Optical Network Phase Noise Correction via Distributed ONU Feedback
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Solution Overview
Problem
Conventional optical network architectures face challenges in maintaining signal coherence and linewidth requirements across multiple Optical Network Units (ONUs) due to varying phase noise experienced through optical splitters and fibers, which cannot be effectively corrected by a single phase shift from the Optical Line Termination (OLT).
Innovation Solution
Implementing Active Noise Cancellation (ANC) mechanisms at both the OLT and each ONU, using reference signals and phase shifters to minimize phase noise, with each ONU generating a reference optical signal and applying phase corrections based on error signals generated from reflections, ensuring that the downstream optical signal meets specific requirements across all ONUs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single phase shift is applied by the OLT to correct phase noise for multiple ONUs, then the device complexity is reduced, but the manufacturing precision of signal coherence and linewidth requirements cannot be met across all ONUs
Solution Approach 1:
The patent segments the phase correction function by implementing separate phase correction units at each ONU rather than a single centralized correction at the OLT. Each phase correction unit independently measures and corrects phase noise for its specific ONU, allowing precise control of signal coherence and linewidth requirements for each user despite the overall system complexity
Solution Approach 2:
The patent implements feedback mechanisms where each ONU measures its actual phase noise characteristics and provides this information back to the OLT. The OLT then uses this feedback to dynamically adjust phase correction parameters, enabling precise control of signal properties for each ONU while managing system complexity through intelligent control
2Manufacturing precision
If phase noise cancellation is implemented at each ONU with reference signals and error signal generators, then the signal coherence requirements are met, but the device complexity at each ONU increases
Solution Approach 1:
The patent implements self-service by having each ONU generate its own reference optical signal and measure its specific phase noise characteristics. Each ONU independently performs phase noise measurement and correction without requiring complex centralized control, reducing the complexity burden at each node while maintaining signal coherence requirements
Solution Approach 2:
The patent uses parameter changes by dynamically adjusting phase shift values based on measured error signals. The phase correction units modify phase parameters in real-time according to actual phase noise conditions, enabling precise signal coherence control through adaptive parameter adjustment rather than fixed complex hardware configurations
3Measurement precision
If reference optical signals are transmitted at different wavelengths than the main optical signals, then phase noise measurement accuracy is improved, but the use of energy increases due to additional wavelength conversion and signal processing
Solution Approach 1:
The patent applies partial action by using wavelength-division multiplexing to combine the reference signal and main signal transmission, where only the necessary portion of the optical spectrum is used for phase noise measurement. This allows accurate phase noise measurement at the required wavelength while minimizing the additional energy consumption that would result from separate dedicated reference signal transmission paths
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
This approach enables the generation of optical signals with reduced phase noise, meeting strict coherence and linewidth requirements, enhancing the performance of optical networks, particularly in applications like Quantum Key Distribution and distributed massive MIMO systems.
Implementation Method 1
each reference optical transmitter is configured to transmit a reference optical signal on the associated second optical fibre
Implementation Method 2
The reference optical signal may be reflected by the optical splitter so as to generate the reflection of the reference optical signal
Implementation Method 3
each reference phase shifter is configured to apply a phase shift to the first optical signal based on the reference error signal
Data Source
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AI summary
This invention provides an optical network, and a method in an optical network, the optical network comprising: a first optical transmitter; an optical splitter; a plurality of optical receivers; a first optical fibre connecting the first optical transmitter and the optical splitter; a plurality of second optical fibres, each second optical fibre connecting the optical splitter to a respective optical receiver of the plurality of optical receivers, wherein the first optical transmitter is configured to transmit a first optical signal to each optical receiver of the plurality of optical receivers via the first optical fibre, the optical splitter and a respective second optical fibre of the plurality of second optical fibres; and a plurality of second optical fibre phase correction units, each second optical fibre phase correction unit being associated with a second optical fibre of the plurality of second optical fibres, each second optical fibre phase correction unit comprising a reference optical transmitter, a reference error signal generator and a reference phase shifter, wherein: each reference optical transmitter is configured to transmit a reference optical signal on the associated second optical fibre of the plurality of second optical fibres, each reference error signal generator is configured to generate a reference error signal based on a reflection of the reference optical signal on the associated second optical fibre of the plurality of second optical fibres, and each reference phase shifter is configured to apply a phase shift to the first optical signal based on the reference error signal.