Optical Signal Pre-Equalization for Nonlinearity Coefficient Estimation
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Solution Overview
Problem
Existing optical transmission systems face challenges in accurately compensating for nonlinearity due to attenuation in electrical components, making it difficult to obtain a level diagram necessary for calculating compensation coefficients.
Innovation Solution
An optical transmission system with pre-equalization units, digital-to-analog and analog-to-digital converters, and scale/coefficient estimation units to accurately determine and compensate for nonlinearity by correlating amplitude distributions and calculating filter coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical modems are disposed at both ends of an optical cable to enable bidirectional communication, then communication capability is improved, but the number of components and device complexity increase
Solution Approach 1:
The patent applies universality by enabling a single optical modem to perform both transmission and reception functions through time-division multiplexing. The modem alternates between transmitting signals in one direction and receiving signals in the opposite direction, allowing one device to replace what would traditionally require two separate devices for bidirectional communication.
2Device complexity
If a single optical modem is used at one end for bidirectional communication, then device complexity is reduced, but signal interference between transmission and reception occurs
Solution Approach 1:
The patent implements periodic action through time-division multiplexing, where the optical modem alternates between transmission and reception modes in periodic time slots. During transmission periods, the modem sends signals; during reception periods, it receives signals. This periodic switching prevents simultaneous transmission and reception, thereby eliminating signal interference while maintaining bidirectional communication capability.
3Reliability
If optical modems are placed at both ends for simultaneous bidirectional communication, then communication reliability is improved, but cost and device complexity increase
Solution Approach 1:
The patent applies universality by designing a single optical modem that can universally perform both transmission and reception functions. This multi-functional design simplifies the overall system configuration from two separate devices to one versatile device, reducing configuration complexity while maintaining communication reliability through proper time-division multiplexing of transmission and reception operations.
Data Source
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AI summary
A transmission apparatus causes a digital-to-analog conversion unit to perform digital-to-analog conversion on transmission signals pre-equalized by using a compensation filter, then converts electrical signals into optical signals, and outputs the optical signals. A receiving apparatus converts the received optical signals into received electrical signals, then performs analog-to-digital conversion, and demodulates the received signals. A scale estimation unit calculates a slope near an amplitude 0 in a correlation between an amplitude distribution of the pre-equalized transmission signals and an amplitude distribution of the received signals. A scale unit scales amplitude of the received signals on the basis of the calculated slope. A coefficient estimation unit calculates a filter coefficient of the compensation filter on the basis of the pre-equalized transmission signals and the scaled received signals. An output amplitude level determination unit determines output levels of the transmission signals from the digital-to-analog conversion unit on the basis of a correlation between distributions of amplitudes of non-pre-equalized and pre-equalized transmission signals.