SCHOTT FIBER OPTICS User Manual
FIBER OPTICS INDUSTRIAL E
Industrial fiber optic components
and LED solutions
Lighting, Sensing, Imaging
Content
2–3|Introduction
4–5|Physical principles and properties of optical fibers
6–13 | Manufacturing/Design of light guides
14–15 | Physical principles of LEDs
16–17 | Manufacturing/Design of image guides
18–23 | Applications
Creative new solutions
Generations of know-how as clear as glass
For more than 40 years, SCHOTT has
developed fiber optic products for a
diverse range of applications. Our name
stands for high quality and innovative
solutions in the field of fiber optic light-
ing, sensing and imaging.
The Fiber Optics Business Segment offers high-tech solutions in markets such
as automotive, lighting, medical, industrial and defense.
By mastering glass, fibers and processes for the production of fiber optic
components, we develop outstanding, market-oriented products. With our
leading technological know-how and innovative ideas we contribute to the
success of our customers – around the world, around the clock.
We work in partnership with you to develop new products:
New fiber optic compontents for widely
differing industrial applications are the
outcome of very close cooperation with
our customers. Customer ideas gener-
ated from knowledge of their product
and their industry coupled with
SCHOTT’s fiber optic know-how result
in new products with clear benefits to
the market.
We will continue to carry out further research and development in the future
to continuously improve our products. We can be your single source fiber
optic specialist to support development stages from basic research and proto-
typing to mass production with competent quality, creativity and support.
The earlier we are involved in your project, the more effectively we can help
to develop optimum solutions for your special requirement.
We are continuously striving to develop new technologies: latest develop-
ments include LEDs (Light Emitting Diodes) for illumination components.
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A highway for light
The physical principles and properties of optical fibers
Optical fibers are the heart of all fiber optic components. Every optical fiber
consists of a core with a high refractive index and a cladding with a low refrac-
tive index. Light rays which enter the fiber at one end are guided along the
core by total internal reflection at the core/cladding interface. The light rays
follow the bends in the fiber and exit the fiber at its other end.
Spectral fiber transmission
Transmission of fiber bundles
The three most important characteristics
Cladding
of an individual fiber are its:
■
Diameter
■
Numerical Aperture
■
Spectral transmission
The principle of light transmission in an optical fiber
Core
Diameter
To ensure total internal reflection, the fiber cladding must have a minimum
thickness of 2 µm for the visible range of the spectrum. An improvement in the
optical efficiency can be achieved by increasing the diameter of the fiber with-
out increasing the thickness of the cladding. This, however, results in a loss of
mechanical flexibility. For the majority of applications an optimum relationship
between transmission and flexibility is achieved with a fiber diameter between
50 and 70 µm.
Cladding
Core
Fiber Ø 70 µm Hair Ø 200 µm
As light is transmitted through a fiber its intensity decreases. The relationship
between the input intensity and the output intensity defines the spectral
transmission T (λ). The spectral transmission depends on three factors:
■
Absorption losses in core glasses. These losses are mainly caused by un-
avoidable traces of coloring metal oxides. Rayleigh light scattering results
from a natural density fluctuation in the glass melt. These losses are pro-
portional to the length of the light guide.
■
Losses resulting from less than ideal total reflection at the core/cladding
interface depend greatly on the angle at which the light enters the fiber,
also impacting the total number of reflections accumulated over the whole
length of the fiber. The greater the number of reflections, the higher the
loss.
■
Fresnel reflection losses – at the input and output surface – amount to
approximately 11% combined.
In addition to the transmission of each
individual fiber, the transmission of fiber
bundles is influenced by another factor.
As a result of round fibers being bun-
dled together, interstitial gaps exist
between the fibers. These gaps – usually
filled with epoxy material – do not
transmit light as well as the glass
cladding.
The total amount of light which can be
transmitted through a single fiber is the
result of length dependent transmission,
numerical aperture and active fiber core
area. The spectral transmission of a
bundled fibers is essentially determined
by the type and quality of glass used for
the core and cladding, its absorption
properties, the packing density of the
fiber bundle and the quality of the end
terminations.
Numerical Aperture
The numerical aperture of an optical fiber depends on the refractive indices of
the two types of glass used for the core and the cladding.
2
The equation: NA = n
· sin α0= √ n
0
the optical axis of a fiber. For simplicity it can be used for a light guide where:
= Refractive index of the surrounding medium
n
0
= Refractive index of the fiber core
n
1
= Refractive index of the fiber cladding
n
2
= Critical angle to the optical axis.
α
0
4
2
- n
applies to light rays which intersect
1
2
All light rays which strike the perpendic-
ular polished end face of the light guide
at an angle of α ≤ α
are transmitted
0
along the fiber. This results in the fact,
that the amount of light which can be
transmitted through a fiber is propor-
2
tional to the NA
.
SCHOTT’s competencies …
Manufacturing/Design of light guides
From single fibers to light guides
Bundles of optical fibers are combined with appropriate end terminations and
protective sheathing to form light guides and image guides. Combining well-
proven
incorporates such fiber bundles into a multitude of engineered components
by modifying their properties to suit the particular application.
materials with in-house developed technologies SCHOTT
Fiber types
The selected fiber type is dependent on
the demands of the application.
flexible fibers as well as rigid fiber optic
rods cover a variety of diameters and
optical characteristics like Numerical
Aperture and Transmission. Fiber types
for the visible and UV spectral range,
plus several types to accommodate near
IR enable manufacturing of fiber optic
components best suited for a variety of
different applications. For further details
please refer to the actual datasheets.
SCHOTT
70
60
50
40
30
Transmission (%)
20
10
0
200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
■ UV fiber ■ IR fiber ■ VIS fiber
Spectral Transmission – Different fiber types (fiber Ø 70 µm, length 1000 mm) – Typical values
Wavelength (nm)
Mechanical Protection
Materials
Flexible or rigid? The first step in designing a fiber optic light guide is the
decision if it needs to be flexible or rigid. Rigid fiber optic rods also referred to
as light conducting rods are solid fiber optic elements which can be used to
transmit light, image or signals over short distances whenever flexibility is not
required. Their advantages over flexible light guides are:
■
No packing losses in interstitial gaps and therefore higher transmission
■
Excellent temperature resistance because epoxied end ferrules and
protective sheathings are not required
■
Vacuum or pressure seals are possible
In addition,
conical light guides for reducing or increasing the effective optical cross-
section and aperture angle (“Light magnification”). Please contact your local
sales person for further details.
SCHOTT can also manufacture fiber optic cones respective
Sheathing
Clearly
fiber bundles; sheathing is an integral structural component used to meet
specific applications.
If, and for how long, a light guide operates reliably depends to a large extent
on the protective sheathing used.
sheathing, so that fiber bundles can be protected in various mechanical,
physical and chemical environments.
A standard range of protective sheathing to suit particular applications is
available (i.e. metal, polymer, compound). Details see separate datasheet.
Ferrules
End ferrules for bonded/epoxied light guides are made out of aluminum,
brass, stainless steel, nickel silver or other materials. For end ferrules in hot
fused components stainless steel is used.
Housings
If requested we can manufacture housings to your specifications. Typical
housing materials are: nickel, silver aluminum, stainless steel and various
plastics.
SCHOTT believes that sheathing is more than simply packaging for
SCHOTT offers many different types of
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