Optical Network Device PDL Position Detection
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Solution Overview
Problem
Current methods for detecting polarization-dependent loss (PDL) in optical fiber transmission lines are inefficient, requiring dedicated test lights and disrupting communication services, and struggle to accurately identify the position of PDL occurrence, especially in long transmission lines.
Innovation Solution
An optical network device that receives optical signals with added polarization information, uses a coherent receiver and digital signal processor to generate electric-field-information signals, and calculates correlation values at multiple positions to identify variations in signal power, allowing for the detection of PDL occurrence without disrupting communication services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated test light is inserted into the transmission line to measure PDL, then measurement accuracy is improved, but communication services must be stopped
Solution Approach 1:
The patent makes the transmission line serve dual purposes: it simultaneously carries both communication signals and measurement signals. By embedding measurement functionality within the existing communication infrastructure, the system can perform PDL measurements without interrupting service, as the measurement process utilizes the same transmission medium already in use for communication.
Solution Approach 2:
The system performs self-measurement by injecting test signals through the same transmission line and analyzing the returned signals to detect PDL. The transmission line itself provides the measurement capability through its interaction with the injected test signals, eliminating the need for separate dedicated measurement equipment or service interruptions.
2Measurement precision
If optical power is tapped at multiple positions to detect PDL position, then position detection capability is improved, but effort and time required increase significantly
Solution Approach 1:
The patent introduces a virtual measurement point concept that acts as an intermediary. Instead of physically tapping at multiple positions, the system calculates equivalent optical power at various virtual positions along the transmission line by analyzing signals at a single physical location. This mathematical intermediary enables multi-position detection capability without the physical complexity and time consumption of actual multi-point measurements.
Solution Approach 2:
The patent replaces the mechanical approach of physically tapping and measuring at multiple positions with a computational method. By using signal processing and mathematical calculations on signals obtained at a single position, the system substitutes physical multi-point measurement with virtual multi-point analysis, dramatically reducing measurement time and effort.
3Measurement precision
If polarization angle is changed step by step to measure PDL, then measurement completeness is improved, but measurement time increases
Solution Approach 1:
The patent applies partial action by measuring PDL at a limited set of critical polarization angles rather than continuously sweeping through all possible angles. By identifying and measuring only the angles that produce maximum and minimum optical power (which are sufficient to calculate PDL), the system achieves complete PDL measurement with significantly reduced measurement time compared to exhaustive angular scanning.
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
Enables efficient detection of PDL positions along the transmission line without interrupting communication services, reducing the effort and time required to identify issues, even in long fiber lengths.
Implementation Method 1
a receiver configured to generate electric-field-information signal that indicates an electric field of the optical signal
Data Source
AI summary
An optical network device receives an optical signal, to which polarization information is added, from a transmitter via a transmission line. The receiver generates electric-field-information signal of the optical signal. The processor acquires, for respective polarization rotation amounts, the electric-field-information signal during a period specified by the polarization information. The processor calculates, for respective polarization rotation amounts and based on the electric-field-information signal, evaluation values corresponding to powers of the optical signal at a plurality of positions on the transmission line. The processor calculates, for respective positions, variations in the evaluation values corresponding to the polarization rotation amounts. The processor output information that indicates a first position when the variation in the evaluation values for the first position is larger than that for a second position where the second position is adjacent to the first position on a transmitter side.