What is Pre-connected ODN?

1 Introduction

In ODN, from the service aggregation point to the user is generally divided into backbone, distribution, introduction, home multiple segments. The construction of the introduction section of the traditional ODN cable involves a large number of fiber core splices. In the user installation, the home section of the butterfly-shaped cable ends also need to be end-to-end splicing. Cable splicing on the construction and installation and maintenance of personnel with high technical requirements, on-site construction and operation is also more time-consuming, so that there is no need for on-site core splicing pre-connection ODN technology came into being.

2 The main problems faced by traditional ODN in construction and maintenance

2.1 High failure rate of active connection

ODN in the cross-connect box and splitter box are used in the movable connection. Due to the installation and maintenance process need to often open and close the handover box and splitter box door, installation and maintenance personnel will find it very inconvenient, intentionally or unintentionally, the handover box and the splitter box door has become a normally open state, as shown in Figure 1. Over time, affected by the environment, the box within the optical splitter, pigtail and other devices are easily aging, the connector end face is also susceptible to contamination, resulting in connection failures.

2.2 Low construction and maintenance efficiency

In the construction of the introduction section of traditional ODN fiber optic cable, almost every fiber optic splitter box involves fiber fusion splicing, as shown in Figure 2. Cable placement, fiber fusion splicing, splitter box installation and other work can only be carried out step by step, can not be constructed in parallel, which also leads to the introduction of cable construction cycle is relatively long. In the broadband users put installed, because the home cable deployment is completed at both ends need to be fused to a section of pigtail fiber into the end, which also increases the length of time required for the user to put installed.

2.3 High technical requirements for construction and installation and maintenance

Fiber splicing must be equipped with fusion splicing machine, the operator also requires certain skills, so the construction of traditional ODN, broadband subscribers, installation and maintenance of the technical requirements of the relevant personnel are relatively high.

3 Pre-connected ODN technology used

In order to solve the above problems faced by traditional ODN in construction and maintenance, pre-connection ODN adopts the following technologies.

3.1 Pre-connection Technology

Pre-connection refers to the two ends of the fiber optic cable in the factory prefabricated movable connectors to become prefabricated cable, in the wiring equipment (handover box, splitter box) and fiber optic cable connections are also prefabricated movable connectors to become pre-connected wiring equipment, so that in the ODN construction and installation and maintenance of ODN fiber optic link connection without fusion splicing, only through the movable connection can be completed.

For example, Figure 4 for the home section of the prefabricated cable, the A end of the cable for the SC/APC waterproof connector, can be directly connected with the pre-connectivity splitter box user port (equivalent to the ordinary splitter box in the optical splitter output port) for the activity of the connection, as shown in Figure 5; the B end of the cable for the ordinary SC-type connector, can be directly connected to the ONT. In this way, home wide users put installed, the home section of the cable can be assembled only on-site to complete the connection of the optical cable link, without the need for on-site welding.

3.2 Unequalized optical splitting

Traditional ODN adopts unequal score optical, the introduction section has many cable models, complex fiber core distribution relationship, and a large number of fiber core splices, which is not suitable for pre-connection. when ODN adopts unequal score optical, the introduction cable can be a single-core optical cable, with fewer cable models and simple fiber core connection relationship, so unequal score optical is usually adopted for pre-connection ODN.

3.3 Fully sealed protection measures

The box of the pre-connecting optical intersection and the box of the pre-connecting splitter box adopt the sealing structure, which seals the fused fiber unit and optical splitter in the box/box, avoiding the influence of the surrounding environment and personnel's accidental touch on the optical splitter and the connected optical fiber. At the same time, the downlink interface of the pre-connected optical intersection and the uplink/downlink interface of the pre-connected splitter box are set outside the box/cabinet, and the interface adopts the type adapted to the prefabricated cables, so as to facilitate the connection with the prefabricated cables.

The SC/APC waterproof connector is adopted for the movable connection used in outdoor, underground and other environments where waterproof and dustproof are required, and the connector is fully sealed before and after connection, which avoids the influence of ultraviolet rays, water vapor, dust and other influences on the quality of the movable connection. The factory value of insertion loss of common single-core movable connector is generally not more than 0.25dB/pcs. In traditional communication line engineering, considering the long-term influence of environment on the quality of movable connection, the attenuation standard of common single-core movable connection is 0.5dB/pcs. Pre-connected ODN activity connection due to the use of full sealing protection measures, insertion loss generally does not exceed 0.3dB/pcs.

4 Conclusion

Pre-connection technology is mainly applicable to the introduction of ODN section and home section, trunk section, distribution section due to the cable core number is relatively large, and is not suitable for the use of pre-connection. There are also manufacturers to provide 12-core pre-connected fiber optic cable user wiring section, limited to space, this paper will not be introduced. Pre-connection technology to enhance the construction and installation and maintenance efficiency, reduce the activity of the connection failure, but pre-connection technology also has many shortcomings, for example: the attenuation of the activity of the connection to be higher than the fusion bonding more than one times, pre-connection of the length of the optical cable segment specification is difficult to adapt to the actual scene, etc., so the pre-connection technology needs to be further explored applicable scenarios.