Optical Modulator Bias Control for DMT Transmission Nonlinearity
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Solution Overview
Problem
The degradation of transmission characteristics in optical signals modulated by DMT modulation format due to nonlinear characteristics in optical modulators and amplifiers, which affects signal quality and transmission capacity.
Innovation Solution
A transmission apparatus that measures and compares the frequency distribution of intensity of both the electrical and optical signals, and controls the modulation characteristics of the optical modulator and amplifier to optimize transmission, specifically adjusting bias voltage and modulation amplitude to reduce non-linearity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DMT modulation format is applied to optical transmission, then transmission capacity increases, but transmission characteristics degrade due to nonlinear characteristics in optical modulators and amplifiers
Solution Approach 1:
The patent changes the operating parameters of the optical modulator by adjusting the bias voltage to operate in a linear region rather than a nonlinear region. This parameter adjustment resolves the contradiction by maintaining transmission capacity while improving transmission characteristics through optimal parameter selection
Solution Approach 2:
The patent implements a feedback mechanism where the frequency distribution of the optical signal is measured and compared with the electrical signal, and the modulation characteristics are controlled based on this comparison. This closed-loop feedback system dynamically adjusts the modulator operation to maintain optimal transmission characteristics while preserving high transmission capacity
2Reliability
If bias voltage is adjusted to operate in linear region, then transmission characteristics improve, but modulation amplitude decreases
Solution Approach 1:
The patent adjusts multiple parameters simultaneously - bias voltage and modulation amplitude - to achieve optimal operation in the linear region. By coordinating changes in both parameters, the system maintains adequate modulation amplitude while operating in the linear region for improved transmission characteristics
Solution Approach 2:
The patent employs dynamic adjustment of modulation characteristics through feedback control, allowing the system to adaptively optimize the balance between transmission characteristics and modulation amplitude based on real-time signal conditions rather than using fixed parameter settings
3Reliability
If frequency distribution measurement and comparison is implemented, then modulation characteristics are optimized, but device complexity increases
Solution Approach 1:
The patent integrates multiple functions into the existing transmission system - the frequency distribution measurement and comparison operations are incorporated into the normal signal processing path, allowing the same hardware components to serve both signal transmission and optimization control functions, thereby minimizing additional device complexity
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
Improves transmission capacity by up to 2.8 times by minimizing the impact of non-linear areas in modulation and amplification characteristics, thereby enhancing signal quality and maintaining optimal transmission characteristics.
Implementation Method 1
a first modulator configured to modulate a first electrical signal to a second electrical signal that is a multicarrier signal including a plurality of subcarriers
Implementation Method 2
a light source configured to generate light having a predetermined wavelength
Implementation Method 3
a second modulator configured to modulate the light generated by the light source to the optical signal, based on the second electrical signal modulated by the first modulator
Data Source
AI summary
There is provided a transmission apparatus includes: a first modulator configured to modulate a first electrical signal to a second electrical signal that is a multicarrier signal including a plurality of subcarriers to which transmission capacities are allocated, respectively; a light source configured to generate light having a predetermined wavelength; a second modulator configured to modulate the light generated by the light source to an optical signal, based on the second electrical signal modulated by the first modulator; and a processor configured to: measure a first frequency distribution of intensity of the second electrical signal modulated by the first modulator, measure a second frequency distribution of intensity of the optical signal modulated by the second modulator, compare the first frequency distribution and the second frequency distribution, and control modulation characteristics of the second modulator according to a result of comparing the first frequency distribution and the second frequency distribution.