Introduction to the performance of fiber optic connectors
Fiber optic connector is a kind of devices which are necessary to connect various devices in the optical fiber communication system, and are also the most used fiber devices. Due to the gradual fiber-optic of local communication network, the demand of metropolitan area Network and user access networks has increased, the total demand of the global fiber optic connector market has been expanding in recent years, and the annual growth rate is expected to be around 20% in the next ten years.
Although there are more than 70 kinds of optical connectors worldwide, and new varieties are still emerging, but the market (especially the Chinese market), its mainstream varieties are still in the early years have been followed down by the diameter of φ2.5mm precision ceramic core and ceramic tube connectors (such as FC, SC, St, etc.). In addition, the φ1.25mm ceramic core small connectors (such as LC, MU, etc.), as well as ribbon fiber connectors, mainly multi-core connectors (such as MTP, etc.) the demand is also gradually increased.
In general, the main optical properties measuring the quality of fiber connector products are insertion loss (insert loss) and return loss (return loss). In addition, the impact of product quality reliability of the core geometry parameters such as the physical characteristics of the index is also increasingly valued by the system manufacturers or high-end customers. The following is a brief introduction to the insertion and return loss of connectors based on the working principle of the optical fiber connector:
The fiber optic connector cannot be used alone, it must be matched with other connectors of the same type, in order to form the connection of optical pathway, at present, the more popular optical fiber connector assembly and docking mode: the use of epoxy resin heat curing agent, fiber bonding in high-precision ceramic insert pinhole, and then the two-pin in the role of external forces, Through the positioning of the adapter sleeve, the docking of the optical fiber is realized (figure I).
It can be seen from figure one that the key to ensure the connector's excellent connection quality is to make a straight line when the two light cores are contacted, which depends mainly on the physical properties of the optical fiber itself and the manufacturing precision of the connector pins, as well as the assembly machining accuracy of the connectors. At the same time, optical properties of optical fiber and the polishing quality of pin end face have a direct effect on the optical performance and reliability of the connectors.
Insertion loss refers to the optical power attenuation caused by the connecting connector to the system (i.e. the relative reduction of the output power of the optical connector relative to the input power). The insertion loss is mainly caused by the transverse deviation between the two optical fibers in the phase continuation.
As shown in figure one, if the two fibers are aligned in a straight line and the transverse deviation is zero, the insertion loss is minimal. But in the actual docking process of the connector, this is unlikely to be achieved, because the fiber core and fiber cladding of different hearts, fiber cladding and inserting pin inner hole of the different heart and the internal diameter of the needle pin and the concentricity error, will cause the transverse deviation between the fiber.