History of fiber optic
Back into 1954, the transmission of images through a bundle of fibers was conducted successfully with lower loss in which the fiber covered by a transparent cladding gave less attenuation compared to the one without cladding layer . That was the beginning of the general standard of the fiber until nowadays that an optical fiber must contain at least two layers acting as a data transmission medium. The data transmission is in the form of light pulse along the fiber until the end. Those two layers of an optical fiber are “core” and “cladding”. During that time, the scientists found out that the data transmission could be conducted in short distance because of the large attenuation. More than a decade later, the material selected to produce an optical fiber was a silica. It yielded further distance of data transmission up to thousand miles away with low attenuation about 10 dB/km . The significance of those mentioned two layers is “total internal reflection” that we want the data transmitted only inside the fiber, not to be leaked away somewhere. The core layer states inside layer having higher refractive index compared with the cladding layer which covers the core layer. The higher refractive index of core layer lets the signal transmitting only inside the core. The transmitted data as a light signal reflects back into the core when it reaches the cladding layer.
In commercial, the optical fiber itself has several specifications, especially the size of its tube. Fiber for indoor installation has thinner jacket diameter and it is easy to align in curved area along the ceiling, wall, and any edges. Fiber for outdoor installation of course has a larger diameter which is the thicker jacket layer protecting the fiber from harsh environment i.e., heat from the sun, heavy rain, even strong wind, and the filler rod inside to increase its strength. The comparison of fiber specification between indoor and outdoor usage is displayed in Fig. 1(a) and Fig. 1(b), respectively.
Figure 1 Fiber specification for (a) indoor, 2016, VRS Tech and (b) outdoor installation, OTSCABLE [2,3]
Fiber optic worldwide
In present day, the famous selected medium for telecommunication is still an optical fiber. Several advantages include that the fiber can carry a large amount of data, it has low loss power transmission, and especially, it has no effect with any electromagnetic interference. It means that you can install the fiber optic in parallel together with an electric wire. The optical network has already linked worldwide from one side to another side of the world: from USA to Australia, from Brazil to Portugal, from South Africa to India, and so on. This network connection is possible by lying the fiber under the ocean as displayed in Fig. 2. As of late 2021, there are about 436 submarine cables in service around the world. 
Figure 2 Worldwide submarine cable map (as of April 2019), MAPFRE Global Risks 
When the fiber cable is installed and laid on the sea floor, it is surrounded by uncertainty surroundings, especially giant animals like sharks, whales, and giant squid as they can bite the cable and cause the damage. Another phenomenon that attacks the submarine cable is an earthquake. Partial route of the network is lying on the Ring of Fire from Eastern Asia heading up and go along the Western coast of North and South America. Sometimes, ship’s anchor also causes the damage to the cable. Therefore, the material for protecting shield of the cable has been developed against those harsh environments to expand its life of service up to more than 20 years. However, there are backup routes available once one route is interrupted or cut. This may cause the slower speed of the connection, but the service is not completely lost.
On land, there are several techniques to install fiber cable networks like hanging mid-air between electric poles or even lying underground. Household clients can reach the high-speed internet from the technology called “Fiber-to-the-home or FTTH”. The optical fiber network is routed from the internet provider directing to the customer’s house, then connecting to the router and transform the data signal to LAN cable and wireless network (wifi).
Fiber optic in Thailand
The internet connection from main providers in Thailand has begun transforming from using a copper wire to fiber optic almost a decade ago to enhance the service quality of the internet. Under the same price, customers can get the experience more than hundred times faster internet connection. There are four spots that the submarine cable comes ashore, there are Sriracha, Rayong, Satun, and Songkhla . Those spots are main gateways of the country linking the network to around the world.
The transformation technology of the internet connection has changed our lifestyle to an online platform with an increasing rate. For instance, in the past, we had to visit the store to purchase goods we want, but today we can purchase by scrolling the screen in the smart phone. In case of watching TV program, there was a schedule time we had to wait, but today we can watch anytime anywhere on the smart device as it is called “on demand”. Those digital lifestyles are the results of the network that consisting of an optical fiber. Even the wireless communication on the mobile phone or tablet such as 3G, 4G, and even 5G technologies, they all need fiber optic as a part of a backbone network for telecommunication.
The fastest broadband internet speed as of 2021, Thailand is ranked the seventh place with an average internet speed at 225.17 Mbps . Main internet providers are TRUE, AIS, 3BB, and NT. All providers serve the high-speed internet connection and cable TV subscribers via an optical fiber network. In fact, we can use the internet with the high speed under the reasonable price because of our own designed infrastructure. Fig. 3 is the one describing the network infrastructure of an optical fiber as a very messy alignment hanging on an electric pole.
Figure 3 Several optical fiber networks tangled on an electric pole, photo by Ted McGrath 
Those internet providers rent the Electrical Authority to hang the fiber on its property. This is the cheapest fiber installation, and it is the easiest way to expand the network to the new customers who request for the internet installation in their houses. When an accident occurs such as the truck crashes the pole, the technicians can fix and repair the network within only one day. Most major cities such as downtown Bangkok, Phuket, etc. have their policy to put those fiber cables underground to improve the scenery of the city to become the city without any wires.
Fiber optic with the smart city
The era of digital technology has already begun several years ago. Many cities around the world have enhanced their economics and lifestyles becoming cyber technology. Internet of Things (IoT) is the most famous trend to understand how we transform from analog to digital lifestyle. We may see wireless connection between hardware crossing over the network via 4G, LTE, and 5G to respond the action of smart devices and utilities. Behind those wireless connection, fiber optic is the main infrastructure for telecommunication inside the smart city as it has low latency, and it is more stable comparing with using another medium such as satellite. The 4G and 5G are implemented in limited boundary area whereas the fiber connection can go beyond that boundary. These integration of infrastructure between fiber optic and wireless communication increases the performance of digital technology responding our lifestyle in the new era of transformation becoming a “smart city”. Therefore, the fiber optic is still being selected for the telecommunication in great-far distance either intercity or intracity.
Ravivudh Khun-in, Ph.D
Smart City Promotion Division