Passive devices is an important part of the fiber-optic communications equipment. It is an optical component, the process to comply with the basic principles of law and the theory of electromagnetic wave theory of light and optics, the technical indicators, a variety of formulas and a variety of testing methods, fiber optics, integrated optics are closely related; so it is with electricity passive components are essentially different. In the optical fiber cable, which serves as a connection, allocation, isolation, filtering and so on. In fact there are many passive devices, limited space, here only about several common - optical splitter, optical attenuator, optical isolators, connectors, jumpers, optical switch.

  Fiber optic connectors are passive optical components to achieve an active connection between the optical fiber, it also has the fiber and active devices, optical fiber and other passive components, fiber optic systems and instrumentation and functional connections. Events connector with the development of optical communication and development, now has formed a wide range, wide variety of systems products, is the fiber optic applications indispensable, the most widely used basic component.

  Common types of optical passive devices and principle

  Although the optical fiber (cable) connectors that vary in structure, the species diversity, but its function can be divided into the following parts: a connector plug, fiber jumpers, converters, inverters and the like. These components may be used alone as the device to be used together to become component. In fact, the last active connector is used to refer two connector plug plus a converter.

(1) connector plug.
  Optical fiber components to complete the swap function converter or converter called plug connector pin plug from the body and the number of external mechanical structure parts. Two plug after insertion converter or converter can achieve docking optical fiber (cable) between; connector mechanical structure for effective protection of the optical fiber. Pin is a precision cylinder with micropores, and its main dimensions are as follows:
An outer diameter
Ф2.499 ± 0.0005mm
Outside diameter roundness
<0.0005mm
Pore diameter
Ф126 ± 0.5μm
Microporous eccentric amount
<1μm
Pore depth
4mm or 10mm
Pin outer cylinder finish
▽ 14
The radius of curvature of the end face
20-60mm
  Pin materials are stainless steel, all-ceramic, glass and some plastics. Now the market is the most used ceramics, ceramic material has excellent temperature stability, wear resistance and corrosion resistance, but the price is also more expensive. Plastic plugs are cheap, but not durable. The market also has more plug in plastic posing ceramics, engineers at the time of purchase, please pay attention to recognize.

  Pins and fiber combined to become the pin body. Pins making body is inserted into the pores of the fiber good option, after using glue, reprocessing its end face, a large radius of curvature of the end face of the plug reflection loss impact, generally smaller radius of curvature, the greater the reflection loss. Plug its end face shape can be divided into three categories: PC type, SPC type, APC type. PC plug maximum radius of curvature of the end face, almost planar contact, minimum reflection loss; radius of curvature of the end face of the SPC type plug is 20mm, up to 45dB return loss, insertion loss can be less than 0.2dB; reflection loss is highest APC type, it in addition to using spherical contact, but also beveled face processing, so that the reflected light reflected fiber, avoid light reflected back to the transmitter. Incline plane the greater the reflection loss, the insertion loss increases, generally the angle is 8 ° ± 0.2 °, the insertion loss of about 0.2dB In this case, the reflection loss of up to 60dB, all CATV systems optical fiber connector end faces are APC type. To ensure the quality of the pin body, the geometry of the fiber must meet the following requirements: a pore diameter smaller than the outer diameter of the fiber 0.0005mm; misalignment of the fiber core is less than 0.0005mm. Thus, both the pin and fiber as well as optional Quality of connector plug on the great, good or bad is the key to the quality of the connector plug. Level of technology products from different manufacturers are not the same, so the difference is great, in practice, I have repeatedly encountered a plug insertion loss of 1dB or more, but less than the normal general 0.3dB. In engineering applications, do not underestimate a small plug, plug the impact of poor quality and the system is great; in the purchase be sure to use a high reputation, well-known manufacturers.

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