WDM Optical Transmission Apparatus with Chirp Control
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Solution Overview
Problem
Wavelength division multiplexing optical transmission systems face challenges in maintaining signal quality due to narrowed dispersion tolerance, especially at high bit rates, and struggle to efficiently increase the number of multiplexed wavelengths without incurring significant cost or compatibility issues with existing CWDM systems.
Innovation Solution
The system employs optical transmitting units with intensity modulators that set wavelength chirp for each optical signal, allowing for multiplexing of signals with varying group delays to prevent transmission characteristic deterioration and ensure dispersion tolerance, using a combination of CWDM and DWDM techniques with SMF and DSF fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wavelengths are arranged across the zero-dispersion wavelength of the transmission line to enable CWDM multiplexing, then the number of multiplexed wavelengths is limited and transmission characteristic deterioration occurs due to identical group delay, but if wavelengths are arranged to avoid identical group delay, then transmission quality improves but the number of multiplexed wavelengths is reduced
Solution Approach 1:
The patent applies parameter changes by introducing wavelength chirp as a new control parameter. Instead of only selecting wavelengths to avoid identical group delay, the system actively adjusts the chirp parameter of each optical signal through intensity modulation. This allows signals with identical group delay to be transmitted without deterioration by compensating for the dispersion effect through appropriate chirp setting, thereby enabling more wavelengths to be multiplexed while maintaining transmission quality.
Solution Approach 2:
The patent implements preliminary action by pre-setting the wavelength chirp for each optical signal before transmission. The intensity modulators in the optical transmitting units apply the appropriate chirp to each signal in advance, so that when the signals are multiplexed and transmitted through the dispersion-prone fiber, the pre-applied chirp compensates for the dispersion effects, preventing transmission characteristic deterioration before it occurs.
2Reliability
If intensity modulation with wavelength chirp is applied to each optical signal, then transmission quality and dispersion tolerance are improved, but device complexity increases due to additional modulation components
Solution Approach 1:
The patent applies universality by using intensity modulators that serve multiple functions: they not only modulate the intensity of optical signals for transmission but also simultaneously set the wavelength chirp parameter. This multi-functional approach avoids the need for separate chirp control components, thereby improving dispersion tolerance and transmission quality without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the intensity modulation function and wavelength chirp setting function into a single intensity modulator component. By combining these two functions that were previously handled by separate components, the system achieves both signal transmission and dispersion compensation capabilities through one device, reducing overall system complexity while maintaining improved transmission quality.
3Productivity
If the number of multiplexed wavelengths is increased to improve system capacity, then productivity increases, but transmission characteristic deterioration occurs due to nonlinear optical effects from identical group delay
Solution Approach 1:
The patent uses parameter changes by introducing wavelength chirp as an additional degree of freedom. When increasing the number of multiplexed wavelengths, the system can adjust the chirp parameter of each signal to ensure that even signals with identical group delay do not suffer from nonlinear optical effects. This allows the system to scale capacity while maintaining transmission characteristics through active parameter adjustment.
Solution Approach 2:
The patent implements feedback mechanisms where the system monitors transmission characteristics and adjusts the wavelength chirp settings accordingly. By using feedback information about the transmission quality and dispersion conditions, the system can dynamically optimize the chirp parameters of individual signals to prevent nonlinear effects, enabling higher system capacity without sacrificing transmission reliability.
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, high-quality wavelength division multiplexing transmission without signal deterioration, even at narrowed dispersion tolerance, and allows for efficient increase in the number of multiplexed wavelengths, reducing power penalty and ensuring compatibility with existing systems.
Implementation Method 1
a plurality of optical intensity modulating units intensity-modulating the optical signals, and a wavelength multiplexing unit multiplexing the optical signals having the amount of wavelength chirp set respectively
Implementation Method 2
a characteristic of dispersion and a characteristic of group delay in each of SMF (Single Mode Fiber) and DSF (Dispersion Shifted Fiber)
Implementation Method 3
the amount of group delay of transmitted optical signals may be identical
Data Source
AI summary
A wavelength division multiplexing optical transmission apparatus for transmitting wavelength division multiplexing optical signals, the apparatus including a plurality of optical transmitting units outputting optical signals having a different wavelength from each other, a plurality of optical intensity modulating units intensity-modulating the optical signals, and a wavelength multiplexing unit multiplexing the optical signals. The plurality of optical intensity modulating units sets the amount of wavelength chirp adapting to each wavelength of the optical signals for the optical signals outputted from each of the plurality of optical transmitting units, and the wavelength multiplexing unit multiplexes the optical signals having the amount of wavelength chirp set respectively and then outputs the multiplexed optical signals.