Ijet V3i4p4
Ijet V3i4p4
Ijet V3i4p4
Abstract:
Optical Code Division Multiple Access (OCDMA) is an attractive multiple accessing technique that is used
in fiber optics network. As the data being transmitted can be analysed be the eavesdroppers. Therefore, security is a
major concern in OCDMA. We have analysed and examined different modulation schemes for three dimensional
Single Pulse per plane for direct detection in case of On-Off Keying or differential detection in case of Code Shift
Keying and Differential Phase Shift Keying to deduce which of these techniques are best suited against
eavesdroppers.
Keywords — Optical Fiber Communication, Optical Code Division Multiplexing (OCDMA), On-Off Keying
(OOK), Code Shift Keying (CSK), Differential Phase Shift Keying (DPSK), Four Wave Mixing (FWM).
Figure 1 Simulation setup for implementation of 3D SPDD codes with eavesdropper using On-Off Keying.
The performance of the setup is analysed using
B. Code Shift Keying
BER analyser and eye diagram. As for the security
analyses we use the eavesdropper. As the light As shown in Figure 2, the light is transmitted for
travelling in the fiber may leak out of the core and both ‘0’ and ‘1’ in this case. So, the energy in
clad, the person eavesdropping may place a tap that present at all-time intervals which makes
receives a portion of the light that is leaked out. By eavesdropping using the Simple Eavesdropper
analysing this light and then analysing, there is a difficult. Therefore DPSK eavesdropper is used.
chance that the eavesdropper will be able to decode Basic setup is same as On-Off Keying.The encoder
the user data successfully. We have studied two is used to encode both the signals separately. Due to
types of eavesdropper devices: Simple energy this the actual number of users is half of the code
detector eavesdropper and DPSK eavesdropper. It set size and OOK users. Signal for space channel 1
has been observed in pass studies that an isolated and 2 for both data and data bit is first multiplexed
user is more vulnerable to the eaves dropping, and then transmitted over optical fiber.For the
therefore we have analysed a single user more security analysis both simple and DPSK
carefully. In case of OOK, the simple eavesdropper eavesdropper are analysed. This scheme is the one
works well so we didn’t analyse DPSK which shows best results among all the other
eavesdropper but it will be analysed for other studied schemes.
methods.
Figure 2 Simulation setup for implementation of 3D SPDD codes with eavesdropper using Code Shift Keying.
Figure 3 Simulation setup for implementation of 3D SPDD codes with eavesdropper using Differential Phase Shift Keying.
Figure 7 Effect of Received power on BER performance of Different OCDMA modulation schemes.
Figure 8 shows how the BER of the signal is Figure 9 shows that with the variation in the Bit
affected with the change in number of space Rate of the system, the BER also changes.As the
channels used. As the number of lanesincreases,the Bit rate of the system increases the BER value of
BER value of the signal decreases.By varying the the signal decreases. By varying the bit rate (in
value of number of planes S = 2, S = 3 and S = 4 for Gbps) on which the systemperforms for all three
OOK, CSK and DPSK, their corresponding BER modulation schemes OOK, CSK and DPSK, their
value is measured and compares the varied Number corresponding BER value is measured using the
of Planes versus BER for all the modulation BER analyser.After that the results are compared
schemes and find out among all of the analysed for all the schemes using varied Bit Rate versus
scheme which one shows the better performance BER and we find out that among all these schemes
and security than the rest. By observing the graph, it which one performs better.On observing the graph,
can be interpreted that DPSK receiver shows best it can be deduced that the BER performance of
performance among all the three schemes, them OOK with respect to changing Bit Rate is best
after the DPSK is CSK which also shows better among all the schemes. After the OOK, the CSK
performance than OOK. As far as the security is modulation performs better and DPSK performs
concerned, for simple eavesdropper, OOK is the least good of all. Also it can be noted that around
least secure and DPSK is the most secure but for 4.5 Gbps all the scheme converges to almost same
the DPSK eavesdropper the security of the DPSK is BER and as we increase the Bit Rate from that
least among all the other techniques. point all the scheme shows similar performance.
Also, Security of the DPSK against the DPSK
Figure 8 Effect of Number of Space Channels on BER performance of Different OCDMA modulation schemes.
Figure 9 Effect of Bit rate on BER performance of Different OCDMA modulation schemes
Figure 10 shows how the change in number of previously no other users were active. Figure 11
users affects the BER of the User 1 while shows how the change in number of users affects
Figure 10 Effect of increasing users on BER performance of Different OCDMA modulation schemes at User 1.
Figure 12 Effect of increasing users on BER performance of Different OCDMA modulation schemes at User 3.