PAM Signal Level Distribution for Optical MPI Tolerance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multipath interference (MPI) in optical fiber systems degrades signal quality due to contaminated fiber end faces, requiring costly manual cleaning with optical time-domain reflectometer (OTDR) technology.
Innovation Solution
Implementing pulse amplitude modulation (PAM-N) with specific strength or optical power value distributions to enhance signal tolerance to MPI noise, using electro-optic modulators like Mach-Zehnder modulators for signal conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual cleaning with OTDR technology is used to reduce MPI impact, then signal quality is improved, but labor costs increase
Solution Approach 1:
The system enables self-diagnosis and self-correction by automatically detecting contaminated fiber end faces through OTDR technology and triggering cleaning operations without manual intervention. The cleaning apparatus is automatically controlled based on detection results, eliminating the need for manual cleaning while maintaining signal quality.
Solution Approach 2:
The system implements a closed-loop feedback mechanism where the OTDR continuously monitors the optical fiber system for contamination, and when contamination is detected, the system automatically activates the cleaning apparatus. The cleaning operation is controlled based on real-time feedback from the detection system, ensuring signal quality is restored while minimizing manual intervention.
2Reliability
If PAM-N modulation with non-uniform strength distribution is used, then tolerance to MPI noise is improved, but signal complexity increases
Solution Approach 1:
The system changes the parameter distribution of the PAM-N signal from uniform to non-uniform strength distribution. Specifically, the signal uses N strength values where the strength differences are non-uniformly distributed, with larger strength differences for higher strength values and smaller strength differences for lower strength values. This parameter change increases tolerance to MPI noise while the complexity is managed through standardized modulation schemes.
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
Improves signal tolerance to MPI noise in a low-cost manner without manual cleaning, maintaining signal quality by accurately distinguishing signal values despite interference.
Implementation Method 1
generating an optical signal based on the first signal; and transmitting the optical signal through an optical fiber link
Data Source
Figure 1~3
Figure 4(a)~4(b)
Figure 5~6
AI summary
This application provides an optical communication method and a communication apparatus. The method provides a solution that can reduce impact of multipath interference (multipath interference, MPI) in an optical fiber system on a transmitted signal in a low-cost manner. The method includes: A sending device sends, to a receiving device, a transmitted signal generated by the sending device based on pulse amplitude modulation-N, where strength distribution of the transmitted signal includes N strength values, the N strength values correspond to N-1 strength differences, a strength difference corresponding to a high strength value in the N strength values is greater than a strength difference corresponding to a low strength value, and the transmitted signal may be an optical signal, or may be an electrical signal. A strength distribution rule of the transmitted signal is changed, so that the strength difference corresponding to the high strength value is greater than the strength difference corresponding to the low strength value. This can effectively improve tolerance of the transmitted signal to MPI noise, and further reduce impact of the MPI in the optical fiber system on the transmitted signal in a low-cost manner.