An Introduction to ATM (Asynchronous Transfer Mode) Networks
The standards for ATM were first developed in the mid 1980s. The goal was to design a single networking strategy that could transport real-time video and audio as well as image files, text and email.
ATM (Asynchronous Transfer Mode) has been proposed as an enabling network technology to support broadband integrated services. It was designed to provide a single platform for the transmission of voice, video and data at specified quality of service and at speeds varing from fractional T1 to...
Dummies' Guide to Fiber Optic Bit Error Ratio (BER) Measurement
Bit error ratio (BER) measurement is the fundamental measurement of the quality of the fiber optic communication system. It measures the system's probability that transmitted bits will be correctly received as logic ones and zeros.
Bit error ratio is the ratio of the number of bits received incorrectly compared to the number of bits transmitted in a specified time interval or quantity of bits. The typical acceptable BER levels range from 1e-9 to 1e-12.
Equipment for testing BER
The equipment...
Dummies' Guide to Fiber Optic Sensors
What are fiber optic sensors?
The fundamental characteristic of all fiber optic sensors is that they depend on some optical properties, such as intensity, phase, state of polarization and wavelength, to be modulated by measurands. Measurands could be pressure, temperature, electromagnetic field or displacement.
All fiber optic sensors have an optical element that is sensing these property changes. For most sensors, this element is the optical fiber itself or a non-fiber optical...
Everything You Need To Know About Aerial Fiber Optic Cable Installation
Understanding The Basic Terms
1. Dead end pole: Dead end pole is a utility pole on which self-supporting figure 8 aerial cable or a steel messenger is tensioned and terminated into a dead-end fixture.
2. Messenger span: Messenger span refers to the length of continuous steel messenger tensioned between two dead-end poles.
3. Intermediate poles: Intermediate poles are all the poles between two dead-end poles.
Planning
1. Careful planning and preparation are necessary before any aerial cable...
Everything You Need to Know About Computer LAN (Local Area Network) Backbone Wiring
:: The Definition of Backbone Cabling
Backbone cabling may be within one building or between buildings on a campus. All wiring between telecommunication rooms is called as backbone cabling.
In many cases, backbone cabling is actually between wiring closets on the same floor of a building, but the more typical case is the floor to floor wiring in a multi-floor building. Many call it vertical cabling in contrast to horizontal cabling.
:: How are backbone wiring implemented?
Typically...
Everything You Need to Know About Fiber Optic Ethernet
In the last decade, a wide variety of applications have been developed that covers a dozen of datacom networking technologies. The transmission speed ranges from 10Mbits up to 10Gbit/s and growing.
High distance-bandwidth product is the major selling point for fiber optic transceivers. Another major benefit of fiber optic systems is their high reliability compared to other media.
Now fiber optic transceivers are commercially available for almost all international and industrial standards,...
Everything You Need to Know About Fiber Optic Testing Fiber Optic Technology Tutorial Series
Overview of Fiber Optic Testing
There are mandatory tests for every stage of the design, manufacture, and installation of the fiber optic components, link, cable plant, and network.
Most fiber optic test procedures have been thoroughly tested and codified as industry standards. These standards are part of EIA/TIA RS455 and are being adapted into IEC standards.
Most of these standards refer to tests of individual components under a variety of environmental conditions; therefore, only a few...
FAQ On Fiber Optic Cable Handling And Installation
:: 1. What is the difference between copper cable and fiber optic cable?
Even though fiber optic cables may look like traditional copper cables, we should always keep in mind that inside fiber cables are fragile glass fibers which can be broken easily if not properly handled.
:: 2. What are the most important things to obey in fiber cable installation?
During any fiber optic cable installation project, we must keep two very important things in mind: First, never over-bend the fiber cable...
How Do Fiber Optic Couplers Work And How Are They Made?
:: The need for fiber optic couplers
We use electronic couplers all the time: such as a telephone coupler which lets you connect both a telephone and a fax machine to the same telephone line. Or a CATV coupler which lets you connect several TV sets to a single cable from Comcast. Basically you can buy these couplers from Home Depot or other electronic retailers.
Optical couplers have the same functionality as electronic couplers: They split the signal to multiple points(devices). Fiber optic...
How to Design a High Performance Optical Receiver?
The structure of an optical receiver is simple: consisting of just a photodiode to produce the electrical current and an amplifier. But do not be fooled: it is far more complex to design a really high performance optical receiver. So we will talk about some of the criteria of actual receivers.
The are a bunch of factors involved in the process. You have to take into count of signal current noise, noise from the photodiode such as from an avalanche diode, noise from the amplification...
How to Design a Highly Reliable Fiber Optic Network
What happens if a major fiber optic cable is cut or a major hubbing location is destroyed in a fiber network? Will the whole system be brought down?
That is the subject of this article: the survivability of a well designed fiber network.
Modern fiber optic transmission systems have provided tremendous capacity for voice, video and data traffic. At the same time, the fiber network needs to be designed to take the full advantage of this economies of scale while minimizes maintenance cost.
The...
How To Install Outdoor Fiber Optic Cables In Underground Ducts And Innerducts
:: Duct/Innerduct materials and colors:
Fiber ducts are usually made from HDPE (high-density polyethylene), PVC or other compound. They are usually in black or gray. Fiber innerduct is usually orange or yellow.
:: Why usually fiber ducts and innerducts are corrugated?
Fiber ducts and innerducts are corrugated to provide the following benefits:
1. Decreasing pulling tensions during installation
2. Very flexible and can be used in installation locations where many turns are involved
3....
Introduction to SONET (Synchronous Optical Networking) Fiber Optic Technologies Tutorial Series
The SONET standards were developed in the mid-1980s to take advantage of low-cost transmission over optical fibers. It defines a hierarchy of data rates, formats for framing and multiplexing the payload data, as well as optical signal specifications(wavelength and dispersion), allowing multi-vendor interoperability.
SONET is sometimes described as "T-1 on steroids". Why is that? As we know, the digital hierarchy (DS-0, DS-1, DS-2, DS-3 and more) was created to provide cost-effective...
Optical Fiber Fusion Splicing and Its Applications
What is optical fiber fusion splicing?
Optical fiber fusion splicing is a welded joint formed between two optical fibers. Fusion splicing is a permanent, low-loss, high-strength joint compared with other temporary joint such as a mechanical splice. Optical fiber fusion splices play a crucial role in the optical network.
The Ideal Fusion Splicing Process
The goal of fiber fusion splicing is to create a joint with minimum insertion loss yet with mechanical strength and long-term reliability...
Some Basic Concepts of Fiber Optic Loss Testing
When testing loss in a fiber optic link, some basic principles must be kept in mind all the time.
1. The testing wavelength should always be the same as the working wavelength. Because optical fiber loss varies with light wavelength, you will get incorrect result if your measuring wavelength is different from the actual working wavelength. For example, if a system is designed for 1550nm but you test it with 1310nm light source and power meter, the result will not be correct.
2. The testing...
The Current Status of FTTH in the US and the Rest of the World
Understanding FTTH (Fiber To The Home)
FTTH is an all-fiber connection to the home which provides a minimum of 155Mbps bandwidth on both up stream and down stream directions. Basically, it is composed of a fiber from the service node to the optical splitter, the optical splitter which separates to (fan out) terminate on single home ONU.
So similar to FTTC (Fiber To The Curb), FTTH is a point-to-point architecture with a dedicated connection from the home to the network. This fiber link...
The Future of Fiber Optic Communication
There is no question that fiber optic communication is our future. Fiber optic communication industry has been enjoying amazing growth for over 15 years. These are driven by both technology advance and market demand. There are some obvious trends in the development of new technology and market. Let's examine some of the most important ones here.
All-Optical Network
All-optical network has been a top topic in fiber optic communication industry for over a decade now. Its ultimate goal is to...
The Secret Of A Successful Underground Fiber Optic Cable Installation
The two most common outdoor fiber optic cable installations are pole line aerial installation and underground cable installation. Underground cable installation can be buried directly underground or placed into a buried duct.
Direct burial installation:
Direct burial installations are most common for long cross-country installations. The cables are plowed in or buried in a trench; the installation process can be very quick. The most common cables used for direct burial are steel armored...
The Secrets of Choosing Ribbon Fiber
Do you know why it is so expensive to install Fiber To The Home? Why Bell companies are reluctant to deploy fiber optic network directly to consumers in a large scale?
It's not the material cost. It's the labor! The introduction of fiber into the subscriber loop has increased the installation of short cable lengths with large number of splices. The speed at which the cables can be placed, spliced, accessed and reconfigured are becoming extremely important.
So the need for new technologies...
The Story Of Legacy Fiber Optic Connectors
:: Choices of connectors
Over the years, a large variety of fiber optic connectors have been designed for most fiber optic installations. Lightwave equipment manufacturers have never standardized on any one connector type, they actually provide a selection of connectors for their equipment interface.
It is very important to choose the fiber connector type for your applications. You should maintain a connector standard throughout a fiber optic project.
:: The components of a fiber...
The Tremendous Applications of Fiber Optics
The use of fiber optic systems is expanding at a amazing rate. Only in the past 10 years, fiber optic communications systems have replaced almost all coaxial and twisted pair cables especially in network backbones. This is especially true in any long distance communication links.
Why? This can be explained simply. Fiber optic cables are easier to install, are lighter than traditional copper cables, are much smaller than their electronic counterparts, and most importantly, they have much more...
Troubleshooting Your Optical Fiber Networks: Introduction to OTDR Optical Time Domain Reflectometer
How Does an OTDR Work?
In fiber optic networks, OTDR (Optical Time Domain Reflectometer) is an opto-electronic instrument used to characterize an optical fiber. OTDR is both the best known and least understood fiber optic instrument.
OTDR does not measure loss, but instead implies it by looking at the backscatter signature of the fiber. It does not measure cable plant loss that can be correlated to power budgets.
An OTDR injects a series of optical pulses into the fiber under test. It also...
Understanding Basic Terms in Indoor Fiber Optic Cable Installation
Fiber optic cables are exposed to electrical, mechanical, chemical and environmental elements, so proper installation is critical for the long-term stability and survival of fiber cables.
Cable installation must also meet the NEC(National Electric Code) and local building codes. NEC indicates that fiber optic cables can be placed in the same raceway, cable tray or enclosure with CATV, telephone, communication circuits and Class 2 and 3 remote control signaling circuits.
Note that you should...
Understanding The Basics Of All Optical Switching
What is all-optical switching?
All-optical switching is a process by which light, usually in the form of digital communication signals, is routed from one transmission channel to another, or modulated, without intermediate conversion to another format.
In previous technologies, the routing usually involves the following steps: detection of an optical signal, an electronic routing decision, electronic triggering of a laser in the appropriate output channel, and generation of a new optical...
What Are Fiber Optic Attenuators? Fiber Optic Communication Tutorial Series
Why Do We Need Fiber Optic Attenuators?
A fiber optic attenuator, also called an optical attenuator, simulates the loss the would be caused by a long length of fiber. Typically, this device performs receiver testing. While an optical attenuator can simulate the optical loss of a long length of fiber, it cannot accurately simulate the dispersion that would be caused by a long length of fiber.
Put it simply, for a fiber optic receiver, too much light can overload it and degrade the bit error...
What Are Fiber Optic Circulators? Fiber Optic Communication Tutorial Series
What is an optical circulator?
The optical circulator has similar function and design as the optical isolator. An optical circulator is an nonreciprocal passive device that directs light sequentially from port 1 to port 2, from port 2 to port 3, and so on in only one direction. The operation of a circulator is similar to that of an isolator except its constructions is more complex. Like the isolator, its uses polarization to do its job.
The typical construction of an circulator consists of a...
What Are Fiber Optic Isolators? Fiber Optic Communication Tutorial Series
Why do we need fiber optic isolator?
Light can be reflected back and forth. This is also true in fiber optic communication networks. But in fiber optic networks, most of the reflections are harmful to the stability of the system which is especially true for lasers.
Laser is essentially a resonant cavity between two semi-transparent mirrors. The lasing process happens between these two mirrors. The lasing process is very delicate and can be easily interfered. If back-reflected and scattered...
What Are OFNP, OFNR, OFNG And OFCG? Understanding Fiber Optic Cable Fire Ratings
Just like copper cables, NEC (National Electrical Code) requires indoor fiber optic cables be marked with their fire and smoking ratings. NEC requires all indoor fiber cables be marked correctly and installed properly for its intended use.
According to NEC, a building's inside area is divided into three types of sections: plenums, risers and general purpose areas.
:: What is a Plenum area?
A Plenum area is a building space used for air flow or air distribution system. In most buildings, the...
What Are Optical Fiber Amplifiers And How Do They Work?
:: Why do we need optical fiber amplifiers?
Basically what the optical fiber amplifiers solve is the traditional distance problem as in any long distance telecommunication system such as a trans-Atlantic link. As optical signals travel through the fiber, the signals become weaker in power. The farther you go, the weaker the signal become until it becomes too weak to be detected reliably.
Fiber optic communication systems solve this problem by using fiber amplifiers along the way. A repeater...
What Is Structured Cabling For Computer LAN Networks?
:: What is structured cabling?
Modern computer LAN (local area network) wiring has the concept of structured cabling.
With todays high speed networks, people realize that the networking system must be broken up into shorter chunks that allow workstation wiring to be concentrated, with each cable length short enough to support the high data rate.
Based on aforementioned reasons, structured wiring standard has been developed to help define a computer wiring system that stays within the...
What is WDM (Wavelength Division Multiplexing) For Fiber Optic Communication? Fiber Optic Tutorial Series
What is WDM?
WDM is the abbreviation for Wavelength Division Multiplexing. What it does is to split the the light in an optic fiber into a number of discrete wavelengths (colors). Each wavelength (color) is a independent channel running at data rate at 2.5Gbit/s, 10Gbit/s, 40Gbit/s or even 100Gbit/s (still under development). So if the light in the fiber is split into 16 wavelengths (colors or channels), and each wavelength is running at 40Gbit/s data rate, we get a total of 40Gbit/s x 16 =...
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