Third-Order Dispersion Compensator for Optical Signals
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Solution Overview
Problem
Chromatic dispersion in optical fibers causes signal distortion and errors during long-haul transmission, particularly affecting isolated 1 bits and not adequately addressed by existing methods.
Innovation Solution
An optical transmitter system with a directly modulated laser and optical spectrum reshaper, combined with a third-order dispersive element, which imposes third-order dispersion to compensate for second-order dispersion in optical fibers, using a Gaussian profile filter to enhance amplitude modulation and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency modulated signal is transmitted through optical fiber, then data transmission is achieved, but chromatic dispersion causes signal distortion and transmission errors
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for chromatic dispersion effects before signal transmission. A dispersion compensating filter is inserted in the optical path to pre-distort the signal in a way that counteracts the expected dispersion during transmission, thereby reducing transmission errors caused by chromatic dispersion.
Solution Approach 2:
The patent uses an optical spectrum reshaper as an intermediary device between the laser and the optical fiber. This reshaper converts frequency modulated signals into amplitude modulated signals with a shaped spectral profile, which are more resistant to chromatic dispersion effects during transmission.
2Reliability
If optical spectrum reshaping is applied to convert frequency modulation to amplitude modulation, then isolated 1 bits are improved, but complex bit patterns still experience dispersion errors
Solution Approach 1:
The patent applies local quality by designing a dispersion compensating filter with specific frequency-dependent characteristics. The filter provides different compensation levels for different frequency components and different bit patterns, optimizing performance for isolated 1 bits while also improving complex patterns through its frequency-selective compensation approach.
Solution Approach 2:
The patent employs dynamic dispersion compensation by using a filter whose effective compensation characteristics can be optimized for different signal conditions. The system adapts to different bit patterns by maintaining a filter design that provides appropriate compensation across varying signal densities and patterns.
3Device complexity
If directly modulated laser is used for transmission, then system complexity is reduced, but chromatic dispersion effects are exacerbated
Solution Approach 1:
The patent introduces an optical spectrum reshaper as an intermediary device between the directly modulated laser and the optical fiber. This reshaper shapes the spectral profile of the laser output to reduce sensitivity to chromatic dispersion, allowing the use of simple directly modulated lasers without suffering from severe dispersion effects.
Solution Approach 2:
The patent changes the spectral parameters of the laser output by using an optical spectrum reshaper. The reshaper modifies the frequency spectrum of the directly modulated signal, creating a spectral profile that is more robust against chromatic dispersion while maintaining the simplicity of direct modulation.
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 system effectively reduces signal errors and maintains data integrity over long distances by reversing spurious peaks caused by chromatic dispersion, ensuring clear data transmission even after 400 km of fiber transmission.
Implementation Method 1
different frequency components of a signal travel at different speeds. Transmitted pulses will therefore tend to broaden
Implementation Method 2
A third-order dispersive element is positioned to receive the reshaped signal and is adapted to impose third-order dispersion on the reshaped signal
Implementation Method 3
an optical spectrum reshaper that converts a portion of the frequency modulation to amplitude modulation
Implementation Method 4
a directly modulated laser that emits frequency modulated pulses
Implementation Method 5
generates a frequency modulated signal encoding the data signal
Data Source
AI summary
An optical transmitter is disclosed including an optical signal source generating a frequency modulated signal encoding data. An optical spectrum reshaper is positioned to receive the frequency modulated signal and converts the frequency modulated signal into a reshaped signal having increased amplitude modulation relative to the frequency modulated signal. A third-order dispersive element is positioned to receive the reshaped signal and is adapted to impose third-order dispersion on the reshaped signal to generate a compensated signal having third-order dispersion effective to compensate for second-order dispersion caused by an optical fiber positioned between the optical transmitter and a receiver.