Nonlinear Equalization for VCSEL Optical Transmitters
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Solution Overview
Problem
Current optical links, particularly those using VCSELs, face bandwidth limitations and nonlinearities that affect data integrity at high speeds, leading to increased power consumption and reduced mean time to failure, which hinder the full utilization of optical links for high-speed data transmission.
Innovation Solution
A driver with embedded logic that selectively applies coefficients to adjust the amplitude and phase of input signals during transitions, using Pulse Amplitude Modulation 4-level (PAM-4) encoding, to mitigate nonlinearities such as reflections and ringing, while maintaining steady-state power levels and reducing bit error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If VCSELs are operated at higher average bias currents to improve linearity of response, then linearity is improved, but mean time to failure decreases and power consumption increases
Solution Approach 1:
The patent applies equalization coefficients to the input signal before transmission through the VCSEL, pre-compensating for the nonlinearities that would otherwise require higher bias currents to mitigate. This preliminary signal processing allows the VCSEL to operate at lower, more reliable bias currents while maintaining linear response characteristics.
Solution Approach 2:
The patent changes the parameter of bias current from high to low levels, and compensates for the resulting nonlinearity by applying equalization coefficients to the signal. This parameter change reduces power consumption and improves reliability while maintaining response linearity through digital compensation.
2Stability of the object's composition
If VCSELs are operated at higher average bias currents to improve linearity of response, then linearity is improved, but power consumption increases
Solution Approach 1:
The patent applies equalization coefficients to the input signal before transmission through the VCSEL, pre-compensating for the nonlinearities that would otherwise require higher bias currents to mitigate. This preliminary signal processing allows the VCSEL to operate at lower, more efficient bias currents while maintaining linear response characteristics.
3Productivity
If transmission speeds are increased to support growing data traffic, then productivity is improved, but signal attenuation and distortion increase
Solution Approach 1:
The patent applies equalization coefficients to compensate for frequency-dependent losses and nonlinearities that become more severe at higher transmission speeds. This parameter adjustment maintains signal integrity despite increased attenuation and distortion at higher data rates.
4Productivity
If bandwidth of optical links is increased to support speeds over 100 Gbps, then productivity is improved, but nonlinearities such as gain nonlinearities and relaxation nonlinearities increase
Solution Approach 1:
The patent applies equalization coefficients to the input signal before transmission, pre-compensating for the gain and relaxation nonlinearities that occur at high bandwidths. This allows the system to achieve over 100 Gbps transmission speeds while maintaining signal linearity through digital pre-distortion.
Data Source
AI summary
An optical or an optoelectronic device and methods are provided for data transmission across two interconnects. First, an electrical signal is obtained from an interconnect. Next, the electrical signal is modulated. Within the modulated electrical signal, an occurrence of a transition is determined, in which a change in a power of the electrical signal by more than a threshold amount. In response to the determination of the occurrence of the transition, coefficients indicative of respective amounts of compensation to resolve or mitigate nonlinearities associated with the transition are determined. According to the coefficients, a filter is applied in a vicinity of the transition to obtain a modified electrical signal. The modified electrical signal is converted into an optical signal and coupled to a fiber to transmit the optical signal to a destination at a second interconnect.