COL 11(10), 100602(2013) CHINESE OPTICS LETTERS October 10, 2013
Multilevel photon communication on BPPM with
convolutional coding
K. Sripimanwat
1∗
, J. Wongpoom
2
, and O. Sangaroon
2
1
Optical and Quantum Communications Laboratory, NECTEC, NSTDA, Thailand
2
Department of Computer Engineering, Faculty of Engineering, KMITL, Thailand
∗
Corresponding author: ksripima@ieee.org
Received July 8, 2013; accepted September 4, 2013; posted online September 27, 2013
Multilevel p hoton combined with binary pulse position modulation (BPPM) ( Manchester pulsed signals),
is introduced in this letter. Initially, error probability derivation and explanation for four-level photon
communications with that BPPM is presented. Next, the 2-level photon communications matching with
BPPM is proposed. For performance comparison, it is done with t hat the conventional scheme by fixing the
background noise and also increasing number of ph oton per slot. Successfully with applying convolutional
coding for system improving, the proposed multilevel photon on BPPM with this coding scheme achieves
higher gain. Finally, this work also benefits t o improving for further performance when considering with
multilevel error control coding as well.
OCIS codes: 060.0060, 350.0350.
doi: 10.3788/COL201311.100602.
Basically optical modulation as one of those major parts
of lig htwave system has been developing continuously fo-
cusing more on advance technologies in order to provide
better and higher information rates. That is to support
the growth in user demand on broa dband communica-
tion and for next gener ation networks. To emphasize
on modulation techniques, multilevel photon communica-
tion as o ne of those proposed schemes in lightwave com-
munication, has been focusing. It is proposed to achieve
higher throughput or to increase the sy stem efficiency to
be better than that of traditional binary photon com-
munications. Basically, regular pulse position modula-
tion (PPM) has been developed consequently to be the
multi-pulse version (MPPM), or the overlapping sense
(OPPM), and the differential pulse style (DPPM)
[1]
.
Subsequently based on that principle of PPM, the “mul-
tilevel concept” has been s hown as a hig her performance
achieved method to add on, for instance as an invention
in Ref. [2]. However apart from working on that PPM
pulse format of modulation, another branch of “multi-
level” PPM by consideration on other bound bre aking
idea such as multilevel dual-polarizatio n signal constella-
tions or polarized and amplitude hybrid, have been intro-
duced in Refs. [3 ,4] respectively. In the similar direction
of “multilevel” sense, the multilevel photon for mat from
Ref. [5] is considered as another potential modula tion
fo c using on light intensity within each pulse. Mo reover,
bandwidth-efficient techniques by using this multiple-
level related technologies, has been also focusing in other
various fields such as in free space channel, indoor broad-
band communications
[6]
, quantum key distribution
[7]
,
and ultra wideband co mmunication
[8]
. Thus, it becomes
highly promising as a new modulation sy stem when these
two schemes are proposed jointly.
Eventually, this letter discovers above combination
technique in order to improving overall system perfor-
mance. In addition, matched convolutional codes as an-
other promising solution, is also proposed in conjunction
with those improved modulation scheme for obtaining
further gain.
Considering firstly on a binary photon pulse or on-off
keying system
[1,9]
, transmitting symbol “l”, the sender
(T
x
) delivers a rectangular pulse containing average num-
ber of photons α and pulse width of T
D
seconds. Other-
wise, transmitting s ymbol “0”, sender will send no pulse.
Then, the light signal denoted by the intensity is
λ
s
(t) =
(
α
T
D
, 0 6 t 6 t
D
0, elsewhere
. (1)
When the pro bability of those two symbols is equa l,
transmitted power in terms of transmitted photons is
given in average by
P
2
= α/(2T
D
). (2)
Next from above background, a multilevel photon com-
munication style is now realized. This modulatio n is sim-
ilar to that a multilevel format of the traditional ampli-
tude modulation (AM). It is only excepted on the signal
constellations, those are specified by the light pulse in-
tensity. Starting here with a signal set when considering
on a 4-level photon style, the binary 2-tuples are placed
onto four different recta ngular pulses re sulting with pulse
width of T
D
seconds and average number of photons (α
i
)
is then defined. Similarly, it is an analogous to that 4-AM
modulation scheme (4 levels amplitude mo dulation)
[10]
.
Refer to a binary pulse format, the Rx or receiver
will count for the photons number in that pulse interval
T
D
. Then, it will estimate what is that the transmitted
symbol. In the case of 4-level photon of Fig. 1, when all
Fig. 1. Format of a 4-level photon communication signals.
1671-7694/2013/100602(5) 100602-1
c
2013 Chinese Optics Letters