Tunable Fiber Bragg Grating for 1550 nm Laser Filtering

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Solution Overview

Problem

Existing techniques for frequency control of semiconductor lasers are not applicable for wavelengths in the 1550 nm band used in standard coarse and dense wavelength division multiplexing (WDM), as semiconductor amplifiers do not operate effectively at these wavelengths, limiting spectral filtering capabilities.

Innovation Solution

A tunable fiber Bragg grating is integrated with the back facet of a laser diode to form a resonant coupled cavity structure, allowing for selective transmission or rejection of optical frequency components, enabling spectral filtering and dispersion control in the 1550 nm wavelength band.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If semiconductor amplifiers are used for spectral filtering, then frequency control of semiconductor lasers can be achieved, but this approach is not applicable for wavelengths in the 1550 nm band where semiconductor amplifiers do not operate

Engineering Contradiction:

Improvespectral filtering capabilityVSAvoidwavelength band applicability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces a fiber Bragg grating as an intermediary element to perform spectral filtering in the 1550 nm wavelength band. Instead of relying on semiconductor amplifiers that cannot operate at this wavelength, the fiber Bragg grating acts as a mediator that reflects specific wavelengths while transmitting others, enabling spectral filtering capabilities where conventional semiconductor amplifiers fail.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the fundamental parameter of the filtering mechanism by transitioning from semiconductor amplifier-based filtering (which operates at specific wavelengths) to fiber Bragg grating-based filtering (which can be designed for any wavelength by adjusting the grating period). This parameter change enables adaptability to the 1550 nm band while maintaining spectral filtering functionality.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a fiber Bragg grating is integrated with the laser diode to form a resonant coupled cavity structure, then spectral filtering and dispersion control can be achieved in the 1550 nm band, but the device complexity increases

Engineering Contradiction:

Improvespectral filtering performanceVSAvoidcavity structure integration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the fiber Bragg grating with the laser diode cavity to form an integrated resonant coupled cavity structure. By combining these two components into a unified system where the fiber grating becomes part of the optical feedback path, the invention achieves spectral filtering and dispersion control without requiring separate external filtering components, thereby managing device complexity while enhancing functionality.

Inventive Principle:

Principle #5Merging (Combining)

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 solution provides effective spectral filtering and dispersion control for wavelengths in the 1550 nm band, enhancing the performance of WDM and DWDM networks by minimizing dispersion over long distances and increasing information carrying capacity.

Implementation Method 1

a tunable fiber Bragg grating is integrated with the back facet of the laser diode. This forms a resonant coupled cavity structure which can be tuned to pass or reject the desired optical frequency components

Methodology Applied

Scientific EffectBragg reflection: Bragg Diffraction

Implementation Method 2

Methodology Applied

Scientific EffectOptical resonance: Resonance

Implementation Method 3

The optical fiber has a first end and a second end opposite the first end, wherein the first end of the optical fiber is connected to the second end of the laser diode

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS7734132B2Optical spectral filtering and dispersion control for wavelength multiplexed laser sources using fiber Bragg gratings

Publication Date: 2010.06.08 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

The embodiments of the invention provide an apparatus for optical spectral filtering and dispersion control for wavelength multiplexed laser sources using fiber Bragg gratings. More specifically, the apparatus includes a laser diode having a first end and a second end opposite the first end. The first end of the laser diode has a first semi-transparent portion; and, the second end of the laser diode has a second semi-transparent portion. The apparatus further includes an optical fiber connected to the second end of the laser diode. The optical fiber has a first end and a second end opposite the first end, wherein the first end of the optical fiber is connected to the second end of the laser diode. The laser diode comprises a laser cavity; and, the optical fiber comprises an extension of the laser cavity. Moreover, the second end of the optical fiber has a reflective surface.