Technical Article

Intro to Fiber-Optic Communication Systems

February 03, 2021 by Kamanda Dennis

Learn some basic, foundational info about fiber optic communication systems in this primer.

This article discusses optical communication systems and explains transmitter and receiver circuits for fiber-optic communication systems.


What Is an Optical Communication System?

For decades, electronic signals have been sent effectively via normal ‘hard-wired’ connections or by the use of different kinds of radio links which had their own downfalls. On the contrary, optic fiber links, whether utilized for video or audio links over long or short ranges, offer some unique advantages as compared to the standard wired cables. This article delves to discuss the optical transmitters and receiver circuits for fiber-optic communication systems.

Presently, the growth in information technology has had increased use of the current telecommunication systems. Often, optical fiber communication plays a significant role in the development of telecommunication systems with high quality and speed. Nowadays, optical fiber applications majorly involve telecommunication systems with an inclusion of internet and local area networks (LAN) to achieve high signaling rates.


How Fiber Optics Work

In optical fiber technology, an optical fiber link is utilized to transfer analog or digital data in light frequency form via a cable with a highly reflective central core. The role of the highly reflective central core is to act as a light guide for the transfer of light through it through continuous reflections across its characteristic reflective walls. As is illustrated in the block diagram below, the optical fiber communication module mainly comprises a transmitter (Tx) circuit and a receiver (Rx) module.


A simple receiver-transmitter block diagram


As shown in the fiber-optic data link above, the transmitter is located on one end of the fiber cable while the receiver is located on the other sides. As is common, a transceiver- a module that includes a transmitter and receiver- is employed in most systems. The input to the transmitter comprises an electrical signal which converts into an optical signal from either a light-emitting diode (LED) or laser diode. As required, the light signal from the transmitter is linked to the fiber cable with the use of a connector and broadcasted via the cable. Subsequently, the light signal from the fiber terminal can be linked to a receiver, anywhere a detector converts the light to an electrical signal, after which it is suitably conditioned for use by the receiving equipment. The figure below depicts a block diagram for a typical optical transmitter and receivers.


Block diagram for a typical optical transmitter and receivers


Pros and Cons of Fiber Optics

A most important aspect of the fiber optic circuit links is the perfect immunity to the electrical interference and stray picks ups. While the problem of electrical interferences and stray pick-ups may be reduced by designing the standard cable links, it may be increasingly difficult to entirely eliminate the issue. In contrast, the non-electrical attributes of the optical fiber cables aids in making the electrical interference inconsequential with an exception of the possible disturbance at the receiver terminal, which may be eradicated via effective shielding of the receiver circuit.

Systems that incorporate optic fiber cables working together have close to no complication or issues associated with cross-talks. This is so given the encapsulation of the fiber optic cables preventing any light leakage. As such, links done by fiber optic guarantee a reasonably safe and reliable transfer of data.

Besides, through suitable transmitting and receiving circuits, it is increasingly suitable for the fiber optic links to have the capacity of handling substantial bandwidth ranges, especially due to the improved electrical isolation in the entire like making sure no complications with earth loops develop. Notably, optic cables are typically slim and lightweight with immunity to climatic conditions and various other chemical substances. As a consequence, they are frequently used with ease in inhospitable environments where electrical cables, particularly coaxial cables would otherwise be very ineffective.

Like any system, although fiber optic circuits boast various advantages, it has its shortcomings. For instance, a shortcoming that is quite apparent is the impossibility of having the electrical signals transferred directly into the fiber optic cable. The problems and cost associated with the crucial encoder and decoder circuits are contradictory. Besides, bending optical fibers is often undesirable as twisting them with a sharp curve exposes them to physical damage making them functionally useless since propagation of light signals will be hindered resulting in drastic losses.