Single-Fiber Optical Ring Networks Using Double Sideband Modulation
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Solution Overview
Problem
Single-fiber optical ring networks require twice the number of optical WDM wavelengths compared to dual-fiber networks to avoid interference, necessitating two optical transmitters and increasing costs due to the need for counter-propagating signals at different wavelengths.
Innovation Solution
Implementing double sideband modulation (DSB) to produce two optical WDM wavelengths from a single carrier beam, allowing for counter-propagating signals to carry the same channel, reducing the number of transmitters needed and increasing spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If single-fiber optical ring networks use counter-propagating signals at different wavelengths, then interference is avoided, but the number of optical WDM wavelengths required doubles compared to dual-fiber networks
Solution Approach 1:
The patent combines the functions of multiple optical transmitters into a single transmitter by using double-sideband modulation. The single transmitter generates both upper and lower sideband signals that propagate in opposite directions through the single fiber, eliminating the need for separate transmitters for each direction and reducing the total number of WDM wavelengths required.
Solution Approach 2:
The patent changes the modulation parameters by using double-sideband modulation with carrier suppression. This modulation technique generates symmetric sidebands around a carrier frequency, where the upper sideband propagates in one direction and the lower sideband propagates in the opposite direction. This parameter change allows a single transmitter to produce counter-propagating signals at different wavelengths without requiring twice the number of transmitters.
2Reliability
If twice the number of optical WDM wavelengths are used, then counter-propagating signals can be distinguished, but the number of optical transmitters increases and costs increase
Solution Approach 1:
The patent merges multiple transmitter functions into a single optical transmitter by implementing double-sideband modulation. This single transmitter generates both upper and lower sideband signals that are automatically differentiated by their frequency offsets from the carrier, allowing counter-propagating signals to be distinguished without requiring multiple separate transmitters, thereby reducing device complexity and cost.
Solution Approach 2:
The single optical transmitter becomes multi-functional by generating both upper and lower sideband signals that serve different propagation directions. The transmitter simultaneously performs the functions of multiple transmitters would otherwise be needed, making it universal for bidirectional communication in the single-fiber ring network.
3Device complexity
If double sideband modulation is used to produce two optical WDM wavelengths from a single carrier, then the number of transmitters is reduced, but spectral efficiency must be maintained
Solution Approach 1:
The patent uses parameter changes in the modulation domain by applying double-sideband modulation with carrier suppression. This technique generates upper and lower sidebands symmetrically positioned around the carrier frequency, with each sideband offset by the modulation frequency. This parameter arrangement allows efficient spectral utilization where the total bandwidth occupied by both sidebands is minimized while still providing distinguishable wavelengths for counter-propagating signals.
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 maintains network capacity within a given spectral band while reducing the number of optical transmitters required, thereby lowering costs and enhancing spectral efficiency in single-fiber ring networks.
Implementation Method 1
modulate the optical carrier beam in response to at least one modulation signal at a modulation frequency carrying a signal channel as a baseband signal to produce a modulated optical beam carrying, at least, a first optical add signal at the first optical WDM frequency greater than the optical carrier frequency by the modulation frequency and a second optical add signal at the second optical WDM frequency less than the optical carrier frequency by the modulation frequency while energy at the optical carrier frequency is suppressed
Data Source
AI summary
Systems, apparatus and methods for implementing single-fiber optical ring networks based on double side band modulation.