Reduced Diameter Multicore Optical Fiber Microbending
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Solution Overview
Problem
Submarine optical fiber cables face challenges in increasing transmission capacity without increasing diameter, which is limited for easy deployment, and existing methods like wavelength division multiplexing and advanced modulation formats are nearing practical limits.
Innovation Solution
The development of optical fibers with reduced diameters and optimized coating properties, including a depressed cladding layer and higher modulus secondary coating, to maintain microbending characteristics and puncture resistance, allowing for higher fiber density in submarine cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of fibers within submarine cables is increased to increase transmission capacity, then the transmission capacity increases, but the cable diameter increases making deployment difficult
Solution Approach 1:
The optical fiber is segmented into multiple functional layers with distinct purposes: core region for light transmission, cladding region with inner/outer cladding and trench for optical confinement, and coating regions for mechanical protection. This segmentation allows optimization of each layer's function while maintaining overall compact dimensions
Solution Approach 2:
The optical fiber structure employs nested concentric layers where the core is surrounded by the cladding region, which is in turn surrounded by the coating region. The inner cladding is nested within the outer cladding, and the trench region is nested between them. This nested configuration maximizes space utilization and enables high fiber density in submarine cables
2Quantity of substance
If the glass diameter is reduced to increase fiber density, then the fiber density increases, but the microbending sensitivity increases
Solution Approach 1:
The fiber employs composite material structure with silica glass core and cladding regions, and polymer coating regions with different mechanical properties. The coating materials provide mechanical cushioning that compensates for the reduced glass diameter, maintaining microbending performance while enabling higher fiber density
Solution Approach 2:
The coating region is applied beforehand to the glass fiber to provide mechanical protection and cushioning. This pre-applied cushioning layer protects the reduced-diameter glass fiber from microbending stresses before the fiber is deployed in the submarine cable
3Volume of moving object
If the coating thickness is reduced to decrease fiber diameter, then the fiber diameter decreases, but the puncture resistance decreases
Solution Approach 1:
The coating region uses composite material structure with primary and secondary coating layers having different mechanical properties. This composite structure provides enhanced puncture resistance while maintaining reduced overall fiber diameter
Solution Approach 2:
The coating design optimizes parameters including thickness, Young's modulus, and in situ modulus to achieve the desired balance between reduced diameter and maintained puncture resistance. The secondary coating has higher Young's modulus (≥1500 MPa) to provide puncture resistance despite reduced thickness
Data Source
AI summary
A multicore optical fiber is provided that includes a first core with silica glass doped with chlorine and/or an alkali metal, a first inner cladding surrounding the first core, and a first outer cladding surrounding the first inner cladding and having a first trench region having a volume of about 30%Δ-micron2 or greater. The multicore optical fiber also includes a second core with silica glass doped with chlorine and/or an alkali metal, a second inner cladding surrounding the second core, and a second outer cladding surrounding the second inner cladding and having a second trench region having a volume of about 30%Δ-micron2 or greater. Additionally, a common cladding surrounds the first core and the second core, and the first core and the second core each have an effective area at 1550 nm of about 100 micron2 or less.