Superstructured fiber Bragg grating (FBG) technology has emerged as an attractive means to produce compact, and potentially low-cost in-fiber devices for a variety of lightwave applications. In this paper, a secure optical communication system based on tunable FBG arrays is described. Utilizing the inherent characteristics of FBG array to decompose broadband pulses simultaneously in wavelength and time, one broadband light pulse reaching a series of different Bragg gratings may be split into a number of separated pulses, each with different wavelength and is positioned at different time. To recover the original pulse, an inverted grating array is needed at the receiver side, i.e., the transmission is secure in case that the exact structure of the FBG array is unknown. Some of the factors affecting the process of encryption/decryption are indicated. To further increase the security of the system, theories about bent functions are presented and applied to generate bent sequences so as to charge the modes of FBG arrays because of the bent functions' excellent cryptographic properties. Simulations results are presented and analyzed to show the feasibility of the system. The paper is concluded with a discussion of the advantages for such an optical encryption/decryption system.
Secure optical communication systems based on general bent sequences have been described which encode/decode information with arrays of fiber Bragg gratings (FBG). A broadband pulse coming from an optical source will be split into a series of separated pulses when it reaches the encoding FBG array. These pulses have different spectrums and different time delays. Because it is difficult for an attacker to recover the original pulse if he doesn't know the exact structure of the encoding FBG array, one can say that the information from the optical source has been encrypted. The coded signal will be recovered by the decoding FBG array having the inverse structure of the encoding FBG array. Because various structures of encoding FBG arrays could generate different reflected pulses to ensure the security of
communication in the unsafe channels, grating tuning techniques are used broadly to increase the modes of the systems. Some models of the systems will be introduced and their security will be discussed. Bent sequence is generated by a general class of bent functions to charge the modes of FBG arrays in order to increase the security of our systems because of its excellent characteristics in cryptology. That makes the optical communication system safe against the interception. Simulation and discussion will be included and the applicability of the system in the future has been prospected.
Performance of all-fiber fast frequency hop optical code division multiple access system (FFH-OCDMA) is studied in case parametrical difference exists between the fiber Bragg grating (FBG) arrays based encoder/decoder, i.e., the relevant gratings' Bragg wavelengths or relative positions are not strictly consistent. If there are such parametrical differences, some optical pulses with specific frequencies will be lost partially, or even entirely, which reduces the peak value of the self-correlation decoding output. The multi-users simulation model of FFH-OCDMA system is presented amply in the
paper, which consists of these components: signal source, encoder, decoder, fiber channel, receive detector, and data analysis module. Simulation result is presented and discussed. It shows that the system performance drops down sharply with a larger wavelength inconsistency or with a larger position relative offset, especially when the number of FBG is smaller. It is also concluded that performance degradation can be alleviated by employing longer FBG array, but with the expense of higher system complexity.