Wavelength-Reuse Optical Transceiver Using Time-Gap Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In optical wavelength division multiplex (WDM) passive optical networks, the cost of installation, administration, and maintenance is high due to the complexity and cost of components required for bi-directional digital optical signal transmission, particularly when using wavelength-reuse systems that necessitate costly modulation formats and components like FSK demodulators or IRZ/RZ pulse shaping.
Innovation Solution
The method employs a non-return-to-zero (NRZ) optical bit-interleaved seeding signal with duobinary coding, allowing for wavelength reuse without the need for pulse shaping at the optical line terminal, using a Mach-Zehnder modulator or dual electro-absorption modulator, which reduces bandwidth and enhances tolerance against chromatic dispersion, and allows direct detection at the optical network unit, thereby reducing component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wavelength-reuse transmission systems use standard modulation formats like FSK or IRZ/RZ, then bi-directional optical signal transmission can be achieved, but component costs and system complexity increase significantly
Solution Approach 1:
The patent changes the timing parameter of the optical signal by introducing a time gap within the symbol interval. The downstream signal uses NRZ-OOK modulation with a specific time gap structure that allows the upstream signal to be modulated on the same wavelength without interference, eliminating the need for complex FSK or IRZ/RZ modulation formats
Solution Approach 2:
The symbol interval is segmented into multiple sections, with the first section carrying downstream bit information and the second section available for upstream modulation. This temporal segmentation allows bidirectional communication on the same wavelength by separating the two directions in time within each symbol interval
2Reliability
If wavelength-reuse systems use complex modulation formats like FSK, then bidirectional transmission is enabled, but bandwidth requirements and component costs increase
Solution Approach 1:
The patent changes the temporal distribution of optical power within the symbol interval by introducing a time gap. This parameter change allows the downstream NRZ-OOK signal to occupy only part of the symbol interval, reducing the effective bandwidth requirement and enabling upstream modulation on the same wavelength without requiring broader bandwidth
3Ease of manufacture
If reflective optical transmitters are used for colorless ONU design, then installation and maintenance costs are reduced, but the downstream signals cannot use standard NRZ-OOK modulation
Solution Approach 1:
The patent changes the time-domain structure of the downstream signal by introducing a gap within the symbol interval. This parameter change enables standard NRZ-OOK modulation to be used with reflective optical transmitters, as the time gap provides the necessary conditions for the reflective modulator to operate correctly while maintaining colorless ONU design benefits
4Device complexity
If standard NRZ-OOK modulation is used for downstream signals in wavelength-reuse systems, then simplicity is maintained, but upstream modulation becomes impossible or suffers severe penalties
Solution Approach 1:
The patent segments the symbol interval into distinct time sections, with the first section carrying downstream NRZ-OOK signal and the second section reserved for upstream modulation. This temporal segmentation resolves the conflict by providing dedicated time slots for each direction, allowing standard NRZ-OOK to be used downstream while enabling upstream transmission without severe penalties
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 significantly reduces the bandwidth and costs associated with implementing wavelength-reuse transmission systems, achieving efficient bi-directional digital optical signal transmission with improved tolerance to chromatic dispersion, especially suitable for WDM-PON access networks providing 10 Gbit/s channel signals.
Implementation Method 1
using a Mach-Zehnder modulator or dual electro-absorption modulator
Data Source
AI summary
A method for bi-directionally transmitting digital optical signals over an optical transmission link in which a first optical transmit signal is created according to a first binary digital signal in such a way that the bit information of the first binary digital signal is included in first sections of the symbol interval of the first optical transmit signal. A second optical transmit signal is created by creating an optical wavelength reuse signal using the first optical transmit signal received at the second end of the optical transmission link, the optical wavelength reuse signal being modulated according to a second digital signal in such a way that the bit information of the second digital signal is included in second sections of the symbol interval of the first optical transmit signal received.