Performance Assessment of Optical Networks with CDMA
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Performance Assessment ofOptical Networks with CDMA
Paulo M. Mendes
ConclusionsA new methodology for performance evaluation of optical DS/CDMA systems was developed;The prime codes are more sensitive to the fibre length than optical orthogonal codes;The dispersion tolerance depends of the relation between the code length and number of chips in the code and a longer code does not imply an improvement on dispersion tolerance;The codes to be used in DS/CDMA systems must be selected taking into consideration their dispersion tolerances;We simulated a system operating at 20 Gchip/s with a penalty < 2 dB, for L=10 km and Pe=10-9.
Th
10T
dtc
T NTc
Coding Sequence (1001101)
Data Sequence (1011)
Coded Sequence
L
nndb
ssDwbsDFss2
1)1(
0022 )()()(
2
1exp)()1(
0
APD input
MGF of V(ts)
( ) ( ) ( )
( )
,( )t
Tm h t lT jT
Th t lT jT
cl j
nc n
j
N
ln
L
cc n
j
N
ln
L
d
1 1
0
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1
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Simulation Methodology
Generation of the optical symbol sequence, propagation through linear fibre channel and reception with Butterworth low-pass filter;
Performance estimation using the moment generating function of the output distribution with the saddle point approximation.
Effect of Dispersion on Eye Opening
System Operating at 10 Gchip/s
0 0.5 1 1.5 20
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1x 10
-3
t/T0 0.5 1 1.5 2
0
1
2
3
4
5
6
7x 10
-4
t/T
PC with N = 121w = 11C = 11
TC with N = 129w = 3C = 6
-54 -52 -50 -48 -46 -44 -42
10-10
10-5
100
Pe
Chip Received Power [dBm]
PC with
N = 529 w = 23
-55 -50 -45 -40 -35
10-10
10-5
100
Pe
Chip Received Power [dBm]
PC and
OOC
PC with N = 529 L = 5
D = 37 Mbit/s
PC with N = 121 L = 5
D = 165 Mbit/s
-50 -45 -40 -35 -30
10-10
10-8
10-6
10-4
10-2
100
Chip Received Power [dBm]
Pe
-50 -45 -40 -35 -30
10-10
10-8
10-6
10-4
10-2
100
Chip Received Power [dBm]
Pe
DS/CDMA System Model
Developed Simulator
Effect of Dispersion on Probability of Error
System Operating at 20 Gchip/s
RX
TX