Fiber optic connector and things to know

Fiber optic connector and things to know

Fiber optic connection plays an important role in network performance. Increasing data transfer speeds will entail more stringent requirements for optical fiber loss. Customers always have demand for connectors with low attenuation, compact, easy to construct, use and especially low cost. Therefore, the standard and design house also offers a variety of options to meet the needs of different objects.
Common optical connectors today include SC (Subscriber Connector), ST (Straight Tip) and FC (Fiber Connector) standards. In addition, small-format-factor (LC) connectors are used to save space, especially for space-constrained environments. data center. MPO (Multi-Fiber Push-On) is also becoming popular, used in high density environments with up to 12 MPO connectors or more.
Each design has its own advantages and disadvantages, so when selecting the connector, it is important to consider important factors such as: application, data transfer speed, training requirements for construction workers on the type Fiber optic (singlemode fiber and multimode fiber require different connectors). This article will give you an overview of the features and features of common connector types, giving users the choice they need to optimize their network performance.
1. The role of the connector
The connector is used to connect two optical fibers together, allowing the light to pass from one fiber core to another, or connect the fiber to an optical fiber transmitter. In order to achieve a good connection with low attenuation, the two optical fiber cores must be in straight line contact and the optical connector surface must be thoroughly cleaned, dust and debris cleaned, or debris removed. scratched. Connecting straight to two multimode fiber cores (large core diameter) is easier than singlemode fiber. Singlemode connection requires more rigorous tolerance, the connector surface must be more carefully cared for. Any stains, scratches or defects on the fiber surface will directly affect the connection performance.
2. Construct a connector

One connector has the main components as shown in Figure 1. The front ferrule is designed to support the fiber cores in direct contact, limiting the connection loss. This ferrule is held by a collar assembly at the inside of the connector body, which pushes the ferrule forward to make good contact when connecting the two ends of the connector or connecting it to the device. . In addition, at the end of the optical connector usually has a component that increases the resistance against twisting and the load when pulling the cable. At the same time, the protective plastic end of the connector also helps to reduce bending when connecting the cable to the device, minimizing optical signal loss.
It is important to read the specification from the manufacturer and compare the application performance of the application. Also, consider factors such as the size or type of cable connected to select the appropriate product code.
3. Problems affect performance

For good connectivity, fiber optic cores need to be connected in a straight line and ensure surface quality. In the left corner of Figure 2, it can be seen that when two optical fibers are deflected, some light will leak out, causing loss of signal, reduced bandwidth and reduced transmission distance of light in the fiber.
The angle of the connector is also a case to be considered (in the upper right corner of Figure 2). Cross connectors can be avoided using a PCR (Physical Contact) surface ferrule. These ferrules are designed to keep the fiber in position when connected, while reducing the risk of gaping at the contact surface between the two ends.
Incorrect optical fiber opacity is also responsible for light loss. This error can be due to the connection of different fiber types or by different manufacturers. Due to the development and improvement of the technology of fiber optic cable manufacturers, different issues such as different core diameters, non-concentric core, epoxy core or different cladding layer diameters have disappeared. half.
4. Connect Surface Care
Surface connectivity plays a decisive role in optical fiber performance. After initial application, the grinding surfaces need to be smoothened to remove stains and defects. This process is usually done in the factory, but there are several types of connectors that need to be grinded in the field. This must be done on a soft pad and abrasive paper. The grinding technique is also very special with the eight figure motion, which perfectly grips the corners of the optical connector.
A common type of optical connection surface is UPC (Ultra Physical Contact), which provides high connectivity performance. APC (Angled Physical Contact) is also a common connector with a beveled surface of 8 degrees. The APC reduces light reflection at the contact surface, reducing the attenuation of the fiber optic cable. This type of connector is commonly used in telecommunications and television applications.
Temperature issues should also be considered. In harsh environments with a temperature of -40 ° C to 85 ° C, the fiber and the ferrule may be shifted, changing shape, resulting in reduced connection performance.
5. Performance Requirements
The ANSI / TIA-568-C.3 standard defines the performance of optical connectors used in structured cabling systems. Optical attenuation is the most important parameter used to measure performance and to be the yardstick of field test acceptance. Although the standard defining maximum limit for optical attenuation is 0.75 dB per pair of couplings (one coupler), but depending on the application, the owner may require more stringent parameters. Reflection, also known as Return Loss, is limited to a minimum of 20 dB with multimode fiber and 26 dB with singlemode fiber. To reduce the reflectance, use the APC connector surface type. The operating temperature range for optical connectors is also determined in the TIA 568-C standard, from -10 ° C to 60 ° C, which can withstand the humidity, impact and strain types caused by twisting. twisted and bent. To understand this requirement, refer to the manufacturer's documentation for product restrictions.

6. Select the optical connector
On the market today there are dozens of connectors, this article only focuses on common standards, but will also refer to connectors such as LC and MPO are being used as a trend in the specific environment. , high speed support and space saving.
ST is a twisted-pair connector that has been used for many years for intranet systems with applications that support 10Base-F and 100Base-F. At present, ST is no longer common but can be easily found in the millions of connections that have been installed on older networks. The ST connector uses a 2.5 mm ferrule with a conventional attenuation of 0.25 dB.

SC: is a connector that uses a plug / play method when connected. Easy to use and high performance, SC connectors are one of the most popular, in systems that run Gigabit Ethernet applications. SC connectors also use a 2.5 mm ferrule and a conventional attenuation of 0.25 dB.
LC is a compact size connector (SFF) half the size of a SC head, using a 1.25 mm ferrule, a conventional loss of 0.25 dB.
MPO is a high-density connector that holds multiple fiber connections at the same time. The connection method is still SC and LC. Each MPO connector can accommodate 4, 6, 12 to 24, 48 or even 60 optical fibers. Due to complexity and high accuracy requirements, this type of connector is currently only available by the manufacturer. Users are required to order at a given length of time and not be able to perform a field press.

7. Terminal connection method
Over the years, fiber optic technology has been developed. Manufacturers have developed a variety of fiber optic connectors. Choosing a terminal connection method usually depends on the skill of the worker, the tools available or simply the preferences. Some methods have different optical performance, while others are easier to use, saving time and labor.
There are four basic methods commonly used: abrasive grinding, heat welding (also known as arc welding), mechanical welding and pruning.
Optical tipping - this method has been in use since the 1980s, when optical fiber connectivity began to grow, and is still used due to its low attenuation, reliability and very competitive cost. This method has complex disadvantages and takes time to remove glues during construction. At the same time, the quality of the connector also depends on the skill of the construction workers, so they need to be trained and supervised.
Heat-welding using a pigtail that uses a high temperature of the machine to melt and seal the joint. The advantage of this method is that the connector has been pre-wired by the manufacturer, supporting connection with attenuation and low reflectivity. However, the downside is the high cost of equipment, the need for on-site power supplies to provide welding equipment, high requirements for training and skills training.
Mechanical welding - also uses pigtail fibers as heat welding but does not use welding equipment. This method involves cutting and stripping the fiber head with specialized tools, then holding them together by means of a component called a mechanical joint. This method is done quickly, using less tools, short training time. However, the high cost of materials, the attenuation greater than the heat-welding method is also a factor to consider.
Trim Light - Unlike previous models, the connector is pre-wired by the manufacturer but does not include a short fiber optic such as a pigtail. Workers only need to cut and cut the fiber using a dedicated tool and then insert it into the connector, using the appropriate headset to lock the fiber optic connector. Easy and fast operation, capable of performing in tight spaces, high position. The disadvantage of this method is that the cost of materials is higher, the higher attenuation is the heat dissipation and there is no reusability at the beginning of the defect.

8. Clean and take over
In the previous articles there were many articles that mentioned the importance of cleaning the optical connector, so this article will not cover in depth the cleaning methods, except to repeat the need to clean the surface. Connect properly with specialized tools and solutions. Dirt, debris or oil traces from the fingers of a person impose severe strain on the performance.
Once completed, the fiber optic network shall be tested and tested. The most common way is to measure optical attenuation using specialized meters. However, this method only gives the loss-of-fit parameter across the cable, and does not provide detailed attenuation on each connector. When the attenuation exceeds the allowable limit and the test results are not accepted, the operators will be confused as to where faults are occurring, especially with multiple articulated fiber optic cables. In this case, it is necessary to use the OTDR measuring device to determine the distance to the error point, determine the attenuation and quality of each coupling, thereby limiting the time required to unseal and replace the terminals in a useless manner.
Conclude
The fiber optic network is growing, pulling the optical connector technology has made great strides with many designs in the market. As the network moves in the direction of density and high application rates, the connector market will also move to smaller connector types such as LC or fiber optic integrated connectors such as MPO.
In order to meet the increasingly stringent limit of attenuation allowed for applications such as 40 GbE or 100 GbE, technicians must comply with the manufacturer's procedures including inspection and cleaning of all heads. Connect before making a connection. This approach will ensure the performance, quality and reliability of the fiber optic cabling system.