Research on Technology and Standard of Fiber Optic Fast Connector

In the past two years, with the development of the communications industry and the implementation of national policies, China's FTTH has seen rapid development from its initial pilot project to its current scale deployment.

Optical fiber connection is an important part of the FTTH construction, and its project volume has doubled. At the same time, the extension of the FTTH construction connection point to the interior has also brought about a substantial increase in the difficulty of work. There are two increases here: one is the increase in volume, and the other is the increase in difficulty. This makes the traditional hot-melt connection method unable to adapt to the current FTTH terminal connection work. It is imperative to choose a quicker and more convenient alternative to hot melt. The quick connector has such advantages that the use of quick connectors is currently revolutionizing the current optical fiber connection work.

For the current FTTH construction terminal connection, thermal fusion has some limitations: 1. The fusion splicer needs to operate the platform, space is limited; 2. The fusion splicer is expensive and the construction cost is high; 3. The active construction, battery life Limited; 4, hot melt equipment, large volume, inconvenient to carry; 5, for FTTH terminal more scattered and contiguous long time.

Advantages of the quick connector: 1, simple operation, optical fiber stripping only once, construction speed; 2, no special requirements for the operating environment; 3, passive construction; 4, simple tools, easy to carry.

Rapid connector for its characteristics, the main application of the current two categories: one is the distribution of fiber optic cable and home leather cable cable connection point (fiber distribution box); the other is the user's home access point, mainly optical information The end of the panel is terminated with a fiber optic cable, and the cable is terminated in the multimedia box to connect directly to the home terminal ONU.

Quick connector classification and analysis currently include domestic and foreign domestic manufacturers of quick connectors, and their structures and materials also have their own characteristics. Structural classification: mechanical connection and hot-melt two major categories. Mechanical connection is divided into: straight type and embedded type. Straight-through type: Optical fiber cable is stripped, cut directly from the tail end to the top of the connector, there is no connection point inside the connector; embedded type: the connector ferrule embedded in a section of optical fiber, optical fiber cable stripping, cutting and embedded fiber The internal v connector of the connector is docked, and the V container is filled with a matching liquid.

Straight-through structure disadvantages:

First, the cutting end face is highly dependent; because the through-type structure is to directly pass the fiber from the tail of the connector to the top of the connector, this means that the fiber cutting end face is the end face of the connector. If the fiber is not cut flat, it will definitely affect The connector performance index, especially the return loss, is even more insecure. Traditional pigtails and jumpers are ground during production to ensure their echo specifications. The end faces are differentiated according to different ferrules and grinding processes. , divided into PC, UPC, APC, and direct-through structure is only hand-cut end face, and no grinding, let alone PC, UPC, APC, if you want to ensure quality, can only rely on the cutting level of the operator, so the required operation Personnel have strong optical fiber construction capabilities and experience. Second, the ceramic ferrule and fiber diameter matching requirements are strict; the same is also due to the straight-through structure is the fiber from the connector directly to the top of the connector, which requires the ceramic ferrule inner diameter is greater than or equal to the fiber diameter, otherwise Can't wear it. However, it cannot be too large. Too much of it causes the optical fiber to sway in the ceramic ferrule, resulting in an eccentric core. This affects the connector performance. Thirdly, strict requirements are placed on the cutting length and the strength of the clamp; if the fiber is left long or short when cut, it will lead to large attenuation when the fiber passes through the head or not. In addition, even if the length is in place, the strength of the clamps for fixing the rear optical fiber cable is also very high; because of the construction and the user's pull during use, and with the increase of the service life, the deformation of the material may cause the optical fiber cable and connection. Relative displacement of the device occurs. Experiments have shown that in the case of projections or recesses exceeding 50 nm, the connector loss becomes large. Of course, the through-type structure also has its advantages, that is, the structure of the connector itself is simple, and the factory production is relatively easy, so the cost is low.

Pre-embedded fiber structure advantages:

1. The ceramic fiber ferrule is embedded in the top of the fiber and the return loss is ensured; 2. The matching liquid is filled in the internal docking station, but it does not depend on the fiber end face cutting; 3. The pre-set optical fiber is cured by the glue injection and no shaking will occur. And eccentricity;

Of course, he also has his shortcomings, that is, difficult to handle after fiber cut.

At present, most manufacturers use pre-embedded fiber structures, and only a few use straight-through models.

Hot melt type quick connector, here is a comparison with hot melt:

Heat fusion welding into the end, as shown in Figure 3 below, in fact, is the fiber optic cable and pigtails were peeled off after the heat fusion butt fusion welding machine, docking after the need to use the welding disk for fixed protection;

The hot-melt type quick connector, as shown in Figure 4 below, is actually an optical fiber fusion splicer, but the splicing point is inside the connector's tail end. This is equivalent to the fact that the hot-melt splicer pigtail cable is omitted. The advantage of this is that it is spliced. After good, no extra protection is needed.

However, in terms of its operation, the use of a fusion splicer is the same, as is active hot-melt, and in fact there is no difference in nature from ordinary hot-melt. The disadvantages of heat welding, it also exists, so this type of approach has not been widely used.

Material classification: plastics and metals, here mainly refers to the V-groove material, other parts of the material are basically the same;

The V-slot is actually the core part of the quick connector, so the choice of its material is related to the entire quick connector. For now, there are two kinds of commercial products in the market, one is metal and the other is plastic; there is also a type of glass V-groove, but such materials are still under research and development.

In terms of performance, the metal V-groove performs slightly better than the plastic in terms of average loss. This is mainly because the plastic V-groove is restricted by the accuracy of the grinding tool. The quality of the V-groove formed by injection is uneven, which requires the manufacturer to spend Time to pick and identify. But the price, the metal V tank to engage in some, one is the material itself is more expensive than the plastic, on the other hand its processing is more difficult than plastic, with high temperature resistant to low temperature, corrosion resistance, metal V tank selection and coating Processing is very critical; due to the gradual maturity of PLC planar optical waveguide technology, some manufacturers in the industry are already using fiber array V-groove technology to research and develop glass V-grooves to make quick connectors. The stability of quartz glass is particularly strong in terms of environmental resistance and corrosion resistance compared with plastics and metals. Therefore, the quick connector for V-grooves is worth looking forward to. Currently, due to the huge market demand for quick connectors, there are a large number of quick connector manufacturers in foreign countries and countries. In order to compete for the market, the industry has now formed a bad trend of low-price competition and vicious competition. In order to reduce costs and even purchase low-quality inferior raw materials for individual manufacturers, the overall quality of quick connector products on the market is reduced. Therefore, when selecting a quick connector product, the focus should be on its quality and ease of operation, rather than blindly pursuing prices. Here I give an example: For the embedded fiber optic quick connector, one of the important raw materials is the optical fiber matching liquid. The function of the matching liquid is to compensate for the tiny gaps caused by the unevenness of the end face during the optical fiber docking, so that the optical signal can be refracted smoothly. The qualified matching liquid has very strict requirements on the accuracy of its refractive index, and has good oxidation resistance and is extremely difficult to volatilize. There is a misunderstanding here: Many people think that the matching liquid matches the liquid and the liquid is always volatile. In fact, the main components of the matching liquid are silicon-based compounds and quartz microparticles, which are difficult to evaporate. High-quality matching liquids are also expensive, but if there are individual manufacturers to reduce costs, the use of inferior matching liquids will inevitably lead to a reduction in the quality of the quick connectors and a significant reduction in the service life. Therefore, the use of good structure and good materials is important for the quality of quick connectors.