Wavelength Conversion Device Using Frequency Modulation
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Solution Overview
Problem
Current wavelength conversion devices do not effectively address the degradation of polarization multiplexed signal light, leading to instability in signal characteristics, particularly when using C-band optical components for L-band and S-band transmission, due to limitations in wavelength conversion efficiency and the high cost of developing separate optical components for these bands.
Innovation Solution
A wavelength conversion device that modulates signal light of both X-polarization and Y-polarization before wavelength conversion, and cancels out modulation components after conversion, using a degenerate four-wave mixing method with frequency modulation to suppress stimulated Brillouin scattering and maintain signal quality across different wavelength bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-power excitation light is input to increase wavelength conversion efficiency, then wavelength conversion efficiency is improved, but stimulated Brillouin scattering occurs causing input light to scatter backward
Solution Approach 1:
The patent applies periodic frequency modulation to the excitation light at a modulation frequency of 1 GHz or higher. This periodic variation in frequency prevents the buildup of coherent scattering that causes stimulated Brillouin scattering, allowing high-power excitation light to be input without triggering the harmful nonlinear effect, thereby maintaining high wavelength conversion efficiency
Solution Approach 2:
The patent changes the frequency parameter of the excitation light by applying frequency modulation. By varying the frequency dynamically rather than using a fixed monochromatic frequency, the system avoids the resonance conditions that lead to stimulated Brillouin scattering while still delivering high optical power for efficient wavelength conversion
2Object-generated harmful factors
If spectral width of excitation light is increased by modulation to suppress SBS, then stimulated Brillouin scattering is suppressed, but wavelength conversion efficiency may be reduced
Solution Approach 1:
The patent uses high-frequency periodic modulation (1 GHz or higher) that is fast enough to suppress stimulated Brillouin scattering effects while being brief enough in each cycle to maintain the effective spectral density needed for efficient four-wave mixing wavelength conversion. This timing-based approach resolves the contradiction between scattering suppression and conversion efficiency
3Reliability
If modulation is performed on signal light and excitation light to cancel modulation components, then signal characteristic degradation is suppressed, but device complexity increases
Solution Approach 1:
The patent applies the same frequency modulation to both the signal light and excitation light paths, creating identical modulation patterns. After wavelength conversion, the modulated components appear in both the converted signal and the excitation light, allowing them to be canceled through differential detection or filtering, thus maintaining signal integrity while using a relatively simple modulation approach
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 solution stabilizes polarization multiplexed signal light transmission by reducing modulation components and enhancing wavelength conversion efficiency, thereby reducing signal degradation and operational costs associated with using C-band components for L-band and S-band communication.
Implementation Method 1
a wavelength conversion device 20A that performs wavelength conversion on C-band signal light 11A to obtain L-band signal light 11D or S-band signal light 11E by using excitation light 12A and a highly nonlinear fiber 41
Implementation Method 2
when a fiber having a small core diameter referred to as a highly nonlinear fiber is used
Implementation Method 3
stimulated Brillouin scattering (SBS) occurs in which input light is scattered backward and does not propagate
Implementation Method 4
the spectral width of excitation light is increased by performing modulation of about some hundred MHz to some GHz on monochromatic excitation light
Implementation Method 5
modulation is performed on signal light and excitation light before wavelength conversion, and a modulation component of the modulated signal light and a modulation component of the modulated excitation light are canceled out each other
Data Source
AI summary
A method includes multiplexing signal light of first polarization and excitation light, and multiplexing signal light of second polarization, which is perpendicular to the first polarization, and the excitation light, modulating the signal light of the first polarization before the wavelength conversion, and reducing a modulation component in signal light after wavelength conversion, modulating the signal light of the second polarization before the wavelength conversion, and reducing the modulation component in the signal light after the wavelength conversion, and multiplexing the signal light of the first polarization after the wavelength conversion and the signal light of the second polarization after the wavelength conversion.