Semiconductor Mach-Zehnder Modulator Phase Presetter
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Solution Overview
Problem
Semiconductor Mach-Zehnder modulators exhibit non-linear phase variation with bias, complicating driving conditions and making it difficult to achieve the required phase statuses of 0 and π for QPSK modulation.
Innovation Solution
Incorporating a phase presetter in one arm waveguide that shifts the phase of the optical beam by π, and using complementary modulation signals with the same swing range and bias for both arm waveguides, allowing for simplified driving conditions and linear phase variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If semiconductor material is used for MZ-modulator, then integration and compactness are improved, but phase variation non-linearity increases making driving conditions complex
Solution Approach 1:
The patent applies preliminary action by introducing a phase presetter that pre-shifts the phase of one optical beam by π before the modulation process. This preliminary phase adjustment ensures that both optical beams start from the same phase reference point, allowing the modulation signals to be complementary with equal swing ranges and biases, thereby simplifying the driving conditions despite using semiconductor material.
2Ease of operation
If complementary modulation signals with same swing range and bias are used, then driving conditions are simplified, but achieving required phase statuses of 0 and π becomes more difficult due to non-linearity
Solution Approach 1:
The phase presetter performs a preliminary phase shift of π on one optical beam, establishing a common reference point before modulation. This ensures that even with non-linear phase variation characteristics of semiconductor materials, the complementary modulation signals with equal swing ranges and biases can accurately achieve the required phase statuses of 0 and π, maintaining both driving simplicity and phase precision.
Solution Approach 2:
The patent changes the phase parameter by introducing a fixed π phase shift through the phase presetter. This parameter modification compensates for the non-linear phase variation characteristics of semiconductor materials, enabling the system to achieve precise phase statuses while maintaining simplified driving conditions with complementary signals of equal swing range and bias.
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 enables effective BPSK and QPSK modulation by ensuring the phase statuses of 0 and π are maintained, reducing phase distortion and enhancing optical data transmission quality.
Implementation Method 1
Providing a bias V(π), where V(π) means a voltage corresponding to the phase shift of an optical beam propagating therein by π, to the electrode, the equivalent refractive index of the optical waveguide is varied, which means that the optical length thereof varies and the phase of the optical beam passing therethrough is also varied.
Data Source
AI summary
A Mach-Zehnder (MZ) modulator made of semiconductor material and a method to drive the MZ-modulator are disclosed. The MZ-modulator includes a pair of arms to vary the phase of the optical beam propagating therein. One of the arms further provides the phase presetter that varies the phase of the optical beam by π. The arms are driven by modulation signals complementary to each other but with the DC bias equal to each other.