鉴于目前普遍选用的水下弱湍流模型无法准确拟合实测数据的缺陷，选取经实验测试验证的广义Gamma分布来表征海洋弱湍流，以期合理评估受湍流等因素影响的水下无线光通信系统的误码性能。提出一种包含广义Gamma分布弱湍流、零/非零视轴指向误差以及无衰落信道冲激响应隐路径损耗和多径效应的混合衰落信道模型，据此推导混合衰落串行中继无线光通信系统平均误码率的数学闭型表达；通过数值仿真验证所推导的误码率理论表达式的准确性，并考察不同系统核心参数对误码率的影响。研究结果表明：串行中继节点的引入可有效提高系统的误码性能，以零视轴指向误差、最终传输距离达45 m、误码率需求10^-3为例，引入1至3个串行中继节点后，系统从一开始的无法工作，变为所需的发射功率分别降低至24 dBm、12 dBm和6 dBm；而光源初始发散角增大导致的无衰落信道冲激响应时延扩展，即符号间干扰，则会严重降低此性能改善。

The channel fading generated by seawater absorption and scattering, oceanic turbulence, and pointing error will severely reduce the communication quality of an Underwater Wireless Optical Communication (UWOC) system. Many scholars directly transplanted the weak atmospheric turbulence model to depict the oceanic turbulence statistics, and this had been proven to be incorrect by a series of laboratory measurements and associated data-fitting tests. So, it is obviously of great significance to study and evaluate the effects of a composite fading channel on the key performance of the UWOC system, especially with a proper weak oceanic turbulence model.In this paper, the Generalized Gamma Distribution (GGD) verified by a series of experimental tests was selected to characterize the weak oceanic turbulence. Then, a new hybrid fading channel model was proposed to more reasonably simulate the communication environment in the ocean, which had integrated the GGD weak turbulence, the zero/nonzero boresight pointing error, the implicit path loss and multipath propagation effect characterized by Fading Free Impulse Response (FFIR). Next, the mathematical expressions of the Probability Density Function (PDF) considering GGD weak turbulence and zero/nonzero boresight pointing errors were derived using higher transcendental Meijer-G and Whittaker functions. Subsequently, based on this, the closed-form expressions of the average Bit Error Rate (BER) were derived for the serial-relayed UWOC systems with both zero and nonzero boresight pointing errors, respectively. Finally, the accuracy and rationality of the derived closed-form formulas for the average bit error rate of the relaying UWOC system derived above were verified by some Monte Carlo numerical simulations; meanwhile, the influences of different key parameters on the system BERs were also investigated.The results show that the introduction of serial relaying nodes can effectively improve the end-to-end BER performance of the UWOC systems in a long-distance communication environment. With the increase of the relaying nodes number, the system's BER decreases rapidly at the same transmission power, indicating that the serial-relayed scheme dramatically improves the performance. For instance, if the end-to-end distance is fixed as 45 m and the target BER is set to be 10^-3, under the zero boresight pointing error condition, the required node transmission power will be reduced to 24 dBm, 12 dBm, and 6 dBm, respectively, when the relaying node number is assumed to be 1 to 3 individually. Similar to the working situation of zero boresight pointing error, when there is a non-zero boresight pointing error, the serial relaying node still effectively improves the system's BER performance. Unfortunately, the delayed spread expansion of the FFIR caused by the increase of the initial divergence angle of light source, that is, the so-called Inter-symbol Interference (ISI), will seriously degrade this performance improvement. For example, when the initial divergence angle is increased from 0.01° to 3°, the transmission power needs to be increased in general by about 10~15 dBm to obtain the same BER compared with the original transmission one. In addition, the jitter standard deviation and the initial boresight displacement associated with the pointing error will also significantly impact the BER performance of the relaying UWOC systems. For instance, if the jitter standard deviation is enhanced from 10 cm to 20 cm, the node transmission power needs to be increased by nearly 20~25 dBm to achieve the same BER value; meanwhile, when the initial boresight displacement increases from 5 cm to 10 cm, the transmission power needs to be added by about 5 dBm to reach the same BER target. Therefore, when one considers the BER evaluation of the serial-relayed UWOC systems, it is necessary to consider the impacts of the initial divergence angle, the jitter standard deviation, and the initial boresight displacement on performance thoroughly.The analytical results of this paper can provide calculation support for analyzing the BER performance of the relaying UWOC systems.