The Inline Closure is an important supporting device in the optical transmission system. It is mainly used for optical fiber fusion, optical connector installation, optical path connection, redundant pigtail storage and optical cable protection for optical cable terminals. Safe operation and flexible use play an important role. In the past 10 years, the optical cable used in the construction of optical communication is usually several cores to several tens of cores, and the capacity of inline closures is generally less than 100 cores. It shows the shortcomings of pigtail storage capacity, inconvenient connection and connection, less function, simple structure, etc. Now optical communication has been widely used in long-distance trunk and local network relay transmission, and fiber opticization has become an access network. Development direction. In the construction of new optical fiber networks, large-core optical cables are used as much as possible, which puts higher requirements on the capacity, function and structure of inline closures. Inline closure features: In recent years, in the actual work of optical communication construction, through the comparison of the use of several products, we believe that the selection of Inline closures should focus on the following aspects. 1. Core capacity A inline closure should be able to complete the maximum number of core cables in the office. When possible, several cables that are connected to each other can be placed in one rack to facilitate the deployment of the optical path. At the same time, the capacity of the terminal box should be The universal optical cable core series corresponds to each other, so that when used, it can reduce or avoid the waste of the optical fiber terminal box due to improper matching. 2. Function type: The inline closure as the terminal equipment of the optical cable line should have four basic functions: Fixed function After the optical cable enters the rack, the outer sheath and the reinforcing core are mechanically fixed, the grounding protection components are installed, the end protection is processed, and the optical fibers are grouped and protected. Capacitor function After the fiber drawn from the cable is spliced to the tail cable, the excess fiber is coiled and protected, and the fusion joint is protected. Dispensing function: Plug the connector attached to the tail cable to the adapter, and optically connect with the optical connector on the other side of the adapter. The adapter and connector should be able to be flexibly inserted and removed; the optical path can be freely deployed and tested. Storage function: Provide storage for various cross-connected optical connecting lines between racks, so that they can be placed neatly and neatly. There should be proper space and way in the inline closure, so that the optical connecting lines are clear and easy to adjust. And can meet the minimum bending radius requirements.