Introduction of Optical Fiber Couplers and How Do They Work?

 What are optical fiber couplers?

A fiber optic coupler can be defined as an optical component used with one or more input fibers and several output fibers in fiber optic systems. A coupler essentially puts two or more cores of fibers together to connect. The simple coupler is the fused fiber 2x2 coupler.

Couplers are used as multiplexers that are resistant to certain wavelengths. A fiber output depends on the wavelength of light and the frequency of polarization. The fiber refractive index also plays a significant role in the performance. Let’s checkout how do optic couplers work to understand this better.

How do fiber optic couplers work?

Either fiber optic couplers separate optical signals into multiple paths or combine multiple signals in one direction. Optical signals are more complicated than electrical signals, making it more difficult to design optical couplers than their electrical copy. Unlike electrical currents, the optical signal consists of a stream of signal carriers, in this case photons.

The optical signal, however, does not stream to the ground through the receiver. Alternatively, a sensor absorbs the signal stream at the transmitter. Many receivers, connected in a row, would not receive a signal after the first receiver absorbs the whole signal.

Multiple parallel optical output ports therefore need to split the signal between the ports, increasing their magnitude. A coupler is defined by the number of input and output ports expressed as a N x M configuration.  The letter N is the number of input fibers, and the number of output fibers is expressed by M. In any configuration, fused couplers can be made, but they typically use multiples of two (2x 2, 4x 4, 8x 8, etc.).

We always use digital couplers: like a telephone coupler that allows you to connect a telephone and a fax machine to the same telephone line. Or a CATV coupler that allows you to connect multiple TV sets from Comcast to a single cable. Essentially, you can purchase these couplers online at Connect Zone. Optical couplers have the same features as digital couplers: they distribute the signal to different (devices) points.

Fiber optic couplers are of two kinds – active and passive. The distinction between active and passive couplers is that without optical-to-electrical conversion, a passive coupler redistributes the optical signal. Active couplers are electronic devices that electrically separate and blend the signal and use input and output fiber optic detectors and sources.

Electronic couplers are easy to make as long as you have physical contact between conductors, electrical current flows. But optical signal is a completely different field. The tiny optical fiber cores need to be precisely spaced (9um for single mode and 50um or 62.5um for multimode fibers), so when you break the signal, there will not be a huge power loss.

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Types of Fiber Optic Coupler

Fiber Optic Couplers are broadly classified into two, the active or passive devices. For the operation of active fiber coupler an external power source is required, conversely no power is needed when it comes to operate the passive fiber optic couplers.

Fiber Optic Couplers can be of different types for instance X couplers, PM Fiber Couplers, combiners, stars, splitters and trees etc. Let’s discuss the function of each of the type of the Fiber Optic Couplers:

Combiners: This type of Fiber Optic Coupler combines two signals and yields single output.

Splitters: These supply multiple (two) outputs by using the single optical signal. The splitters can be categorized into T couplers and Y couplers, with the former having an irregular power distribution and latter with equal power allocation.

Tree Couplers: The Tree couplers execute both the functions of combiners as well as splitters in just one device. This categorization is typically based upon the number of inputs and outputs ports. These are either single input with a multi-output or multi-input with a single output.

PM Coupler: This stands for Polarization Maintaining Fiber Coupler. It is a device which either coalesces the luminosity signals from two PM fibers into a one PM fiber, or splits the light rays from the input PM fiber into multiple output PM fibers. Its applications include PM fiber interferometers, signal monitoring in its systems, and also power sharing in polarization sensitive systems etc.

Star Coupler: The role of star coupler is to distribute power from the inputs to the outputs.

Benefits of Fiber Optical Couplers

There are several benefits of using fiber optic couplers. Such as:

Low excess loss,

High reliability,

High stability,

Dual operating window,

Low polarization dependent loss,

High directivity and Stumpy insertion loss.

The listed benefits of Fiber Optical Couplers make them ideal for many applications for instance community antenna networks, optical communication systems and fiber-to-home technology etc.