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Appendix E Principles of Operation
E.1 The NanoTrak
E.1.1 Introduction
For simplicity, the following example refers to the alignment of two opposing butt
coupled single mode fibers, however the principles of operation are method is equally
valid for the physical alignment of any two opposing optically coupled faces or indeed
any two objects that can provide a feedback signal (voltage) that varies as a function
of their alignment with respect to each other.
Fig. E.1 Alignment of optical fibers
In Fig. E.1, one of the fibers is fixed, the other is mounted on a piezo-actuated stage
that moves the fiber in the horizontal and vertical axes. The NanoTrak must adjust the
position of the moving fiber until the power transmitted between the two is maximized.
Fig. E.2 shows a block diagram of the NanoTrak control loop. In many applications, a
waveguide or similar device replaces one of the fibers, however this makes no
difference to the principle of operation.
Fig. E.2 NanoTrak control loop
vertical
horizontal
light
Auto
Piezo
Vertical
Horizontal
Piezo-actuated stage
Optical fibers
Detector
circuit
alignment
control
and
NanoTrak unit
amp
Piezo
control
and
amp