90°
Spec
Ellipticity:
< 1. 2
Beam shape:
Near Gaussian
Spot size:
2. 5 µm ±10%
Polished sample
2. 37 µm
Tapered axicon
2. 41 µm
Ellipticity = 1.03 Ellipticity = 1.02
Advanced manufacturing techniques
benefit fiber-optic components
BRAD HENDRIX and MIKE HARJU
Continued advances in optical fiber
processing technologies and new re-
search into the field of specialty fibers
have helped to create a new generation
of fiber-optic components. With the
advent of very high precision glass-pro-
cessing platforms, the fiber-component
field has moved from the confines of
independent and academic laborato-
ries to the use of commercially available machines with either specific or
universal capabilities.
Task-specific machines are available
today that can be used
for the unique purpose
of forming a ball lens or
using a carbon dioxide
(CO2) laser to ablate fi-
ber to form an axicon
lens (a lens with a con-
ical shape). In addition,
It should be noted that without the
development of this new era of equip-
ment, the ability to make these com-
ponents in mass production would
still pose many challenges. Although
there is a broad spec-
trum of components
in this field, this arti-
cle will be limited to
the following fiber-
component technol-
ogies: fiber-lensing
techniques, endcap technology, ta-
pers, multicore-fiber fan-outs, fiber
combiners, mode-field adapters, and
overcladding.
Lensing technologies
Today’s technologies enable the for-
mation of many lens shapes from optical fiber. For example, axicon lenses
are used to increase the efficiency of
coupling lasers and LEDs into fibers
at the chip level, while ball lenses are
used in the medical field for the purposes of detecting cancer and destroying kidney stones.
The axicon lens has typically been
produced by either polishing the tip of
the fiber with a special polishing process or by using a CO2 laser to obliterate the fiber end to remove the cladding material in a conical shape (see
Fig. 1). Fabrication changes the prop-
erties of the end of the fiber, expos-
ing the core, which is then surround-
ed by air rather than cladding material.
The difference in refractive index be-
tween the air and glass is substantially
different than the difference in index
between the core and cladding.
Additionally, the conical shape
produces a lensing effect at the
tip of the fiber, enabling the col-
lection of more light into the fi-
ber from an LED or laser diode.
The polishing process used to
create an axicon on the end of a
fiber, while effective, is also very
labor-intensive. The fiber must
be held at a very precise angle
Fiber lensing techniques, end cap
technology, tapers, multicore fiber
fan-outs, fiber combiners, mode
field adapters, and overcladding all
benefit from versatile new optical fiber
processing technologies.
