Research On Construction And Performance Of Two-dimensional Variable Weight Optical Orthogonal Code And SAC Address Code In OCDMA System

Optical code division multiple access(OCDMA)technology has the characteristics of high security,strong security,and providing multiple quality of service(QoS).This technology can achieve the asynchronous sharing of the entire channel between different users.Among them,voice,image,video and other multimedia applications can be effectively received according to different quality of service,which can be realized by variable weight or variable length coding technology.Because users with high service quality requirements use high code weight codes for information transmission,variable weight address codes can help achieve flexible and diverse service quality.One of the main reasons why the technology has not been commercialized is that the address code with good performance has not been found.Therefore,the main content of this paper is to construct optical address codes with excellent performance and can provide multiple quality of service,and analyze the performance of codes.The main work content is as follows:1.A Two-Dimensional variable weight address code based on time-domain/ frequency-domain OCDMA system is designed,in which Quadratic Congruent Hopping Code(QCHC)is used as the frequency hopping sequence and Strict Variable Weight Optical Orthogonal Code(SVWOOC)is used as the time spreading sequence.The code can support multiple QoS requirements,and the wavelength frequency hopping sequence can reach the maximum code capacity of the frequency hopping code,and the code weight can be selected flexibly according to the user's requirements.The error characteristics of different parameters are analyzed.When the frequency hopping sequence is the same,increasing the code weight can reduce the bit error rate(BER)more effectively.The bit error rate of this code is 3~9 orders of magnitude lower than that of the same 2D-VWOOC in the same time spreading sequence.In Optisystem simulation,when the transmission rate of the system is 14 Gbps,the BER of users with code weight 4 is 7 orders of magnitude lower than that of users with code weight 2,and a clear and correct eye diagram can be obtained.2.A Two-Dimensional variable weight optical orthogonal code for OCDMA system is designed.The Mutually Orthogonal Latin Square(MOLS)is used as frequency hopping sequence,and the one-dimensional strict variable weight optical orthogonal code is used as time spreading sequence.The code frequency hopping sequence breaks through the limitation of the prime power of wavelength number,has large code capacity and can support different users' differentiated QoS requirements.The performance of codes with different parameters is analyzed.When the code weight is the same,increasing the number of wavelengths can reduce the bit error rate more effectively.Under the same time spreading sequence,the code has a larger code capacity than similar variable weight optical orthogonal codes,and the bit error rate is 9 to 17 orders of magnitude lower than other similar codes.In Optisystem simulation,when the transmission rate of the system is 16 Gbps,the BER of users with code weight 4 is 2 orders of magnitude lower than that of users with code weight 2,which has good bit error performance.3.A one-dimensional constant weight address code based on spectral amplitude coding optical code division multiple access(SAC-OCDMA)system is studied —— one-dimensional multiple diagonal(1D-MD)code.Its error performance is analyzed.The code has zero cross-correlation and can ignore the influence of incoherent intensity noise.Under the same effective power and bit error rate,the larger the code weight,the more users can be supported.Two kinds of one-dimensional variable weight address codes based on SAC-OCDMA system are designed.The first is one-dimensional variable weight optical orthogonal code based on mapping technology(1D-MTVWOOC).The code has large capacity,the maximum cross-correlation is 1,and can eliminate the influence of Multiple Access Interference(MAI).In this system,based on the complementary subtraction(CS)detection technology,the error simulation analysis is carried out,and the error performance under different noises is compared.At the same number of users,the bit error rate decreases with the increase of the effective power,and at the same effective power,the bit error performance of the code with high code weight is better than that of the code with small code weight.When the effective power is small,thermal noise becomes the main factor affecting the BER,and when the effective power is large,phase induced intensity noise(PIIN)becomes the main factor affecting the BER.The second one is the one-dimensional zero cross-correlation variable weight optical orthogonal code based on magic square matrix(1D-MSVWOOC).There are two methods to construct the code.One is to construct the magic square matrix of odd order first,and then to construct a new type of variable weight optical orthogonal code by using the mapping technology.The other is to generate the required code sequence directly according to the mathematical derivation.The code can provide odd matrix according to the number of users with different code weight,and ensure the maximum cross-correlation of 0 in synchronous SAC-OCDMA system,which can eliminate the impact of MAI.Under the direct detection(DD)technology,the PIIN effect can be suppressed.The performance of the code is analyzed.Under the same effective power,the code with high code weight has better error performance,and the bit error rate decreases with the increase of effective power.4.Two kinds of two-dimensional constant weight address codes based on SAC-OCDMA system are studied.The first is two-dimensional multi diagonal(2D-MD)code.The error performance of different effective power is analyzed.When the number of users is 80,the effective power is-10 dBm,which is 9 orders of magnitude lower than the bit error rate of the-20 dBm 2D-MD code.The second is two-dimensional single weight zero cross-correlation(2D-SWZCC)code.The influence of PIIN,shot noise and thermal noise on the bit error performance is analyzed,and the relationship between different rate,different effective power and different number of users and the bit error rate is analyzed.When the transmission rate is the same,the larger the number of users,the smaller the effect of the change of the effective power on the BER,the greater the effective power,and the greater the effect of the change of the number of users on the BER.When the effective power is small,the thermal noise is the main reason that affects the system error performance.When the effective power is large,the main reason that affects the system error performance is PIIN.