Multicore Fiber Bragg Grating Ripple Reduction via Cladding Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for manufacturing multicore fiber Bragg gratings face issues with large ripple widths in transmission spectra due to interference between core and cladding mode lights, leading to performance deterioration in long-haul optical fiber communication systems.
Innovation Solution
A multicore optical fiber with a specific refractive index profile and cladding structure, combined with a grating manufacturing method using a condensing lens and diffraction grating to form gratings in each light guiding structure, minimizing interference and improving ripple characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multicore optical fiber is simultaneously irradiated with ultraviolet light to form gratings in multiple light guiding structures, then manufacturing time is reduced and productivity is improved, but ripple width in transmission spectra increases due to interference between core and cladding mode lights
Solution Approach 1:
The patent extracts and eliminates the harmful cladding mode light from the system by introducing a cladding mode suppressor. This suppressor prevents the generation and propagation of cladding mode light that would otherwise interfere with core mode light, thereby resolving the ripple width issue while maintaining simultaneous multi-core grating formation
Solution Approach 2:
The cladding mode suppressor acts as an intermediary component between the ultraviolet light source and the light guiding structures. It selectively suppresses cladding mode light while allowing core mode light to pass through, preventing interference without affecting the grating formation process in multiple cores
2Manufacturing precision
If matching oil is used to fill the surroundings of the multicore optical fiber during irradiation, then the condensing effect is compensated and uniformity of grating characteristics is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The patent removes the matching oil from the manufacturing process entirely. Instead of using matching oil to compensate for the condensing effect, the invention employs a cladding mode suppressor that achieves uniform grating characteristics through optical field control rather than environmental modification
Solution Approach 2:
The patent changes the approach from modifying the external environment (using matching oil) to modifying the optical field distribution internally (using cladding mode suppressor). This parameter change simplifies the manufacturing process by eliminating the need for matching oil while maintaining uniformity of grating characteristics
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
The solution enables the fabrication of fiber Bragg gratings with improved ripple characteristics, enhancing the performance of multicore fiber Bragg gratings in long-haul transmission systems by reducing optical loss and optimizing transmission spectra.
Implementation Method 1
An optical fiber including a core or a cladding comprised of silica glass in which a photosensitive material (for example, GeO2 or B2O3) is doped is irradiated with ultraviolet light with spatially modulated intensity in an axial direction of the core, whereby a grating having refractive index distribution according to intensity distribution of the ultraviolet light in the axial direction of the core can be written
Implementation Method 2
a phase mask method for causing ±1 order diffracted light generated using a chirped grating phase mask to interfere with each other
Implementation Method 3
a two-light flux interference exposure method for causing two of causing two branched light beams to interfere with each other after branching laser light into two
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present embodiment relates to an MCF and the like suitable for fabricating an FBG with improved ripple characteristics. The MCF is mainly composed of silica glass, and comprises a plurality of light guiding structures and a common cladding. Each of the light guiding structures includes a core, a first cladding, and a second cladding. The refractive index of the second cladding is higher than that of the first cladding and is lower than those of the core and the common cladding. Further, at least a part of an inner cladding region, constituted by the first cladding and the second cladding, contains a photosensitive material having photosensitivity of changing a refractive index of a glass region containing the photosensitive material in response to irradiation of light with a specific wavelength.