Electro-Optic Modulator DC Bias Correction and Carrier Suppression
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Solution Overview
Problem
Electro-optic modulators face challenges in maintaining precise DC bias and suppressing optical carrier frequencies due to manufacturing inconsistencies, environmental drifts, and noise interference, which affect their dynamic range and signal-to-noise ratio.
Innovation Solution
A matched pair of electro-optic modulators on a common substrate is used, where one modulator is dedicated to signal transmission and the other to bias control, allowing for precise bias correction and carrier suppression without degrading the signal path's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electro-optic modulator is used for both signal transmission and bias control, then device complexity is reduced, but measurement precision and control accuracy deteriorate due to noise interference and performance degradation in the signal path
Solution Approach 1:
The patent divides the single modulator into two separate modulators: a first modulator dedicated to signal transmission and a second modulator dedicated to bias control and carrier suppression. This segmentation allows each modulator to perform its specific function optimally without interfering with the other, thereby improving measurement precision and control accuracy while maintaining reasonable device complexity
Solution Approach 2:
The bias control function is extracted from the signal transmission path and implemented in a separate second modulator. This extraction removes the noise and performance degradation that would otherwise occur in the signal path during bias adjustment, improving the signal-to-noise ratio and overall system performance
2Measurement precision
If DC bias is adjusted in the signal path to correct manufacturing inconsistencies, then bias accuracy is improved, but signal-to-noise ratio deteriorates due to noise introduction and performance degradation
Solution Approach 1:
The DC bias adjustment and carrier suppression operations are extracted from the signal transmission path and performed in a separate second modulator. This extraction eliminates the noise and performance degradation that would occur in the signal path during bias adjustment, thereby improving the signal-to-noise ratio while maintaining DC bias accuracy
Solution Approach 2:
The second modulator acts as an intermediary device that handles all bias control and carrier suppression functions. By using this intermediary, the signal path remains clean and undisturbed, avoiding direct noise introduction while still achieving precise bias control through the intermediary modulator
3Object-affected harmful factors
If carrier suppression is performed in the signal path, then optical carrier frequency is reduced, but signal performance deteriorates due to noise and dynamic range reduction
Solution Approach 1:
The carrier suppression function is extracted from the signal transmission path and implemented in a separate second modulator. This extraction allows carrier suppression to be performed without introducing noise or degrading signal performance in the main signal path, thereby maintaining signal dynamic range while effectively suppressing the optical carrier frequency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the spur-free dynamic range and signal-to-noise ratio by decoupling bias control from signal transmission, maintaining optimal performance despite manufacturing and environmental variations.
Implementation Method 1
In the presence of a DC electric field, this lithium niobate's non-centrosymmetric crystal exhibits a change in the optical refractive index, or dielectric susceptibility, as described by the field of nonlinear optics. Similar modification of the optical refractive index is achieved in silicon, indium phosphide, and other materials via the injection or depletion of electrons, or the modification of electronic band structures, through applied electric fields. Applying an electric field to the electro-optical substrate changes the net polarization and refractive index of the material. Thus, the phase of light propagating through the material may be altered by applying an electric field to the material.
Data Source
AI summary
This application relates to circuits and methods for dynamically correcting DC bias and suppressing optical carrier frequency in electro-optic modulators (EOMs). A DC bias voltage for a control path may be determined using a control path DC bias structure. DC bias in a signal path may be corrected by applying the DC bias voltage, or a function thereof, to a signal path DC bias structure. Signal path and control path RF signal structures may be operated for a time period during which their DC biases drift together. An updated DC bias voltage for the control path may be determined using the control path DC bias structure. The drift of DC bias in the signal path may be corrected by applying the updated DC bias voltage, or a function thereof, to the signal path DC bias structure.