Optical Transmission System Amplitude Correction for Signal Uniformity
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Solution Overview
Problem
In optical transmission systems using the A-RoF solution, as the number of signal channels increases, a wider frequency band is required, leading to variations in signal channel levels due to the comprehensive frequency characteristic of the transmission system.
Innovation Solution
The optical transmission system incorporates a transmission-side digital signal processor with a correction processor and a calibration signal generator, and a reception-side digital signal processor with a digital separation processor and a weight correction value calculator. These processors work together to generate calibration signals, separate them into baseband signals, calculate parameter coefficients, and correct the amplitude of input radio signal strings using these coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of signal channels is increased to fully use the Nyquist bands of ADC and DAC, then the bandwidth utilization is improved, but a variation in signal channel level occurs due to frequency characteristics of transmission system components
Solution Approach 1:
The patent applies preliminary action by performing amplitude correction in advance through digital signal processing before transmission. The correction processor pre-adjusts the amplitude of each signal channel based on calculated correction values, compensating for the frequency characteristics of transmission components beforehand. This prevents signal level variation from occurring during transmission, allowing full bandwidth utilization while maintaining signal uniformity.
Solution Approach 2:
The patent changes the amplitude parameter of each signal channel dynamically based on its frequency characteristics. The correction processor modifies the amplitude parameter of individual channels using correction values derived from frequency response measurements. This parameter adjustment compensates for variations caused by transmission components, enabling both high bandwidth utilization and uniform signal levels across all channels.
2Productivity
If frequency multiplexing of multiple radio signals is performed in an IF band, then the transmission efficiency is improved, but the comprehensive frequency characteristic of the transmission system causes variation in signal channel levels
Solution Approach 1:
The patent implements feedback by measuring the actual frequency characteristics of the transmission system and using this information to calculate correction values. The system measures the frequency response, determines the amplitude variation across channels, and feeds this information back to the correction processor. The correction processor then applies appropriate amplitude adjustments to each channel, ensuring consistent signal quality while maintaining efficient frequency multiplexing transmission.
Solution Approach 2:
The patent applies preliminary action by pre-correcting the amplitude of multiplexed signals before transmission. The correction processor adjusts the amplitude of each frequency-multiplexed channel in advance based on predetermined correction values, compensating for the comprehensive frequency characteristics of the transmission system. This ensures that signals maintain consistent levels throughout transmission, preserving reliability while achieving high transmission efficiency through frequency multiplexing.
Data Source
AI summary
An IFoF scheme optical transmission system according to the present disclosure includes a transmission-side digital signal processing device including a correction processing unit and a calibration signal generating unit, and a reception-side digital signal processing device including a digital separation processing unit and a weight correction value calculating unit, in which the calibration signal generating unit generates a calibration signal (Scal(t)), the digital separation processing unit performs demultiplexer processing to separate the calibration signal (Scal(t)) into a plurality of baseband signals (SOUT_1(t), SOUT_2 (t), . . . , SOUT_n(t)), the weight correction value calculating unit calculates parameter coefficients (a1, a2, . . . , an) on the basis of the baseband signals (SOUT_1(t), SOUT_2(t), . . . , SOUT_n(t)), and the correction processing unit corrects an amplitude of each of a plurality of input radio signal strings that is input using the parameter coefficient (a1, a2, . . . , an).