Optoelectronic Data Transmission Device Using Electro-Optic Modulation
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Solution Overview
Problem
Conventional directly modulated semiconductor lasers face difficulties in achieving high-speed data transmission above 10 Gb/s due to limitations in bandwidth, parasitic capacitance, inductance, and resistance in VCSELs, as well as high power dissipation and complexity in indirect modulation methods.
Innovation Solution
A data transmission optoelectronic device with a waveguide between mirrors, incorporating an active section for optical gain, an absorption section for self-pulsating mode-locking, and an electrooptic modulator to frequency-modulate the pulsed laser light, allowing for high-bit rate frequency-modulated data signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If direct modulation by current injection is used, then device cost is reduced, but bandwidth is limited and requires very high photon densities in the resonant cavity
Solution Approach 1:
The device is divided into two independent sections: a gain section for generating optical gain and a modulator section for high-speed modulation. This segmentation allows each section to be optimized independently, enabling high-speed operation without requiring extremely high photon densities in the gain region.
Solution Approach 2:
An electro-optic modulator is introduced as an intermediary component between the gain section and the output. This modulator uses the electro-optic effect to modulate the light from the gain section at high speeds without requiring high current densities, thus achieving high bandwidth while maintaining reasonable operating conditions.
2Speed
If pump current density is increased to increase laser bandwidth, then bandwidth increases, but power dissipation and heat generation become excessive
Solution Approach 1:
By separating the gain generation function from the modulation function, the device allows the gain section to operate at moderate current densities while the high-speed modulation is achieved through the electro-optic modulator. This eliminates the need to increase pump current density to achieve high bandwidth.
Solution Approach 2:
The patent replaces direct current modulation (electrical mechanism) with electro-optic modulation (optical mechanism). The electro-optic modulator uses electric field-induced changes in refractive index to modulate light, achieving high-speed modulation without the thermal issues associated with high current densities.
3Device complexity
If VCSELs are used for high-speed operation, then device integration is improved, but parasitic capacitance, inductance and resistance limit high-speed performance
Solution Approach 1:
The electro-optic modulator acts as an intermediary that decouples the gain generation from high-speed modulation. This allows the use of VCSELs with their inherent integration advantages while overcoming their parasitic limitations by performing modulation in a separate section optimized for high-speed operation.
4Speed
If indirect modulation methods are used to achieve high-speed transmission, then bandwidth increases, but device complexity and power consumption increase
Solution Approach 1:
The patent merges the gain section and modulator section into a single integrated device structure with a shared waveguide. This combination achieves high-speed indirect modulation while maintaining relatively simple device architecture and avoiding the complexity of completely separate modulation systems.
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
Enables high-speed data transmission with reduced parasitic effects and power dissipation, achieving frequency modulation of pulsed laser light for efficient data transfer at ultrahigh bit rates.
Implementation Method 1
an active section (230) having an active element for generating an optical gain if a forward bias is applied
Implementation Method 2
an absorption section (240) for self-pulsating mode-locking
Implementation Method 3
an additional modulator incorporated in the waveguide, the additional modulator being configured to modulate a refractive index thereof such that a repetition frequency of the pulsed laser light is frequency-modulated
Data Source
AI summary
An optoelectronic data transmission device has an active section with an active element that generates an optical gain if a forward bias is applied, and an absorption section. A waveguide incorporates the active section and the absorption section. Mirrors providing feedback for light are placed to frame the waveguide. The device can be operated in a pulsed regime emitting pulsed laser light. An additional modulator allows modulating its refractive index due to the electrooptic effect. A device providing for the modulation of the refractive index of the modulator. The refractive index of the additional modulator can be varied such that the repetition frequency of the output pulsed laser light is varied. The waveguide further incorporates the additional modulator.