THORLABS vytran LDC450B User Manual page 27

LDC450B Large Diameter Cleaver
The Micrometer Backstop acts as a backing for the fiber during the Cleave Process. When using the Micrometer
Backstop, it is possible to reduce the tension applied to the fiber because the Micrometer Backstop will prevent the
fiber from flexing when struck by the blade to produce a longer initial scribe. The longer initial scribe causes the
fiber to cleave, despite the relatively low tension. Since the tension is lower, the crack propagates slowly with little
driving force, and a smoother cleave surface results. The Micrometer Backstop may be used in conjunction with the
"Subcritical Process" to produce cleaves with very good end face quality.
A general rule to follow when using the Micrometer Backstop is that the Cleave Tension should initially be lowered
to 85% of the Auto Parameter value that Handset Controller recommends for the diameter of the part. Adjust the
tension based upon visual inspection of the end face. Increase the tension if there is no end face damage but the
cleave has an angle. Decrease the tension if there is end face damage but no angle. Do not go below 60% of the
Auto Parameter value or severe blade damage may result.
To use the Micrometer Backstop, load the fiber in to the unit in the normal way, but do not initiate a cleave
immediately. Rotate the micrometer until it just contacts the fiber. It is a good idea to use a 10X eye loupe to make
sure that the Micrometer Backstop just barely touches the fiber (see Figure 20). After the Micrometer Backstop is
set, initiate the cleave as per standard procedure. Be careful not to flex the fiber forwards, or the results will be
poorer than not using the micrometer at all!
Figure 20 Using an Eye Loupe to Check that the Micrometer Backstop just Touches the Fiber
After cleaving, back the micrometer away from the cleaved fiber prior to unloading. This will ensure that the fiber
does not contact the micrometer during unloading.
The following chart offers guidelines for when to use the Subcritical Process and the Micrometer Backstop.
Process Selection Chart
Fiber Type
Singlemode fiber
Multimode
Thick-Walled Capillary Tubing
Thin-Walled Capillary Tubing
PM, Cladding ≤Ø400 µm
PM, Cladding >Ø400 µm
PCF
1
Wall thickness is at least 10% of the diameter.
2
Wall thickness is less than 10% of the diameter.
Rev A, July 28, 2020
Standard
Process
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Chapter 6: Cleaving
SubCritical Micrometer
Process Backstop
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