Abstracto

Protection Of WDM FSO Network Over Fading Channels

Rakhi.J.Nair, S.Manikandan

FSO uses modulated optical focused beams to establish atmospheric data transmission. This re-emerging technology combines high data rates around 2.5 Gbps in commercial implementations.This characteristic, along with high network reconfigurability (provided by the short deployment time), license-free operation and low sensitivity to electromagnetic interference and jamming, makes FSO systems even more interesting for defense applications. ON-OFF keying (OOK) modulation, used by most FSO systems, is not adequate to logically hide the information, if the beam is intercepted. This scenario should be considered, in the case of long-haul military mobile system with large divergence angles. Other disadvantage is that these systems are vulnerable to atmospheric phenomena, such as attenuation and scintillation. All these factors must be considered during the design of a new FSO system for military purposes.In the proposed system, encoding is done at each relay path to protect the transmitted data from any kind of security attack.Data security in this system comes from the physical signal encoding and decoding processes , because a corresponding process is required to decode the code pattern in order to successfully receive the transmitted data. When the encoding and decoding information is kept secret, the data security is ensured. Physical encoding imposes complex encoding to the physicaly transmitted signals . After the physical encoding, the signal carrying data is transformed to an unpredictable form which is being modulated using PPM modulation