Research On Optical Layer Encryption Mechanism Of Passive Optical Network

With the development and overall deployment of access network,the environment of passive optical network becomes more complex,and many access network infrastructure devices will be exposed in public places.This brings potential security threats to data transmission in passive optical networks,such as data eavesdropping.In order to ensure the safe transmission of data in passive optical network,the existing data encryption method is the electrical encryption of data link layer and above.However,the upper encryption can’t solve the security problem of the physical layer,and it is limited by the processing speed of electronic devices,so the electric encryption can’t meet the requirements of the communication system with high real-time processing requirements.In the optical layer,the optical physical layer is encrypted by optical signal processing.It not only solves the bottleneck of processing speed of electronic devices,but also provides security protection for data transmitted transparently in the physical layer.Therefore,the thesis proposes an optical layer encryption method to solve the problem of secure transmission of keys and data in passive optical networks.It includes the following main contents:In the third chapter,aiming at the problem of secure key transmission in passive optical network,a key hiding system based on super-structured fiber Bragg grating is proposed.Super-structured fiber Bragg grating can hide the key signal in time domain and encode the signal,and provide double protection for the key information.The simulation results show that in the single-user key hiding system based on superstructured fiber Bragg grating,the key signal can be hidden under the system noise,thus ensuring the safe transmission of the key,and the received optical power of the singleuser key without error is-21.7 d Bm;In the three-user key hiding system based on superstructured fiber Bragg grating,besides the secure hiding of the key,the received optical power of the three user keys transmitted without error is-25.85 d Bm,-24.85 d Bm and-23.7d Bm,respectively.In the fourth chapter,aiming at the problem of data security transmission in passive optical network,an optical encryption system based on degenerate four-wave mixing effect is proposed.Degenerate four-wave mixing effect makes it easier to achieve phase matching between multi-wavelength signals.The simulation results show that after the degenerate four-wave mixing effect,the phase of the user’s four-phase shift keying signal is encrypted and disturbed,making it difficult to eavesdrop.In addition,in order to ensure the security of the key signal in the four-wave mixing encryption system,the thesis proposes a hybrid optical encryption system combining super-structured fiber Bragg grating and high nonlinear fiber.The system simulation shows that besides the abovementioned phase disturbance,the key signal encoded by super-structured fiber Bragg grating can be hidden under the signal encrypted by four-wave mixing.Thereby ensuring the security of the key signal.Finally,in WDM passive optical network,the three-user hybrid optical encryption system is verified by simulation.The results show that the minimum received optical power is-14.87 d Bm at the receiving end when the key and data signals are transmitted safely.