OADM Branching Unit Fiber Reduction via Null-Compensation
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Solution Overview
Problem
The existing Optical Add-Drop Multiplexer (OADM) Branching Units in submarine cable systems require 4 fibers to add or drop wavelengths from 2 trunk fibers, leading to complex designs and high costs for optical repeaters due to the imbalance in optical channel wavelengths between branches and trunks.
Innovation Solution
The implementation of a first optical coupler to separate and couple optical signals of different wavelengths from two trunk fibers, a first optical demultiplexer to separate and transmit these signals to a branch station, a second optical demultiplexer to separate null-compensation light and adjust its power, and a second optical coupler to couple the signals with the adjusted null-compensation light for transmission, reducing the number of fibers required to 2 and simplifying the optical repeater design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If 4 fibers are used to implement adding or dropping wavelengths of 2 trunk fibers, then the OADM BU can provide sufficient optical channels, but the device complexity and cost increase
Solution Approach 1:
The patent combines bidirectional optical signal transmission into a single fiber by merging the forward and reverse direction signals. The optical coupler merges signals from two trunk fibers and the optical multiplexer combines dropped wavelengths with null-compensation light, reducing the fiber count from 4 to 2 while maintaining full functionality
Solution Approach 2:
Each fiber in the invention serves multiple functions simultaneously. The single branch fiber carries both forward and reverse direction signals, and the optical coupler handles both signal combining and power distribution, making the system more efficient and reducing overall complexity
2Quantity of substance
If the number of optical channel wavelengths on the branch is less than half of trunk wavelengths, then the branch has fewer channels, but the optical repeater design becomes complicated due to wavelength imbalance
Solution Approach 1:
The invention introduces null-compensation light as an intermediary element. This dummy optical signal acts as a placeholder that balances the wavelength count between trunk and branch, allowing the optical repeater to see equal numbers of wavelengths on both sides even when the actual data channels are unbalanced
Solution Approach 2:
The system changes the optical power parameter of the null-compensation light to match and balance the power levels of actual data channels. By adjusting this parameter, the invention creates electrical balance at the optical repeater without requiring physical changes to the fiber infrastructure
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 configuration reduces the complexity and cost of the OADM BU, enhances reliability, and controls optical power within the required range, effectively addressing the challenges of wavelength imbalance and repeater complexity.
Implementation Method 1
a first optical coupler, configured to couple a part of optical signals that have different wavelengths and are respectively separated from two trunk fibers
Implementation Method 2
a first optical demultiplexer, configured to separate, according to wavelengths, optical service signals that have different wavelengths
Implementation Method 3
a second optical demultiplexer, configured to separate null-compensation light from the optical service signals transmitted by the branch station through a fiber
Implementation Method 4
a second optical coupler, configured to couple the optical signals that are output by the first optical coupler with the null-compensation light that is output by the second optical demultiplexer
Data Source
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AI summary
Embodiments of the present invention provide an Optical Add-Drop Multiplexer (OADM) Branching Unit (BU) and the corresponding optical transmission method and system. The method includes: separating a part of optical signals of different wavelengths from two trunk fibers respectively, coupling the part of optical signals of different wavelengths, and transmitting the coupled optical signals to a branch station through a fiber; separating, according to wavelengths, optical signals that have different wavelengths and are transmitted by the branch station through a fiber, and then transmitting the optical signals to the two trunk fibers respectively; separating null-compensation light from the optical service signals transmitted through a fiber by the branch station to obtain the null-compensation light; coupling the null-compensation light with the part of optical signals that have different wavelengths and are respectively separated from the two trunk fibers, and transmitting the coupled optical signals to the branch station through a fiber.