tec.News - Harting

Fig. 3: Schematic diagram of microstructure
duplicate moulding
tic cable leading in from the outside
is coupled to a fibre-optic
element located (or integrated)
inside the component. Fig. 3 shows
the manufacturing process: the
master structure À is made from
various materials, depending on
the level of precision required. For
tolerances smaller than one micrometre,
it is produced from silicon
using methods of surface
micromechanics. For precision between
one and several micrometres,
it is produced from so-called
thick photo-resist, and for waveguide
structures with cross sections
larger than 200 micrometres,
ultrafine milling in metals is
used. In a microstructure plating
process similar to CD electroplating,
the master structure is recopied
several times in nickel up
to the 3rd generation Á – Ã.
Since each nickel copy can itself
be duplicated several times, a
large number of 3rd-generation
mould inserts for plastic moulding
can be produced from a single master
structure. The production
of microstructured plastic substrates
Ä can then take place
with numerous mould inserts in
parallel in a single manufacturing
process. These plastic substrates
have grooves where the optical
waveguides will be produced later
and the appropriate adjustment
structures where the fibre-optic
cables are to be connected.
The next step in the process is to
coat the substrate with a transparent
plastic film in such a way that
the grooves are filled but the adjustment
structures do not come
into contact with the coating material.
For this purpose, the socalled
microstructure strip-off
process is used. In a similar way
to the mould insert à used for
producing the substrate, a microstructured
thin metal foil, known
as the strip-off foil Å, is made.
It has virtually the same surface
structure as the mould insert, but
does not have a cross-piece for
producing the waveguide groove.
As a microstructured component,
the strip-off foil can be manufactured
with extremely high fitting
accuracy relative to the substrate.
If a liquid plastic with a suitable
refractive index is inserted between
substrate and strip-off foil
and cured, an integrated optical
component Æ is produced which
can be passively coupled with fibreoptic
cables via the guide structure.
Fig. 4 shows a 1x2 splitter produced
in this way for 1 millimetre
thick polymer-optical fibres (POF)
operating with a fibre-optic cable
connected on one side.
Fig. 4: 1x2 splitter for 1 mm POF operating
with a fibre-optic cable connected on one side
Corresponding components can be
manufactured for virtually any
type of fibre-optic cable through
39
People Power Partnership