Compact Wavelength-Swept DFB Laser for OFDR Systems
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Solution Overview
Problem
Current optical frequency domain reflectometry (OFDR) systems require a single longitudinal mode laser for accurate fiber Bragg grating detection, but existing wavelength-tunable lasers, such as external-cavity lasers, are expensive and prone to vibration issues, while distributed feedback (DFB) lasers lack sufficient tunability for swept-wavelength applications.
Innovation Solution
A compact wavelength-swept single longitudinal mode laser using a DFB laser with a thermoelectric cooler (TEC) feedback system for continuous temperature control, allowing linear wavelength tuning over a 4.5 nm range, enabling accurate and cost-effective OFDR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external-cavity lasers are used for wavelength tuning in OFDR systems, then single longitudinal mode capability and wavelength sweep range are achieved, but device complexity, cost, and susceptibility to vibration increase
Solution Approach 1:
The patent replaces the mechanical tuning system of external-cavity lasers with a semiconductor-based DFB laser that achieves wavelength tuning through electrical current modulation and temperature control. This substitution eliminates moving parts, reduces mechanical complexity, and maintains single longitudinal mode operation while achieving a wavelength sweep range of 4-5 nm.
Solution Approach 2:
The patent utilizes parameter changes in the DFB laser diode, specifically modulating the injection current and temperature, to achieve wavelength tuning. By changing these operational parameters, the laser wavelength can be swept continuously over 4-5 nm while maintaining single longitudinal mode operation, avoiding the need for complex mechanical tuning mechanisms.
2Ease of manufacture
If DFB lasers are used for wavelength tuning, then cost is reduced, but wavelength sweep range and tunability are insufficient
Solution Approach 1:
The patent transforms the static wavelength operation of conventional DFB lasers into a dynamic wavelength sweep capability. By implementing continuous modulation of the injection current and temperature control through TEC, the DFB laser achieves dynamic wavelength tuning over 4-5 nm, making it suitable for swept-wavelength OFDR applications while maintaining cost-effectiveness.
Solution Approach 2:
The patent exploits parameter changes in the DFB laser diode characteristics, where wavelength varies with injection current and temperature. By carefully controlling these parameters, the system achieves a wavelength sweep range of 4-5 nm, significantly expanding the tunability of cost-effective DFB lasers for OFDR applications.
3Adaptability or versatility
If DFB laser temperature is increased for wavelength tuning, then wavelength sweep range is achieved, but temperature stability and single longitudinal mode operation may be compromised
Solution Approach 1:
The patent implements a feedback control system using a temperature controller and TEC to maintain precise temperature management of the DFB laser. This feedback mechanism ensures that temperature changes are controlled within tight tolerances, preserving single longitudinal mode operation while enabling the required wavelength sweep range through coordinated current and temperature modulation.
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 solution provides a cost-effective and accurate method for OFDR systems, capable of interrogating multiple fiber gratings with a clean clock acquisition signal and interferogram, replacing expensive external-cavity lasers with semiconductor-based DFB lasers, suitable for applications like liquid level sensing.
Implementation Method 1
a thermoelectric cooler operatively connected to the distributed feedback laser
Implementation Method 2
a distributed feedback laser operatively connected to the optical fiber
Implementation Method 3
Each FBG creates a periodic variation of the optical refractive index in the core of its associated optical fiber
Implementation Method 4
the positions of the FBGs along the fiber are detected by interferometry, e.g., by measuring the beat frequency of individual FBG reflections
Data Source
AI summary
A method and system for using a wavelength tunable semiconductor laser as an excitation source of a fiber optics sensing system (FOSS) based on a thermoelectric control of a laser sweep. A device can include an optical fiber; a set of fiber Bragg gratings disposed within the optical fiber; a single-frequency laser (SFL) operatively connected to the optical fiber; a thermoelectric cooler operatively connected to the SFL; a controller comprising a processor in communication with the thermoelectric cooler; and a nontransitory, computer-readable storage medium in communication with the processor. The nontransitory, computer-readable storage medium can store instructions that, when executed by the processor, cause the processor to perform operations including determining a strain value at a first fiber Bragg grating of the set of fiber Bragg gratings based on a second laser signal received at the device that is reflected from an interaction of a first laser signal with the first fiber Bragg grating.