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随着通信的飞速发展,高速数据、高质量图象等宽带业务的需求也日趋迫切。在市场的推动下,加速了宽带综合业务数字网的开发和应用进程。在当前的通信网中交换局和用户终端之间通常采用Z接口,它们之间以模拟用户线连接。随着光纤和数字用户系统的引入,Z接口已满足不了广大用户对新业务的要求。此外,数字业务的发展要求交换局至用户终端设备之间实现透明的数字连接,要求用户接口数字化。因此,用户线这一部分已逐渐成为整个电信网发展的瓶颈。用户线的成本要占整个电信网成本的30％～50％,因此接入网技术越
With the rapid development of communication, the demand for broadband services such as high-speed data and high-quality images is also becoming more and more urgent. Driven by the market, the development and application of broadband integrated services digital network has been accelerated. In the current communication network, the Z interface is usually used between the exchange and the user terminal, and they are connected by analog subscriber lines. With the introduction of optical fiber and digital subscriber systems, the Z-interface has not met the needs of new subscribers. In addition, the development of digital services requires a transparent digital connection between the exchange and the user terminal device, requiring the user interface to be digitized. Therefore, this part of subscriber line has gradually become the bottleneck of the development of the entire telecommunications network. The cost of the subscriber line accounts for 30% to 50% of the cost of the entire telecommunications network, so the access network technology