Plastic Optical Fiber Sheath Design for Low Green-Light Loss
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Solution Overview
Problem
Existing plastic optical fibers suffer from high transmission loss of green light (525 nm or 570 nm) due to contamination from foreign matter in the sheath material and thick sheaths, limiting their use in long-distance communication applications.
Innovation Solution
The development of a plastic optical fiber with a core and sheath structure, where the sheath is formed under clean room conditions using fluorine-based resins, and the sheath is designed with specific refractive indices and thicknesses to minimize foreign matter and reduce transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sheath material is treated in a general environment, then the manufacturing cost is reduced, but the amount of foreign matter in the sheath material increases, causing deterioration of transmission loss
Solution Approach 1:
The patent applies clean room treatment (a controlled inert environment) during sheath material processing to prevent foreign matter contamination. This resolves the contradiction by maintaining low transmission loss through controlled manufacturing conditions while still being economically viable through standardized clean room protocols.
2Strength
If a thick sheath is used, then the mechanical strength and protection are improved, but the transmission loss of light in higher-order mode or cladding mode increases
Solution Approach 1:
The patent optimizes the sheath thickness parameter to a specific range that balances mechanical protection with optical performance. By precisely controlling the sheath thickness, the invention achieves adequate mechanical strength while minimizing transmission loss in higher-order and cladding modes.
3Loss of energy
If green light (525 nm or 570 nm) is used for long distance communication, then the transmission loss is reduced compared to red light, but the communication distance is still restricted when transmission loss increases
Solution Approach 1:
The patent utilizes green light wavelength (525 nm or 570 nm) which has lower transmission loss characteristics compared to red light. By selecting this specific wavelength range and optimizing the optical fiber parameters, the invention extends communication distance while maintaining low transmission loss.
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 a transmission loss of 120 dB/km or less for green light, enabling longer distance communication suitable for applications like airport entry prevention fences and security cameras.
Implementation Method 1
The low loss window of the plastic optical fiber containing a methyl methacrylate homopolymer (PMMA) as a core material exists in a visible light region, and the transmission loss thereof is low around 520 nm, 570 nm, and 650 nm
Data Source
Figure 1(a)~1(b)
AI summary
The present invention provides a plastic optical fiber comprising a core and a sheath consisting of at least one layer, the plastic optical fiber having a transmission loss of 120 dB/km or less as measured by a 25m-1m cutback method under conditions of a wavelength of 525nm and an excitation of NA=0.45, and satisfying either one of the following conditions when a thickness of the innermost sheath layer is 0.5µm to 4.5µm, an amount of foreign matter having a size of 2 µm or greater contained in the innermost sheath layer is 2000/cm3 or less, or a size X (µm) of foreign matter contained in the innermost sheath layer and an amount Y of the foreign matter (number/cm3) satisfy formula (1) below: Y ≤ 1200 X e(-0.067xX) (1). Such optical fibers have a low transmission loss of green light (in particular, light having a wavelength of 525nm), enabling longer distance communication.