Untappable Optical Fiber Link via Vanishing Core Coupler
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Solution Overview
Problem
Conventional methods for interfacing optical high NA waveguide devices with conventional low index contrast optical fibers face challenges such as size differences and refractive index mismatches, leading to increased insertion losses and decreased coupling efficiency, and existing security measures for fiber optic links are inadequate against unauthorized tapping.
Innovation Solution
The development of a multicore single mode fiber optical coupler array with vanishing core waveguides, allowing for adjustable channel-to-channel spacing and refractive index matching, combined with PROFA interconnects for secure, physically untappable fiber optic links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional optical fiber coupling methods are used to interface high NA waveguide devices with low index contrast fibers, then the device can be connected, but insertion losses increase and coupling efficiency decreases due to size differences and refractive index mismatches
Solution Approach 1:
The patent introduces an intermediary coupling structure with a gradient refractive index profile that bridges the high NA waveguide device and the low index contrast optical fiber. This intermediate layer gradually transitions the refractive index from the waveguide core to the fiber cladding, minimizing reflection and mode mismatch losses while maintaining a relatively simple overall device structure.
Solution Approach 2:
The patent employs a gradient refractive index profile in the coupling layer, where the refractive index parameter varies continuously from the waveguide core through the coupling layer to the fiber cladding. This parameter change optimizes mode field matching and reduces insertion losses without requiring complex multi-element coupling systems.
2Reliability
If conventional fiber optic link security measures are implemented, then basic protection is provided, but the links remain vulnerable to unauthorized tapping and information leakage
Solution Approach 1:
The patent converts the potential harm of light leakage from fiber bends or imperfections into a security benefit by deliberately designing the fiber with controlled micro-bends and irregularities that cause light scattering. This scattering prevents coherent light extraction for tapping while maintaining acceptable transmission through the use of optical phase conjugation to compensate for the induced distortions.
Solution Approach 2:
The patent integrates multiple functions into a single fiber optic link: data transmission, security anti-tapping, and distortion compensation. The same fiber structure with controlled irregularities provides both the security feature (preventing tapping) and the transmission medium, while optical phase conjugation simultaneously compensates for the induced distortions, eliminating the need for separate security devices.
3Manufacturing precision
If optical phase conjugation is used to compensate for distortion in secure fiber links, then signal quality is maintained, but the system complexity increases due to additional components required
Solution Approach 1:
The patent merges the distortion compensation function with the transmission fiber itself by writing phase-conjugate gratings directly into the fiber structure during manufacturing. This integration eliminates the need for separate external phase conjugation devices, maintaining signal quality while reducing overall system complexity and component count.
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 easy alignment and enhanced security by minimizing signal leakage through noise channel integration, ensuring secure transmission with minimal impact on signal quality.
Implementation Method 1
The section of the VC waveguide located between positions B and D is embedded in the common housing structure
Implementation Method 2
each comprising an inner core, an outer core, and a cladding, wherein the VC waveguide comprises a first end having a first channel-to-channel spacing and a second end having a second, smaller channel-to-channel spacing
Data Source
AI summary
The inventive configurable optical fiber polarization mode coupler 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, and that are preferably optimized for use with photonic integrated circuits, such as coupling to dense optical input/output interfaces, wafer-level testing, etc. 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. Advantageously, at least one embodiment of the present invention comprises a physically untappable secure optical fiber link component comprising at least one optical fiber polarization mode coupler configured as a pitch reducing optical fiber array (PROFA) interconnect.