Optical Fiber W-Type Profile Microbending Loss
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Solution Overview
Problem
Optical fibers with increased effective cross-sectional area suffer from wavelength-dependent microbending loss, which deteriorates the optical signal-to-noise ratio (OSNR) due to light leakage from the fundamental mode to cladding modes caused by random microbending, particularly in W-type and trench-type refractive index profiles.
Innovation Solution
An optical fiber with a W-type or trench-type refractive index profile, featuring a depression-type cladding structure with specific refractive index differences between core and cladding regions, is designed to minimize microbending loss by optimizing the wavelength dependency of coupling coefficients, ensuring the shortest wavelength for 10% maximal microbending loss is longer than 1560 nm, and maintaining low microbending loss across the C- and L-bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the effective cross-sectional area of the optical fiber is increased to reduce non-linearity, then the non-linearity is reduced, but the confinement of propagation light to the core is weakened and microbending loss increases
Solution Approach 1:
The patent applies local quality by creating a trench-type refractive index profile where the cladding region has a localized depression (lower refractive index) surrounding the core. This localized modification of the cladding structure provides strong optical confinement at the core-cladding interface while maintaining a large effective cross-sectional area, thereby reducing non-linearity without increasing microbending loss.
Solution Approach 2:
The patent changes the refractive index parameter distribution by introducing a trench structure with specific refractive index differences (Δ1 between core and inner cladding, Δ2 between inner and outer cladding). By optimizing these parameter relationships, the fiber achieves both large effective area and strong mode confinement, resolving the contradiction between non-linearity reduction and microbending loss prevention.
2Reliability
If the effective cross-sectional area is increased, then the non-linearity is reduced, but the optical signal-to-noise ratio (OSNR) is deteriorated due to increased microbending loss
Solution Approach 1:
The trench-type refractive index profile creates a localized depression in the cladding region with lower refractive index than both the core and the outer cladding. This local structural modification provides strong optical confinement that prevents light leakage to cladding modes, thereby maintaining high OSNR even with large effective cross-sectional area that reduces non-linearity.
Solution Approach 2:
The optical fiber structure comprises multiple regions with different refractive indices (core, inner cladding with trench, outer cladding), forming a composite structure. This composite design allows simultaneous achievement of large effective area for non-linearity reduction and strong mode confinement for OSNR maintenance.
3Reliability
If a W-type or trench-type refractive index profile is used to increase effective cross-sectional area, then the non-linearity is reduced, but wavelength-dependent microbending loss increases and confines light less effectively
Solution Approach 1:
The patent optimizes the refractive index parameters by defining specific relationships between Δ1 (core to inner cladding) and Δ2 (inner to outer cladding). This parameter optimization ensures that the trench structure provides sufficient mode confinement across the wavelength band, reducing wavelength-dependent microbending loss while maintaining large effective area for non-linearity reduction.
Solution Approach 2:
The trench structure introduces a localized refractive index depression in the cladding region, creating a potential well that confines the fundamental mode. This local modification effectively suppresses coupling to higher modes and cladding modes, thereby reducing wavelength-dependent microbending loss while preserving the large effective cross-sectional area.
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 optical fiber achieves reduced microbending loss and improved OSNR by extending the shortest wavelength for 10% maximal microbending loss beyond 1560 nm, effectively confining light within the core and reducing transmission losses in the C- and L-bands, thus enhancing the optical communication system's performance.
Implementation Method 1
confinement of propagation light (fundamental mode light) to a core is weakened
Implementation Method 2
transmit signal light
Data Source
AI summary
The present embodiment relates to an optical fiber having a W-type refractive index d profile or a trench-type refractive index profile and having reduced microbending loss in a wavelength band to be actually used. The optical fiber includes a center core, an inner cladding surrounding the center core, and an outer cladding surrounding the inner cladding. The inner cladding has a refractive index lower than a refractive index of at least the center core and the outer cladding has a refractive index lower than the refractive index of the center core and higher than the refractive index of the inner cladding. Wavelength dependency of microbending loss has a local maximal value and a shortest wavelength λth where the microbending loss becomes 10% of the local maximal value is longer than 1560 nm.