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About MTRJ Connector —- Only Few People Know

MT-RJ connector, or Mechanical Transfer Registered Jack, is a type of fiber optic connector that is commonly used in telecommunications and data networking applications. It is a small form factor connector that combines two fibers into a single unit, allowing for high-density installations. You can find it on the market easily even It is not as popular as SC or LC connector now. You will find that in the market, almost all the MRTJ patch cords are duplex, no matter it is MTRJ to LC, or MTRJ to SC, MTRJ to ST.

MTRJ to LC Multimode fiber patch cord

MTRJ to LC Multimode fiber optic patch cord

MTRJ connector was developed by AMP Netconnect which belongs to CommScope and at that moment was advertised as the ultimate SFF connector. AMP used the MT ribbon connector design as an inspiration to invent an economic MT connector that could hold two fibers in one plastic ferrule.

connector MTRJ

MTRJ Connector

MTRJ was developed before 2000. Comparing to SC connector, it can hold two fibers in a similar size connector, which means can save 50% space. Saving space always means saving cost.

Only the MTRJ connector is not enough, it can not work. This must be a whole fiber connect system, all the segments of the enterprise network — transceiver, equipment, fiber assembly etc must be supported/compatible with MR-RJ connector. So the MT-RJ optical fiber system is achieved through a cooperative effort of many related companies not only one company. A consortium of world-class electronic and connector companies (AMP, Hewlett-Packard, Siecor, Fujikura and USConec) formed to develop the solution for overall network applications. The consortium pooled a wealth of expertise together for all segments of the network – ferrules, cables, assemblies, and active electronics.

Through the team development effort, customers realized a lower cost of optical fiber implementation, increased bandwidth and extended distances.

According to industry reports published by Electronicast, when it ran into the market, the MT-RJ is the most popular and fastest-growing of all small form factor (SFF) connectors, with over 6 million installed until June 2001.

It looks the MTRJ connector has a very bright future, almost no competitor in the market. But the truth is that it is not as popular as it expected till now. In my opinion, it is due to the LC connector.  LC stands for Lucent Connector, it was developed by Lucent Technologies, LC is also considered as an SFF (Small Form Factor connector) due to its small assembly. You can see on the market almost all the SFP modules are compatible with LC connector, not MT-RJ connector.  Why?

1. LC connectors deliver better Insertion Loss and Return Loss;

Multimode Connectors LC Duplex MT-RJ
Insertion Loss 0.3 dB 0.5 dB
Return Loss -30 dB -20 dB

2. LC connectors can be cleaned by the traditional way as cleaning SC or ST. It is more convenient than cleaning MTRJ since MTRJ have two alignment pins which make the cleaning not so easy.

3. LC connectors can be spliced and installed in the field by the same way as SC and ST, while MT-RJ connectors require two fibers to be installed/spliced at the same time, which could do harm to the overall performance.

4. LC duplex connector has similar size to MTRJ size, LC duplex connector can change the polarity easily, while MTRJ can not do it.

However, MT-RJ multimode connectors are still used in some applications, especially for 100BASE-FX interfaces.  Some transceivers and LAN equipment still select MTRJ as their interface.


MTRJ is an approved connector per ANSI/TIA/EIA-568-B.3. On the market, It looks that all MTRJ assembly are duplex configurations. Actually, according to TIA-604-12-2000 & IEC 61754-18:2001, there are 4 types interface for MT-RJ family.

  • Interface for 1 fiber;

  • Interface for 2 fiber with a pitch of 0.25mm

  • Interface for 2 fibers with a pitch of 0.75mm

  • Interface for4 fibers with a pitch of 0.25mm.

All these types have two versions, with or without PINs.


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