Nested Optical Modulator for Stable Zero-Intensity State Generation
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Solution Overview
Problem
Existing optical modulation techniques fail to stably generate a zero-intensity state required for phase-time coding schemes using nested modulators, lacking specific methods to achieve this in existing literature.
Innovation Solution
A nested optical modulator comprising Mach-Zehnder modulators connected in parallel with a phase shifter, where the phase shifter generates a predetermined phase difference, and control means adjust the phase and intensity modulation to produce four constellation points, including a zero-intensity state, by controlling RF and DC voltages applied to the modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a nested modulator is used to generate four-state signal light for phase-time coding, then the device complexity is reduced, but the ability to stably generate zero-intensity state is insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the phase difference (set to 90 degrees) and modulation depths (I and Q modulation depths) of the nested modulator. By adjusting these parameters, the system achieves stable generation of zero-intensity states while maintaining device simplicity. The control means dynamically adjusts voltage applications to maintain optimal parameter settings for reliable four-state signal generation.
2Adaptability or versatility
If arbitrary voltages are applied to high frequency electrodes and DC bias electrodes for vector synthesis, then constellation points can be generated, but the specific method for generating zero-intensity state is not disclosed
Solution Approach 1:
The patent implements feedback control through a control means that monitors and adjusts the voltages applied to the nested modulator's high-frequency and DC bias electrodes. This feedback mechanism ensures that the phase difference and modulation depths are maintained at optimal values for generating zero-intensity states, making the process reliable and manufacturable. The control system compensates for variations and maintains precise control over the modulation parameters.
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
Stably generates a four-state optical signal with a zero-intensity state, enabling efficient phase-time coding and reducing size and cost by using a single nested optical modulator.
Implementation Method 1
the phase shifter generates a predetermined phase difference between output lightwaves of the first modulator and the second modulator
Implementation Method 2
a first modulator and a second modulator of Mach-Zehnder type
Data Source
AI summary
An optical modulation method and device capable of stably generating an optical signal including a zero-intensity state among four states required for phase-time coding scheme by a nested modulator, is provided.A controller controls the phase difference generated by the phase shifter and an intensity and a magnitude of phase modulation provided by each of the first modulator and the second modulator to change an output lightwave of the nested modulator between four constellation points (S1-S4) on IQ plane. A first constellation point (S4) of the four constellation points has an intensity of 0, a second constellation point (S1) has a relative intensity of 1, each of a third constellation point (S2) and a fourth constellation point (S3) has a relative intensity ranging from 0 to 1, and the third and the fourth constellation points has a phase difference of 90 degrees.