Surface Emitting Laser Diode Noise Suppression
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Solution Overview
Problem
Existing optical transmission systems face challenges in securing a long transmissible distance while maintaining low communication errors, as increasing emission output of electro-optical conversion devices leads to increased noise floors and communication errors.
Innovation Solution
The implementation of an optical transmission system using an electro-optical conversion device with a light source capable of emitting 0.8 mW or more and a noise index of 10.0 dBμV or less, utilizing a surface emitting laser diode with a beam diameter of 7.8 μm or more or single mode similarity of 0.85 or more, to suppress communication errors and ensure long transmissible distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the emission output of the electro-optical conversion device is increased to secure a long transmissible distance, then the transmissible distance is improved, but the noise floor is increased and communication errors increase
Solution Approach 1:
The patent changes the physical parameters of the light source by specifying a beam diameter (FWHM) of 7.8 μm or more and SM similarity of 0.85 or more. These parameter changes optimize the light distribution mode to enhance basic mode influence and suppress mode competition noise, thereby reducing the noise floor while maintaining sufficient emission output for long transmissible distance
Solution Approach 2:
The patent dynamically optimizes the light source characteristics by controlling the beam diameter and SM similarity parameters. This dynamic adjustment of light distribution properties allows the system to achieve low noise floor performance while maintaining the emission output necessary for long-distance transmission, resolving the contradiction between distance and error rate
2Length of stationary object
If the emission output of the electro-optical conversion device is increased, then the transmissible distance is improved, but the noise floor is increased
Solution Approach 1:
The patent applies parameter changes by specifying the beam diameter (FWHM) of 7.8 μm or more and SM similarity of 0.85 or more. These parameter specifications transform the light distribution characteristics to suppress mode competition noise, thereby reducing the noise floor while maintaining the emission output needed for long transmissible distance
Solution Approach 2:
The patent converts the potentially harmful mode competition noise into a beneficial low-noise operation by optimizing the light source parameters. By controlling the beam diameter and SM similarity, the system transforms what would normally be noise-generating mode competition into a regime where the basic mode dominates, converting the harmful effect into a benefit for long-distance transmission
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 effectively suppresses communication errors while securing a long transmissible distance by optimizing the light source's output and noise index, reducing mode competition noise and enhancing the basic mode's influence.
Implementation Method 1
a light source capable of emitting light at output of 0.8 mW or more, and a beam diameter (FWHM: full width at half maximum) obtained by near-field pattern measurement of the light source is 7.8 μm or more
Implementation Method 2
an electro-optical conversion device for receiving an RF signal, converting the RF signal into an optical signal, and transmitting the optical signal
Implementation Method 3
an opto-electrical conversion device for converting the optical signal transmitted from the optical transmission line into an RF signal and transmitting the RF signal
Data Source
AI summary
An optical transmission system transmits a Radio Frequency (RF) signal by a frequency division multiplexing method. The optical transmission system includes a Transmitter Optical SubAssembly (TOSA), an optical fiber, and a Receiver Optical SubAssembly (ROSA). The TOSA includes a surface emitting laser diode configured to be capable of emitting light at output of 0.8 mW or more. In the optical transmission system including the surface emitting laser diode, a noise index obtained by a measurement method including a predetermined step is 10.0 dBμV or less.