OTDR Variable Attenuator for Reflective Peak Measurement

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Solution Overview

Problem

In fiber optic networks, particularly in PONs, measuring insertion loss with low-loss splitters is challenging due to OTDR saturation and insufficient dynamic range, making it difficult to accurately detect reflective peaks without saturating the reception stage or falling below the noise floor.

Innovation Solution

An OTDR-based high reflective event measurement system utilizing a micro-electromechanical systems (MEMS) switch for calibrated attenuation to reduce and measure reflective peaks, ensuring the OTDR operates within its linear mode by using an N by M optical switch with a variable attenuator mode and fiber optic reflectors to manage signal amplitude.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the OTDR reception stage detects reflective peaks directly, then the measurement process is simple, but the OTDR saturates and cannot accurately measure insertion loss

Engineering Contradiction:

Improvemeasurement process simplicityVSAvoidinsertion loss measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

A variable optical attenuator is introduced as an intermediary component between the fiber optic link and the OTDR reception stage. This attenuator mediates the signal transmission by dynamically adjusting the attenuation level to prevent saturation of the OTDR while maintaining accurate measurement capability. The attenuator acts as a buffer that allows the OTDR to measure reflective peaks without being overwhelmed by high signal amplitudes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the OTDR dynamic range is increased to detect low-level signals, then signal detection capability improves, but the OTDR cannot handle high-amplitude reflective peaks without saturation

Engineering Contradiction:

Improvesignal detection capabilityVSAvoidOTDR saturation

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system employs a variable optical attenuator that can dynamically adjust its attenuation level based on the signal conditions. This dynamic adjustment allows the OTDR to handle both low-level signals and high-amplitude reflective peaks effectively. The attenuator transitions between different attenuation states to prevent saturation while maintaining sufficient signal strength for accurate measurement, resolving the contradiction between detection capability and saturation avoidance.

Inventive Principle:

Principle #15Dynamics

3Reliability

If a fixed attenuator is used to prevent OTDR saturation, then saturation is avoided, but the measurement flexibility and adaptability are reduced

Engineering Contradiction:

Improvesaturation preventionVSAvoidmeasurement flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The variable optical attenuator replaces fixed attenuators with a dynamically adjustable component. This allows the system to adapt to different measurement scenarios by changing the attenuation level as needed. The controller can adjust the attenuator's transmission characteristics to match the specific requirements of each measurement, providing both saturation prevention and measurement flexibility.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the attenuation parameter dynamically based on measurement requirements. By adjusting the attenuation level rather than using a fixed value, the system can adapt to varying signal conditions, different fiber link characteristics, and various reflective event magnitudes, thereby maintaining both reliability and versatility.

Inventive Principle:

Principle #35Parameter changes

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 accurate measurement of insertion loss in low-loss splitters by preventing OTDR saturation and improving signal detection, allowing for precise characterization of optical losses beyond the splitter location.

Implementation Method 1

An optical time domain reflectometer (OTDR)-based high reflective event measurement system may include an OTDR, and an N by M optical switch with a variable attenuator mode

Methodology Applied

Scientific EffectMEMS (Micro-electromechanical systems): Microelectromechanical Systems

Implementation Method 2

A variable optical attenuator may reduce, for the at least one optical fiber including the at least one fiber optic reflector, an amplitude of reflective peaks

Methodology Applied

Scientific EffectOptical attenuation: Absorption (EM radiation)

Implementation Method 3

at least one fiber optic reflector disposed at an end of the at least one optical fiber

Methodology Applied

Scientific EffectOptical reflection: Reflection

Data Source

PatentUS11646789B2Optical time-domain reflectometer (OTDR)-based high reflective event measurement

Publication Date: 2023.05.09 VIAVI SOLUTIONS INC(US)

AI summary

In some examples, an optical time-domain reflectometer (OTDR)-based high reflective event measurement system may include an OTDR, and an N by M optical switch optically connected to the OTDR or disposed within the OTDR. The optical switch may include a variable attenuator mode and at least one optical fiber connected to at least one output port of the optical switch. At least one fiber optic reflector may be disposed at an end of the at least one optical fiber. A variable optical attenuator may reduce, for the at least one optical fiber including the at least one fiber optic reflector, an amplitude of reflective peaks.