EADFB Optical Transmitter Waveguide Layout for SOA Output and Waveform Quality
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Solution Overview
Problem
In semiconductor laser elements with integrated SOAs, there are challenges with optical waveform quality deterioration and insufficient optical output due to constraints in designing the SOA structure.
Innovation Solution
The optical transmitter incorporates a DFB laser, an EA modulator, and an SOA with a waveguide structure where the core layer width of the SOA differs from that of the DFB laser, allowing for optimized optical confinement and carrier density management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same MQW structure is used for both DFB laser and SOA to simplify manufacturing, then manufacturing process is simplified, but optical waveform quality deteriorates and optical output becomes insufficient
Solution Approach 1:
The patent applies local quality by making the SOA core layer width different from the DFB laser core layer width. Specifically, the SOA region has a wider core layer (e.g., 3.0 μm) compared to the DFB laser core layer (e.g., 1.5 μm). This localized structural differentiation allows the SOA to have optimized optical confinement and carrier density for high-quality waveform amplification, while the DFB laser maintains its optimized structure for stable wavelength generation. The different core layer widths enable independent optimization of each component's performance without compromising manufacturing simplicity.
2Power
If the SOA core layer width is increased to improve optical output, then optical output increases, but optical confinement factor changes affecting waveform quality
Solution Approach 1:
The patent applies parameter changes by systematically varying the SOA core layer width to find the optimal balance between optical output and waveform quality. The core layer width is specifically set to 3.0 μm (compared to 1.5 μm for DFB laser), which provides sufficient active volume for high optical output while maintaining appropriate optical confinement. This parameter optimization ensures that the SOA can deliver high amplified power without degrading the optical waveform quality, resolving the contradiction between power output and 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 configuration effectively mitigates issues of optical waveform quality deterioration and insufficient optical output, achieving improved transmission quality and increased optical output.
Implementation Method 1
a distributed feedback (DFB) laser including an active region with a multi quantum well
Implementation Method 2
oscillates at a single wavelength determined by a driving current source 8 and a diffraction grating 5 formed in a cavity
Implementation Method 3
an electro-absorption (EA) optical modulator... changes an amount of light absorption through control of an electrical signal source 9
Implementation Method 4
a semiconductor optical amplifier (SOA) having an active region with an identical composition as the active region of the DFB laser and configured to amplify signal light from the EA modulator
Data Source
AI summary
In the present disclosure, in an EADFB laser in which an SOA has been integrated, a new configuration in which a problem of deterioration of optical waveform quality and insufficient optical output is solved or mitigated while taking advantage of characteristics that the same layer structure can be used and a manufacturing process can be simplified is shown. In an optical transmitter of the present disclosure, a waveguide structure having different core widths (waveguide widths) is adopted while using the same layer structure for a DFB laser and the SOA. Waveguides with different core widths are adopted so that a problem of insufficient saturated optical output or waveform deterioration due to a pattern effect is solved and mitigated. A passive waveguide region having a tapered shape is introduced in a part between an EA modulator and the SOA so that a waveguide width is continuously changed.