Fiber Stretcher Module Dispersion Matching at 1550 nm
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Solution Overview
Problem
Fiber stretcher modules for the 1550 nm wavelength range face challenges in matching dispersion values with compressor gratings, particularly in achieving the desired fourth-order dispersion value, which is approximately 50% off when using existing combinations of Dispersion Compensation Fiber (DCF) and Super Large Effective Area (SLA) fibers.
Innovation Solution
A fiber stretcher module comprising a first fiber with a relative dispersion slope (RDS) over relative dispersion curvature (RDC) value of less than 30 nm and a dispersion value of less than -10 ps/(nm·km) at 1550 nm, and a second fiber with a RDC value of zero and a RDS value greater than 0.002 nm^-1 and a dispersion value greater than 10 ps/(nm·km), where the lengths of both fibers are adjusted to achieve a best possible dispersion match to a corresponding compressor grating or other compression devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a combination of existing DCF and SLA fiber is used to build a fiber stretcher module, then the second-order dispersion (β2) and third-order dispersion (β3) values can be matched closely to the target grating specifications, but the fourth-order dispersion (β4) value remains approximately 50% off from the desired matching value
Solution Approach 1:
The patent introduces a new fiber parameter - relative dispersion curvature (RDC) - and specifies that the first fiber should have an RDC value greater than 0.0002 nm^-2 at 1550 nm. By changing the fiber selection criteria to include this additional parameter, the patent enables achievement of target β4 values that were previously unattainable with conventional DCF and SLA fiber combinations alone
Solution Approach 2:
The patent creates a composite fiber structure by combining three different fiber types (DCF, SLA, and the newly specified first fiber with high RDC) in a multi-stage configuration. This composite approach allows each fiber type to contribute its unique dispersion characteristics, enabling simultaneous matching of β2, β3, and β4 values to the target grating specifications
2Reliability
If fiber stretcher modules are used instead of bulk optics or chirped fiber Bragg gratings, then group delay and amplitude ripples are reduced along with improving stability, lifetime, and cost, but achieving the desired dispersion matching (particularly β4) becomes more challenging
Solution Approach 1:
The patent expands the parameter space for fiber selection by introducing RDC as a critical specification. By requiring the first fiber to have RDC > 0.0002 nm^-2, the patent transforms the fiber stretcher module from a component that can only approximately match dispersion values to one that can precisely match all three dispersion parameters (β2, β3, β4) to the target grating
Solution Approach 2:
The patent divides the fiber stretcher module into three distinct stages, each using a different fiber type optimized for specific dispersion compensation needs. This segmentation allows independent optimization of each stage's contribution to the overall dispersion characteristics, enabling precise matching of higher-order dispersion terms while maintaining the reliability advantages of fiber-based technology
Data Source
AI summary
Embodiments of the present invention are generally related to embodiments of the present invention relate to a fiber stretchers module for use in the 1550 nm wavelength range. In one embodiment of the present invention, a fiber stretcher module for use in the 1550 nm wavelength range comprises a fiber having a relative dispersion slope, RDS, and a relative dispersion curvature, RDC, wherein a ratio of said slope to said curvature is between about 30 nm and about 0 nm, having a dispersion value of less than about −10 ps/(nm·km) at about 1550 nm, and a RDS is equal to or greater than 0.