Tunable Optical Comb Source via Gain-Switched Fabry-Perot Laser

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Solution Overview

Problem

Conventional optical comb sources face limitations in tunability, spectral flatness, and optical linewidth, which restrict their application in advanced modulation formats and multicarrier transmission techniques.

Innovation Solution

A tunable optical comb source is achieved by using a single mode laser as a master to drive a gain-switched Fabry-Perot semiconductor laser, with RF and DC bias control to determine comb line spacing and maintain coherence, and optional phase modulation for spectral expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If mode-locked semiconductor lasers are used to generate comb sources, then multi-carrier signals spanning wide bandwidth can be generated, but the cavity complexity increases and the free spectral range becomes non-tunable

Engineering Contradiction:

Improvebandwidth coverageVSAvoidcavity complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The invention separates the comb generation function from the laser cavity by using external modulation. The laser generates a single carrier, and the comb structure is created externally through optical modulators, eliminating the need for complex mode-locked cavity designs while achieving wide bandwidth coverage

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

External optical modulators are introduced as intermediary devices between the laser source and the output. These modulators create the comb structure without requiring complex laser cavities, and enable independent tuning of the free spectral range through electrical control signals

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If mode-locked semiconductor lasers are used, then comb lines can be generated, but the optical linewidth of individual comb lines becomes relatively large

Engineering Contradiction:

Improvecomb line generationVSAvoidoptical linewidth

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

External optical modulators serve as intermediaries that transfer the comb structure from the electrical domain to the optical domain. This approach inherits the narrow linewidth of the continuous-wave laser while creating well-defined comb lines through precise modulation, achieving both comb line generation and narrow linewidth

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If external optical modulators are used for wavelength tunable comb generation, then line spacing and central wavelength can be varied, but the insertion loss becomes prohibitive

Engineering Contradiction:

Improvewavelength tunabilityVSAvoidinsertion loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The invention optimizes modulation parameters including driving signal amplitude, frequency, and phase to maximize modulation efficiency. By carefully controlling these parameters, the system achieves wide wavelength tunability and adjustable line spacing while minimizing insertion loss through efficient modulation operation

Inventive Principle:

Principle #35Parameter changes

4Quantity of substance

If phase modulation in amplified fiber loop is used, then comb generation is achieved, but the spectral flatness becomes poor and optical linewidth is limited

Engineering Contradiction:

Improvecomb generationVSAvoidspectral flatness

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The invention replaces the mechanical amplified fiber loop system with an external modulation approach using optical modulators. This substitution eliminates the spectral flatness issues and optical linewidth limitations inherent in fiber-based systems, achieving superior spectral characteristics through direct electrical-optical modulation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach provides a highly coherent, tunable optical comb with narrow linewidth and improved spectral flatness, suitable for advanced modulation formats and efficient transmission.

Implementation Method 1

a single mode laser as a master to drive a gain-switched Fabry-Perot semiconductor laser

Methodology Applied

Scientific EffectLight emission: Laser

Implementation Method 2

the output from the tunable laser is injected into the lasing cavity of the F-P laser

Methodology Applied

Scientific EffectOptical injection: Injector

Implementation Method 3

gain-switched Fabry-Perot semiconductor laser, with RF and DC bias control to determine comb line spacing

Methodology Applied

Scientific EffectGain switching:

Implementation Method 4

Fabry-Perot semiconductor laser having a lasing cavity

Methodology Applied

Scientific EffectFabry-Perot resonance: Fabry-Perot Interferometer

Implementation Method 5

the output from the tunable laser is injected into the lasing cavity of the F-P laser and the output of the laser assembly is provided by the F-P laser

Methodology Applied

Scientific EffectOptical injection seeding: Injector

Data Source

PatentEP2756565B1Wavelength tunable comb source

Publication Date: 2018.10.31 DUBLIN CITY UNIVERSITY

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AI summary

The present application provides an optical comb source (1) in which the comb is produced by seeding a gain switched Fabry-Perot laser (2) with light (10) from a single mode laser (4), whilst at the same time driving the Fabry-Perot laser (2) with a DC bias and RF signal.