Auto-equalization Network Device for Optical Channel Self-Calibration
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Solution Overview
Problem
The increased modulation levels in fiber-optic communication systems, such as QPSK, 8-QAM, 16-QAM, and 64-QAM, result in longer interconnect lines between digital signal processors and photonic integrated circuits, leading to greater losses and connector issues, which are not effectively compensated by existing technologies.
Innovation Solution
An auto-equalization network device that determines frequency domain forward transmission loss characterization, generates a model, and iteratively adjusts finite impulse response filter taps to achieve frequency-dependent preemphasis, optimizing signal transmission and compensation for specific plug-in modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If digital signal processors are moved from pluggable modules to the main body of the network device, then packaging density is improved, but interconnect line length increases causing greater losses and connector issues
Solution Approach 1:
The system performs preliminary characterization of the interconnect channel by transmitting test signals and measuring the frequency response. Based on this pre-acquired channel information, the DSP pre-emphasizes the data signal before transmission to compensate for anticipated losses, thereby resolving the contradiction between compact packaging and signal integrity over long interconnect lines
Solution Approach 2:
The system dynamically adjusts signal parameters (amplitude and phase) across different frequency components based on the characterized channel response. By applying frequency-dependent pre-emphasis with adjusted gain and phase parameters, the system compensates for frequency-selective losses in the extended interconnect path while maintaining compact packaging
2Reliability
If existing compensation technologies are used, then some signal losses are managed, but frequency-dependent losses in longer interconnect lines are not effectively compensated
Solution Approach 1:
The system uses feedback from channel characterization measurements to adaptively adjust pre-emphasis parameters. By continuously monitoring the channel response and adjusting the compensation filter coefficients accordingly, the system effectively compensates for frequency-dependent losses that vary with channel conditions, thereby improving signal transmission reliability
Solution Approach 2:
The system performs preliminary channel sounding and characterization before actual data transmission. The measured frequency response is used to pre-calculate optimal pre-emphasis parameters that specifically address the frequency-dependent losses of that particular channel, enabling effective compensation before the harmful effects manifest in data transmission
Data Source
AI summary
An auto-equalization network device for optical transmitting and receiving is provided. The device includes a network device having an optical transmitter and an optical receiver. The network device is configured to determine a frequency domain forward transmission loss characterization for a signal transmitted by the optical transmitter, looped back and received by the optical receiver. The device is configured to generate a model in the frequency domain having control points based on the characterization, generate and load finite impulse response (FIR) filter taps into a finite impulse response filter based on the model in the frequency domain. The device is configured to iterate transmission of a signal with frequency-dependent preemphasis by the finite impulse response filter, characterization for the frequency-dependent preemphasized signal as looped back and received by the optical receiver, comparison to previous characterization, adjustment of the control points, and reloading the finite impulse response filter taps, until the comparison meets an optimum, so that the network device is auto-equalized for optical transmitting.