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Fiber Optic Transmission and Networking

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Optical Networking: Enabling Massive, Scalable, And Flexible Connectivity For All Networks.



- Fiber Optic Cables and Communication

Fiber optic communication is a communication technology that uses fiber optic cables for data transmission. Fiber-optic cables, also known as light-pipes, are designed to transmit digital data and information in the form of light signals over long distances with very little loss. These cables are made from bundles of optical fibers which are long, thin strands of pure glass, each strand being nearly as thin as human hair. 

A high quality communication cable is made of glass or silicon dioxide. Normally, we think glass is brittle and can break easily, but when it is made thinner than a human hair, it becomes very flexible and strong. You can also find fiber-optic cables made of plastic, which are used for very short distance (a few meters) communication, for example, that is used in hi-fi systems to carry audio information.

In leading markets, much of the fixed-line network has already been replaced by fiber-optic cables to benefit from optical fiber’s far better performance for broadband services than twisted-copper networks. For example, fiber-optic cables are being used commercially to carry data at speeds of about 2 terabits per second (tbps; a terabit is 1000 gigabits or 1,000,000 megabits). Also, optical fiber has virtually unlimited capacity, low signal attenuation allowing long distances without amplifier or repeater, no exposure to parasite signals or crosstalk, and no electromagnetic interference (EMI).  


- Optical Networking Technology

Since ushering in the telecommunications revolution with the invention of low-loss optical fiber in 1970, Corning has been continually innovating to increase the speed and capacity of optical networks, while reducing installation costs. Today, we are delivering optical communications solutions for growing segments like fiber to the home, wireless technology, and hyper-scale data centers.

Optical networking is a means of communication that uses signals encoded in light to transmit information in various types of telecommunications networks. These include limited range local-area networks (LAN) or wide-area networks (WAN), which cross metropolitan and regional areas as well as long-distance national, international and transoceanic networks. It is a form of optical communication that relies on optical amplifiers, lasers or LEDs and wave division multiplexing (WDM) to transmit large quantities of data, generally across fiber-optic cables. Because it is capable of achieving extremely high bandwidth, it is an enabling technology for the Internet and telecommunication networks that transmit the vast majority of all human and machine-to-machine information.


- FTTH Access Networks – AON vs. PON Networks

Fiber-to-the-home (FTTH) is a system that installs fiber optics directly from a central point to individual buildings such as homes and apartments. FTTH deployments have come a long way before users adopt fiber optics instead of copper wires for broadband Internet access. There are two basic paths for deploying high-speed FTTH networks: Active Optical Network (AON) and Passive Optical Network (PON).

AONs are used in long-distance areas up to 90 km, while PONs are used in small-distance areas up to 20 km. Passive optical networks work on shared fiber systems while active optical networks work on dedicated fiber systems.  


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- Modernizing Telephone Networks

The telephone network was the first major user of fiber optics. Fiber optic links are used to replace copper cables or digital radio links between telephone exchanges, starting with long-distance links, called long lines, where the distance and bandwidth capabilities of fiber optics make them significantly more cost-effective.

Telcos use fiber to connect all their central offices and long-distance switches because it has thousands of times the bandwidth of copper wire and can carry hundreds of times more signals before needing repeaters -- making it cheaper to connect phones via fiber Only a few percent of the cost of the same connection on copper. They even use fiber optics to connect cell towers to save limited radio spectrum.

After long-distance links were converted to fiber, telcos began replacing shorter links between switches, such as links between switches within the same metropolitan area, with fiber. Today, almost all telephone networks have been converted to fiber optics. Telcos and other groups are now running fiber-to-the-home (FTTH) with low-cost passive optical network (PON) systems that use splitters to share the cost of certain fiber optic components among as many as 32 customers.

The telecommunications industry and service provider networks must evolve rapidly to handle the surge in digital traffic driven by multimedia services, mobile applications, social media, VoIP and cloud computing. In addition, there are an increasing number of bandwidth-hungry applications.

In the past, network traffic was all about voice calls made over circuit-based networks in predictable network connections between pairs of endpoints. Most network traffic today is packet-based, generated by a multitude of services and applications in bursty, unpredictable traffic patterns, with widely varying and more stringent requirements for bandwidth and data transfer performance.


- Optical Transport Networking

ITU-T defines an Optical Transport Network (OTN) as a set of Optical Network Elements (ONE) connected by optical fiber links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals. An ONE may Re-time, Re-Amplify, Re-shape (3R) but it does not have to be 3R – it can be purely photonic.

OTN was designed to provide support for optical networking using wavelength-division multiplexing (WDM) unlike its predecessor SONET/SDH. ITU-T Recommendation G.709 is commonly called Optical Transport Network (OTN) (also called digital wrapper technology or optical channel wrapper).  

As of December 2009, OTN has standardized the following line rates: Please check out [Wikipedia: Optical Transport Network] for more details.

Signal Approximate data rate
OTU1 2.66   Transports SONET OC-48 or synchronous digital hierarchy (SDH) STM-16 signal
OTU2 10.70   Transports an OC-192, STM-64 or wide area network (WAN) physical layer (PHY) for 10 Gigabit Ethernet (10GBASE-W)
OTU2e 11.09   Transports a 10 Gigabit Ethernet local area network (LAN) PHY coming from IP/Ethernet switches and routers at full line rate (10.3 Gbit/s). This is specified in G.Sup43.
OTU2f  11.32    Transports a 10 Fibre Channel. 
OTU3 43.01   Transports an OC-768 or STM-256 signal or a 40 Gigabit Ethernet signal.
OTU3e  244.58  Transports up to four OTU2e signals 
OTU4 112   
Transports a 100 Gigabit Ethernet signal

- Mobile Infrastructure 

In mobile telephony and data traffic, radio signals transport voice and data to and from portable transceivers (mobile phones or other devices). This system relies on a network of ‘cells’, each of which is served by a fixed-location transceiver, such as a Wi-Fi access point, or a mobile ‘base station’, such as a communication tower. These fixed access points and base stations are in turn connected to a fixed-line cable network. When a mobile device is turned on, it registers with the mobile network and starts ‘listening’ for the strongest signal received from the surrounding base stations, switching from one site to the next to maintain the signal as the user of the mobile device moves around the network.  

As mobile traffic continues to escalate, the ‘backhaul’ capacity of the cable-based network which supports mobile communications also has to increase. For example, a cell site carrying only GSM voice would typically Short-Haul Fiber with intermediate Access Points Cell Tower Allied Fiber Cell Tower & Colocation Hut Subsea Landing Point Education/Government Enterprise Data Center/ Carrier Hotel Long-Haul Fiber Role of fibre in broadband network connecting homes, office buildings, communication towers and data centres. 

5G operators have already started using optical fiber to connect mobile base stations, but there are still many mobile base stations that depend on ‘old’ technology which needs to be replaced. And where a new connection is required, optical fiber is installed in view of its superior transmission speed, as well as its potential to expand transmission speed supporting 5G. 

Hough et al. (2013) note that, ‘as wireless and wireline technologies converge and the dividing lines become less clear, the common denominator will be optical fiber. Whether considering fiber-to-the-x (FTTx), LTE or 5G, future access networks will include fiber as an essential part of the network infrastructure


[More to come ...]


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