Pre-equalized Optical Transmitter for WDM Power Fluctuation
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Solution Overview
Problem
Combining WDM transmission and pre-equalization transmission methods in optical communication systems leads to significant transmission power fluctuations, requiring expensive high-performance optical amplifiers and VOAs, which increases manufacturing and installation costs and can result in deteriorated transmission quality.
Innovation Solution
A pre-equalization optical transmitter that switches between RZ and NRZ methods based on tap coefficients adjusted according to transmission power fluctuations, using a tap coefficient selecting unit to generate and output RZ or NRZ pre-equalization signals, thereby reducing power fluctuations and optimizing transmission quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pre-equalization transmission is combined with WDM transmission to reduce dispersion compensating fiber installation, then transmission capacity and cost are improved, but transmission power fluctuates significantly requiring expensive optical amplifiers and VOAs
Solution Approach 1:
The patent applies dynamics by making the pre-equalization method adjustable and adaptable. The system can dynamically switch between different pre-equalization methods (NRZ, RZ, or combined) based on transmission distance and other parameters. This dynamic adaptability allows the system to optimize performance for different scenarios without requiring expensive fixed high-performance components, resolving the contradiction between transmission capacity and device complexity.
Solution Approach 2:
The patent changes parameters by introducing multiple pre-equalization methods with different characteristics (NRZ for short distance, RZ for long distance, combined for medium distance). By selecting and switching between these methods based on transmission parameters like distance and wavelength, the system achieves high transmission capacity while avoiding the need for expensive optical amplifiers and VOAs, thus resolving the contradiction.
2Reliability
If the amount of dispersion compensation is adjusted in pre-equalization transmission, then transmission quality is improved, but transmission power fluctuates instantaneously requiring high-performance equipment
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal tap coefficients for different transmission scenarios. Instead of dynamically adjusting dispersion compensation in real-time (which would require fast VOAs), the system pre-computes the necessary equalization parameters and selects them based on transmission distance. This eliminates the need for high-speed VOA adjustment while maintaining transmission quality.
Solution Approach 2:
The patent uses copying by storing multiple sets of pre-computed tap coefficients corresponding to different transmission conditions. The system copies the appropriate coefficient set based on current transmission parameters rather than performing real-time calculations or physical adjustments, thereby maintaining transmission quality without requiring complex high-performance VOAs.
3Reliability
If RZ method is used for pre-equalization transmission, then intersymbol interference resistance is improved, but bandwidth consumption increases
Solution Approach 1:
The patent applies dynamics by making the modulation format selectable based on transmission requirements. The system can dynamically choose between NRZ (narrower bandwidth) and RZ (better ISI resistance) formats, or use a combined approach. This dynamic selection allows optimization of the bandwidth-ISI resistance trade-off according to specific transmission scenarios.
Solution Approach 2:
The patent applies local quality by using different pre-equalization methods for different transmission scenarios. For short distances where ISI is less problematic, NRZ is used to save bandwidth. For long distances where ISI is severe, RZ or combined methods are used to improve reliability. This localized optimization of method selection resolves the contradiction between bandwidth efficiency and ISI resistance.
4Area of stationary object
If NRZ method is used for pre-equalization transmission, then bandwidth efficiency is improved, but intersymbol interference resistance decreases
Solution Approach 1:
The patent applies dynamics by enabling flexible switching between NRZ and RZ methods based on transmission distance and channel conditions. For short-distance transmissions where bandwidth is critical and ISI is minimal, NRZ provides efficient bandwidth usage. For long-distance transmissions where ISI becomes problematic, the system switches to RZ or combined methods, thus dynamically resolving the contradiction between bandwidth efficiency and ISI resistance.
Solution Approach 2:
The patent changes parameters by introducing a family of pre-equalization methods with varying characteristics. By adjusting the modulation format parameter (NRZ, RZ, or combined) based on transmission requirements, the system optimizes the balance between bandwidth efficiency and ISI resistance for each specific scenario.
Data Source
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AI summary
A pre-equalization optical transmitter includes: a tap coefficient selecting unit (2) for saving, in advance, a tap coefficients for generating an RZ pre-equalization signal and an NRZ pre-equalization signal, and for selecting and outputting one of the tap coefficients according to the value of a parameter that is a factor of transmission power fluctuations; a pre-equalization signal generating unit (1) for generating the RZ pre-equalization signal or the NRZ pre-equalization signal based on the tap coefficient; and a modulating unit (8) for generating a pre-equalization optical transmission signal by modulating an optical signal input from a light source (7) by using a signal obtained through D/A conversion and amplification of the RZ pre-equalization signal or the NRZ pre-equalization signal, wherein a transmission method is switched between an RZ method and NRZ method by switching the tap coefficients by the tap coefficient selecting unit (2).