Pseudo QPSK Modulation for Polarization Demultiplexing
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Solution Overview
Problem
Polarization demultiplexing of BPSK optical signals is challenging due to phase differences between polarized waves, which complicates circuit design and increases scale, making it difficult to achieve high-reliability and cost-effective transmission in optical communication systems.
Innovation Solution
The system modulates BPSK signals into pseudo QPSK signals using optical phase modulation, allowing for polarization demultiplexing with a small-scale circuit by converting BPSK signals into pseudo QPSK signals, enabling reliable digital domain processing without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polarization demultiplexing is performed on BPSK optical signals using conventional methods, then transmission capacity can be increased, but circuit scale increases and device complexity increases
Solution Approach 1:
The patent changes the modulation parameter from BPSK to pseudo-QPSK, which fundamentally alters the signal characteristics and enables polarization demultiplexing without requiring complex phase difference detection and compensation circuits. This parameter change resolves the contradiction by maintaining high transmission capacity while reducing circuit complexity.
2Reliability
If phase difference compensation circuits are added to enable polarization demultiplexing of BPSK signals, then demultiplexing becomes possible, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-modulating the signal into pseudo-QPSK format before transmission, which inherently encodes the polarization information in a manner that eliminates the need for subsequent phase difference compensation circuits. This preliminary modulation choice resolves the contradiction by enabling reliable demultiplexing without additional complex circuits.
3Duration of action of moving object
If BPSK modulation is used to maximize Euclidean distance, then transmission distance can be increased, but polarization demultiplexing becomes difficult without additional circuits
Solution Approach 1:
The patent changes the modulation parameter from BPSK to pseudo-QPSK, which maintains the long Euclidean distance advantage for extended transmission while simultaneously enabling polarization demultiplexing without additional complex circuits. This parameter change resolves the contradiction by achieving both long transmission distance and simple circuitry.
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 efficient polarization demultiplexing of BPSK signals, enhancing transmission capacity and distance in optical communication systems with reduced circuit complexity and cost.
Implementation Method 1
an optical phase modulation means for modulating phases of a plurality of optical signals employing BPSK modulation system
Implementation Method 2
a 90-degree hybrid mixes each separated optical signal with local oscillation light and outputs optical signals corresponding to an in-phase component and a quadrature component
Implementation Method 3
a photodiode converts each of the output optical signals of the 90-degree hybrid into an electric signal
Data Source
AI summary
In order to perform the polarization demultiplexing of the polarization multiplexed BPSK signal using a small-scale circuit by means of optical phase modulation of the polarization multiplexed BPSK signal into the pseudo polarization multiplexed QPSK signal, an optical communication system for communicating by using polarization multiplexed optical signals includes an optical phase modulation means for modulating phases of a plurality of optical signals employing BPSK modulation system including information to be communicated, and for generating a plurality of optical signals to become signals by pseudo QPSK modulation system; and a signal restoration means for performing polarization demultiplexing of a plurality of polarization multiplexed optical signals from a plurality of optical signals modulated into the pseudo QPSK modulation system, and for restoring the information to be communicated.