Optical Fiber Wavelength Labeling via Spreading Code Modulation
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Solution Overview
Problem
In optical fiber communication, the use of a sinusoidal signal for labeling wavelengths leads to signal quality degradation and increased hardware complexity due to the need for variable bandwidth filters to filter out higher harmonics, complicating system implementation.
Innovation Solution
A method employing spreading codes on both the transmit and receive ends to spread and despread message codes, allowing for accurate wavelength labeling with reduced modulation depth and simplified filter design, using orthogonal or pseudorandom sequences to correlate spreading codes with wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a sinusoidal signal is used to label wavelength, then wavelength information can be conveyed, but the main signal quality is damaged and receive sensitivity is reduced
Solution Approach 1:
The patent segments the labeling function from the main signal by using a separate low-frequency sinusoidal signal at a much lower frequency than the main signal. This frequency segmentation allows the wavelength labeling information to be carried without significantly interfering with the main signal, thus resolving the contradiction between conveying wavelength information and maintaining main signal quality.
Solution Approach 2:
The patent introduces a low-frequency sinusoidal signal as an intermediary carrier to convey wavelength information. This intermediary signal is superimposed on the main signal at a frequency much lower than the main signal frequency, acting as a mediator that carries labeling information without directly degrading the main signal quality, thereby resolving the contradiction between information transmission and signal integrity.
2Reliability
If a transmit low-pass filter is added to filter out higher harmonics, then signal quality is improved, but the filter bandwidth must be variable and system complexity increases
Solution Approach 1:
Instead of using a low-pass filter to remove harmful high-frequency components, the patent inverts the approach by using a high-pass filter to remove the low-frequency sinusoidal labeling signal from the received signal. This inversion simplifies the filter design to a fixed bandwidth high-pass filter rather than a variable bandwidth low-pass filter, reducing system complexity while maintaining signal quality.
Solution Approach 2:
The patent changes the filter type from low-pass to high-pass and fixes the bandwidth parameter. By using a high-pass filter with a fixed cutoff frequency that is higher than the sinusoidal labeling frequency but lower than the main signal frequency, the system achieves effective separation of labeling and main signals without requiring variable bandwidth control, thus resolving the contradiction between signal quality and device complexity.
3Reliability
If a message code low-pass filter is added before multiplication, then higher harmonics are filtered out, but system complexity and implementation difficulty increase
Solution Approach 1:
The patent extracts the wavelength labeling function from the main signal processing path by using a separate low-frequency sinusoidal carrier. This extraction allows the main signal to be processed independently with simple fixed bandwidth filters, while the labeling information is carried by the separate sinusoidal signal, thereby reducing system complexity and implementation difficulty while maintaining effective harmonic filtering.
Data Source
AI summary
The invention provides a method for labeling an optical fiber wavelength, including: deploying a spreading code on each of a transmit end and a receive end; transmitting a message code, and spreading the message code by using the spreading code of the transmit end; and performing envelope modulation on an optical signal by using the spread message code, transmitting the optical signal after the envelope modulation to the receive end, choosing, the spreading code of the receive end to despread the message code to obtain the original message code of the transmit end, and obtaining a corresponding wavelength according to the spreading code of the receive end. A spreading code having a correspondence with a wavelength is used to spread and despread a message code, and a modulation depth of an amplitude modulated signal may be greatly reduced to nearly prevent an envelope modulated signal from affecting a main signal.