GPX3800 and GPX3850 Glass Processors
Chapter 5: Operation
Page 44
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The software allows the user to define up to five stages to run the full taper process. At each stage the user can
control the filament power, the duration or elongation of the stage, scan width, pulling velocity, and argon gas flow
rate.
Filament Power Control
The power delivered to the filament can be controlled in four ways:
1. Tension.
The software will reduce the filament power by the amount specified per second when the
tension applied to the fiber is below the target value. When the applied tension is above the target value,
the system does not modify the filament power.
2. Displacement.
The software will reduce the filament power by the specified value per displacement (e.g.,
0.2 W per 0.2 mm elongation).
3. Time.
The software will drop the filament power by the specified value per time increment (e.g., 0.2 W per
2.0 s).
4. Disabled.
The filament power remains unchanged during the stage.
Stage Advance Control
The full taper process can be divided in up to five different stages. The stage advance control parameters define
when to stop the current stage and move to the next one. In the case of the last stage, it will indicate when to end
the full taper process. This control can be achieved in four separate ways:
1. Power.
The software will compare the reading from the connected power detector with the type and value
of the power target (i.e. Min target, Max target or dB or % target).
2. Displacement.
The software will stop the current stage when the “Target Displacement” value has been
reached.
3. Time.
The software will stop the current stage after the specified period of time has elapsed.
4. Disabled.
The software will not automatically end the current stage and the process will have to be
stopped manually.
Furnace Scan Distance
The furnace scan distance is the distance in mm that the furnace (i.e. filament assembly) will move around its
zero position as defined by the “Furnace Z Offset” value. The filament will scan from –d to +d, where d is the
specified furnace scan distance. A larger scan width will create a gentle taper (small diameter change over a long
taper distance) that reduces losses in the resultant taper. Alternatively, a smaller scan width will generate a higher
slope taper that results in a higher loss device. One method for achieving low loss devices while minimizing
overall device length is to use a multi-stage process with a large scan width during early stages and a reduced
scan width during later stages.
Fiber Holding Block Pull Velocity
The fiber holding block pull velocity is the speed at which the fiber is pulled apart during the taper process. When
using a reduced pulling velocity, the amount of heat delivered to the fiber is larger and therefore the power of the
filament needs to be adjusted accordingly. The pull velocity will control the overall process time, where a larger
pull speed will result in a faster taper process, all other parameters being equal. Use a constant pull velocity
throughout the process stages to avoid any jerking motions that could affect the taper quality. If varying the pull
velocity is necessary, do not increase the velocity such that the required filament power is too large for the
filament in use. The pull velocity also needs to be slow enough to allow the system enough time to respond to the
tension feedback measurements.