Passive Optical Network Protection Mechanism Using Wavelength Reflection
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Solution Overview
Problem
Passive optical transmission networks face challenges in implementing cost-effective protection mechanisms for high-capacity transmission links, particularly in long-distance connections, where providing redundant wavelength channels and active optical switches increase operational and financial burdens.
Innovation Solution
A protection mechanism is implemented by assigning both working and protection paths to the wavelength-division multiplex signal in the remote node, with a controllable optical switch in the OLT that switches between these paths upon detection of faults, using bidirectional or unidirectional optical paths, and employing passive wavelength-dependent units for signal combination and separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If line protection is implemented with a ring connection and complete replacement wavelength band, then transmission reliability is improved, but device complexity and financial effort increase
Solution Approach 1:
The patent uses optical copying/reflecting principles where the optical signal is reflected back through the same fiber using a reflector at the remote node, eliminating the need for complete replacement wavelength bands and complex switching circuitry. The protection path is created by reflecting the working signal rather than requiring separate protection wavelengths.
Solution Approach 2:
The patent replaces active mechanical/optical switching systems with a passive reflector-based system. Instead of using complex optical switches and wavelength conversion equipment, a simple reflector element is used to create the protection path, significantly reducing device complexity.
2Reliability
If redundant wavelength channels are provided for protection, then transmission reliability is improved, but loss of substance increases
Solution Approach 1:
The patent makes the working wavelength channel serve dual purposes: it carries the normal working signal and simultaneously provides the protection signal through reflection. The same physical channel and wavelength are used for both working and protection functions, eliminating the need for separate redundant wavelength channels.
Solution Approach 2:
The protection signal is created as an optical copy/reflection of the working signal rather than requiring a separate physical wavelength channel. This copying approach allows the same channel resources to be shared between working and protection functions.
3Ease of operation
If active optical switches are used for path switching, then ease of operation is improved, but use of energy and maintenance efforts increase
Solution Approach 1:
The system uses passive reflectors that automatically create protection paths without requiring active control or energy input. The protection mechanism is self-activating through optical reflection principles, eliminating the need for powered switches and reducing energy consumption.
Solution Approach 2:
The patent replaces active optical switching mechanisms with passive reflector-based path selection. The optical signal itself controls the path selection through reflection principles, eliminating the need for externally powered switching devices.
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 solution minimizes maintenance efforts and reduces costs by enabling efficient switching between working and protection paths, maintaining data transmission integrity while reducing the need for active control and additional wavelength channels.
Implementation Method 1
a controllable optical switch unit (23) is provided in the OLT (5)
Implementation Method 2
data transmission between an ONU and the RN usually taking place using a single optical fiber optic cable
Data Source
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AI summary
The invention relates to a method for protecting a passive optical transmission network comprising an optical line terminal (OLT) connected to at least one remote node having a plurality of optical networking units (ONU) connected thereto. A bidirectional optical signal transmission can be established between each ONU and the OLT, wherein the connection between the OLT and the at least one RN occurs by means of a first bidirectional optical transmission route, by means of which an optical wavelength multiplex signal is transmitted in the downstream direction from the OLT to the at least one RN and the upstream direction from the at least one RN to the OLT. According to the invention, a second bidirectional optical transmission route is provided between the OLT and the at least one RN, wherein the wavelength multiplex signal is fed in the at least one RN in the upstream direction by means of a passive optical splitter unit both to the first optical transmission route and to the second optical transmission route, and wherein upon detecting a fault state in the OLT indicating an impairment of the first or the second transmission route, an optical switching unit for transmitting the wavelength multiplex signal in the downstream direction and/or for receiving the wavelength multiplex signal in the upstream direction switches to the other optical transmission route. Said principle can also be applied according to the invention in an analogous manner to a ring-shaped connection of a plurality of RNs to an OLT. The invention further relates to a passive optical transmission network wherein said method is implemented.