Optical Signal Power Control via Counter-Propagating Supervisory Signal

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Solution Overview

Problem

Current lightwave communication systems pose safety risks due to high-power optical signals, and existing fault detection methods are slow and unreliable, particularly in multi-wavelength systems, as they rely on handshaking between network elements, which can fail if the downstream element cannot communicate with the upstream element.

Innovation Solution

The method involves using a counter-propagating supervisory signal to automatically reduce optical signal power at both upstream and downstream network elements upon detection of a fault in the optical fiber, eliminating the need for additional signaling and reducing response time by employing APR circuitry within repeaters to control gain elements like optical amplifiers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If downstream network elements monitor fault and notify upstream elements, then fault detection capability is achieved, but response time is increased due to handshaking delay

Engineering Contradiction:

Improvefault detection capabilityVSAvoidresponse time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

A supervisory signal is continuously transmitted upstream from downstream network elements before any fault occurs. This preliminary action ensures that the upstream elements are already aware of the downstream status, eliminating the need for post-fault handshaking and enabling immediate power reduction when the supervisory signal is lost.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If handshaking between network elements is used for fault notification, then upstream elements can be alerted, but the system fails when downstream element cannot communicate with upstream element

Engineering Contradiction:

Improvefault notification reliabilityVSAvoidsystem failure risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of having downstream elements actively notify upstream elements of faults, the system inverts the approach by having downstream elements continuously transmit a supervisory signal upstream. The loss of this signal automatically indicates a fault, eliminating the need for downstream-upstream communication and ensuring reliability even when downstream elements cannot initiate communication.

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If optical amplifier power is increased to meet networking demands, then system capacity is improved, but safety risk from optical exposure increases

Engineering Contradiction:

Improvesystem capacityVSAvoidoptical exposure risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system implements continuous feedback through the supervisory signal transmitted from downstream to upstream elements. When a fault is detected (supervisory signal loss), the upstream elements automatically reduce their optical amplifier power, providing real-time feedback control that maintains high power during normal operation but quickly reduces it when safety risks arise.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7957643B2Method and apparatus for automatically controlling optical signal power in optical transmission systems

Publication Date: 2011.06.07 NOKIA OF AMERICA CORP

AI summary

A method and apparatus for controlling the power level of an optical signal includes detecting the loss of a supervisory signal counter-propagating in an optical fiber.