Optical Transceiver Adaptive Frequency Control
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Solution Overview
Problem
In dense wavelength division multiplexing (DWDM) optical communication systems, the increased density of channels leads to cross-talk due to tight packing, which is undesirable and can be mitigated by reducing spectral gaps without sacrificing data rate.
Innovation Solution
The use of a common optical frequency reference in the downlink signal to stabilize the center frequency of uplink sub-channels, allowing for tight packing with small guard bands and reduced cross-talk, achieved through an optical transceiver with a signal processor that adjusts the optical frequency of modulated light based on the frequency offset of the sub-channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If channels are tightly packed to reduce spectral gap, then spectrum utilization is improved, but cross-talk between channels increases
Solution Approach 1:
The patent changes the frequency parameter of optical channels by using adaptive frequency control. The system measures the actual optical frequency of each channel and adjusts it dynamically to maintain optimal spacing, thereby reducing cross-talk while preserving tight packing for high spectrum utilization.
Solution Approach 2:
The patent implements a feedback mechanism where the optical frequency of each channel is measured and the information is used to adjust the frequency of subsequent channels. This closed-loop control ensures that channels remain properly spaced despite variations in laser frequency or environmental conditions, resolving the cross-talk issue while maintaining tight packing.
2Productivity
If guard bands are reduced to increase channel density, then spectral efficiency is improved, but cross-talk potential increases
Solution Approach 1:
The patent dynamically adjusts the optical frequency parameter of each channel to compensate for reduced guard bands. By measuring the actual frequency and making real-time adjustments, the system maintains effective channel separation even with minimal guard bands, achieving high channel density without increasing cross-talk.
Solution Approach 2:
The feedback mechanism measures the actual optical frequency of transmitted channels and uses this information to adjust subsequent channels. This ensures that even with reduced guard bands, the effective spectral separation is maintained through active frequency control, preventing cross-talk while maximizing channel density.
3Adaptability or versatility
If more channels are added with reduced data rate per channel, then wavelength granularity is improved, but cross-talk between channels increases
Solution Approach 1:
The patent applies adaptive frequency control to each individual channel, measuring and adjusting the optical frequency parameter to maintain proper spacing across the entire spectrum. This allows the system to support fine wavelength granularity with many channels while preventing cross-talk through dynamic parameter adjustment.
Solution Approach 2:
The feedback mechanism operates across all channels, measuring the actual frequency of each channel and using this information to adjust subsequent channels. This coordinated frequency control enables high wavelength granularity with many closely-spaced channels while maintaining spectral separation to prevent cross-talk.
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 effectively reduces cross-talk between optical channels while maintaining high data rates by ensuring coordinated frequency alignment of uplink sub-channels, minimizing spectral overlap and maintaining data integrity.
Implementation Method 1
an optical front end for receiving signal light comprising an optical sub-channel, and for providing an electrical signal based on the optical sub-channel; a light source optically coupled to the optical front end for providing local oscillator light thereto for mixing with the signal light
Data Source
AI summary
An optical transceiver is provided with an optical front end for receiving signal light comprising an optical sub-channel, and for providing an electrical signal based on the signal light; a light source optically coupled to the optical front end for providing local oscillator light thereto for mixing with the signal light; an electro-optical modulator coupled to the light source for receiving output light therefrom and for modulating the output light with digital information to obtain modulated light; and a signal processor operably coupled to the optical front end. The signal processor is configured for processing the electrical signal to obtain a frequency offset of the sub-channel; and adjusting an optical frequency of the modulated light based on the frequency offset. When applied to a multiple-access environment, this may allow access nodes to generate optical sub-channels in the uplink direction using the downlink optical signal as an optical frequency reference.