Dual Segment Fiber Light Source for Stable Wavelength
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Solution Overview
Problem
Conventional broadband fiber light sources exhibit unstable mean wavelength with variations in pump laser power, which is critical for interferometric fiber optic gyroscopes requiring stable scale factor stability.
Innovation Solution
A dual segment fiber light source is implemented, comprising two rare-earth doped fibers with different sensitivities to pump power, where one fiber has a positive slope and the other a negative slope, and their combined output is optimized to achieve zero sensitivity to pump power fluctuations using specific power coupling ratios and lengths of fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional broadband fiber light sources are used, then the device is simple and easy to manufacture, but the mean wavelength is unstable with pump power variations
Solution Approach 1:
The light source is divided into two separate fiber segments: a first rare-earth-doped fiber segment and a second rare-earth-doped fiber segment with different doping concentrations. Each segment contributes differently to the overall emission spectrum, and their combined output achieves wavelength stability that neither segment could achieve alone. This segmentation allows the system to compensate for pump power variations through the complementary characteristics of the two segments.
Solution Approach 2:
Different regions of the fiber light source are given different doping concentrations to create local quality variations. The first segment has a higher rare-earth ion doping concentration while the second segment has a lower concentration. This local quality differentiation enables each segment to have distinct spectral characteristics that, when combined, produce a stable mean wavelength across pump power variations.
2Illumination intensity
If the rare-earth ion doping concentration is increased, then the emission intensity is improved, but the sensitivity to pump power fluctuations increases
Solution Approach 1:
The fiber light source implements local quality by creating regions with different doping concentrations. The first segment uses higher doping concentration to provide strong emission intensity, while the second segment uses lower doping concentration to provide wavelength stability. This spatial variation in doping quality allows the system to simultaneously achieve both high intensity and wavelength stability.
Solution Approach 2:
The system combines two fiber segments with different doping characteristics into a composite light source structure. The first segment with higher doping concentration contributes to emission intensity, while the second segment with lower doping concentration contributes to wavelength stability. The composite nature of this dual-segment structure enables the system to achieve properties that neither homogeneous segment could achieve alone.
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 dual segment fiber light source provides a stable mean wavelength output, reducing sensitivity to pump power variations, achieving a wavelength instability of less than 0.000065 parts per million, suitable for applications in interferometric fiber optic gyroscopes.
Implementation Method 1
The rare-earth doped fiber is an active medium for the broadband light source and includes a fiber core doped with rare-earth ions
Data Source
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AI summary
A fiber light source (605, 705) comprises a laser pump (654, 754) configured to generate a pump laser beam at a predetermined wavelength;a first segment of rare earth doped fiber (652-1, 752-1); a second segment of rare earth doped fiber (652-2, 752-2); and an optical coupler (656, 756) coupled to a first end of the first segment and a first end of the second segment. The optical coupler (656, 756) is configured to split the pump laser beam based on a power coupling ratio. The first segment generates a first stimulated emission having a first mean wavelength sensitivity to pump laser power fluctuations and the second segment generates a second stimulated emission having a second mean wavelength sensitivity to pump laser power fluctuations such that an output (664, 764) of a combined stimulated emission from first and second stimulated emissions presents a mean wavelength which is approximately insensitive to pump laser power fluctuations. An optical fiber gyro comprising the above-described fiber light source is also disclosed.