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随着相位编解码器关键技术的突破,精确分析相位编码光码分多址(OCDMA)系统误码率性能显得十分必要。本文研究了相干光码分多址系统中拍频噪声、多址干扰、散粒噪声和热噪声对系统性能的影响。在充分考虑了干扰信号输入光偏振影响的情况下.根据系统噪声和干扰的矩母函数,采用高斯近似的方法得到误码率的计算公式,并比较了多址干扰和拍频噪声对系统性能的影响。当所有干扰用户与目标用户平行时得到误码率上界;当所有干扰用户与目标用户垂直时得到误码率下界;干扰用户随机偏振时的误码率介于两者之间。结果表明:拍频噪声是影响相干OCDMA系统性能的主要因素;随着接收光功率的增加,干扰信号偏振对系统误码率的影响趋于明显。当系统误码率小于10~(-10)时,误码率随用户数目的增加迅速增加;当误码率大于10~(-10)时,误码率随用户数目的变化缓慢。
With the breakthrough of the key technologies of phase codec, it is very necessary to accurately analyze the bit error rate performance of OCDMA system. In this paper, the effects of beat frequency noise, multiple access interference, shot noise and thermal noise on the system performance are studied in coherent optical code division multiple access system. Considering the influence of the polarization of the input signal of the interfering signal, the calculation formula of the bit error rate (BER) is obtained by using the Gaussian approximation of the system noise and interference matrix. The performance of the system against multiple access interference and beat frequency noise Impact. When all interfering users are parallel to the target user, the error rate upper bound is obtained; when all interfering users are perpendicular to the target user, the lower bound of the error rate is obtained; and the error rate of interfering users with random polarization is in between. The results show that beat frequency noise is the main factor affecting the performance of the coherent OCDMA system. With the increase of the received optical power, the influence of the polarization of the interfering signal on the system BER tends to be obvious. When the system error rate is less than 10 ~ (-10), the bit error rate increases rapidly with the increase of the number of users. When the error rate is more than 10 ~ (-10), the bit error rate changes slowly with the number of users.