1. 3D test: guarantee of high quality connector end face
3D test is the key test to ensure the performance of optical fiber connector. When producing optical fiber jumper assembly, Yingda Photonic will use 3D interferometer (an optical interferometry instrument) to check the end face of optical fiber connector and strictly control the size of connector end face. The 3D test mainly measures the radius of curvature, vertex offset and fiber height. Details are as follows:
1.1 radius of curvature
The radius of curvature refers to the radius from the insert axis to the end face, as shown in the figure below, that is, the curve radius of the ferrule end face. The curvature radius of the end face of high-quality optical fiber jumper connector shall be controlled within a certain range. If the radius of curvature is too small, it will exert greater pressure on the optical fiber, while if the radius of curvature is too large, it will not exert pressure on the optical fiber, resulting in an air gap (i.e. air gap) between the connector and the end face of the optical fiber. Whether the radius of curvature is too large or too small, it will lead to insufficient light scattering or physical contact, which can not ensure the best transmission performance. Only the appropriate radius of curvature can ensure the correct pressure and the best transmission performance.
Pic.1：3DTest radius of curvature
1.2 vertex offset
Vertex offset refers to the distance from the highest point of the core inserting end face curve after grinding and polishing to the axis of the optical fiber core. This is a key item in the polishing process, and inaccurate polishing will lead to vertex offset.
Pic. 2：3D Test vertex offset
In the technical standard, the vertex offset of optical fiber jumper is generally required to be ≤ 50 μ m。 If the top offset is large, an air gap will be formed, resulting in high insertion loss (IL) and return loss (RL) of the optical fiber jumper. Ideally, the vertex offset of PC and UPC optical fiber connectors is almost zero, because during polishing, the ferrule end face is perpendicular to the polished surface, and the vertex coincides with the fiber core axis. However, for APC optical fiber connector, its end face is at an included angle of 8 degrees with the optical fiber axis, which is not completely vertical.
1.3 Fiber height
The fiber height is the distance from the fiber end face to the core inserting section, that is, the extension height from the fiber core to the ferrule end face. Similarly, the fiber height cannot be too low or too high. If the optical fiber height is too high, the pressure in the optical fiber will be increased when docking two optical fiber connectors, thus damaging the optical fiber; If the fiber height is too low, there will be a gap when docking two fiber connectors, resulting in increased insertion loss. This must be avoided for transmission with strict requirements on insertion loss.
Pic. 3：3D test fiber height
Different polishing methods and types of optical fiber jumpers use 3D interferometer to test different values, but the tested optical fiber jumpers shall meet or exceed the end face geometric dimension standards recognized by the industry. The following table is the geometric dimension requirements of MTP single-mode optical fiber connector end face based on IEC / PAS 61755-3-31 and IEC / PAS 61755-3-32.
|Ferrule x angle (SX)||-0.2~0.2°（PC和APC）|
|Ferrule Y angle（SY）||±0.2°|
|Ferrule X radius（RX）||≥2000mm|
|Ferrule Y radius（RY）||≥5mm|
|Fiber radius of curvature（RF）||≥1mm|
|Maximum fiber height difference（HA）||500nm|
|Maximum adjacent height difference（HB）||300nm|
|Core inclination||-100nm~+ 200nm|
Table 1: Fiber radius of curvature (RF)
2. IL and RL tests: key tests for optical deployment
Insertion loss (IL) refers to the loss of signal power due to the insertion of a device somewhere in the transmission system. Return loss (RL) is the power loss caused by the reflection of some signals back to the signal source during transmission due to the discontinuity of the transmission link.
Whether in the manufacturing process or installation process, the test of insertion loss and return loss is very important. There are also clear specifications in the world. For example, the TIA standard specifies that the maximum insertion loss of optical fiber jumper is 0.75db (that is, the maximum acceptable value). For most optical fiber jumpers on the market, the normal insertion loss ranges from 0.3dB to 0.5dB, and some low insertion loss ranges from 0.15dB to 0.2db. If the customer does not specify the instructions, the jumpers produced by Yingda company are all below 0.3dB. All jumpers are tested by plug-in loss test instruments. After passing the test, subsequent packaging, labeling and other processes can be carried out.
The end user can test the echo insertion loss by using optical power meter, optical time domain reflectometer (OTDR) and optical frequency domain reflectometer (OFDR).
3. End face test: ensure the cleanliness and smoothness of the end face
The so-called optical fiber cleaning actually refers to the cleaning of the end face of the optical fiber connector. In the production process of Inda, the optical fiber end face detector will be used for end face inspection to confirm whether there are pollutants, scratches or cracks on the end face of the optical fiber connector. For optical fiber engineers, optical fiber cleaning tools (such as optical fiber cleaning pen, cassette cleaning box, etc.) are usually used to clean the end face of optical fiber during wiring to ensure no pollution.
Why should the end face test be carried out? Because having a good end face of optical fiber connector is the basic condition to ensure high-quality optical fiber connection. If there are pollutants (such as dust) or scratches or even deformation on the end face of the optical fiber connector, the return loss will be increased, and even the optical fiber connector may be permanently damaged, resulting in failure to use. In addition, the dust between the end faces will scratch the surface, resulting in the misalignment of the air gap or fiber core, thus reducing the transmission quality of the optical signal. Since these contaminants cannot be identified with the naked eye, if the end face is not tested and cleaned, it will pollute the socket connected to it. Therefore, even if our company has tested and cleaned the end face of the optical fiber connector before shipment, it is necessary to clean the end face before and after inserting and pulling out the optical fiber connector. At the same time, if it will not be used again temporarily, it is necessary to cover its end face with a dust cap.
Finally, If the fiber optic patch cord cable passes the above four tests and the test results meet the standards, they will help achieve high-quality optical signal transmission. Patch cables produced by Yingda are generally equipped with neutral English labels to display the test parameter values, so as to ensure that each product can meet the requirements of customers and international standards. If there are other special needs, they can be put forward separately. Welcome to inquiry us SALES DEPT. at email@example.com, Tel: +86 18688982406.
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