Depressed Cladding Optical Fiber for Raman Amplification
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Solution Overview
Problem
Existing optical communication systems face challenges in enhancing the optical signal-to-noise ratio (OSNR) due to increased effective area of transmission optical fibers, which leads to higher splice loss and bending loss, while prior art fails to optimize the effective area for improved OSNR while considering splice loss and fundamental-mode cutoff.
Innovation Solution
A silica-based optical fiber with a depressed cladding type refractive index profile, having an effective area of 120 µm² to 150 µm² and a fiber cutoff wavelength of 1.3 µm to 1.53 µm, designed to minimize bending loss and prevent leakage loss by setting the fundamental-mode cutoff wavelength to 2400 nm or more, allowing for improved OSNR in Raman amplification systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the effective area of the transmission optical fiber is increased to improve OSNR and suppress nonlinear optical phenomena, then the OSNR is enhanced, but the splice loss increases when connecting to devices or other optical fibers with smaller effective areas
Solution Approach 1:
The patent optimizes the effective area parameter to a specific range (100-150 μm²) rather than maximizing it indefinitely. This parameter change balances the competing requirements: large enough to suppress nonlinear effects and improve OSNR, but not so large as to cause excessive splice loss when connecting to standard optical fibers and devices.
2Reliability
If the effective area of the transmission optical fiber is increased to improve OSNR, then the OSNR is enhanced, but the Raman amplification efficiency decreases requiring enormous pump light power
Solution Approach 1:
The patent specifies an optimal effective area range (100-150 μm²) that maintains efficient Raman amplification. By not exceeding this range, the patent ensures that pump light power remains at practical levels while still achieving the desired OSNR improvement and nonlinear effect suppression.
3Reliability
If the effective area of the transmission optical fiber is increased to improve OSNR, then the OSNR is enhanced, but the bending loss increases
Solution Approach 1:
The patent optimizes the effective area to a moderate range (100-150 μm²) rather than maximizing it. This parameter optimization balances the trade-off between improving OSNR through larger effective area and minimizing bending losses that increase with larger effective areas.
4Object-generated harmful factors
If the effective area of the transmission optical fiber is much larger than that of connected optical fibers, then nonlinear optical phenomena are suppressed, but the splice loss becomes greater deteriorating the overall OSNR
Solution Approach 1:
The patent sets the effective area to an optimal range (100-150 μm²) that provides sufficient suppression of nonlinear optical phenomena without creating excessive splice loss when connecting to standard optical fibers and devices. This parameter optimization achieves the right balance between suppressing harmful nonlinear effects and maintaining low connection losses.
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 optical fiber achieves an OSNR improvement of 1 dB or higher in optical communication systems, enabling efficient Raman amplification and reducing splice and bending losses, while maintaining practical pumping light power levels.
Implementation Method 1
a silica-based optical fiber (100) having a transmission loss of 0.19 dB/km or less at a wavelength of 1550 nm
Implementation Method 2
having a depressed cladding type refractive index profile... the refractive index n3 satisfies n1>n3>n2 (condition 1)
Implementation Method 3
optical communication system using Raman amplification... Raman amplification efficiency decreases when the effective area Aeff of the transmission optical fiber is greater
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The invention relates to an optical fiber employable in an optical communication system using Raman amplification and adapted to improve OSNR and suppress bending loss at the same time, and the like. The optical fiber is a silica-based optical fiber having a depressed refractive index profile constituted by at least a core, an inner cladding having a low refractive index, and an outer cladding, an effective area Aeff of 110 µm2 or more at the wavelength of 1550 nm, and a fiber cutoff wavelength λC of 1.3 µm or more but 1.53 µm or less. The depressed refractive index profile is designed such that the ratio Ra (= 2b/2a) of the diameter of the inner cladding to the diameter of the core is 2.5 or more but 3.5 or less and that the relative refractive index difference Δ- of the inner cladding with respect to the outer cladding is at least the relative refractive index difference Δ-min where the bending loss at the wavelength for use is minimized but not exceeding (Δ-min + 0.06)%.