Dual Polarization QPSK Modulator Using Multimode Interference Coupler
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Solution Overview
Problem
Conventional Dual Polarization Quadrature Phase Shift Keying (DP QPSK) optical modulators require multiple optical elements, leading to increased optical loss due to the need for four optical operations, which complicates the design and reduces efficiency.
Innovation Solution
A DP QPSK optical modulator configuration using an optical multiplexer and a multimode interference coupler with a taper-shaped waveguide, reducing the number of optical elements required for optical coupling, polarization rotation, and polarization combining, thereby minimizing optical loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional DP QPSK optical modulator configuration with multiple optical elements is used, then optical operations (coupling, polarization rotation, combining) can be performed, but optical loss increases and device complexity increases
Solution Approach 1:
The patent merges multiple optical functions (polarization beam combining and polarization rotation) into a single integrated optical element. Specifically, the output stage combines the functions of a polarization beam combiner and a polarization rotator into one component, reducing the total number of optical elements from four to three while maintaining all necessary optical operations for DP QPSK signal generation
Solution Approach 2:
The integrated optical element performs multiple functions simultaneously: it acts as both a polarization beam combiner and a polarization rotator. This multi-functional design allows a single element to replace what would traditionally require separate components, thereby reducing optical loss through fewer interfaces and connections while achieving the same overall optical operation
2Reliability
If multiple optical elements are used for optical coupling, polarization rotation, and polarization combining, then complete DP QPSK signal generation is achieved, but coupling efficiency decreases due to increased optical loss
Solution Approach 1:
By combining polarization beam combining and polarization rotation functions into a single optical element, the patent reduces the number of optical interfaces and connections. This merging reduces cumulative optical loss at each interface, thereby improving the overall signal-to-noise ratio and enhancing noise resistance of the generated DP QPSK signal
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 reduced number of optical elements results in lower optical loss and improved coupling efficiency, facilitating the generation of robust DP QPSK signal light with enhanced noise resistance.
Implementation Method 1
a multimode interference coupler including a multimode interference waveguide
Implementation Method 2
an output port having a taper-shaped waveguide, the first through third input ports being provided along a direction orthogonal to the optical waveguide direction
Data Source
AI summary
A DP QPSK optical modulator includes an input port; an optical branching unit; an optical modulation unit having first through fourth Mach-Zehnder interferometers; a first phase-change unit connected to the third Mach-Zehnder interferometer; a second phase-change unit connected to the fourth Mach-Zehnder interferometer; an optical multiplexer; and a multimode interference coupler including a multimode interference waveguide, first through third input ports, and an output port having a taper-shaped waveguide. The first Mach-Zehnder interferometer is connected to the first input port. One end of the optical multiplexer is connected to the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer via the first phase change unit. The other end of the optical multiplexer is connected to the second input port. The fourth Mach-Zehnder interferometer is connected to the third input port via the second phase-change unit.