Optical Network Remote Node Frequency Offset Modulation
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Solution Overview
Problem
Conventional optical networks suffer from interference caused by Rayleigh backscattering noises, which are difficult to distinguish from upstream signals due to shared wavelengths, leading to signal reception interference.
Innovation Solution
An optical network with a remote node that modulates continuous carrier waves to generate frequency offset carrier waves, allowing user devices to re-modulate and transmit upstream signals with distinct frequencies, thereby reducing interference from Rayleigh backscattering noises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same wavelength is used for continuous carrier waves and upstream signals, then wavelength division multiplexing can be simplified, but Rayleigh backscattering noises interfere with signal reception
Solution Approach 1:
The patent changes the frequency parameter of the carrier wave by introducing a frequency offset Δf. The modulated carrier wave has a frequency of f0 + Δf instead of f0, which distinguishes it from the upstream signal frequency f0. This parameter change allows the system to maintain simple wavelength division multiplexing while eliminating Rayleigh backscattering noise interference through frequency differentiation.
2Reliability
If frequency offset modulation is applied to carrier waves, then Rayleigh backscattering noise interference is reduced, but device complexity increases
Solution Approach 1:
The frequency offset modulation is applied in advance at the transmitting end before the carrier wave enters the optical fiber. By pre-modulating the carrier with a frequency offset Δf, the system proactively prevents Rayleigh backscattering noise from interfering with the upstream signal. This preliminary action simplifies the overall system operation by avoiding the need for complex noise cancellation mechanisms at the receiving end.
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
The frequency modulation technique effectively separates upstream signals from Rayleigh backscattering noises, improving signal reception quality by altering the frequency of the signals to match the frequency offset carrier waves, thus reducing interference and enhancing network performance.
Implementation Method 1
The RN receives a continuous carrier wave from the optical fiber and modulates the continuous carrier wave to generate a first frequency offset carrier wave, wherein the frequency of the first frequency offset carrier wave is different from that of the continuous carrier wave.
Implementation Method 2
the continuous carrier wave 151 produces a reflected wave 152 after traveling every small distance in the optical fiber 120, and this reflected wave 152 is the so-called Rayleigh backscattering noise.
Data Source
AI summary
An optical network and an optical signal modulation method thereof are provided. The optical network includes an optical fiber and a remote node (RN). The RN receives a continuous carrier wave from the optical fiber and modulates the continuous carrier wave to generate a first frequency offset carrier wave The frequency of the first frequency offset carrier wave is different from that of the continuous carrier wave. A first user device re-modulates and loads data to the first frequency offset carrier wave to generate a first upstream signal. The frequency of the first upstream signal is the same as that of the first frequency offset carrier wave. The RN inputs the first upstream signal into the optical fiber.