PROGAMMABLE DEMULTIPLEXER USING ELECTRO-OPTICALLY MODULATED POLYERIC GRAGTING ARRAY

DEMULTIPLEXEUR PROGRAMMABLE UTILISANT UN RESEAU A GRILLE POLYMERE A MODULATION ELECTRO-OPTIQUE

English Abstract

A programmable demultiplexer employing electro-optically modulated polymeric
grating array in conjunction with substrate guided waves is proposed. Among
these
electro-optic gratings in the grating array have different coupling
wavelengths so that
each of them can couple an expected wavelength out from the substrate guided
waves.
Thus, this architecture can be used as a programmable demultiplexer to
implement
reconfigurable wavelength-division-multiplexing lightwave systems.

Claims

Claims:
1. An programmable demultiplexing device comprising:
a substrate for guiding bouncing waves;
an electro-optically modulated polymeric grating array;
a polymeric layer, an upper grating modulating electrode and a lower
modulating
electrode in each grating spot.
2. As an electro-optically modulated device, both the transparent lower
electrodes 24 and
the upper grating electrodes 26 are needed. The transparent lower electrodes
can be ITO
material. The modulated layer 22 is only an electro-optic ploymer and the
poling process
for the polymer is needed.
3. Based on claim 1, the modulated gratings according to the present invention
can also
be thermo-optically modulated. In this case, the modulated layer 22 can be
either a
polymer or a polyimide and the poling process is not needed. The transparent
lower
electrodes for all the gratings are unnecessary and can be removed. The
modulation
effect can be applied from the two ends of the upper electrodes. Therefore,
the
fabrication for the thermo-optic devices is easier than that for the electro-
optic devices
according to the present invention.

Description

CA 02264324 1999-03-03
PROGAMMABLE DEMULTIPLEXER USING ELECTRO-OPTICALLY
MODULATED POLYERIC GRAGTING ARRAY
Technical Field
This invention relates to electro-optic demultiplexing devices for
reconfigurable
wavelength-division-multiplexing (WDM) lightwave systems in fiber-optic
communication.
Background of the Invention
The WDM lightwave system is the optical communication in the wavelength
multiplex
mode. This novel approach allows modulated radiation from several light
sources of
clearly distinct wavelengths to be transmitted simultaneously over a single
fiber and is
one most promising approach to improve the number of communication channels
and
capacity in the fiber-optic communication. The use of this novel approach WDM
has the
potential of improving the performance of the fourth generation lightwave
systems by a
factor of more than 1000. The commercialization of high-capacity WDM lightwave
systems requires the high performance channel multiplexers and demultiplexers
with add-
drop capacity.
Recently, research on the devices and techniques for high capacity WDM systems
or
dense wavelength division multiplexing (DWDM) systems having effective network
restoration capability, i.e., reconfigurable WDM systems has received much
more
attention. Most of currently available demultiplexers are passive devices, so
they can not
satisfy the requirements of the reconfigurable WDM systems. In future high-
capacity
WDM systems or DWDM systems, the routing of optical signals will be performed
in
optical cross-connects (OXCs). The functions and applicability of the WDM
systems
will be extended by the reconfigurable structures.
The reconfigurable WDM networks would facilitate transport of large
bandwidths.
The switching nodes in this kind of WDM networks could be directly connected
to each
other without electronic processing. This relaxes the capacity requirements of
electronic
switching systems when all the links can be by passed all optically. A dynamic
reconfigurable WDM network layer could be set up such direct links. This could
be used
to adapt the network to any structural changes in traffic load.
So far, there has not been much work focusing on developing new types of
demultiplexing devices for the dynamic reconfigurable WDM systems.
Summary of the Invention
A new optical interconnect architecture using multiple electro-optically
modulated
polymeric gratings in conjunction with substrate guided waves is proposed.
These
electro-optically modulated polymeric gratings are designed to have different
coupling
wavelengths and fabricated on a high-index substrate. When a chosen grating
spot is
activated by an appropriate modulation effect, the modulated polymeric grating
is formed
and then it +couples an optical beam having the expected wavelength out from
the
substrate guided waves. Namely, different grating spots can be used to couple
different
wavelength beams from the substrate guided waves. Therefore, the electro-
optically
programmable optical interconnect devices according to the present invention
can be

CA 02264324 1999-03-03
used as demultiplexers to implement the reconfigurable WDM lightwave systems
for
fiber-optic communication.
In accordance with the present invention, the structure of the gratings must
meet two
conditions. One condition is the total internal reflection (TIR) for optical
beam bouncing
within the substrate when no modulation effect is not applied onto the
gratings. The
other condition is the matching condition among all the momentums at the
expected
wavelength for grating coupling when the modulation effect is applied onto the
grating.
Theoretical study shows that a perfect matching with the structures according
to the
present invention can not always be implemented, so the compensation for the
mismatch
existing in the structures is needed to be made by some special design. The
better design
of a grating structure directly impacts coupling efficiency of the grating and
the
bandwidth of the coupled beam at the expected wavelength.
Brief Description of the Drawi
FIG.1 is the configuration of the programmable demultiplexer using electro-
optically
modulated polymeric grating array in conjunction with substrate guided waves.
FIG.2 is the amplified structure of one electro-optically modulated polymeric
grating
fabricated on the substrate of FIG.1.
Detailed Description
As shown in FIG.1, the demultiplexer is composed of a high-index substrate, an
electro-optic ploymer layer 22, multiple modulating gratings: G, , Gz ,..., G"
. As shown in
FIG.2, each of the gratings ( G, , G, ,..., G" ) has the same structure of
three layers. They
are an electro-optic ploymer layer 22, a lower electrode 24, and an upper
electrode 26.
In principle, when an optical beam is coupled into the substrate 20, a
bouncing beam is
formed if no grating is activated. If an appropriate moc:alation effect is
applied onto the
grating electrode G; , a modulated grating is formated at G; and an optical
beam having
the expected wavelength ~.; is coupled out from the bouncing waves. Therefore,
totally
there are two conditions to support two operations. The first condition is the
TIR at any
grating spot to form the bouncing beam within the substrate if no modulation
effect is
applied onto this device. The second condition is the momentum matching for
coupling
an optical beam having the expected wavelength with a high efficiency. When
the
second condition is met to perform the second operation, the first condition,
i.e., the TIR
condition is broken. If the second condition, i.e., the momentum matching, can
not be
completely met in this structure, a compensation for the mismatch of the
momentums
need to be made to improve the coupling efficiency of the electro-optically
modulated
polymeric grating. For more detailed information about the compensation for
the
mismatch of the momentums, see Applied Optics 63 (2), 629-634 (1997).

Representative Drawing