Tunable Laser OTDR in Optical Network Units
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Solution Overview
Problem
In optical point-to-multipoint (p2mp) fiber scenarios, conventional OTDR measurements are hindered by high attenuation and signal superposition, making it impossible to determine which reflected signal comes from which subscriber's device, thus complicating fiber failure identification and repair.
Innovation Solution
A method and device utilizing a tunable laser for OTDR operations within an optical network unit (ONU) to send a signal and detect reflections, allowing for distance determination of fiber failures, even in p2mp scenarios, using homodyne or heterodyne receivers and enabling OTDR measurements at the subscriber's home, without requiring additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional OTDR measurements are used in p2mp fiber scenarios, then fiber failure detection is possible, but the high attenuation and signal superposition make it impossible to identify which reflected signal comes from which subscriber's device
Solution Approach 1:
The patent segments the p2mp network measurement problem into individual subscriber measurements by assigning each ONU a unique wavelength. This allows the reflected signals from different subscribers to be separated and identified individually, resolving the signal superposition issue that prevents precise failure location identification in conventional p2mp OTDR measurements.
Solution Approach 2:
The patent introduces wavelength as an intermediary parameter to differentiate between signals from different subscribers. By assigning unique wavelengths to each ONU and using a tunable laser to scan these wavelengths, the system can identify which subscriber's fiber contains a failure, overcoming the limitation of signal superposition in p2mp configurations.
2Measurement precision
If a tunable laser is used for OTDR measurements in each ONU, then precise failure location determination is enabled, but the device complexity and cost increase
Solution Approach 1:
The patent makes the tunable laser serve multiple functions: it acts as both the measurement signal source for OTDR and the data transmission source for normal communication. The same laser is tuned to different wavelengths for different purposes, eliminating the need for separate measurement and communication hardware in each ONU, thereby reducing overall device complexity despite the precision measurements enabled.
3Reliability
If OTDR measurements are performed during normal traffic, then failure detection is immediate, but other subscribers' traffic is influenced and degraded
Solution Approach 1:
The patent implements periodic OTDR measurements by scheduling them during designated measurement windows when no data transmission occurs. The tunable laser scans through assigned wavelengths during these windows to perform reflections measurements, while normal data communication resumes in between windows. This periodic alternation enables immediate failure detection while preserving network throughput during non-measurement periods.
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 fiber failure detection and location within p2mp networks, allowing for precise identification of failure points and reducing repair costs by allowing subscribers to report findings via wireless interfaces, without influencing other subscribers' traffic.
Implementation Method 1
a receiver detects a reflected signal sent by the tunable laser
Implementation Method 2
OTDR (Optical Time Domain Reflectometry) can be used to identify such problem and to locate the point of failure
Implementation Method 3
wherein the receiver is a homodyne receiver or a heterodyne receiver
Implementation Method 4
wherein the receiver is a homodyne receiver or a heterodyne receiver
Data Source
Figure 1
AI summary
A method and a device for signal processing in an optical network unit are provided, said method comprising the steps of (i) a tunable laser sends a signal via an optical fiber; (ii) a receiver detects a reflected signal sent by the tunable laser; and (iii) based on said reflection a distance to the reflection is determined. Furthermore, a communication system is suggested comprising said device.