Optical Fiber Preform PCVD Velocity Control
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Solution Overview
Problem
Existing methods for manufacturing optical fibers result in geometric and optical taper, variable optical properties, and high attenuation at specific wavelengths due to the inclusion of OH groups, which affect signal loss and usability across a wide wavelength range.
Innovation Solution
The method involves setting different sledge-velocities for the reaction zone during the internal deposition process, with a higher velocity from the supply side to the discharge side compared to the discharge side to supply side, using a PCVD process to minimize OH incorporation and reduce attenuation at 1385 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard reciprocating plasma CVD process is used, then glass layers are deposited on the substrate tube, but OH groups are incorporated into the glass leading to high attenuation at 1385 nm
Solution Approach 1:
The patent applies dynamic velocity variation of the reaction zone during reciprocation. The reaction zone velocity is set higher when moving from supply side to discharge side and lower when moving from discharge side to supply side. This dynamic adjustment prevents OH group incorporation while maintaining deposition efficiency, resolving the contradiction between manufacturing precision and harmful factor reduction.
Solution Approach 2:
The patent changes the velocity parameter of the reaction zone during the deposition process. By varying the velocity according to the direction of reciprocation (higher velocity in one direction, lower in the other), the process minimizes OH incorporation into the glass layers while achieving uniform deposition, thus improving optical quality without the harmful effects.
2Productivity
If the reaction zone velocity is increased to improve productivity, then deposition efficiency increases, but geometric and optical taper increases
Solution Approach 1:
The patent introduces asymmetric velocity profiles during the reciprocating motion of the reaction zone. The velocity is deliberately made different in the two directions of reciprocation (higher from supply to discharge side, lower from discharge to supply side). This asymmetric approach compensates for the effects of high velocity, maintaining deposition efficiency while preventing geometric and optical taper, thus resolving the contradiction between productivity and manufacturing precision.
3Loss of time
If conventional deposition velocity is used, then deposition time is reduced, but attenuation at 1385 nm increases due to OH incorporation
Solution Approach 1:
The patent uses dynamic velocity adjustment during reciprocation to simultaneously achieve fast deposition and low OH incorporation. By varying the velocity according to direction (higher in one direction, lower in the other), the process maintains short deposition time while preventing the harmful effects of OH group incorporation, thus resolving the contradiction between time loss and harmful factors.
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
This approach reduces attenuation by 10% to 20% at 1383 nm, maintaining consistent optical properties over the fiber length and minimizing signal loss, making the fibers more suitable for commercial use.
Implementation Method 1
a non-isothermal plasma is reciprocated between two reversal points along the substrate tube... the reaction zone, in particular a plasma generator, supplies high-frequency energy, as a result of which a plasma is generated in the interior of the substrate tube, under which plasma conditions the reactive, glass-forming gases will react (the plasma CVD technique)
Implementation Method 2
subjecting the substrate tube thus obtained to a collapsing treatment so as to form a solid preform
Data Source
AI summary
A method for manufacturing an optical preform via an internal vapor deposition process, wherein during the inside deposition process the velocity of the reaction zone is set so that the velocity of the reaction zone over the length of the supply side-to-discharge side is higher than the velocity of the reaction zone over the length of the discharge side-to-supply side.