Digital Receiver AD Level Control for Low-SNR Optical Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional digital coherent receivers face challenges in maintaining high precision and resolution due to fluctuations in AD converter elements, circuit speed limitations, and power consumption, especially when dealing with low optical signal-to-noise ratios and high dispersion in multi-level modulation systems.
Innovation Solution
A digital receiver with an AD converter that adjusts discrimination levels based on signal quality monitoring, using a discrimination level adjusting circuit to optimize discrimination levels for high-resolution and high-speed operation, and a transfer function correcting circuit to ensure linear transfer characteristics, thereby enhancing the effective resolution and compensating for waveform distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrimination levels of the AD converter are kept equally spaced for linear transfer characteristics, then the AD converter achieves high resolution and low distortion, but it cannot adapt to signal quality variations and maintains optimal performance under limited conditions only
Solution Approach 1:
The patent implements dynamic adjustment of discrimination levels in the AD converter based on real-time signal quality monitoring. The discrimination level adjusting circuit continuously adapts the spacing of discrimination levels according to the monitored signal characteristics, transitioning from static equal spacing to dynamic variable spacing that optimizes performance for current signal conditions while maintaining adaptability to changing environments
Solution Approach 2:
The patent changes the parameter of discrimination level spacing from fixed equal intervals to variable intervals based on signal quality. By monitoring signal quality parameters and adjusting the discrimination level spacing accordingly, the system optimizes the AD converter's transfer characteristics for different signal conditions, achieving both high resolution and adaptability
2Speed
If the AD converter operates at high speed with sampling rate exceeding several tens GSps, then it meets the demand for next-generation optical communication systems, but element characteristics fluctuations and circuit limitations make high-precision control difficult
Solution Approach 1:
The patent introduces a feedback mechanism where the signal quality monitoring circuit continuously monitors the output signal quality and feeds this information back to the discrimination level adjusting circuit. This feedback loop enables real-time adjustment of discrimination levels to compensate for element fluctuations and maintain high precision control even at high sampling rates exceeding several tens GSps
Solution Approach 2:
The system performs self-adjustment by automatically monitoring its own output signal quality and correcting discrimination level spacing without external intervention. The signal quality monitoring circuit and discrimination level adjusting circuit work together to self-optimize the AD converter performance, maintaining high precision under high-speed operation conditions
3Measurement precision
If discrimination levels are adjusted dynamically based on signal quality, then the effective resolution of the AD converter is improved, but the device complexity increases due to additional monitoring and control circuits
Solution Approach 1:
The patent merges the signal quality monitoring function and discrimination level adjustment function into an integrated control system. By combining these functions and sharing circuit resources, the system achieves dynamic discrimination level adjustment and improved effective resolution while minimizing the increase in device complexity through functional integration
Data Source
Figure 1
Figure 2(a)~2(d)
Figure 3(a)~3(d)
AI summary
A digital receiver includes: an analog-to-digital (AD) converter (102) for setting discrimination levels in accordance with a discrimination level control signal and converting an analog input signal into a digital signal based on the set discrimination levels; a discrimination level adjusting circuit (104) for generating the discrimination level control signal and outputting the discrimination level control signal to the AD converter; a signal quality monitoring portion (108) for generating a transfer function correction control signal, which is information about a transfer function of the AD converter; and a transfer function correcting circuit (106) for performing signal processing on the digital signal so as to cancel a gap between the transfer function of the AD converter and an initial transfer function based on the transfer function correction control signal.