DBR Laser Modulation Region for Chirp-Free Optical Transmission
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Solution Overview
Problem
Existing optical communication devices using directly modulated lasers and electro-absorption modulator integrated distributed feedback lasers suffer from frequency chirp, limiting transmission distance, especially at high data rates, and intensity modulation occurs unintentionally when a modulation electric field is applied, reducing operation speed.
Innovation Solution
An optical device with a gain region and a light modulation region using a material with electro-optical effects, such as lithium niobate, modulates the frequency of laser light by adjusting the effective refractive index through a modulation electric field, suppressing intensity modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a modulation electric field is applied to the phase shift region to modulate frequency, then frequency modulation is achieved, but intensity modulation occurs unintentionally reducing operation speed
Solution Approach 1:
The device is divided into distinct functional regions: a gain region for light generation and a light modulation region for frequency modulation. This segmentation allows the modulation region to be optimized for electro-optical modulation without the complications of carrier injection present in the gain region, thereby eliminating unwanted intensity modulation and improving operation speed.
Solution Approach 2:
A light modulation region acts as an intermediary between the gain region and the output, using materials with strong electro-optical effects to modulate the frequency of laser light without causing intensity modulation. This intermediary region isolates the frequency modulation function from the gain generation process, ensuring pure frequency modulation and maintaining high operation speed.
2Productivity
If DML or EA-DFB is used for intensity modulation, then transmission capacity increases to 100 Gbit/s/λ, but frequency chirp limits transmission distance
Solution Approach 1:
The patent replaces the direct intensity modulation mechanism (mechanical/electrical) with an electro-optical frequency modulation mechanism. By using materials with strong electro-optical effects in the light modulation region, the system modulates frequency rather than intensity directly, eliminating frequency chirp while maintaining high transmission capacity, thereby extending transmission distance.
3Reliability
If band gap is controlled to suppress quantum confined Stark effect or Franz-Keldysh effect, then intensity modulation is reduced, but carriers still flow in and out causing intensity modulation
Solution Approach 1:
The patent extracts the light modulation function from the gain region and places it in a separate light modulation region. This extraction removes the carrier injection and flow issues present in the gain region, allowing frequency modulation without unwanted intensity modulation caused by carrier dynamics, while maintaining high operation speed through electro-optical effects.
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 device effectively modulates frequency while minimizing intensity modulation, enhancing operation speed and transmission distance in optical communication systems.
Implementation Method 1
a light modulation layer including a material having an electro-optical effect and disposed in a range couplable to propagating light, and a frequency of laser light oscillated by the semiconductor laser is modulated by modulating an effective refractive index of a propagating light mode by applying a modulation electric field to the light modulation layer
Data Source
AI summary
The optical device includes a gain region constituting a waveguide type semiconductor laser, and a waveguide type light modulation region that modulates laser light of the semiconductor laser. The semiconductor laser is a distributed Bragg reflector laser, and the gain region is disposed between a first distributed Bragg reflector region and a second distributed Bragg reflector region. Further, the light modulation region is disposed between the gain region and the first distributed Bragg reflector region. The light modulation region includes a light modulation layer including a material having an electro-optical effect and disposed in a range couplable to propagating light.