Directly Modulated Laser THz Generation With Optical Beating
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Solution Overview
Problem
Current light-based THz signal transmission systems are costly and complex due to the use of high-cost, power-consuming, and large-sized components like external cavity lasers and optical comb generators, which complicate the configuration and increase the initial cost and maintenance of the system.
Innovation Solution
A THz signal generating apparatus using directly-modulated lasers, a band-pass filter, a coupler, and a uni-travelling-carrier photodiode (UTC-PD) to generate THz signals through an optical beating process, simplifying the configuration and reducing costs by suppressing spectral components and optimizing the optical extinction ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external cavity lasers and optical comb generators are used to generate THz signals, then transmission performance is improved, but system cost and complexity increase significantly
Solution Approach 1:
The patent replaces expensive external cavity lasers and optical comb generators with directly-modulated lasers that are cheaper and simpler in structure. The directly-modulated laser uses a standard laser diode with direct current modulation, eliminating the need for complex external cavities and comb generation apparatus, thus reducing system cost and complexity while maintaining functional capability for THz signal generation
Solution Approach 2:
The patent extracts and removes unnecessary components from the traditional THz generation system. By using directly-modulated lasers, the system eliminates external cavity lasers, optical comb generators, and associated control equipment, keeping only the essential components (laser, modulator, photodiode) needed for optical beating and THz signal generation
2Productivity
If external modulators and additional control apparatus are used for THz signal generation, then bulk transmission capability is improved, but initial cost and system complexity increase
Solution Approach 1:
The patent merges the modulation function directly into the laser diode through direct current modulation, eliminating the need for separate external modulators. The directly-modulated laser integrates the light source and modulator into a single component, and the optical beating process in the photodiode simultaneously achieves both modulation and frequency conversion, reducing component count and system complexity
Solution Approach 2:
The directly-modulated laser serves multiple functions: it acts as both the light source and the modulator. The laser diode generates coherent light while simultaneously imposing the modulation signal through direct current modulation. The photodiode then performs optical beating to generate the THz signal, making each component multi-functional and reducing overall system complexity
3Reliability
If optical comb generators with RF synthesizers and optical amplifiers are used, then THz signal generation is achieved, but configuration complexity and installation cost increase
Solution Approach 1:
The patent replaces expensive optical comb generators, RF synthesizers, and optical amplifiers with a simple directly-modulated laser system. The directly-modulated laser uses standard laser diodes with direct current modulation, eliminating the need for costly comb generation apparatus and associated control equipment, thus significantly reducing installation and maintenance costs
Solution Approach 2:
Instead of using complex optical comb generation methods to create multiple frequency components, the patent inverts the approach by using direct current modulation on a single laser diode to directly generate the desired frequency components. This reverse approach simplifies the system by eliminating the need for optical comb generators and RF synthesizers
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 simplifies the configuration and reduces costs by generating THz signals using directly-modulated lasers, improving transmission performance and increasing the wireless transmission distance while reducing the complexity and initial cost of the system.
Implementation Method 1
a uni-travelling-carrier photodiode (UTC-PD) configured to generate a THz signal by beating the baseband signal and the LO signal coupled to each other
Implementation Method 2
a uni-travelling-carrier photodiode (UTC-PD) configured to generate a THz signal by beating the baseband signal and the LO signal coupled to each other
Implementation Method 3
a second directly-modulated laser configured to receive a baseband signal used as data and optically modulate the baseband signal
Data Source
AI summary
Provided are an apparatus and method of generating a terahertz (THz) signal using a directly-modulated laser. An apparatus of generating a THz signal includes a first directly-modulated laser configured to output a local oscillator (LO) signal, a second directly-modulated laser configured to receive a baseband signal used as data and optically modulate the baseband signal, a band-pass filter configured to filter a spectral component of the baseband signal optically modulated and outputted through the second directly-modulated laser by using a specific frequency bandwidth, a coupler configured to couple the baseband signal filtered through the band-pass filter and the LO signal to each other, and a uni-travelling-carrier photodiode (UTC-PD) configured to generate a THz signal by beating the baseband signal and the LO signal coupled to each other.