Reflective Optical Network Unit Reducing Rayleigh Backscatter Noise
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Solution Overview
Problem
Optical fiber communication systems face interference noise from Rayleigh backscatter effects, particularly affecting upstream data transmission due to the elliptical cross-sectional area of fibers, leading to increased carrier and signal Rayleigh backscattering noise.
Innovation Solution
The system generates two downstream signals through different fibers, with only one being modulated to generate an upstream signal, thereby reducing signal Rayleigh backscatter noise by preventing the reflection of noise back to the reflective modulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a reflective optical network unit with reflective modulator is used to deliver upstream signals, then the system can reuse optical carriers and simplify the network structure, but Rayleigh backscatter noise increases significantly affecting upstream data transmission
Solution Approach 1:
The downstream signal is segmented into two separate fibers (first fiber and second fiber). The first fiber carries the optical carrier to the reflective modulator, while the second fiber carries a separate downstream signal that does not undergo modulation. This segmentation prevents the interaction between the optical carrier and the reflective modulator that generates Rayleigh backscatter noise, while still allowing the system to use a reflective ONU structure.
Solution Approach 2:
A second downstream signal is introduced as an intermediary element that travels through a separate fiber path. This intermediary signal serves as a placeholder that prevents the optical carrier from being modulated by the reflective modulator, thereby eliminating the source of Rayleigh backscatter noise while maintaining system functionality.
2Ease of manufacture
If the optical fiber has an elliptical cross-sectional area due to manufacturing, then the fiber can be produced with standard manufacturing processes, but Rayleigh backscatter interference is enhanced
Solution Approach 1:
The harmful interaction that generates Rayleigh backscatter noise is extracted from the system by separating the optical carrier path from the signal modulation path. The optical carrier in the first fiber does not interact with the reflective modulator, effectively removing the source of noise generation while preserving the ease of manufacturing standard optical fibers.
3Speed
If carrier Rayleigh backscattering is generated during optical carrier delivery, then the optical carrier can be transmitted through the fiber, but the reflected noise degrades signal transmission quality
Solution Approach 1:
The optical carrier transmission is segmented into a dedicated first fiber that does not interact with the reflective modulator. This separation allows the optical carrier to be transmitted at full speed through the fiber without generating Rayleigh backscatter noise, while the second fiber carries the modulated signal, thereby maintaining both transmission speed and signal quality.
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 effectively decreases Rayleigh backscatter noise, improving signal transmission quality as evident from reduced bit error rates and clear eye diagrams in upstream signal reception.
Implementation Method 1
The first terminal of the optical circulator receives the optical carrier and delivers the optical carrier to the fiber coupled to the second terminal of the optical circulator
Implementation Method 2
A reflective optical network unit (RONU) having at least one reflective modulator is established, in which the reflective modulator reuses the optical carrier and delivers the upstream signal of the client
Implementation Method 3
the portions of the light signal or the radio frequency signal delivered in fibers are constantly reflected by the fibers. Finally, the reflected signals delivered to the receiver of the central office become Rayleigh backscatter noise
Data Source
AI summary
An optical fiber communication system is provided, including a central office and an optical network unit. The central office generates a first downstream signal and a second downstream signal according to a radio frequency signal and a baseband signal, respectively. The optical network unit is coupled to the central office to receive the first downstream signal and the second downstream signal through a first fiber and a second fiber different from the first fiber, respectively, such that the optical network unit only modulates the second downstream signal to generate an upstream signal and then delivers the upstream signal to the central office through the first fiber, thereby decreasing signal Rayleigh backscatter noise.