Bidirectional Waveguide Signal Transmission with Frequency Divergence
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Solution Overview
Problem
Existing bidirectional optical communication systems face challenges in efficiently transmitting upstream and downstream signals in a waveguide due to backscattering and the need for optimal channel spacing, which compromises high capacity and signal filtering capabilities.
Innovation Solution
The method involves transmitting upstream and downstream optical signals with defined baud rates, using a Wavelength Selective Switch (WSS) to filter counter-propagating pairs of signals with a narrow frequency divergence, allowing for efficient channel spacing and filtering, and employing bidirectional amplifiers to amplify both signal directions, thereby optimizing capacity and cost-efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two separate wavebands are allocated for bidirectional transmission to avoid backscattering, then signal interference is eliminated, but waveguide resource utilization is reduced
Solution Approach 1:
The patent segments the bidirectional transmission problem by allocating different channel groups for upstream and downstream directions within the same waveguide. Each direction uses interleaved channels with specific frequency spacing, allowing separate handling of counter-propagating signals while sharing the physical medium, thus improving waveguide utilization without causing backscattering interference
Solution Approach 2:
The patent transitions from temporal multiplexing (TDM) to frequency domain multiplexing by introducing specific frequency spacing relationships. By defining minimum spacing between adjacent channels and between upstream/downstream channels, the system resolves the bidirectional interference problem in the frequency dimension rather than requiring separate time slots or wavebands
2Productivity
If channel spacing is reduced to increase transit capacity, then more channels can be transmitted, but individual channel filtering becomes difficult
Solution Approach 1:
The patent applies different spacing requirements to different channel relationships: minimum spacing between adjacent channels in the same direction, and a different minimum spacing between upstream and downstream channels. This localized quality assignment allows tight overall spacing for high capacity while maintaining sufficient separation for individual channel filtering using standard filtering windows
Solution Approach 2:
The patent changes the frequency domain parameters by defining specific minimum spacing values that are higher than the baud rate. This parameter adjustment enables the use of filtering windows with widths between the baud rate and the minimum spacing, allowing individual channel filtering even when channels are closely spaced for high capacity transmission
3Reliability
If more WSSs and amplifiers are deployed to enable individual channel filtering and bidirectional amplification, then channel selectivity and signal quality improve, but system cost increases
Solution Approach 1:
The patent makes WSSs and amplifiers multi-functional by enabling them to handle both upstream and downstream channels through the defined frequency spacing relationships. A single WSS can filter channels from both directions, and bidirectional amplifiers can amplify both upstream and downstream signals, reducing the total number of devices required while maintaining full channel selectivity and signal quality
Solution Approach 2:
The patent merges the handling of upstream and downstream channels into shared infrastructure components. By defining frequency spacing that accommodates both directions, the system allows single WSSs and bidirectional amplifiers to serve multiple channel groups, combining functions that would traditionally require separate dedicated devices for each direction
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 enables a higher transit capacity while allowing individual filtering of frequency channels, reducing the number of required WSSs and amplifiers, and improving the overall efficiency of the optical communication system.
Implementation Method 1
using a Wavelength Selective Switch (WSS) to filter counter-propagating pairs of signals with a narrow frequency divergence
Implementation Method 2
employing bidirectional amplifiers to amplify both signal directions
Data Source
Figure 1~4
AI summary
The disclosure comprises a method for transmitting both upstream (9) optical signals and downstream (10) optical signals in a bidirectional waveguide (2), comprising : transmitting a plurality of downstream optical signals at a defined baud rate, and transmitting a plurality of upstream optical signals at the defined baud rate, a minimum downstream spacing (12) between the downstream frequencies (7, 8) of two adjacent downstream optical channels and a minimum upstream spacing (12) between the upstream frequencies (3, 4) of two adjacent upstream optical channels being both higher than the baud rate, wherein the optical signals comprise a pair (3, 7) of counter-propagating optical signals carried by a downstream optical channel and an adjacent upstream optical channel, wherein the downstream frequency and the upstream frequency of the pair of counter propagating signals are separated by a frequency divergence (13) which is lower than half the minimum downstream spacing (12) and lower than half the minimum upstream spacing (12).