Optical Transmitter Frequency Control to Prevent Subcarrier Overlap
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In optical subcarrier multiplex signal transmission, overlapping of optical subcarriers on the frequency axis occurs when uplink signal wavelengths deviate, leading to reception issues and the use of an expensive optical intradyne detector with a complex configuration.
Innovation Solution
An optical transmission apparatus with an optical transmitter that modulates laser output with a subcarrier, a heterodyne detection unit, and a control unit to calculate and adjust the laser frequency to align intermediate frequencies, preventing subcarrier overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical intradyne detection is used to suppress interference noise, then signal performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the expensive and complex optical intradyne detector with a simpler, lower-cost detection system. By using heterodyne detection with intermediate frequency conversion, the system achieves adequate signal performance without requiring the sophisticated components of intradyne detection, effectively substituting a cheap solution for an expensive one.
Solution Approach 2:
The patent substitutes the optical intradyne detection mechanism with a heterodyne detection system that converts optical signals to intermediate frequency signals. This replacement changes the detection approach from direct optical domain processing to a combined optical-electrical domain process, simplifying the overall system while maintaining signal performance.
2Reliability
If carrier wave suppression is used to reduce interference noise, then signal quality is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements a feedback mechanism where the intermediate frequency detection unit detects the frequency of the received signal, and the control unit adjusts the laser frequency based on this detection to maintain proper intermediate frequency alignment. This closed-loop feedback system automatically compensates for frequency deviations, reducing the need for high manufacturing precision while maintaining signal quality.
Solution Approach 2:
The patent changes the operating parameters by introducing intermediate frequency conversion. Instead of directly suppressing the carrier wave at optical frequencies, the system converts signals to an intermediate frequency domain where frequency adjustments and alignments are more manageable, thereby reducing the stringent precision requirements while maintaining signal quality.
3Device complexity
If multiple ONUs transmit at the same frequency, then system simplicity is improved, but subcarrier overlap occurs causing reception failure
Solution Approach 1:
The patent resolves the frequency overlap problem by introducing a new dimension - intermediate frequency conversion. Instead of managing frequency allocation in the optical domain, the system converts all signals to an intermediate frequency domain where they can be properly separated and processed. This dimensional transformation allows multiple ONUs to transmit simultaneously without subcarrier overlap while maintaining system simplicity.
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 effectively suppresses subcarrier overlap on the frequency axis at a lower cost by aligning intermediate frequencies, ensuring proper reception and reducing the complexity and cost of the optical intradyne detector.
Implementation Method 1
a heterodyne detection unit that receives an optical signal in a downlink direction by heterodyne detection
Data Source
AI summary
An optical transmission apparatus includes an optical transmitter that generates an optical signal in an uplink direction by modulating output light of a laser that outputs light of a first frequency with a subcarrier on which transmission data is superimposed, a heterodyne detection unit that receives an optical signal in a downlink direction by heterodyne detection, a control unit that calculates a first intermediate frequency based on the frequency of the downlink signal received by the heterodyne detection and the first frequency of the laser, and controls the first frequency of the laser when there is a difference between the calculated first intermediate frequency and a reference second intermediate frequency by a threshold or more.