput requirement.
Solution Approach 2:
The patent employs dynamic modulation schemes that can adaptively adjust modulation depth and format based on real-time channel conditions. This allows the system to optimize the balance between transmission capacity and signal quality by switching between different modulation modes (e.g., QPSK, 16QAM, 64QAM) depending on OSNR and dispersion conditions.
2Device complexity
If fixed modulation schemes are used, then system simplicity is maintained, but flexibility to respond to varying network conditions is reduced
Solution Approach 1:
The patent implements dynamically adjustable modulation schemes that can change modulation format, rate, and other parameters in response to varying network conditions such as traffic demand, transmission distance, and channel quality. This enables the system to adapt between simple low-order modulation for long distances and complex high-order modulation for short distances, optimizing both simplicity and flexibility.
Solution Approach 2:
The patent changes key transmission parameters including modulation order, symbol rate, and wavelength spacing dynamically based on network requirements. By adjusting these parameters, the system can respond to varying traffic volumes and transmission distances without requiring complete system redesign, thus maintaining relative simplicity while achieving high adaptability.
3Productivity
If uniform frequency spacing is used, then spectral efficiency is improved, but adaptability to different signal bandwidths is reduced
Solution Approach 1:
The patent employs dynamically adjustable frequency spacing between sub-wavelength channels based on the specific bandwidth requirements of different signals. This allows the system to maintain tight frequency spacing for narrowband signals to maximize spectral efficiency, while allowing wider spacing for broadband signals to prevent interference, thus achieving both efficiency and adaptability.
Solution Approach 2:
The patent applies different frequency spacing strategies to different parts of the spectrum based on local signal characteristics and bandwidth requirements. Each sub-wavelength channel can be assigned optimal spacing according to its specific needs, allowing narrowband signals to pack tightly while broadband signals receive sufficient separation, thereby achieving local optimization of spectral efficiency and adaptability.
Data Source
AI summary
A clock signal from a single reference clock is frequency converted, and the frequency-converted signal is input to an equal-interval-optical-frequency-comb generator and a modulator of an optical modulator. By varying the electric frequency of the clock signal input to the equal-interval-optical-frequency-comb generator, frequency intervals of a frequency comb to be generated can be varied, while by selectively employing a particular optical frequency from among the continuous light beams of the generated frequency comb, a frequency comb having unequal intervals can be generated. It is also possible to vary the modulation rate by varying the clock frequency of a driving signal to be input to the optical modulator. By using a clock signal of a single reference clock, the frequency intervals of the frequency comb and the variation of the modulation rate synchronize with each other.