Optical fiber connector types and installation technology ov
TIME：2023-09-30
summarize
The optical fiber connector is a detachable connection between the optical fiber and the optical fiber, also known as the "live connector", which is the two end faces of the optical fiber precision docking, so that the output light energy of the transmitting optical fiber can be coupled to the receiving optical fiber to the maximum. Optical fiber connectors are the most used optical passive components in optical systems, widely used in communications, local area network (LAN), optical fiber to the home (FTTH), high-quality video transmission, optical fiber sensing, test instruments and so on.
Now has been widely used fiber optic connectors, its many types, different structures. However, the basic structure of various types of fiber optic connectors is consistent, that is, the vast majority of fiber optic connectors are generally composed of two pins and a coupling tube three parts (Figure 1).
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Figure 1 General structure of the optical fiber connector
Basic performance requirements of optical fiber connectors
Optical property
The optical performance requirements of fiber optic connectors include insertion loss, return loss, optical discontinuity, crosstalk, ambient light sensitivity, bandwidth (only refers to multi-mode), among which insertion loss and return loss are the two most basic parameters.
Interchangeability and repeatability
Optical fiber connector is a common passive component, for the same type of optical fiber connector, generally can be used in any combination, and can be repeated many times, resulting in additional loss is generally less than 0.2dB.
Mechanical property
The mechanical properties of optical fiber connectors include axial holding strength, end holding force, connection and separation force (moment), impact, torsion, cable holding force, extrusion resistance, external bending moment, vibration, impact, static load, etc., for various optical fiber connectors use different conditions, the focus of the requirements are different.
Mechanical durability refers to the number of insertion and removal of optical fiber connectors under normal use, and the optical fiber connectors currently used can generally be inserted and removed more than l000 times.
Environmental performance
The main environmental properties are: high temperature, temperature shock, moisture, sand and dust, ozone exposure, corrosion (salt spray), flammability, etc.
Some commonly used optical fiber connectors
St-compatible connector
The ST-compatible connector (Figure 2), first introduced in 1986, is a contact type medium-loss connector with a positioning key, but has no tensile or torsional construction. The installation of the ST-compatible connector adopts the rotary insertion method, which is easy and fast to install, but requires a large space on the panel.
Figure 2 ST-compatible connector
FC optical fiber connector
The FC optical fiber connector (Figure 3) was first developed by Japan's NTT company, using the rotary insertion method, requiring a large space on the panel; It is a connector with a positioning key, a contact type, and a tensile or torsional structure.
Figure 3 Fiber optic connector
The improved version of the FC connector, that is, the FC/APC(Figure 4), the insert is spherical (PC) for the end face, and the performance of the insertion loss and return loss has been greatly improved compared with the original FC type, and the other characteristics are basically the same, and the external structure has not changed.
Figure 4 Fibre Channel /APC connector
SC optical fiber connector
The SC connector (Figure 5), which began to be used in 1988, was also developed by Japan's NTT company. Its shell is rectangular glass fiber plastic parts; The pin is made of precision ceramic, the coupling tube is metal slit sleeve, the size is the same as FC type, and the end surface is treated by PC or APC type grinding; The insertion method is "push in/push out"; Fastening method is to use the plug and pull pin latch type. It is a connector with positioning key, contact type, tensile and anti-torsion structure; Easy to insert and remove operation, small fluctuation of insertion loss, high compressive strength, high installation density.
Figure 5 SC connector
Type SC connectors can be duplex (Figure 6), so that the fiber is not easy to reverse, thus improving the reliability of the network. NTT has developed this connector into a series of products, including haplotype, two-body F(flat) type, H(high density) type, high density four hole type.
Figure 6 SC duplex connector
Small Connector (SFF)
Optical fiber jack
In January 1997, Panduit introduced the first duplex fiber jack (Figure 7). The fiber optic jack is packaged in a new form and uses four well-established process technologies: 2.5mm casing, rapid cure bonding mount, slotted alignment casing and RJ-45 shape.
Figure 7 Opti-Jack
The Opti-Jack plug is a connector with positioning key, contact type, medium loss, tensile and torsion resistance. It is a duplex connector with one bushing per fiber. This structure allows each fiber to be aligned individually to achieve minimal power loss.
MT-RJ connector
Mt-rj (FIG. 8) is derived from the MT connector developed by NTT Company. Its shell and locking mechanism are similar to RJ, and the guide pins on both sides of the small sleeve are aimed at the optical fiber. In order to facilitate the connection with the optical receiver/transmitter, the optical fiber on the end of the connector is designed to be double-core (0.75mm apart). The standard size MT-RJ model can connect two optical fibers simultaneously, doubling the effective density.
Figure 8 MT-RJ connector
The MT-RJ connector is a type of connector with positioning key, contact type, and tensile structure. Although the MT-RJ plug is smaller than other SFF connectors, it has the same array density on the panel as other SFF connectors. At the same time, the photoelectric device transmission rate of MT-RJ interface is only 1Gbps.
LC connector
The LC connector (Figure 9) was developed by Lucent Technologies to allow telephone companies to increase the installation density of the connectors they use. In order to obtain extremely low reflection, the early introduction of LC type connectors, using the APC form.
Figure 9 LC connector
LC type is a connector with positioning key, contact type, medium loss, tensile and torsional structure. The sleeve diameter is 1.25mm, which is only half of the sleeve diameter in ST-compatible connectors and SC connectors, greatly improving the density of optical fiber connectors in optical distribution frames. Is a simplex SFF connector, but can be turned into a duplex connector by using a card holder.
The transmission speed of optoelectronic devices with LC interface can reach 10 Gbps.
Type LX.5 connector
The LX.5 connector (Figure 10) developed by ADC Communications is a product similar to the LC connector, which is also used in telephone networks. The LX.5 connector in the form of semi-circle and APC end face has a dust cover, and the dust cover should be removed before installation; Similarly, the type LX.5 adapter (Figure 11) also has a dust cover. Dust covers in connectors and adapters increase product reliability.
Figure 10 LX.5 connector
Figure 11 Type LX.5 adapter
Volition type connector
The Volition duplex connector from 3M is a plug and socket system (Figure 12). The Volition model has a typical structural feature: V-shaped grooves instead of bushings.
Figure 12 Volition type duplex connector
V-shaped slots are used to align the fiber: In the socket, the fiber is secured in a precision plastic V-shaped slot. In the plug, the customized optical fiber floats freely, and the optical fiber in the plug is easily inserted into the V-shaped slot of the socket, bringing the interconnected optical fibers into contact through the pressure generated by the optical fiber deflection.
MU connector
MU connector (Figure 13) is developed by Japan's NTT company on the basis of SC connector, and the size is only 1/2 of the SC connector. The connector features a 1.25-mm diameter bushing and self-holding mechanism for high-density installation. MU type is a connector with positioning key, contact type, medium loss, tensile and anti-torsion structure, and it is a fiber optic connector that can be installed into duplex, triplex or quadruplex.
Figure 13 MU connector
MTP/MPO connector
The MTP/MPO connector (Figure 14) has 6 to 24 optical fibers in a molded composite tube. These connectors reduce the size of accessories and panels. The MPO connector consists of two plugs and a socket. The plug is equipped with MT connector sleeve, each plug can be flexibly inserted into the socket or pulled out, simple and convenient operation. Grind the casing end face into an 8 degree bevel, and make the fiber end face slightly protrude from the bevel. The advantage of this process is that the 8-degree bevel can effectively inhibit the reflected light of the return journey; The fiber end face protrusion can make the fiber end face tight connection, and can effectively restrain the connection loss change.
Figure 14 MTP/MPO connector
Installation technique
For different connector types and to meet different requirements, such as reliability, convenience and installation time/cost, a variety of optical fiber connector installation technologies have been developed.
Epoxy potting technology
Epoxy potting is one of the first installation technologies used for fiber optic connectors, and this technology has four advantages and three disadvantages.
advantage
1) Epoxy has strong environmental resistance and can improve the reliability of the connector, such as high temperature resistance up to 105 ° C.
2) Because the thermal expansion coefficient of epoxy and optical fiber and ceramic bushing is relatively matched, the loss is stable in a wide temperature range.
3) Because an epoxy washer is formed at the end of the sleeve, in the process of manual or mechanical polishing, the washer supports and protects the optical fiber, eliminating the possibility of damage and rupture of the optical fiber end, which can greatly improve the efficiency.
4) Can use low-cost connectors.
shortcoming
1) Inconvenient to use; 2) Low installation efficiency; 3) Increased power consumption.
Hot melt installation technology
Hot melt mounting technology is a technique invented by 3M: hot melt adhesive is pre-loaded into the connector, the connector is preheated to soften the adhesive so that the fiber can be loaded, the fiber and/or cable is loaded into the connector, after cooling, the excess fiber is removed, and the end face is polished.
Compared with epoxy potting, the hot melt process can shorten the time, avoid easy dirty and inconvenient, and improve the installation efficiency. However, hot-melt connectors are more expensive than epoxy connectors, and the heating furnaces and special furnaces used in hot-melt installation methods require power consumption.
Rapid curing bonding technology
The rapid cure bonding technique has two advantages and three disadvantages.
Advantages: 1) Solve the shortcomings and inconvenience of hot melt installation and epoxy potting, and eliminate the requirement for power, improve the installation efficiency, and reduce the installation cost. 2) Suitable for low-cost ceramic sleeve connectors, so that the total installation cost is reduced.
Disadvantages: 1) premature curing of viscose; 2) The support effect on optical fiber is small; 3) Reduced reliability. Due to the small support effect on the optical fiber, it is easy to break the optical fiber in the process of removing excess optical fiber or polishing, and the yield and efficiency are low. When the optical fiber coated with curing agent and coagulant is inserted into the connector equipped with viscose, if the insertion of the optical fiber is too slow, the viscose solidifies, so that the optical fiber is fixed before it is fully inserted in place. In this case, the optical fiber inserted into the connector is few, which will cause the reliability of the connector to decline. In addition, when the temperature, humidity changes or temperature and humidity changes sharply, some rapid curing adhesive performance will be reduced, will also affect the reliability of the connector, so rapid curing bonding is generally used in indoor environments.
Glue-free polishing technology
Glue-free polishing is an installation technology developed by several companies, including AMP(later acquired by Tyco), 3M, and Automatic Tool and Connector, which uses a mechanical method to clamp the fiber and then polish it. Although clamping is convenient and consumes less time, in the polishing process, due to the lack of support and protection of the optical fiber, the optical fiber is easy to damage, so the technical level and responsibility of the installation personnel are high, and the finished product rate is low.
Cutting technique
Cutting is an installation technique for non-epoxy/non-viscose/non-polished connector products. The method is to cut the end of the optical fiber, insert the optical fiber into the connector, and crimp or clamp the optical fiber with the connector.
Because the cutting installation method does not use adhesive and polishing process, it reduces the installation time and reduces the installation cost, and the technical level of the installation personnel is not as high as the above methods, reducing the training cost. However, this method has high requirements for cutting tools and equipment, and the structure of the connector is complex and the price is high, which increases the total installation cost.
peroration
With the continuous development of optical fiber communication technology, especially the development of high-speed local area networks and optical access networks, the application of optical fiber connectors in optical fiber systems will be more extensive. At the same time, optical fiber systems also put forward more and higher requirements for optical fiber connectors - high performance, low cost, miniaturization, multi-fiber, high installation density, easy installation and so on.
While new connector types, such as SFF and MTP/MPO connectors, increase market share and market share, older products, such as ST-compatible connectors and SC connectors, will decrease market share. The cost and density advantages of SFF connectors in optoelectronic devices will lead to an increase in scale and market share. MT-RJ and LC connectors will have great growth due to strong support from optoelectronics manufacturers.
Since MTP/MPO connectors can connect 24 optical fibers, and the volume is only equivalent to 1 to 2 SC connectors, the volume has been reduced by more than 90%, so the amount of MTP/MPO connectors is on the rise.