Optical Transmitter DCSK Control Channel Spectrum Matching
Solution Overview
Problem
In high-capacity optical data transmission systems, time-multiplexing a control signal with a waveform different from the main signal can cause adverse effects on adjacent wavelength channels due to optical fiber nonlinearity, particularly in ultra-large capacity transmissions like 1 Tbit/s, necessitating a control channel with characteristics similar to the main signal to ensure reliable multiplexing.
Innovation Solution
The optical data transmission system employs a Differential Code Shift Keying (DCSK) modulation scheme, where a reference pseudo-random sequence and a signal pseudo-random sequence are generated and time-division multiplexed to create a control signal with a spectrum similar to the main signal, ensuring high reliability and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a control signal with a waveform greatly different from the main signal is time-multiplexed to the main signal, then the control channel can be established, but adverse effects are exerted on the main signal and adjacent wavelength channels due to optical fiber nonlinearity
Solution Approach 1:
The patent applies homogeneity by making the control signal waveform similar to the main signal waveform. Specifically, both signals use the same modulation format (e.g., QPSK, 16-QAM) and are processed through the same signal processing chains, ensuring they have comparable statistical properties and spectral characteristics. This reduces nonlinear distortion differences and minimizes adverse effects on the main signal and adjacent channels.
Solution Approach 2:
The patent changes the parameters of the control signal to match the main signal characteristics. The control signal uses the same modulation scheme, symbol rate, and pulse shaping filter as the main signal. By adjusting these parameters to be consistent, the control signal behaves similarly to the main signal in the nonlinear optical fiber medium, thereby reducing harmful nonlinear effects.
2Productivity
If the transmission capacity is increased by multi-valuing and increase in baud rate, then the transmission capacity increases, but energy distributed per bit decreases causing bit errors and decreasing transmission distance
Solution Approach 1:
The patent merges the control signal transmission with the main signal transmission by time-multiplexing them together. The control signal is inserted into the same optical carrier as the main signal, sharing the same transmission medium and processing chains. This efficient use of resources allows high-capacity transmission while maintaining control channel functionality without requiring separate dedicated channels that would consume additional power.
Solution Approach 2:
The patent implements periodic action by time-division multiplexing the control signal into the main signal stream. The control signal is transmitted in periodic time slots interleaved with main signal symbols. This periodic insertion allows the control channel to operate reliably at high baud rates while maintaining the high transmission capacity of the main data channel, as the control signal benefits from the same high-rate transmission infrastructure.
Data Source
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AI summary
An optical transmitter of an optical data transmission system transmitting data through an optical fiber transmission path includes a main signal generator that converts first transmission data into a predetermined signal format to generate a first signal, a DCSK modulator that DCSK-modulates second transmission data to generate a second signal, a signal-multiplexer that performs time-division multiplexing of the first signal and the second signal, and an electro-optical converter that converts a multiplexed signal obtained by the time-division multiplexing of the signal-multiplexer from an electric signal into an optical signal, and outputs the optical signal to the optical fiber transmission path.