In-Depth Look at the Fiber Optic Connector

In all fiber optic system, it is necessary to join two fibers together with low signal attenuation while maintaining low reflection levels depending upon the type of system used. Fiber optic connectors are used as the mechanical and optic means for cross connecting fibers and linking to fiber optic transmission equipment. With a wide range of fiber optic connectors with different merits and demerits available on the market, many factors, like performance and cost, should be taken into consideration when choosing a fiber optic connector. Every small decision will post a significant influence on deployments speeds and costs of the fiber optic patch cables. To specifically understand the fiber optic connector, this post will give an overall look of it.

Fiber Optic Connector

An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so light can pass. Better connectors loss very little light due to reflection or misalignment of the fibers. In all, about 100 fiber connectors have been introduced to the market. The table below shows some optical connectors.

Commonly Used Types of Fiber Optic Connectors

With so many fiber optic connectors used in fiber optic networks, there are only a few types widely applied. In this part, we will introduce five types of optical connectors

FC Connector

The FC connector was the first optical fiber connector to use a ceramic ferrule, but unlike the plastic bodied SC and LC, it utilizes a round screw-type fitment made from nickel-plated or stainless. The connector end face relies on an alignment key for correct insertion and is then tightened into the adapter/jack using a threaded collet. Although the FC adds complexity both in manufacturing and installation, it is still the connector of choice for precise measuring equipment such as OTDRs. What’s more, the FC connector does make it particularly effective in high vibration environments, ensuring that the spring-loaded ferrule is firmly mated.

ST Connector

Originally developed by AT & T shortly after the arrival of FC, ST or straight tip connector was one of the first connector type widely implemented in fiber optic networking applications. ST connector can be easily mistaken for FC connector at a glance, but the ST uses a bayonet fitment rather than a screw thread. Deployed predominately in multimode datacoms, it is available in network environments such as campuses, corporate networks and in military applications where the quick connecting bayonet had its advantages at the time. Nevertheless, it cannot be terminated with an angled polish, which limits use in single-mode fiber and FTTH applications. It is typically installed into infrastructures that were built at the turn of the century, but nowadays it has almost been swapped out for more cost-effective SC and LC connectors.

SC Connector

The SC or subscriber connector was developed by the laboratories at Nippon Telegraph and Telephone (NTT) in the mid-eighties, which was one of the first connectors to hit the market following the advent of ceramic ferrules. SC connector is a non-optical disconnect connector with a 2.5 mm pre-radiused zirconia or stainless alloy ferrule. It uses a push-on/push-off mating mechanism which is generally easier to use than the twist-style ST connector when in tight spaces. Due to its excellent performance, SC connector has dominated fiber optics for over a decade and now it remains the second most common connector for polarization maintaining applications.

LC Connector

Considered to be the replacement of the SC connector, LC or lucent connector is the most popular small form factor (SFF) connector. Like SC, it is also a push-pull connector, but LC utilizes a latch as opposed to the SC locking tab. Having half the footprint of the SC connector, about 1.25 mm ferrule, gives it huge popularity in datacoms and other high-density patch applications. With more and more density increasingly needed in data centers, the popularity of LC connector will continue growing. The following picture shows the different appearance of FC, ST, SC and LC connector, so you can easily distinguish them.

MPO/MTP Connector

MPO and MTP are compatible ribbon fiber connectors based on MT ferrule which allow quick and reliable connections for up to 24 fibers, so they are larger than the connectors we have mentioned above. MPO and MTP connectors feature male and female connector design. Male connectors have two guide pins and female connectors do not (see in the following image). Both connector types need an adapter to mate a pair of male and female connectors. Since MPO and MTP connectors are trying to align so many fibers at once, their coupling losses are typically bigger than single fiber connectors. This type of connector is extensively used with a fan-out assembly at the opposing end (such as LC, SC, FC etc.) in high-density patching environments, like data centers.

Summary

Knowing the differences among different connector types is necessary to get a deep understanding of the fiber optic connector. Taking time to select the right optical connector for the job can deliver big benefits when it comes to speed and cost. So before making connector choice, please think twice.

High Density MPO/MTP Fiber Patch Cable in Data Center

With the advent and popularity of cloud computing and big data, the demand for high-speed transmission and data capacity is becoming much greater than ever before. In the meanwhile, as the data throughput increases, 40G and 100G are more commonplace and now become a hotspot for data center cabling system, plus the fact that MPO/MTP connector is the up-and-coming standard optical interface for 40G and 100G Ethernet network. In the following part, I will introduce two high-density MPO/MTP fiber cables types—MPO/MTP trunk cable and MPO/MTP harness cable, one by one.

MPO/MTP Connectors

Before the introduction to MPO/MTP fiber cable, we still have to review some knowledge about MPO/MTP connectors.

MPO connectors (multi-fiber push on) is used to connect or cross-connect equipment and cables with minimum attenuation and reflection. It is a multi-fiber connector which is standardized within the international regulatory framework (the ICE 61754-7 standard) and also the U.S. (TIA-604-5 standard). MTP (multi-fiber termination push on) connectors are fully compatible with all MPO connectors standards, regulations, and requirements; however, they also have a number of other features that most generic MPO connectors do not possess. For example, MTP connectors have a removable housing allowing users to rework, re-polish, and scan the ferrule, as well as change the gender, even after assembly or in the field. Here shows a picture of MPO/MTP connectors.

High Density MPO/MTP Fiber Cable

Unlike standard fiber optic patch cords (SC patch cable with maximum rate of 10Gbps) a patch cable terminated with the customers’ choice of 12-fiber or 24-fiber MPO connectors can be applied for 40G, or even 100G Ethernet network. Available in a male-to-male version (with guide pins) and a female-to-female version (without pins), MPO/MTP fiber cables can be used for a wide variety of applications, such as backbones, warehouse, disaster recovery, building fiber optic distribution, and so on. The following part will introduce two commonly used high density MPO/MTP fiber cables respectively—MPO/MTP trunk cable and MPO/MTP harness cable.

MPO/MTP Trunk Cable—MPO/MTP trunk cables, terminated with MPO/MTP connectors at both ends, are typically 12 to 144 fibers and create the permanent fiber links between panels in a structured environment. For example, a 72-fiber trunk cable can be terminated with 6 MPO/MTP connectors (shown in the following picture) and the connectors are manufactured specifically for multi-fiber loose tube or ribbon cable. The MTP/MPO trunk cables, which are constructed from loose tube and gel-filled indoor/outdoor rated cables, are applied to interconnect cassettes, panels or ruggedized MPO/MTP fan-outs, spanning MDA, HAD and EDA zones, or other high fiber environments reducing network installation and reconfiguration. Besides, they offer the flexibility which means that if we need change the connector style in the patch panels, new cassettes might be installed with the new connector style on the cross-connect side of the patch panel, but the connector style on the trunk cable won’t have to be changed. What’s more, MTP/MPO trunk cables greatly reduce the installation and maintenance costs with their efficient plug and play architecture.

MPO/MTP Harness Cable—MPO/MTP harness cable, also named MPO/MTP fan-out cable or MTP/MPO break cable, is terminated with a male/female MTP connector on one side and several duplex LC/SC connectors on the other side, providing a transmission from multi-fiber cables to individual fibers or duplex connectors. There are three commonly used MPO/MTP fiber cables types—MPO/MTP to MPO/MTP harness cable, MPO/MTP to secure keyed LC harness cable and MPO/MTP to standard LC harness cable. Compared to normal LC fiber optic cable, these cables are designed for high density applications which require high performance and fast installation. MTP/MPO harness cables are ideal for interconnecting MTP cassettes, panels or backbone MTP assemblies with the active equipment, saving costly data center rack space and easing fiber management. An image of MPO/MTP harness cable is listed below.

Conclusion

MPO/MTP cables are generally used for 40G or 100G network environment, and they play a significant part in structured cabling. It is predicated that MPO/MTP cables will eventually replace the standard for fiber optics. Whether this prediction will come true or not, no one can deny that MPO/MTP assemblies are absolutely best solutions for high-density deployment.