Configurable Pitch Optical Fiber Coupler Array for Low-Loss Waveguide Interface
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Solution Overview
Problem
Existing optical fiber couplers face challenges in interfacing high numerical aperture (NA) waveguide devices with conventional low index contrast optical fibers due to size and NA differences, leading to increased insertion losses and decreased coupling coefficients, particularly when dealing with arrays of closely spaced waveguides, and back reflection issues that affect performance in telecommunications and sensing applications.
Innovation Solution
The development of an optical fiber coupler array with configurable channel-to-channel spacing and refractive indices at both ends, utilizing vanishing core waveguides embedded in a common housing structure, allowing for customizable NA and mode field diameter matching without the need for lenses, and optimized refractive index profiles to minimize back reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical fibers are used to interface with high NA waveguide devices, then the coupling can be established, but insertion losses increase and coupling coefficients decrease due to size and NA differences
Solution Approach 1:
The patent introduces an intermediate coupling structure comprising a first coupling region and a second coupling region with different numerical apertures. The first coupling region has a larger NA to match the waveguide, while the second coupling region has a smaller NA to match the optical fiber. This intermediate structure acts as a mediator that gradually transitions the optical mode, reducing the abrupt mismatch between the waveguide and fiber interfaces, thereby reducing insertion loss and improving coupling coefficient.
Solution Approach 2:
The patent changes the numerical aperture parameter along the coupling structure length. The coupling structure transitions from a region with larger NA (first coupling region) to a region with smaller NA (second coupling region). This parameter change allows the system to first match the high NA waveguide and then transition to the lower NA fiber, reducing mode field diameter mismatch and improving overall coupling efficiency.
2Reliability
If capillary tube materials with lower refractive index are used, then the fiber-cladding interface quality improves, but the manufacturing cost increases due to fluorine-doped material requirements
Solution Approach 1:
The patent applies different refractive index characteristics to different regions of the coupling structure. The first coupling region uses a material with higher refractive index to match the waveguide interface, while the second coupling region uses a material with lower refractive index to match the fiber interface. This local differentiation allows optimization of interface quality at each region without requiring expensive fluorine-doped materials throughout the entire structure.
Solution Approach 2:
The coupling structure employs composite material construction with at least two different materials having different refractive indices. The first coupling region uses a material with higher refractive index (n1) and the second coupling region uses a material with lower refractive index (n2). This composite approach enables the system to achieve both high interface quality and cost-effectiveness by using appropriate materials in appropriate regions.
3Adaptability or versatility
If channel-to-channel spacing is reduced at the coupler second end, then coupling with closely spaced waveguides is enabled, but alignment precision requirements increase
Solution Approach 1:
The patent divides the coupling structure into multiple segments: a first coupling region with larger channel spacing and a second coupling region with smaller channel spacing. Each segment can be independently optimized and aligned. The first coupling region handles the coarse alignment with loosely spaced channels, while the second coupling region handles the fine alignment with closely spaced waveguides. This segmentation reduces the overall alignment precision requirement by breaking down the complex alignment task into smaller, more manageable steps.
Solution Approach 2:
The coupling structure incorporates adjustable or reconfigurable elements that allow dynamic optimization of channel spacing and alignment. The structure can be designed with movable components or adjustable parameters that enable fine-tuning of the coupling geometry to match the specific spacing requirements of different waveguide arrays, thereby maintaining high coupling capability while adapting to varying alignment precision requirements.
4Reliability
If refractive index is optimized to reduce back reflection, then signal quality improves, but the device complexity increases
Solution Approach 1:
The patent optimizes the refractive index parameters of the coupling structure to reduce back reflection. By carefully selecting and transitioning between different refractive indices in the first and second coupling regions, the system minimizes optical mode mismatch and reduces reflected light. This parameter optimization improves signal quality by reducing back reflection losses while maintaining manageable device complexity through systematic refractive index design.
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 provides a low-loss, high-coupling coefficient interface with improved alignment accuracy and reduced back reflection, enabling efficient coupling between optical fibers and devices with varying NAs and spacings, enhancing performance in telecommunications and sensing applications.
Implementation Method 1
vanishing core waveguides embedded in a common housing structure
Implementation Method 2
optimized refractive index profiles to minimize back reflection
Data Source
AI summary
The inventive optical fiber coupler array is capable of providing a low-loss, high-coupling coefficient interface with high accuracy and easy alignment between a plurality of optical fibers (or other optical devices) with a first channel-to-channel spacing, and an optical device having a plurality of closely-spaced waveguide interfaces with a second channel-to-channel spacing, where each end of the optical fiber coupler array is configurable to have different channel-to-channel spacing, each matched to a corresponding one of the first and second channel-to-channel spacing. The novel optical coupler array includes a plurality of waveguides (at least one of which may optionally be polarization maintaining), that comprises at least one gradually reduced vanishing core fiber, at least in part embedded within a common housing structure. Alternatively, the novel coupler array may be configured for utilization with at least one of an optical fiber amplifier and an optical fiber laser. Advantageously, the refractive indices and sizes of both inner and outer core, and/or other characteristics of vanishing core waveguides in the novel optical coupler array are optimized to reduce the back reflection for light propagating from the plurality of the optical fibers at the coupler first end to the optical device at the coupler second end, and/or vice versa.