Digital Polarization Control for Optical Transmitters
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Solution Overview
Problem
Existing optical communication systems face challenges in maintaining high-speed polarization state variation of transmission signals without using optical parts like polarization scramblers, which are prone to degradation due to incident angle adjustments and aging of optical components, leading to increased error rates and stability issues.
Innovation Solution
A method that employs digital signal processing to vary the polarization state of transmission signals by generating and modulating orthogonal polarized waves, using logical inversion and switching techniques to achieve high-speed polarization multiplexing without optical components, thereby improving estimation accuracy and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polarization scrambler using optical parts is used to vary polarization state, then polarization state variation is achieved, but the system is prone to degradation due to incident angle adjustments and aging of optical components
Solution Approach 1:
The patent replaces the optical polarization scrambler with a digital signal processing system. The transmitter generates digital signals that control phase modulators to vary the polarization state of optical signals without using mechanical or optical switching components. This substitution eliminates the reliability issues associated with optical parts aging and incident angle sensitivity while maintaining the ability to vary polarization states at high speeds.
Solution Approach 2:
The patent creates a digital copy of the polarization state control function. Instead of physically manipulating optical polarization with scramblers, the system generates digital representations of polarization states and uses phase modulators to impose these states on optical carriers. This digital copying approach avoids the physical degradation mechanisms of optical components.
2Ease of operation
If optical parts like polarization scramblers are used, then polarization control is achieved, but power consumption increases and estimation accuracy degrades
Solution Approach 1:
The patent replaces power-intensive optical polarization control components with low-power digital signal processing. The phase modulators consume significantly less power than optical scramblers, and the digital signal processing for polarization estimation is performed in the electrical domain, reducing overall system power consumption while maintaining ease of polarization control through software algorithms.
3Adaptability or versatility
If conventional polarization scrambling is used, then polarization diversity is achieved, but the speed of polarization state variation is limited
Solution Approach 1:
The patent replaces mechanically limited optical switching with electronically controlled phase modulators that can be switched at high speeds limited only by electronic response time. The digital signal processing enables polarization state variation synchronized with data symbol rates, achieving much faster switching speeds compared to mechanical optical scramblers while maintaining polarization diversity for robust signal transmission.
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 high-speed polarization state variation of transmission signals based on symbol rate using digital signals, avoiding the degradation issues associated with optical parts and enhancing estimation accuracy and power efficiency.
Implementation Method 1
a first modulator (302) and a second modulator (303) which respectively modulate orthogonal polarized waves (X-polarized wave and Y-polarized wave) in accordance with first and second signal series (I-signal and Q-signal)
Implementation Method 2
the state of polarization of incident light is changed into linear polarization by use of a polarizer (4), and introduced to the optical waveguide (2) at a 45-degree inclined angle
Implementation Method 3
a polarization beam combiner (304) which performs polarization multiplexing for the signal
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A polarization state of a transmission signal can be changed at a high speed based on a symbol-rate By switching a first switch, a second switch, and a third switch with time, one of an X-polarized wave_I-signal as a Y-polarized wave_I-signal, a signal caused by performing logical inversion for an X-polarized wave_I-signal, an X-polarized wave_Q-signal and a signal caused by logical inversion for an X-polarized wave_Q-singal is input to a second modulator. Further, by switching the first switch, the second switch and the third switch with time, the second modulator is input one of the X-polarized wave_I-singal as the Y-polarized wave_Q-signal, the X-polarized wave_I-signal, the signal caused by performing logical inversion for the X-polarized wave_I-signal, the X-polarized wave_Q-signal and the signal caused by performing logical inversion for the X-polarized wave_Q-signal. Thereby, a polarization state of a transmission signal can be changed at high speed based on a symbol-rate speed.