536 CHINESE OPTICS LETTERS / Vol. 6, No. 7 / July 10, 2008
Terahertz optical asymmetric demultiplexer based tree-net
architecture for all-optical conversion scheme from
binary to its other 2
n
radix based form
Jitendra Nath Roy
1
, Goutam Kumar Maity
2
, Dilip Kumar Gayen
3
, and Tanay Chattopadhyay
4
1
Department of Physics, College of Engineering and Management, Kolaghat
2
Calcutta Institute of Technology, Uluberia, Howrah, W. B. India
3
Department of Computer Science, College of Engineering and Management, Kolaghat
KTPP Township. Midnapur (East). 721171, W. B. India
4
Mechanical Operation (Stage-II), Kolaghat Thermal Power Station, WBPDCL, India
Received August 8, 2007
To exploit the parallelism of optics in data processing, a suitable number system and an efficient encod-
ing/decoding scheme for handling the data are very essential. In the field of optical computing and parallel
information processing, several number systems like binary, quaternary, octal, hexadecimal, etc. have been
used for different arithmetic and algebraic operations. Here, we have proposed an all-optical conversion
scheme from its binary to its other 2
n
radix based form with the help of terahertz optical asymmetric
demultiplexer (TOAD) based tree-net architecture.
OCIS codes: 200.4560, 200.4650, 060.4510, 220.4830, 230.4320.
doi: 10.3788/COL20080607.0536.
The new generation of communication networks is mov-
ing towards terabit per second data rates. Such data
rates can be achieved if the traditional carrier of informa-
tion, electrons, are replaced by photons for devices based
on switching a nd logic. Researches into this field have
also explored new concepts and ideas. Various architec-
tures, algorithms, logical and arithmetic operations have
been proposed in the field of o ptica l/optoelectronic com-
puting and parallel processing in las t few decades
[1−8]
.
To exploit the parallelism of optics in computing, a suit-
able number sy stem and an efficient encoding/decoding
scheme for handling the data are very essential. In the
field of optical computing and parallel information pro-
cessing, several number systems like binary, quaternary,
octal, hexadecimal, etc. have been used for different
arithmetic and algebraic ope rations. These numbers are
2
n
radix based numbers where n is an integer. For a
number represented in binary form the value of n is 1,
for quaternary n = 2, fo r octal n = 3 and for hexadec-
imal n = 4. Therefore an efficient conversion scheme
from one number system to another is very essential. Bi-
nary number is accepted as the b e st representing number
system in almost all types of existing computers. The
main advantages of the use of 2
n
radix based number are
their easier type of representation a nd ea sier conversion
from one 2
n
radix based numb er to other 2
n
radix based
number. In this paper, we have propose d an all-optical
parallel conversion scheme o f binary number to its other
2
n
radix based form with the help of teraha rtz optical
asymmetric demultiplexer (TOAD) based tree-net a rchi-
tecture. High speed (Tb/s) operation can be achieved by
this all-optical scheme.
Sokoloff et al. demonstrated a new device TOAD
capable of demultiplexing data a t 50 Gb/s
[9]
. TOAD
based process ing has been of great interest in the last
few years
[10−13]
. In almost all the a bove cases, the trans-
mitting mode of the device (output port) is used to take
the output signal. But the signal that exits from the
input port (refle c ting mode) remains unused. In this pa-
per, we have tried to take the output s ignal from both
the transmitting and reflecting mode of the devic e . That
is, lig ht coming out from both the input port and output
port is taken into account. In our earlier contribution,
we proposed a TOAD-based tree architecture, a new and
alternative scheme, for all-optical logic and a rithmetic
operations
[14,15]
. In this paper, the same TOAD-based
tree-net architecture has been tactfully used to design an
all-optical conversion scheme from binary number to its
other 2
n
radix based form which is from binary to octa l,
binary to hexadecimal etc. The possibility of practical
implementation of the proposed scheme is also discussed.
The proposed all-optical scheme can exhibit their switch-
ing speed far above present e le c tronic switches.
The TOAD consists of a loop mirror with an a dditional,
intraloop 2× 2 (ideally 50:50) coupler. The loop contains
a c ontrol pulse (CP) and a nonlinear element (NLE) that
is offset from the loop’s midpoint by a distance ∆x as
shown in Fig. 1
[9]
. A signal with field E
in
(t) at angular
frequency ω is split in coupler and travels in clockwise
(cw) and counter clockwise (ccw) direction through the
loop. The electrical field at port-1 and port-2 can be
expressed as follows
[10]
:
E
out,1
(t) = E
in
(t − t
d
) · e
−jωt
d
×
d
2
· g
cw
(t − t
d
) − k
2
· g
ccw
(t − t
d
)
, (1)
E
out,2
(t) = jdkE
in
(t − t
d
) · e
−jωt
d
× [g
cw
(t − t
d
) + g
ccw
(t − t
d
)] , (2)
where t
d
is the pulse round trip time within the loop as
shown in Fig. 1. Coupling ratios k and d are for the cross
1671-7694/2008/070536-05
c
2008 Chinese Optics Letters
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