Optical Signal Transmitter Layout for SOA Carrier Density Stability
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Solution Overview
Problem
The existing optical signal transmitters, such as the AXEL, face issues with carrier density fluctuations in the SOA, leading to decreased amplification gain and distorted optical signal waveforms due to the pattern effect, which increases bit error rates and reduces signal quality when strong light is transmitted.
Innovation Solution
Integrating a DFB laser, an EA optical modulator, and one or more SOAs with a distributed Bragg reflector, where diffraction gratings are formed to overlap with the light propagation mode of the EA optical modulator and SOA, allowing for adjustment of carrier density through electric field modulation, thereby suppressing rapid changes and maintaining signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an SOA is integrated to amplify optical signal output, then light output is improved, but carrier density fluctuates causing pattern effect and signal quality degradation
Solution Approach 1:
An EA optical modulator is introduced as an intermediary component between the DFB laser and the SOA. This modulator uses an absorption layer with multiple quantum well structure that can change light absorption amount through voltage control, thereby stabilizing the optical signal before it enters the SOA and preventing carrier density fluctuations that cause pattern effects.
Solution Approach 2:
The invention changes the operating parameters of the SOA by controlling the electric field intensity applied to the EA optical modulator. By adjusting the voltage applied to the modulator, the light absorption amount is changed, which in turn stabilizes the carrier density in the SOA and maintains consistent amplification gain even when strong light is transmitted.
2Ease of operation
If an EA optical modulator with large optical loss is used, then modulation function is achieved, but it is difficult to increase light output
Solution Approach 1:
The invention merges multiple functions into a single integrated structure: the DFB laser for light generation, the EA optical modulator for signal modulation, and the SOA for signal amplification. This monolithic integration on an InP substrate allows the system to overcome the optical loss of the modulator through the amplification capability of the SOA, achieving both modulation function and high light output.
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 maintains the quality of the optical signal waveform by stabilizing carrier density in the SOA, reducing malfunctions in signal processing, and ensuring consistent amplification even under high light input, thereby enhancing the reliability of the optical signal transmitter.
Implementation Method 1
a diffraction grating is formed in a region overlapping a light propagation mode of the EA optical modulator so as to modulate a light intensity according to an intensity of an electric field added to the EA optical modulator
Implementation Method 2
includes a distributed Bragg reflector coupled to an emission end surface of the one or more SOAs
Implementation Method 3
Depending on an intensity of an electric field added to electric field absorption to the absorption layer 11b of the EA optical modulator 2, the EA optical modulator 2 modulates a light intensity
Implementation Method 4
when strong light enters the SOA 3, a carrier density in the SOA 3 decreases due to simulated emission of light
Data Source
AI summary
An optical signal transmitter (AXEL) in which a quality of an optical signal waveform is maintained includes a distributed Bragg reflector to be coupled with an emission end surface of an SOA in an optical circuit unit including an optical waveguide core portion formed on an upper surface of a substrate. In the optical circuit unit, a diffraction grating formed on an upper surface side opposite to an absorption layer of an EA optical modulator and a diffraction grating formed on an upper surface side of a reflection layer of the distributed Bragg reflector have a wavelength selectivity.