Optical Link Disturbance Sensing via Phase Comparison
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Solution Overview
Problem
Existing techniques for sensing disturbances along optical links, such as interferometric methods, often require backscattering or reflection, which is unsuitable for long haul links due to the presence of repeater amplifiers with optical isolators that block backscattered or reflected light.
Innovation Solution
A method involving the transmission of carrier signals with phase irregularities, generation of check signals from these irregularities, and comparison at the destination to detect disturbances, eliminating the need for backscattered light by using amplitude modulation and interferometric techniques to monitor phase changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If backscattering or reflection techniques are used for disturbance sensing, then measurement capability is provided, but the technique becomes unsuitable for long haul links due to optical isolators blocking backscattered light
Solution Approach 1:
Instead of sending light back along the optical link to detect disturbances (traditional backscattering method), the invention sends light forward through the link and detects disturbances by comparing the phase of the returned light signal with the original transmitted signal. This inversion of the detection direction eliminates the need for backscattering and makes the system compatible with optical isolators in long haul links.
Solution Approach 2:
The invention introduces an intermediary comparison mechanism using a reference signal that is copied and processed alongside the transmitted signal. By comparing the phase of the returned light signal with this reference signal, the system can detect disturbances without requiring the light to backscatter along the entire link, thus solving the compatibility issue with optical isolators.
2Reliability
If optical isolators are used in repeater amplifiers to prevent feedback, then amplifier stability is improved, but backscattering-based sensing techniques become ineffective
Solution Approach 1:
The invention inverts the traditional sensing approach by not relying on light backscattering from the amplifier section. Instead, it sends light through the amplifier section and detects disturbances by comparing the phase of the transmitted and returned light signals, making the sensing technique compatible with the optical isolators that ensure amplifier stability.
Solution Approach 2:
The invention replaces the optical backscattering mechanism with an electronic signal processing approach. By converting optical phase information into electrical signals for comparison, the system can detect disturbances without relying on the optical backscattering process that is blocked by isolators, thus maintaining both amplifier stability and disturbance sensing capability.
3Adaptability or versatility
If check signals are transmitted along the optical link to monitor phase irregularities, then disturbance detection is enabled without backscattering, but additional infrastructure and signal processing requirements are introduced
Solution Approach 1:
The invention makes the existing optical communication infrastructure serve multiple functions: the same optical link used for data transmission is also used to transmit check signals for disturbance detection. The existing receivers and signal processing capabilities are utilized to perform both communication and monitoring functions, reducing the need for additional dedicated infrastructure.
Solution Approach 2:
The system uses its own transmitted signals to monitor for disturbances. By embedding check signals within the existing communication protocol and using the receiver's existing processing capabilities to compare phases, the system performs self-diagnosis without requiring external monitoring equipment or additional infrastructure.
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 effective detection of disturbances along optical links without the need for backscattered light, suitable for long haul links with repeaters, and allows for monitoring of communications traffic while minimizing additional infrastructure requirements.
Implementation Method 1
transmitting along the link carrier signals to a destination, the carrier signals having a waveform with phase irregularities
Implementation Method 2
In one type of interferometric technique, the disturbance is an environmental disturbance, such as an acoustic wave or other time-varying disturbance which causes a phase change to light signals propagating along the link
Data Source
AI summary
The present invention relates to a system for sensing of a disturbance on an optical link. Data traffic from an optical source with a short coherence length is transmitted along the link to a receiver station on one or more of a plurality of time-division-multiplexed channels. One of the channels is used to transmit encoded phase information relating to the phase characteristics of the optical source output. At the receiver station, the actual phase characteristics of the arriving light from the optical source is compared with the encoded phase information. Since a physical disturbance of the link is likely to alter the actual phase characteristics of the arriving light but not the encoded phase information, it is possible to determine if a physical disturbance has occurred. The system can conveniently be used to monitor an optical link carrying communications traffic.