Optical Transmitter SSB Modulation Correction Circuit
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Solution Overview
Problem
The existing optical communication systems using intensity modulation/direct detection face challenges with wide optical frequency bandwidth, leading to low frequency utilization efficiency and difficulties in dense wavelength division multiplexing, which limits transmission capacity and results in poor receiver sensitivity and bit error ratios when applying single-side band (SSB) modulation.
Innovation Solution
An optical communication system is designed with a single-side band modulation circuit that transforms double-side band signals into single-side band signals, incorporating a correction circuit to adjust the intensity of the modulated signals to resemble double-side band signals, and an optical modulator to output these signals, along with an optical receiver for direct detection, which includes a compensation circuit to improve receiver sensitivity and bit error ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If intensity modulation/direct detection is used, then the configuration is simplified, but the optical frequency bandwidth becomes wide leading to low frequency utilization efficiency
Solution Approach 1:
The patent extracts only one sideband (upper or lower) from the double-sideband modulated signal using a single-sideband modulation circuit. This removes the redundant sideband, reducing the optical frequency bandwidth by approximately half while maintaining the simplified intensity modulation/direct detection configuration, thereby resolving the contradiction between configuration simplicity and bandwidth efficiency.
2Quantity of substance
If single-side band modulation is applied, then the optical frequency bandwidth is compressed, but the receiver sensitivity and bit error ratios deteriorate
Solution Approach 1:
The patent applies preliminary intensity correction to the single-sideband modulated signal before optical modulation. The correction circuit adjusts the intensity distribution of the signal to compensate for the asymmetry introduced by single-sideband modulation, ensuring that the intensity waveform maintains appropriate characteristics for direct detection. This preliminary correction prevents receiver sensitivity deterioration while preserving the bandwidth compression benefits.
3Quantity of substance
If single-side band modulation is applied, then the optical frequency bandwidth is compressed, but the waveform deterioration increases
Solution Approach 1:
The correction circuit performs preliminary intensity adjustment on the single-sideband modulated signal to restore the intensity waveform characteristics. By correcting the intensity distribution before optical modulation, the system compensates for waveform distortion that would otherwise occur due to the asymmetry of single-sideband modulation, thereby maintaining waveform stability while achieving bandwidth compression.
4Productivity
If dense wavelength division multiplexing is attempted, then the transmission capacity increases, but the frequency utilization efficiency remains low due to wide bandwidth
Solution Approach 1:
The patent extracts only the necessary sideband information, removing the redundant sideband to compress the bandwidth of each optical signal. This bandwidth compression enables closer spacing of wavelength channels, allowing dense wavelength division multiplexing to be implemented effectively. The result is increased transmission capacity through more efficient frequency utilization.
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 configuration effectively suppresses waveform deterioration, enhances receiver sensitivity, and improves bit error ratios by optimizing the side-band suppression ratio and frequency bandwidth utilization, enabling more efficient transmission capacity.
Implementation Method 1
an optical intensity of the optical signal received through use of a photodetector, for example, a photodiode, is converted into an electronic signal
Data Source
AI summary
Provided is an optical communication system capable of suppressing the deterioration of an intensity waveform of an optical intensity modulated signal subjected to transformation using SSB modulation and improving a bit error ratio and a receiver sensitivity of the optical intensity modulated signal. The optical communication system includes: an optical transmitter section including: a single-side band modulation circuit configured to subject a double-side band modulated signal to generate a single-side band modulated signal; a correction circuit configured to correct an intensity of the single-side band modulated signal so that the intensity of the single-side band modulated signal becomes closer to an intensity of the double-side band modulated signal; and an optical IQ modulator configured to output an optical modulated signal; and an optical receiver section configured to receive the optical modulated signal to directly detect an intensity component of the optical modulated signal.