Optical Fiber SRS Characterization Using In-Service ASE Measurement
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Solution Overview
Problem
Conventional optical fiber characterization methods are time-consuming, costly, and inaccurate, often relying on out-of-service measurements and manual data entry, which do not reflect in-service conditions and lead to uncertainties in fiber span length, SRS, and dispersion measurements, affecting the performance of high-capacity optical networking systems.
Innovation Solution
In-service optical fiber characterization using integrated components at optical nodes, such as OTDR, OSC, and optical amplifiers, performing measurements like OTDR with configurable reflectors, SRS using ASE, and dispersion measurement with synchronized transmitters, enabling accurate fiber length, SRS, and dispersion determination without manual assumptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If out-of-service measurements with test equipment are used, then measurement data can be obtained, but the process is time-consuming and costly
Solution Approach 1:
The optical network element performs self-characterization by using its own operational components (transmitters, amplifiers, detectors) to measure fiber properties during normal service. The system characterizes the fiber span without external test equipment by analyzing the optical signals already present in the system, thereby eliminating the need for time-consuming out-of-service measurements.
Solution Approach 2:
The patent makes existing operational components serve dual purposes: their primary function for signal transmission and an additional function for fiber characterization measurements. The transmitter serves both to send data signals and to provide probe signals for measuring fiber properties, while amplifiers and detectors simultaneously perform signal amplification/detection and measurement functions.
2Ease of manufacture
If manual data entry and database lookups are used for fiber parameters, then fiber type information can be obtained, but errors and uncertainties increase
Solution Approach 1:
The patent replaces manual data entry and database lookup processes with automated optical measurements. Instead of mechanically entering fiber parameters or querying databases based on fiber type, the system uses optical probe signals to directly measure fiber properties such as length, attenuation, and dispersion, thereby eliminating human error and improving accuracy.
Solution Approach 2:
The system continuously monitors fiber characteristics by analyzing the optical signals passing through the fiber and uses this feedback to automatically update configuration parameters. The measured fiber properties feed back into the control system to optimize transmission settings, ensuring accurate and up-to-date fiber characterization without manual intervention.
3Measurement precision
If conventional OTDR methods are used to measure fiber length, then length estimation can be obtained, but the end of fiber cannot be unambiguously identified
Solution Approach 1:
The patent introduces an intermediary reflective element at the far end of the fiber span to create an unambiguous reference point for OTDR measurements. This intermediary device provides a strong, detectable reflection signal that clearly marks the fiber endpoint, solving the problem of identifying the fiber end in long spans where conventional OTDR reflections are too weak to detect.
4Ease of operation
If fiber nonlinearity coefficient is derived from fiber type database, then SRS measurements can be obtained, but fiber type information is often unreliable
Solution Approach 1:
The patent replaces the unreliable database lookup method with direct optical measurements of fiber nonlinearity. Instead of deriving the nonlinearity coefficient from fiber type information in a database, the system uses probe signals to directly measure Stimulated Raman Scattering (SRS) effects in the fiber, providing reliable, empirical data about actual fiber nonlinearity characteristics.
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 precise, automated fiber characterization for launch power optimization and dispersion compensation, reducing time and costs while ensuring accurate configuration of optical networks, supporting high-capacity and flexible modulation.
Implementation Method 1
Another conventional approach includes estimating the length of a fiber span in an optical system using an Optical Time Domain Reflectometer (OTDR) trace
Implementation Method 2
The fiber SRS measurements relate to fiber nonlinearity
Implementation Method 3
measuring power P2 of the optical wavelength at the downstream node with the optical amplifier configured to generate Amplified Stimulated Emission (ASE)
Implementation Method 4
The RTD measurement requires sending a data packet from node A to node B, on one fiber, returning that packet to node A on a second fiber
Data Source
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AI summary
A method (100) for characterizing stimulated Raman scattering, SRS, of an optical fiber span (12) in an optical line system (10), the method being performed, at least in part, by a first optical node (14) and comprising providing, by a wavelength source (18) at the first optical node (14), an optical test wavelength that lies outside an amplification band of an optical amplifier (16) of the first optical node (14), with the optical amplifier (16) disabled, transmitting the optical test wavelength from the first optical node (14) into the optical fiber span (12) and measuring, at a downstream node (20), a first received power (P1) of the optical test wavelength, configuring the optical amplifier (16) to generate amplified spontaneous emission, ASE, and measuring, at the downstream node (20), a second received power (P2) of the optical test wavelength, and determining an SRS metric for the optical fiber span (12) based on at least P1 and P2.