Optical Transmitter Receiver Compensators DAC Clipping SNR
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Solution Overview
Problem
In digital coherent optical communication, signal performance deterioration occurs due to factors like intersymbol interference and noise from DACs, which reduces transmission characteristics, especially when signal power exceeds the upper limit of the DAC, leading to clipping and reduced SNR.
Innovation Solution
An optical transmission and reception system is designed with compensators in both the transmitter and receiver that use specific coefficients to pre-equalize and post-equalize signals, ensuring signal power remains within DAC limits and improving SNR by amplifying lower frequency bands, thereby mitigating signal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal power is increased to improve transmission characteristics, then signal quality improves, but clipping occurs when signal power exceeds DAC upper limit, reducing SNR
Solution Approach 1:
The patent applies pre-equalization in the optical transmitter that includes a first compensator with a first coefficient having an upward peak at higher frequency side, and a second compensator with a second coefficient that increases power at lower frequency side. This preliminary compensation shapes the signal spectrum before transmission, preventing clipping at the DAC while maintaining signal quality through enhanced lower frequency components that are less susceptible to noise.
2Object-affected harmful factors
If signal power is reduced to avoid clipping, then clipping is prevented, but SNR decreases due to reduced signal level
Solution Approach 1:
The patent applies different compensation characteristics to different frequency bands: the first compensator handles higher frequency components with an upward peak, while the second compensator specifically enhances lower frequency components where the power increases as frequency decreases. This localized frequency-dependent compensation allows the signal to maintain adequate power levels in noise-sensitive low frequency bands without causing clipping in higher frequency bands.
Solution Approach 2:
The patent changes the signal's frequency domain parameters by applying compensation coefficients that reshape the power spectral density. The first coefficient introduces an upward peak at higher frequencies, while the second coefficient increases power at lower frequencies, transforming the signal characteristics to achieve both clipping prevention and SNR maintenance through optimal spectral distribution.
3Reliability
If pre-equalization is applied to compensate for transmitter loss, then transmission characteristics improve, but complexity of compensation coefficients increases
Solution Approach 1:
The patent segments the compensation function into two distinct compensators: a first compensator with a first coefficient that provides upward peak at higher frequency side for general transmitter loss compensation, and a second compensator with a second coefficient that specifically addresses lower frequency power enhancement. This segmentation allows each compensator to be optimized for its specific frequency range and compensation task, managing complexity through functional division.
Data Source
AI summary
An optical transmission and reception system includes an optical transmitter that converts an electrical data signal into an optical signal and transmits the optical signal; and an optical receiver that receives the optical signal input from the optical transmitter via an optical transmission line and converts the optical signal into the data signal. The optical transmitter includes a first compensator that compensates for a loss generated in the optical transmitter based on a first coefficient and a second coefficient, and the optical receiver includes a second compensator that compensates for a loss generated in the optical transmission line based on a third coefficient.