GPX3800 and GPX3850 Glass Processors
Chapter 5: Operation
Page 42
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Analog Setup
Defines the tension monitor channel (left or right), the analog power detectors used, and the ratio of filtering
(smoothing data collection) as well as the power units to be used for the process.
Stage Properties
Defines the parameters for each process stage (up to a maximum of 5 stages). During each stage, the user can
control the power variation based on tension, displacement, time or unchanged. The “Stage Advance Control”
area will determine how each stage is to be completed. This can be based on displacement (typical for taper
applications), or based on power (i.e. measure power from detectors) as in the case of couplers. Furthermore,
each stage can have its own set of process parameters such as fiber holding block pull velocity, furnace can
distance and argon flow rate.
Figure 22
Analog Setup (Left) and Stages Properties (Right) Tab
The process to generate a biconic taper consists on heating a section of fiber and pulling outward on the fiber
using the fiber holding blocks in order to stretch it and therefore reducing its diameter. In order to controllably heat
the fiber, the filament is scanned back and forth around its central position. Reducing the furnace scan width will
increase the rate of diameter change in the taper; it will reach a smaller diameter with less elongation and less
pulling distance. Increasing the scan width will lower rate at which the diameter changes while creating a longer
tapered region in the fiber. In general, the pull and scan velocities only affect the power required to fabricate the
taper.
The same interface is used to manufacture 2x2 couplers. The coupling can be monitored between the two legs of
the coupler during the process by using the analog channels available on the glass processor when connected to
power detectors. Typically, a multi-stage process is required to fully manufacture a 2x2 coupler, where the power
delivered to the fibers during each stage is precisely controlled. Our recommended approach is to control the
power delivered by the furnace based on the tension applied to the fibers for the early stages, going from a target
of 20 g tension towards a target of 5 g tension just before the last stage. The last stage however should keep the
power unchanged and monitor the amount of coupling to each leg via the analog channels. One can set-up the
coupler fabrication by targeting a specific coupling value in dB (i.e. 3dB equivalent to 50% coupling), targeting a
minimum value of light remaining in Leg1, or a maximum value of light coupled to Leg2 for example.