Optical fiber transmission is widely used in real life with unparalleled superiority. In the optical fiber communication link, in order to realize the flexible connection between different modules and devices, there must be a device that can movably connect between the optical fiber and the optical fiber, that is, the Fiber optic adapter.

Fiber optic adapter is widely used in the optical transmission network of broadcast transmitting station program transmission, video surveillance and network equipment. As a small connecting device, fiber optic adapter is often neglected in use and maintenance.

As a production factory of Fiber optic adapters for more than 27 years, Melontel has strict requirements for the quality of Fiber optic adapters. At the same time, Melontel also has a variety of its own patented Fiber optic adapter products. Outstanding product control provides strong product support for your network construction. Melontel is also a factory with many certifications such as TUV, ISO9001, etc. We will have engineers to follow up your needs throughout the process and solve product problems for you at the first time.

What is Fiber optic adapter?

Types of Fiber optic adapter, Everything you need to know1

Fiber optic adapter is a passive component used to stably, but not permanently, connect two or more optical fibers. It is a device used for detachable (active) connection between optical fibers. Fiber optic adapter is to precisely butt the two end faces of the fiber, so that the light energy output by the transmitting fiber can be coupled to the receiving fiber to the maximum extent, and the attenuation caused by its intervention in the optical link is minimized.

How many types of Fiber optic adapters?

Types of Fiber optic adapter, Everything you need to know1

In actual use, people generally refer to Fiber optic adapter / fiber patch cord and pigtail as Fiber optic adapter. Fiber optic adapter / fiber jumper is a cable with connectors at both ends, which is used to directly connect two standard interfaces.

A pigtail is only one end with a connector, and the other end is a broken end of a fiber optic cable core. It is connected to other fiber optic cable cores through fusion splicing. There are many types of Fiber optic adapters. There are about 12 types, each of which is produced to meet specific needs and has different technical requirements.

In the labeling of fiber optic connectors, we often see “FC/PC”, “SC/PC”, etc., and their meanings are as follows: The front part of the slash “/” indicates the Fiber optic adapter model of the pigtail, including:

(1) FC round with thread (the most used on the patch panel);

(2) ST snap-on round type;

(3) SC card connection type (the most used on router switches). The slash “/” indicates the cross-sectional process of the Fiber optic adapter, that is, the grinding method, including:

a. SC/PC type Fiber optic adapter: The microsphere surface is ground and polished, and the end surface is spherical.
The contact surface is concentrated in the central part of the end face.

b. SC/APC type Fiber optic adapter: at an angle of 8°, with microsphere grinding and polishing, the central part of the contact end still maintains the PC type spherical surface, but the other parts of the end face are processed into bevels to make the angle between the end face and the fiber axis Less than 90°, which can increase the contact area and make the light coupling more tightly. When the angle between the end face and the fiber axis is 8°, the insertion loss is less than 0.5dB. Connectors of this structure are often used in radio and television optical fiber transmission systems.

c. UPC/PC type Fiber optic adapter: Flat connection, precise processing, convenient connection, reflection loss 50dB, commonly used in the optical fiber system of radio and television transmission network. Its attenuation is smaller than the PC type. The physical map of the most commonly used PC and APC grinding methods

Fiber optic adapter is a high-precision device. It penetrates and fixes the optical fiber in the support sleeve of the plug. After grinding or polishing the butt port, the alignment connection is realized in the sleeve coupling tube. Sleeves for plug coupling alignment are typically made of materials such as ceramic, fiberglass reinforced plastic (FRP), or metal.

In order to align the fibers, this type of connector requires a very high degree of machining precision of the plug and coupler.

Fiber optic adapter can be divided into different structural forms such as FC, SC, ST, LC, D4, DIN, MU, MT-RJ, etc.

In our usual projects, the most common and used ones are FCFiber optic adapter, SCFiber optic adapter, STFiber optic adapter, LC Fiber optic adapter. , UPC, etc.

Only when we have a deep understanding of these interfaces can we correctly purchase fiber jumpers, pigtails, GBIC fiber optic modules, SFP (mini GBIC) fiber optic modules, fiber optic interface switches, fiber optic transceivers, couplers (or adapters), etc. different optical transmission devices.

Below we introduce the four types of Fiber optic adapters, FC, SC, ST, and LC, which are common in engineering.

Read more about Fiber Optic Connector

What is FC Fiber optic adapter?

FC type Fiber optic adapter is a kind of screw type connector, the outside is made of metal sleeve, mainly by locking and aligning between the thread and the nut, so we can simply call it “screw”.

What is SC Fiber optic adapter?

SC type Fiber optic adapter is a plug-in pin-bolt type connector, which can be docked as long as it is directly plugged and unplugged. The shell is rectangular, so we call it “square mouth”. The structure and dimensions of the pins and coupling sleeves used are exactly the same as those of the FC type, and the end faces of the pins are mostly ground by PC or APC type.

What is ST Fiber optic adapter?

The ST Fiber optic adapter has a bayonet-type metal ring to connect with the matching coupler, and there is a slot on it, you can directly insert the key of the jack into the slot and rotate, so we call it “bayonet” “. Before the SC-type Fiber optic adapter appeared, the ST-type was always considered as the standard Fiber optic adapter.

What is LC Fiber optic adapter?

The LC-type Fiber optic adapter is constructed with an easy-to-use modular jack (RJ) latch mechanism. The size of the pins and sleeves used is half the size of ordinary SC and FC connectors, which is 1.25mm. LC type Fiber optic adapter is a new type of Fiber optic adapter developed to meet customer requirements for connector miniaturization and high-density connection.

It compresses the space required for panels, wall panels and distribution boxes in the entire network to take up only half the space of traditional ST and SC connectors.

Its characteristics are: small size, high dimensional accuracy, 1.25mm ceramic ferrule, low insertion loss, and high return loss.

At present, fiber optic adapters are mostly used in SFP (mini GBIC) fiber optic modules, and SFP modules are often used in switches that provide SFP expansion slots.

What are the technical indicators of Fiber optic adapter?

Optical properties:

For the optical performance requirements of the Fiber optic adapter, the two most basic parameters are insertion loss and return loss.

① Insertion Loss, that is, connection loss, refers to the loss of effective optical power of the link caused by the introduction of the connector. Insertion loss refers to the number of dB of the ratio of the output optical power to the input optical power after the optical signal in the fiber passes through the flexible connector. The smaller the insertion loss, the better, and the general requirement should be no more than 0.5dB.

② Return Loss, Reflection Loss refers to the ability of the connector to suppress the reflection of the optical power of the link. Reflection loss, also known as return loss, refers to the dB number of the ratio of retroreflected light to input light at the fiber connection. The larger the return loss, the better to reduce the impact of reflected light on the light source and system.

The way to improve the return loss is to process the end face of the fiber into a spherical or inclined spherical surface. In practical connectors, the pin surface has been specially polished, which can make the return loss larger, generally not lower than 45dB. The general requirement for these two indicators is that the insertion loss should be small and the return loss should be large.

Types of Fiber optic adapter, Everything you need to know1

Interchangeability and repeatability:

Fiber optic adapters are general-purpose passive devices. Fiber optic adapters of the same type can generally be used in any combination and can be used repeatedly. The additional loss introduced by this is generally within the range of less than 0.2dB.

Tensile strength:

For a well-made Fiber optic adapter, it is generally required that its tensile strength should not be lower than 90N.


As a general requirement, the Fiber optic adapter must be used normally at a temperature of -40℃ ~ +70℃.

Times of plugging and unplugging:
The currently used Fiber optic adapter can generally be plugged and unplugged more than 1000 times. Before use, the pin and pin end face must be cleaned with anhydrous alcohol and special fiber lint-free paper.

What should I pay attention to when using Fiber optic adapter?

Types of Fiber optic adapter, Everything you need to know1

(1)When using, the minimum bending radius of the optical fiber is not less than 30mm.

(2)Protect the pin body and pin end face to prevent bumps, and put on a dust cap in time after disassembly.

(3)When the laser signal is transmitted, do not look directly at the end face of the fiber.

(4)When damage occurs due to man-made and other irresistible factors, the damaged fiber jumper should be replaced in time.

(5)The optical fiber connection has very strict requirements on the precision of the equipment, so the connector must be very clean. Fiber optic adapters and accessories are usually packed in a sleeve. A fingerprint or external dust may seriously affect the performance of the connector, and even cause transmission failure. Therefore, when the connector is not connected, it should be kept in a clean protective sleeve. inside.

(6) When there is an abnormal situation in the optical fiber network or system, the troubleshooting method can be used to test one by one. When testing or eliminating the fault of the jumper, the on-off test can be done first, and then the optical fiber insertion loss and return loss instrument can be used to test its indicators. Within the qualified limit, the jumper index is normal, otherwise it is abnormal.

What are the faults of the fiber optic adapter?

With the continuous development of optical fiber communication technology, the application of Fiber optic adapter in optical fiber system will be more extensive. Fiber optic adapter will play an indispensable role in optical fiber communication together with optical passive components such as optical attenuator and optical isolator. important role.

Below we will tell you in detail the failures and solutions of several major Fiber optic adapters.

1) Fault phenomenon:

A certain line needs to temporarily interrupt the optical cable reconstruction due to municipal construction. At this time, the optical cable route needs to be temporarily changed, and the two places need to be connected by several front-end detours. It is found that a data service cannot be recovered.

Troubleshooting and troubleshooting:

When the link is restored, the OTDR detects each fiber core normally, and the received signal is also normal when tested by the optical power meter at the receiving end. But after the connection, the service could not be connected. After further inspection, it was found that the band set by the OTDR was wrong. After switching to the 1550 nm wavelength, the Fresnel reflection curve was measured again and found that the Fresnel reflection curve has strong reflection loss in two places, and the distance should be In two branch front-end computer rooms. After careful cleaning of the connectors on the ODF rack with alcohol, the reflected waves disappeared. The reason is that the scattered echo is too strong due to the poor connection accuracy of the flexible joint, or the flexible joint is not careful to be polluted by dust when jumping the fiber.

(2) Fault phenomenon:

A user of an optical node reported that the signal of the supplementary channel 3 was very poor and there was interference.

Fault finding and cause analysis:

After testing, the received optical power of the optical receiver is normal, and the output RF signal of the optical receiver is also normal. But at its monitoring port, looking at the image on the monitor, it is found that there are many clutter in the supplementary 3 channel, other channels are normal, and the fault of the receiver is still the same. Change the light to the front end

(3) Fault phenomenon:

A user of an optical node reports that the signal quality is poor and snowflakes are severe.

Troubleshooting and troubleshooting:

This failure occurred after six months of overhaul, suspected to be caused by improper overhaul. In the equipment room, the transmitter splitter and the corresponding contacts on the ODF rack are all normal. After recovery, the user reported that the signal was normal, but after a few days, the user reported that the signal became worse again. This time, the corresponding movable connectors in the computer room were carefully inspected, and it was found that the ceramic core in one of the adapters was cracked, so that the movable connectors were not well connected, and the optical fibers were not aligned correctly, resulting in increased signal loss. After replacing the adapter again, the problem is solved.

(4) Fault phenomenon:

The TV signal of the whole district was severely snowed.

Reasons to find and eliminate:

Detect the optical receiver output signal level, only 86 dBμV. The input optical power of the photometric receiver is – 2. 0 dBm, the optical signal is normal. Carefully check the optical receiver and find that the active connector of the optical detector input Fiber optic adapter is not connected well with the adapter. Take off the movable connector and clean it with medical cotton dipped in anhydrous alcohol. Then test the output signal level of the receiver as 105 dBμV, and the fault is eliminated.

(5) Fault phenomenon:

There is no optical signal at the receiving end, or sometimes there is no optical signal, sometimes strong and sometimes weak.

Find the reason:

When it is initially determined that the optical equipment is normal, you should first check whether the Fiber optic adapter is in good contact, and wipe the relevant movable connectors, adapters, etc. with an alcohol cotton ball. Since the Fiber optic adapter is prone to damage and pollution during operation, the failure rate caused by it is also high. The damage to the connector can usually be seen directly with the eyes, such as broken pigtails, poor contact of the movable connector, damage to the inner ceramic core of the adapter, etc. Otherwise, it is necessary to use measuring instruments to further judge whether there are problems with these devices.

How to maintain the Fiber optic adapter?

During the use of the optical fiber equipment, the optical fiber movable joint may be contaminated by dust and dirt to varying degrees, resulting in an increase in the loss of the optical link. The specific phenomenon at this time is that the optical power of the optical receiving end is reduced, and the output of the optical receiver The level is significantly reduced, in this case, proper cleaning and maintenance of the fiber optic connector must be carried out. The following describes the cleaning and maintenance methods in detail:

a. When cleaning the connector, use special fiber lint-free paper and high-purity absolute alcohol. During the cleaning process, attention should be paid to the protection of laser radiation, and do not look directly at the optical power output port with eyes.

b. Unscrew the movable connector to be cleaned, take a special fiber-optic lint-free paper and fold it to a certain thickness, dip it in anhydrous alcohol, wrap the ceramic sleeve cylinder of the fiber-optic movable connector and wipe it by rotating it back and forth several times.

Take another special fiber lint-free paper, fold it to a certain thickness, dip it in anhydrous alcohol, hold it with the tip of your index finger and clamp it with your thumb and middle finger, and gently wipe it along the inclined end face of the fiber optic connector. Use the force in the direction, and the force should be moderate to avoid the fibers on the paper being scraped off. The signal is sent there, and the fault remains the same, indicating that it is not a problem with the signal source. Replaced a live connector on the fiber ODF rack and the fault was eliminated. Look carefully at the movable connector, and you can’t see the problem with your eyes. It is suspected that it may be caused by the quality of the connector. Due to the low precision, the signal reflection causes interference.


With the continuous development of optical fiber communication technology, especially the development of high-speed local area network and optical access network, the application of fiber optic adapter / optical fiber jumper in optical fiber system will be more extensive. At the same time, it also puts forward more and higher requirements for Fiber optic adapter / optical fiber jumper, and its main development direction is: miniaturization of appearance, low cost, and higher and higher performance requirements. In the future, various newly developed Fiber optic adapters will be used together with traditional FC, SC, ST and other connectors. In practice, we need to constantly summarize practical experience.