Optical Signal Processing for Rayleigh Backscattering Cancellation
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Solution Overview
Problem
Single-fiber bidirectional optical transmission systems are limited by Rayleigh backscattering noise, which reduces signal-to-noise ratio and prevents high-speed, long-distance transmission.
Innovation Solution
An optical signal processing method that estimates and removes backward optical signals, such as Rayleigh backscattering, by determining estimation information from the first sending signal and using it to correct the second sending signal, thereby improving the signal-to-noise ratio and enabling long-distance transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single-fiber bidirectional transmission is implemented to reduce fiber quantity and double spectral efficiency, then resource utilization is improved, but Rayleigh backscattering noise increases and reduces signal-to-noise ratio
Solution Approach 1:
The patent uses the forward sending signal itself to generate the estimation of the backward optical signal. By processing the known forward signal through the same optical fiber path and computational algorithms (convolution with impulse response, correlation processing), the system converts the harmful Rayleigh backscattering effect into a predictable and removable component, transforming the problem into a solvable estimation task.
Solution Approach 2:
The system performs preliminary estimation of the backward optical signal using the forward sending signal before the actual reception occurs. By calculating the impulse response and convolving it with the forward signal in advance, the system prepares the subtraction template that will be used to remove the backward signal interference from the received signal, enabling clean signal extraction.
2Length of stationary object
If transmission distance is increased to expand system coverage, then service area is improved, but Rayleigh backscattering accumulation increases and degrades signal quality
Solution Approach 1:
The system uses feedback from the forward transmission signal to continuously estimate and remove the backward optical signal interference. By monitoring the forward signal characteristics and using them to generate real-time estimates of the backward signal, the system adaptively compensates for Rayleigh backscattering effects that accumulate over long transmission distances, maintaining signal quality throughout the extended fiber span.
3Productivity
If high-speed transmission is implemented to increase data rate, then transmission capacity is improved, but the impact of backward optical signal becomes more significant and reduces effective signal reception
Solution Approach 1:
The patent replaces physical isolation methods (such as optical isolators or directional couplers) with a computational approach. Instead of using additional optical components to physically block or separate backward signals, the system uses digital signal processing algorithms to estimate and subtract the backward optical signal from the received signal, achieving interference removal through mathematical operations rather than mechanical/optical isolation.
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 method enhances the signal-to-noise ratio and allows for long-distance, high-speed single-fiber bidirectional optical transmission by effectively mitigating the impact of backward optical signals.
Implementation Method 1
an optical fiber is used to transmit both sent and received optical signals
Implementation Method 2
Rayleigh scattering is caused by a random fluctuation of fiber density during manufacturing, which leads to a local fluctuation of a refractive index. As a result, light is scattered in all directions.
Data Source
AI summary
An optical signal processing method and apparatus. The method includes: obtaining a first sending signal, where the first sending signal is a signal that is sent by a first transmitter to a second receiver through a first optical fiber; determining estimation information of a backward optical signal based on the first sending signal; the backward optical signal is generated during transmission of the first sending signal, the backward optical signal is transmitted through at least one fiber section in the first optical fiber, and a transmission direction of the backward optical signal is opposite to a transmission direction of the first sending signal; and obtaining a second sending signal based on the estimation information of the backward optical signal. According to the embodiments, impact of the backward optical signal on effective signal transmission can be reduced, and a signal-to-noise ratio can be improved.