Fiber optic connectors are indispensable passive devices in fiber optic communication systems. Most fiber optic connectors consist of three parts: two mating plugs (ferrules) and a coupling sleeve. The two ferrules are installed into the tail ends of the two optical fibers; the coupling sleeve plays an alignment role, and the sleeve is mostly equipped with metal or non-metallic flanges to facilitate the installation and fixation of the connector.
The quality of the ferrule directly affects the precise center docking of the two optical fibers. The ferrules are made of ceramic, metal, or plastic. Among them, ceramic ferrules are widely used. They are usually made of high-purity Zirconia ceramic materials, with good thermal stability, high hardness, high melting point, wear resistance, and high processing accuracy. Its manufacturing requirements are very high, and parameters such as dimensional accuracy, roundness, and surface roughness need to meet the standards to ensure the performance and reliability of fiber optic connectors. Ceramic ferrules are widely used in communications, energy, transportation, aerospace, and other fields.
Ceramic ferrule process
The ceramic ferrule blank contains a small hole of 0.1mm, and the concentricity requirement is very high, which can only be achieved through the technology of ceramic powder injection molding. The ceramic ferrule manufacturing process is divided into two parts, namely blank manufacturing and precision machining. First, the specially treated yttrium-stabilized nano-zirconia powder raw material is granulated and then injection molded in a special mold, and then sintered into a blank at high temperature. The second part is to process the blank through a series of precision grinding to achieve sub-micron processing accuracy and to obtain a ceramic ferrule product with good rigidity and high precision.
The premise of precision ceramic ferrule production operation is the matching use of precision ceramic ferrule mold and ceramic ferrule core needle (PIN needle). The manufacturing of optical fiber ceramic ferrules uses the following advanced process technologies:
1. Nano-zirconia powder injection molding material formula and molding process technology;
2. Slender micro-hole forming technology with an inner hole diameter of 0.125mm and a length of 12-15mm;
3. Precision ceramic processing technology with an accuracy of 0.1μm;
4. Process control method for sub-micronization of sintered grains;
5. Low-loss optical communication components with insertion loss ≤0.2dB and return loss ≥40dB
Ferrule end face
To make the end faces of the two optical fibers contact better, the ferrule end faces are usually ground into different structures, and different ferrule end faces affect the loss performance of the connector. PC, APC, and UPC represent the front face structure of the ceramic ferrule.
PC is Physical Contact. PC is micro-spherical grinding and polishing. The surface of the ferrule is ground into a slightly spherical surface. The fiber core is located at the highest point of the bend so that the two fiber end faces are in physical contact;
APC (Angled Physical Contact) is called bevel physical contact. The fiber end face is usually ground into an 8° bevel. The 8° angle bevel makes the fiber end face tighter and reflects the light to the cladding through its bevel angle instead of returning directly to the light source, providing better connection performance.
UPC (Ultra Physical Contact), ultra-physical end face. UPC is based on PC and optimizes the end face polishing and surface finish. The end face looks more dome-shaped. Connector connection requires the same end-face structure. For example, if APC and UPC cannot be combined, otherwise, the connector performance will be reduced.
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