Depressed Waveguide for Accurate Multi-Core Fiber Crosstalk Measurement
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Solution Overview
Problem
Accurate measurement of inter-core crosstalk in multi-core optical fibers is hindered by noise light and large crosstalk during coupling, especially when inter-core crosstalk is low, as output light from the source core exceeds that of the destination core, causing noise in the cladding of the light-receiving fiber.
Innovation Solution
A light-receiving method utilizing a depressed type or trench-assisted type waveguide with a refractive index structure where the core is surrounded by a layer with a lower refractive index than the cladding, inhibiting noise propagation and allowing for accurate measurement of inter-core crosstalk, and optionally using a glass material with a removable coating or adhesive with a higher refractive index for alignment and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional light-receiving optical fiber is used to measure inter-core crosstalk, then the measurement can be performed with simple coupling alignment, but noise light from the cladding couples into the core and masks the small crosstalk signal
Solution Approach 1:
The patent changes the refractive index parameter of the light-receiving waveguide by introducing a depressed layer or trench structure. This parameter change creates a refractive index difference that prevents cladding light from coupling into the core, thereby eliminating noise and enabling accurate crosstalk measurement.
Solution Approach 2:
The depressed layer or trench acts as an intermediary structure between the cladding and the core of the light-receiving waveguide. This intermediate layer with lower refractive index serves as a barrier that blocks the harmful coupling of cladding light into the core, allowing the small crosstalk signal to be measured accurately.
2Reliability
If the coupling destination core and the core of the exit-side light-receiving optical fiber are aligned at the emission end, then coupling efficiency is maximized, but output light from the source core enters the cladding and becomes noise during measurement
Solution Approach 1:
The patent modifies the refractive index distribution parameter of the light-receiving waveguide by adding a depressed layer or trench. This parameter modification creates an optical barrier that prevents source core light from entering the cladding and coupling back into the core, thereby eliminating measurement noise and improving reliability.
Solution Approach 2:
The light-receiving waveguide is segmented into distinct functional layers: the core for signal reception, the depressed layer or trench as a barrier zone, and the cladding for structural support. This segmentation isolates the core from harmful cladding light, enabling reliable crosstalk measurement.
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
Enables precise measurement of inter-core crosstalk even in cases of small inter-core crosstalk by reducing noise and differentiating crosstalk-derived components, and can be applied to measure crosstalk and extract signal light from multiple cores with low noise.
Implementation Method 1
a light-receiving waveguide... having a refractive index structure of depressed type or trench-assisted type in which the core is surrounded by a layer having a refractive index lower than that of a cladding
Implementation Method 2
guides, through the light-receiving waveguide, light outputted from a second core
Data Source
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AI summary
According to the present invention, as a result of using a depressed or trench-assisted light-receiving waveguide in which the core is surrounded by a layer having a refractive index lower than that of a cladding as light-receiving means for receiving light outputted from a multi-core optical fiber, the layer of a low refractive index can inhibit the propagation of noise, etc. from the cladding to the core. Consequently, even in cases where the inter-core crosstalk is small, it is possible to accurately measure the inter-core crosstalk since components different from crosstalk-derived components in optical power are reduced.