Beginners Guide to Fiber Optic Connectors
The basic expectation from a network infrastructure is reliability and speed at a reasonable cost. You can achieve a lot in less time when you can send a massive chunk of information miles away at high data speed without any signal drop. Hence, most enterprises are transitioning to fiber-optic networks as you get superior bandwidth ( >10Gbps) with data transfer at the speed of light.
However, unlike copper cables with a singular connector standard, i.e., RJ-45, the connector choice for fiber optic are several. In case you are wondering why you need different connector types, the answer lies in the application. We shall look into some of the most common connectors used for single-mode and multi mode communication with pre-terminated fiber optic cables.
Types of connectors
Acronym for subscriber connector, the SC was developed by NTT in Japan for fiber optic communications. It is a snap-in type connector that implements a push-pull mechanism for quick insertion and removal. Generally, two SC connectors are bound together with a plastic clip to create a duplex connection. They are low-cost, durable and straightforward. These types of connectors are used for 2.5mm ferrule and used for connections in tight spaces.
The first connector type that was widely used for fiber optic networking is ST connectors. The ‘Straight Tip’ connector was developed by AT&T and also used a 2.5mm ferrule. Instead of the push-pull mechanism in SC connectors, the ST connector implements a twist on//off connection mechanism. The ST connectors are generally deployed alone (instead of pairs in SC) and used for half-duplex communications.
The Lucent connector or LC type is a small form factor connector developed by Lucent Technologies. Also deployed in pairs, the LC connector utilizes a retaining tab mechanism for staying in place. The ferrule size is smaller than those used in ST/SC connector type (1.25mm). It is generally used for single-mode communications and can be quickly terminated with any adhesive.
The MTRJ connectors are Mechanical Transfer-Registered Jack connectors, developed by AMP/Tyco and Corning. It houses two cables in a single connector and is hence used in duplex communications. The connector has a lot of resemblance to the RJ45 connectors. It is available in two variants.
- With the mating pins
- Without the mating pins
You can use this connector type for single or multi mode communications. Yet, it is difficult to test this connector as most tests don’t allow direct adaptation.
The MPO is a Multi-Fiber Push-on type of connector developed by NTT in the early ’90s. It could accept 72 fibers in a single ferrule The MTP (Multi-Fiber Termination Push-on) connector is an MPO type connector developed by UNCONEC and carry either 12 or 24 cable array. This connector type is used for terminating multi-fiber connections in an indoor environment. MTP connectors are engineered for high mechanical and optical specs. Both connectors can be used interchangeably. Connected using a push-pull mechanism, the male connectors have pins, and the female connector has pits to guide the ferrule correctly.
The Multitermination Unibody Connector is a miniature version of the SC connector. It was a connector type developed by the NTT and is mostly used in Japan. With a ferrule size of 1.25mm, the connectors are used for duplex communications. Paired with the push/pull latching mechanism, the MU connectors can be blindly connected in tight spaces.
Used predominantly for single-mode communications, the FC connectors use 2.5mm ferrule. The connectors implemented a screw in/out mechanism for latching. The SC/ST connectors long replaced this type of connector.
Parts of a Connector
While all the connector types are different, the overall construction is somewhat similar. The fiber connector has three parts:
- The connector body
- The cable
- Coupling section
The connector body is generally metal or ceramic and is terminated on the cable to hold it tightly. The connector body can be joined to the cable using adhesive or crimping. The exposed fiber core is passed through the connector body and coupling section. The latching mechanism is present in the coupling section. It can be a threaded screw pattern, guiding pins, raised tracks, or any other mechanisms. An additional strain relief boot is added to the ferrule to keep it from bending over 90o and provides twist relief.
Out of the most discussed here, LC and MTP/MPO are the most widely used connectors due to their thin ferrule size and compatibility with both modes of transmissions. Yet, specific older generation networks still use SC or ST connectors. You can either opt for an adapter for cross-compatibility or order pre-terminated fiber optic cable assemblies for easy installation. Keep in mind that the connector you choose should have the minimum insertion loss to be effective.