Angled Glass Ferrule for Optical Fiber Light Extraction
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Solution Overview
Problem
Existing methods for coupling light out of optical fibers for sensing and monitoring face challenges such as the need for index-matching media, difficulty in controlling polarization-dependent loss, and limited ability to control wavelength dependence, especially when using femtosecond laser radiation and ultrafast laser writing techniques.
Innovation Solution
The use of a glass ferrule with an angled, high-reflectivity surface to reflect light from an optical tap, allowing for external detection by a photosensitive device, and potentially incorporating diffractive elements or sensing materials, enabling direct measurement of the spectrum and improved sensing applications without the need for direct contact with the fiber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If index-matching medium is used to frustrate total internal reflection at the fiber edge, then light coupling from core to cladding is enabled, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts and removes the index-matching medium from the system entirely. Instead of using index-matching glue to frustrate total internal reflection, the invention uses a glass ferrule with an angled surface that directs light through the fiber cladding to a photosensitive device without requiring any index-matching medium, thereby simplifying the device structure while maintaining light coupling functionality
Solution Approach 2:
The glass ferrule serves as a new intermediary component that replaces the index-matching medium. The ferrule's angled surface acts as a light guide, directing light from the fiber cladding to the photosensitive device through total internal reflection at the ferrule's interface, eliminating the need for index-matching materials while enabling effective light coupling
2Reliability
If fiber is bonded directly to photosensitive surface with index-matching glue, then light coupling is achieved, but bonding reliability and manufacturing precision deteriorate
Solution Approach 1:
The patent removes the index-matching glue bonding process entirely. Instead of bonding the fiber directly to a photosensitive surface with glue, the invention uses a glass ferrule that mechanically holds the fiber and directs light to a photosensitive device through optical interfaces, eliminating the need for precise glue bonding and improving manufacturing precision
Solution Approach 2:
The glass ferrule introduces an intermediary structure between the fiber and the photosensitive device. The ferrule's angled surface creates a controlled optical path that guides light to the device without requiring direct bonding, thereby improving bonding reliability and manufacturing precision by replacing adhesive bonding with mechanical positioning and optical interface design
3Reliability
If shallow exit angles are used for the tap coupler, then light tapping is enabled, but control of polarization dependent loss and polarization dependent coupling becomes difficult
Solution Approach 1:
The patent changes the geometric configuration from shallow exit angles to a vertical light path. The glass ferrule with its angled surface directs light vertically upward through the cladding to the photosensitive device, creating a new dimensional approach that maintains light tapping capability while improving polarization control by eliminating the shallow angle geometry that causes polarization-dependent losses
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 configuration enhances the ability to monitor and sense light by allowing external detection without index-matching media, improves bonding reliability, and enables spectrum monitoring, overcoming previous limitations in polarization control and wavelength dependence.
Implementation Method 1
The optical fiber is bonded to a glass ferrule with an angled surface arranged such that the light coupled out of the fiber by the waveguide can propagate to the polished surface to be reflected and exit on a side face
Implementation Method 2
The femtosecond laser light is focused inside the optical fiber and the intense light generated in the focal region produces non-linear absorption in the glass fiber and creates permanent refractive index changes
Implementation Method 3
Co-owned U.S. Pat. No. 7,295,731 B2 describes a method for using femtosecond laser radiation for the creation of optical waveguiding devices inside standard optical fibers
Implementation Method 4
The cylindrical shape of the fiber also adds a layer of difficulty to the process when the fiber is bonded with index-matching glue to a photosensitive surface. Moreover, the shallow exit angles used for the tap coupler makes it difficult to control aspects such as polarization dependent loss or polarization dependant coupling
Data Source
AI summary
A device including an optical tap and waveguide in the core and cladding of an optical fiber together with a glass ferrule that is angle polished to provide a reflection surface (with or without total internal reflection) that produces a reflection of the light tapped from the optical fiber to reach the bottom of the glass ferrule and propagate in a direction that is perpendicular to (or at least different than the direction of propagation close to) the axis of the optical fiber. The fiber waveguide may be created using an ultrafast fabrication method and the glass ferrule can itself be modified by the same ultrafast laser technique to further manipulate the light traveling inside.