<s>
Arrayed	B-Protocol
waveguide	I-Protocol
gratings	I-Protocol
(	O
AWG	O
)	O
are	O
commonly	O
used	O
as	O
optical	O
(	O
de	O
)	O
multiplexers	O
in	O
wavelength	B-Architecture
division	I-Architecture
multiplexed	I-Architecture
(	O
WDM	O
)	O
systems	O
.	O
</s>
<s>
These	O
devices	O
are	O
capable	O
of	O
multiplexing	B-Architecture
many	O
wavelengths	O
into	O
a	O
single	O
optical	B-Architecture
fiber	I-Architecture
,	O
thereby	O
increasing	O
the	O
transmission	O
capacity	O
of	O
optical	O
networks	O
considerably	O
.	O
</s>
<s>
The	O
devices	O
are	O
based	O
on	O
a	O
fundamental	O
principle	O
of	O
optics	B-Algorithm
that	O
light	O
waves	O
of	O
different	O
wavelengths	O
do	O
not	O
interfere	O
linearly	O
with	O
each	O
other	O
.	O
</s>
<s>
This	O
means	O
that	O
,	O
if	O
each	O
channel	O
in	O
an	O
optical	O
communication	O
network	O
makes	O
use	O
of	O
light	O
of	O
a	O
slightly	O
different	O
wavelength	O
,	O
then	O
the	O
light	O
from	O
many	O
of	O
these	O
channels	O
can	O
be	O
carried	O
by	O
a	O
single	O
optical	B-Architecture
fiber	I-Architecture
with	O
negligible	O
crosstalk	O
between	O
the	O
channels	O
.	O
</s>
<s>
The	O
AWGs	O
are	O
used	O
to	O
multiplex	O
channels	O
of	O
several	O
wavelengths	O
onto	O
a	O
single	O
optical	B-Architecture
fiber	I-Architecture
at	O
the	O
transmission	O
end	O
and	O
are	O
also	O
used	O
as	O
demultiplexers	O
to	O
retrieve	O
individual	O
channels	O
of	O
different	O
wavelengths	O
at	O
the	O
receiving	O
end	O
of	O
an	O
optical	O
communication	O
network	O
.	O
</s>
<s>
Conventional	O
silica-based	O
AWGs	O
schematically	O
shown	O
in	O
the	O
above	O
figure	O
,	O
are	O
planar	O
lightwave	O
circuits	O
fabricated	O
by	O
depositing	O
doped	B-Algorithm
and	I-Algorithm
undoped	I-Algorithm
layers	O
of	O
silica	O
on	O
a	O
silicon	B-Architecture
substrate	I-Architecture
.	O
</s>
<s>
Light	O
is	O
coupled	O
into	O
the	O
device	O
via	O
an	O
optical	B-Architecture
fiber	I-Architecture
(	O
1	O
)	O
connected	O
to	O
the	O
input	O
port	O
.	O
</s>
