Choosing the right connectors for simplex and duplex optical fibers

Optical fiber is becoming more popular than ever before. Providing high-speed, reliable data transfer and communications for an extensive range of applications.  As well as the fiber cable, it is just as important to pick the most suitable connectors for the job, weighing up all the options can start to become really confusing.

There are actually three types of fiber connections in most common usage: SC, ST (bayonet twist) and LC (push-pull locking).

In fact, there are three types of fiber connectors in common usage: SC, ST (bayonet-twist) and LC (push-pull locking). The most frequently specified is the LC connector, because it is much more compact than the other two, making it suitable for space-constrained applications, and also because it provides a secure clip connection, so there is less chance of the fiber becoming accidentally disconnected.

Simplex or duplex?  

With that choice out of the way, there is an additional complication: fiber optic LC connectors are available in simplex and duplex options. What does that mean?

Put simply, a simplex optical fiber has a single strand of glass or plastic fiber and is only capable of transmitting data in one direction. This makes it suitable for applications that only need this uni-directional capability, for example transmitting data from a sensor in an Internet of Things (IoT) system.

A duplex optical fiber, on the other hand, consists of two strands of fiber and can transmit data in both directions. It may be ‘half-duplex’, that can only send data in one direction at a time, or ‘full-duplex’, that can handle simultaneous, bi-directional communications – for example, for an IP telephony application.

As you’d expect, simplex fibers cost less than duplex, as there is just one fiber, not two. Bear in mind that simplex and duplex fibers are both available as either single-mode or multimode versions, depending on the needs of any particular use case.

What about connectors in harsh environments?

Once the type of fiber is decided, it is fundamental to specify the appropriate LC connector that matches the fiber – simplex or duplex. For some applications, a standard LC connector will be more than sufficient, but fiber is ever more increasingly being used outdoors in more harsh environments than before. This is where the optical fiber is at risk from moisture, dirt, and dust. This can affect the delicate transmission of light and therefore achieving the data rate that it does.

The fibers themselves are protected by an acrylic layer, but the connectors can be extremely vulnerable in outdoor usage. In extreme situations, water can gain access to a connector and then freeze. This can cause damage to the fiber and potentially halt any communication.

Standard LC connectors are not rugged enough for harsh environments, and there is no guarantee that moisture will not make its way into the connector.  One solution is to use a custom enclosure to protect the connector, but this is typically an expensive option.

A better answer is to specify a rugged LC connector, such as the 4000 series fiber range from Bulgin, which provides an industry-standard LC interface as specified by IEC 61754-20. This connector protects the ends of the optical fiber from dirt and damage and provides a seal to prevent any ice forming.

The fiber connection provided by the 4000 series is UV resistant, salt spray resistant and sealed to IP66, IP68, and IP69K. It also provides a secure quick twist bayonet connection, ensuring durable mechanical mating. The connector operates over a wide operational temperature range of -25 to 70ºC, with an average insertion loss of less than 0.1dB and a maximum insertion loss of 0.2dB.

As the smallest rugged optical connector on the market, the 4000 Series Fiber simplex connector is ideal for outdoor broadcast. FTTx server room engineering, civil engineering, marine, aviation and rail applications. The connectors' small form factor is particularly useful where installation space is limited or multiple connectors need to be accommodated.

4000 Series Fiber connector from Bulgin

The 4000 Series Fiber connector offers reliable performance regardless of the application environment. Its industry-standard LC interfaces feature color-coded O-rings and washers for ease of identification. Mounting body options include Flex, Flex In-Line and Rear Panel styles.

The ideal solution for where ease of connection, space, and appearance are important considerations.

Visit Bulgin’s Connectivity Community for expert advice on optical fiber connectors and installations in harsh environments.