Collimating Lens Assembly Air Gap High Power Density
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Solution Overview
Problem
Conventional fiber optic collimating lens assemblies face issues with high optical power transmission, leading to irreversible darkening and refractive index changes in epoxy and index-matching materials, as well as surface damage due to high energy density, which affects pointing accuracy and data transmission in fiber optic rotary joints.
Innovation Solution
The implementation of a collimating lens assembly that eliminates index-matching materials and epoxy from the optical path by using a singlemode fiber fusion-spliced with step-index and graded-index multimode fibers, creating an air gap to reduce optical power density through a diverging beam trace, thereby handling high power levels while maintaining pointing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high optical power is transmitted through epoxy and index-matching materials in conventional collimating lens assemblies, then data transmission capability is improved, but the materials undergo irreversible darkening and refractive index changes that degrade performance
Solution Approach 1:
The patent removes epoxy and index-matching materials from the optical path by using a fusion-spliced fiber structure where a singlemode fiber is directly coupled to multimode fibers. This extraction eliminates the harmful materials that darkened under high optical power, thereby maintaining both high data transmission capability and optical performance stability.
Solution Approach 2:
The patent introduces an air gap as an intermediary medium between the fiber end and the collimating lens, replacing the problematic epoxy and index-matching materials. This air gap mediator allows high optical power transmission without causing irreversible darkening or refractive index changes, thus resolving the contradiction between productivity and reliability.
2Power
If high energy density is concentrated on the singlemode fiber surface, then optical power transmission is improved, but contaminants are heated to temperatures exceeding silica melting point causing fiber surface cracking and pitting
Solution Approach 1:
The patent segments the fiber structure by transitioning from a singlemode fiber to multimode fibers through fusion splicing. This segmentation distributes the optical power over a larger area in the multimode fibers, reducing the energy density at any single point on the fiber surface and preventing contaminant heating that would cause cracking and pitting.
Solution Approach 2:
The patent transitions from singlemode to multimode fibers, effectively adding spatial dimensions to the optical power distribution. This dimensional change spreads the optical energy across multiple modes and a larger cross-sectional area, reducing the peak energy density that causes harmful heating of contaminants on the fiber surface.
3Measurement precision
If index-matching materials are used in the optical path, then optical coupling efficiency is improved, but the materials are susceptible to high optical power causing darkening and performance degradation
Solution Approach 1:
The patent extracts and removes index-matching materials from the optical path by using direct fusion splicing between fibers and an air gap configuration. This elimination prevents the harmful darkening and refractive index changes that occur when these materials are exposed to high optical power, while maintaining optical coupling efficiency through the fusion-spliced fiber structure.
Solution Approach 2:
The patent replaces the vulnerable index-matching materials with a durable air gap configuration. While air gaps require precise alignment, they provide a permanent solution that does not degrade under high optical power exposure, eliminating the need for replacement or maintenance of sensitive optical materials.
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 solution effectively reduces optical power density by approximately twenty times, enabling the transmission of high data rates through fiber optic rotary joints without the detrimental effects of high energy on the materials, thus enhancing the reliability and accuracy of data transmission.
Implementation Method 1
The step-index multimode fiber reduces the optical power density at its distal end from that at its proximal end. The graded-index multimode fiber reduces the optical power density at its distal end from that at its proximal end.
Implementation Method 2
a collimating lens spaced from the graded-index multimode fiber distal end, and operatively arranged to collimate light rays emanating from the graded-index multimode fiber distal end
Implementation Method 3
a singlemode fiber that terminates in a distal end; a step-index multimode fiber having a proximal end abutting to the singlemode fiber distal end
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
The present invention provides improved collimating lens assemblies (32), improved methods of reducing the optical power density in collimating lens assemblies, and to improved fiber optic rotary joints (31) incorporating such improved collimating lens assemblies. The improved collimating lens assembly broadly includes: a singlemode fiber (38) terminating in a distal end; a step-index multimode fiber (44) having a proximal end abutting to the singlemode fiber distal end, and having a distal end; a graded-index multimode fiber (45) having a proximal end abutting the step-index multimode fiber distal end, and having a distal end; and a collimating lens (34) longitudinally spaced from the graded-index multimode fiber distal end by an intermediate air gap (43), and operatively arranged to collimate light rays emanating from the graded-index multimode fiber distal end. The improved collimating lens assembly is characterized by the fact that there is no epoxy, silicone gel or index-matching material between the graded-index multimode fiber distal end and the collimating lens. Rather, these various elements are fusion-spliced together. The improved collimating lens assembly is capable of handling energy levels that are typically used in various wavelength division multiplexing techniques.