Multi-Core Optical Fiber Reverse Taper for VCSEL Coupling
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Solution Overview
Problem
The challenge lies in connecting densely arranged multi-core optical fibers with a pitch of 40 to 50 µm to a VCSEL array, where the realistic pitch of the VCSEL array is typically 250 µm, making it difficult to optically connect each core portion to the VCSEL elements due to fabrication limitations and yield rate issues.
Innovation Solution
A method of manufacturing a multi-core optical fiber with a cylindrical portion and a reverse-tapered portion, where the gap length between core portions is gradually expanded to match the VCSEL array pitch, facilitating easy optical coupling by adjusting the positional relation and using lenses for alignment, allowing for denser arrangement and easier connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-core optical fiber with pitch of 40 to 50 µm is used, then dense arrangement of core portions is achieved, but difficulty in optical connection to VCSEL array increases
Solution Approach 1:
The optical fiber is divided into multiple core portions (7 cores in the embodiment) arranged in a dense pattern, allowing high-density data transmission while maintaining individual core separability for connection purposes
Solution Approach 2:
A VCSEL array is introduced as an intermediary component with pitch matching the optical fiber core pitch. The VCSEL array serves as a bridge between the dense multi-core fiber and standard optical infrastructure, enabling easy connection through its larger 250 µm pitch while maintaining the dense 40-50 µm core arrangement in the fiber
2Ease of manufacture
If VCSEL array with pitch of 250 µm is used, then fabrication ease and yield rate are improved, but difficulty in optical coupling with dense multi-core fiber increases
Solution Approach 1:
The pitch parameter of the VCSEL array is set to 250 µm, which is significantly larger than the 40-50 µm core pitch in the optical fiber. This parameter change enables standard fabrication processes for VCSEL arrays while the pitch difference is compensated through optical coupling design, achieving both ease of manufacture and acceptable coupling precision
3Reliability
If gap length between core portions is reduced to 40 to 50 µm, then crosstalk suppression and dense arrangement are achieved, but connection alignment difficulty increases
Solution Approach 1:
The fiber is segmented into multiple tightly-spaced cores with 40-50 µm gaps, which suppresses crosstalk between adjacent cores while maintaining individual core integrity for separate alignment and connection to VCSEL elements
Solution Approach 2:
The VCSEL array acts as an intermediary with larger element spacing (250 µm pitch) that simplifies alignment operations. Each VCSEL element couples to a corresponding core in the multi-core fiber, and the pitch difference is managed through the coupling design, making alignment easier while maintaining crosstalk suppression in the dense fiber structure
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 approach enables efficient optical coupling between the multi-core optical fiber and the VCSEL array, enhancing the connection ease and density of core portions while maintaining balanced optical transmission characteristics.
Implementation Method 1
a multi-core optical fiber having a plurality of core portions is assumed to be used for an optical transmission channel
Implementation Method 2
confines light to the core portion by using a refractive index difference between a core portion and a cladding portion
Implementation Method 3
a multi-core optical fiber with a cylindrical portion and a reverse-tapered portion, where the gap length between core portions is gradually expanded
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
A multi-core optical fiber (1) which has a plurality of core portions (111a to 117a) arranged separately from one another in a cross-section perpendicular to a longitudinal direction, and a cladding portion (12a) located around the core portions, the multi-core optical fiber comprises a cylindrical portion (1a) of which diameter is even, and a reverse-tapered portion (1b) gradually expanding toward at least one edge (1c) in the longitudinal direction, wherein a gap (D2) between each adjacent ones of the core portions in the reverse-tapered portion is greater than a gap (D1) between each adjacent ones of the core portions in the cylindrical portion.