Three-arm DQPSK modulator voltage reduction
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Solution Overview
Problem
Conventional Differential Quadrature Phase Shift Keying (DQPSK) modulators require high voltages to maintain phase differences, making them incompatible with lower power technologies like CMOS and are inefficient due to excess voltage application.
Innovation Solution
A phase modulator with three arms between a splitter and a coupler, where equal optical power is supplied to each arm, allowing for constructive or destructive interference to determine the net phase, reducing voltage requirements to π/2 phase shifts, thus enhancing efficiency and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage is applied to maintain phase difference in conventional DQPSK modulator, then phase modulation function is achieved, but power consumption increases and CMOS compatibility is lost
Solution Approach 1:
The modulator is divided into three independent arms (first, second, and third arms) that can be independently controlled. Each arm contains a waveguide with its own electrode, allowing separate phase control. This segmentation enables the invention to achieve the required phase modulation function while using lower voltages, as each arm contributes partially to the overall phase shift rather than requiring one arm to provide the full phase difference.
Solution Approach 2:
The patent applies different phase shift values to different arms locally. Specifically, the first and second arms are modulated with phase shifts that are π/2 out of phase with each other, while the third arm provides a reference. This local differentiation of phase quality allows the system to achieve DQPSK modulation with reduced voltage requirements compared to conventional approaches where all arms must be driven with high voltage to maintain phase differences.
2Ease of operation
If excess voltage is applied to achieve π-phase shift, then phase modulation is achieved, but voltage efficiency decreases
Solution Approach 1:
Instead of applying full π-phase shift voltage to each arm as in conventional modulators, the patent applies partial phase shifts (π/2) to the first and second arms. The combination of these partial shifts through the interferometric structure achieves the required modulation effect without the excessive voltage application, thereby improving voltage efficiency.
3Measurement precision
If π/2 rotator is added to remove phase shift, then phase accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the need for the π/2 rotator component found in conventional DQPSK modulators. By redesigning the phase control mechanism to use three arms with specific phase relationships, the invention achieves the required phase accuracy without the additional rotator hardware, thereby reducing device complexity and associated power consumption.
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
The modulator achieves efficient DQPSK signal generation with lower power consumption, making it compatible with CMOS circuits and improving power efficiency by requiring less energy to shift between constellation points.
Implementation Method 1
A first electrode is provided adjacent the first waveguide and is configured to modulate a refractive index of a portion of the first waveguide in accordance with first information associated with a first data stream
Implementation Method 2
allowing for constructive or destructive interference to determine the net phase
Data Source
AI summary
A modulator is disclosed that includes three arms between a splitter portion and a coupler portion. The modulator typically requires at most a π/2 phase shift between constellation points. Accordingly, the modulator is more efficient and consumes less power.