CAS 50 Chapter 8 Networking & Fiberoptics
14. Distinguishing properties of optic fiber cable include, what?
* Transmission speed * Transmission Distance * Transmission Type * Noise Immunity * Frequency
12. What can be done to prevent the cable from being squashed & so crimping in the fiber core?
Shielding material may be placed under the cable jacket to prevent the cable from being squashed and so crimping the fiber core. It usually takes the form of a steel wrap or braid.
5. Single-Mode Fiber
Single-mode fiber cable transmits a single beam of light in one direction at a time. It uses a smaller core than multi-mode fiber, and has a longer range. Single-mode fiber provides a bandwidth of up to 30 MHz.
31. External Transceivers
Using external transceivers, you can change the cable that connects to a particular NIC.
8. An optical fiber cable consists of several components, they are? (5)
• an optical fiber strand, or core • a buffer • strengthening materials • optional shielding material, and • an outer jacket
21. Name 2 disadvantages of optical fiber cable.
* High cost: Optical fiber cable now costs about the same as high-performance copper cable but requires more expensive devices, including network interface cards, or NICs, and switches. A hybrid network that uses optic fiber for its backbone and untwisted pair, or UTP, copper cable for horizontal cross-connects tends to provide the best cost-to-performance ratio. * Difficult Installation: Copper cable is easy to cut, strip, shorten, and re-connect. After you cut an optical fiber cable, however, you have to polish its rough edge using a polishing tool so that light isn't distorted as it leaves the fiber. This makes installation and maintenance of optic fiber more difficult and time-consuming than for copper cable.
20. Name 4 advantages to fiber cables.
1. it's immune to EMI because, unlike copper cable, it doesn't use a conductive core to transmit electrical signals 2. it can achieve data rates of 40,000 Mbps and beyond, which is much higher than copper rates of a maximum of 10 Gbps 3. it can transmit signals over much longer distances 4. it's more secure because it doesn't produce an electromagnetic signal and simply breaks if it's punctured, making it less vulnerable to wire tapping.
1. Fiber Optic
A fiber optic cable is a network cable that has a core surrounded by one or more glass or perspex strands, which is surrounded by extra fiber strands, or wraps, and a protective outer Jacket.
30. Transceiver
A transceiver is a device that transmits and receives signals over network media. It can be built into a NIC or it can be external.
23. Subscriber Connector (SC)
Also known as a Standard Connector, an SC is square and snaps into a square receptacle. It's often used in a duplex configuration, in which two fibers are terminated into two SC connectors that are molded together.
28. Sub Miniature Type A (SMA)
Also known as a Sub Multi Assembly connector, an SMA connector has a threaded ferrule on the outside of a jacket for locking the connector in place in a waterproof connection.
24. Face Contact (FC)
An FC connector is round with a strong ceramic or metal center tube, or ferrule, that supports the fiber. This is a heavy-duty connector for industrial applications.
25. Fiber Distributed Data Interface (FDDI)
An FDDI connector - also known as a Media Interface Connector or MIC - contains two connectors for full-duplex communications and is designed to snap into a receptacle. It's used for multimode fiber optic networking.
27. Local Connector (LC)
An LC has a small form-factor ceramic ferrule and an RJ45-type latch to secure it to a device. It's smaller than an SC or ST connector. It can be used for single-mode or multimode fiber cable. The RJ45-type latch make it useful for transition installations that also use twisted pair copper cable.
29. Mechanical Transfer Registered Jack (MT-RJ)
An MT-RJ connector connects two optical fiber strands in a snap-to-lock connection. It's used with multi-mode fiber and is also called a Fiber Jack.
22. Straight Tip (ST)
An ST connector has a straight ceramic center pin with a round bayonet lug lockdown, and is most commonly used in multimode patch panels.
3. What surrounds the core & reflects light back into it?
An optical fiber cable carries signals in the form of light pulses, originating from a laser or a high-intensity light-emitting diode, or LED. Opaque material known as cladding surrounds the core and reflects light back into it, ensuring that the light can travel for a significant distance without having to be regenerated.
19. Frequency
Fiber optic cables can transmit signals at very high frequency - such that the upper frequency limit depends on the bandwidth of the transmitting and receiving devices rather than on the cable. Frequency is measured in cycles per second, and is often measured in Megahertz.
11. How does a fiber cable improve it's strength?
If a fiber cable is bent sufficiently, it will break. So strengthening materials are included in the cable to improve its overall strength, as well as to protect against compression from cold temperatures. Strengthening materials are often layered around the buffering but can also be included at the center of the cable. They may consist of Aramid yarn, fiberglass, or steel wire.
7. Graded-Index Multi-Mode Fiber
In graded-index multi-mode fiber, the center of the glass core has a higher refractive index - and therefore transmits light faster - than the outer parts of the core. So the transition between the outer part of the core and surrounding cladding is more gradual than in the case of single-index multi-mode fiber. This helps prevent transmitted light from being dispersed. Graded-index multi-mode fiber provides higher bandwidth than step-index fiber, at up to 2 GHz.
6. Step-Index Multi-Mode Fiber
Multi-mode fiber supports more than one mode, or transmission path, for light. It uses a thicker core and aperture than single-mode fiber, so light can enter the cable at different angles. It can also use a cheaper light source than single-mode fiber - for example, an LED. However, multi-mode fiber has a shorter range. Step-index multi-mode fiber contains a core surrounded by cladding. The refractive index of the core - or the speed at which it transmits light - is much higher than that of the cladding. So when light from the core enters the cladding, a "step-down" occurs and all the light is reflected back into the core, in a process known as total internal reflection.
26. Biconic
Now obsolete, biconic connectors were one of the earliest connector types. They were screw-on connectors with tapered, threaded sleeves. The tapered end helps ensure that a fiber optic thread is kept in the correct position.
18. Noise Immunity
Optical fiber cables are immune to electromagnetic interference, or EMI. They're also more secure than copper cable because they don't create an electromagnetic field - which in the case of copper cable, unauthorized users can theoretically detect and analyze to eavesdrop on transmitted signals.
15. Transmission Speed
Optical fiber cables can transmit data at up to 40,000 Mbps and beyond. The maximum data transfer rate over fiber is continually being raised.
17. Transmission Type
Optical fiber cables support full-duplex transmission - a node can transmit and receive at the same time. There are two strands of fiber, one for each direction of communication.
4. What does optical fiber use to bend light so that it can pass through a cable?
Optical fiber uses refraction to bend light so that it can pass through a cable. A light ray passing from one transparent medium to another bends due to a change in velocity, which occurs due to the differences in the density of the two mediums. The angle between the normal and the light ray as light enters the second medium is called the angle of refraction. The angle of incidence for refraction is the same as for reflection.
16. Transmission Distance
Single-mode fiber cables can transmit data over distances of up to 62 miles between repeaters. Multi-mode fiber can usually transmit signals over a maximum of about 500 meters or 1,640 feet.
32. What are some transceivers called as?
Some transceivers are called fiber media converters because they make it possible to connect optical fiber cable with other cable types. They do this by converting the signals between the cables.
10. What does the buffer do?
The buffer protects the core fibers. It can be loose fitting to cope with outdoor changes in temperature, or it can be tight fitting to provide more durability. Tight-fitting buffers are usually found on indoor cables.
9. How thick is the optical fiber strand, or core?
The optical fiber strand, or core, is between 5 and 100 microns thick. Light pulses from a laser or high-intensity light-emitting diode, or LED are passed through the core to carry a signal.
13. What's the outer jacket of an optical fiber cable?
The outer jacket of an optical fiber cable is a plastic coating that protects the cable from dirt, ultra-violet radiation, and water.
2. Why shouldn't you look into the end of an operating optical fiber cable?
You shouldn't look into the end of an operating optical fiber cable because the light signals it uses are strong enough to cause eye damage. Also, small shards of fiber created when the cable is stripped can enter the skin and blood vessels, or damage the eyes.
33. There are four types of media converters, what are they?
• a multimode fiber to Ethernet convertor extends an Ethernet network connection over a multimode fiber backbone • a fiber to coaxial convertor converts signals on fiber to a coaxial cable • a single-mode to multi-mode fiber convertor transmits multi-mode fiber signals over single-mode fiber devices and links, supporting conversion between multi-mode segments on a network that spans a wider coverage area, and • a single mode fiber to Ethernet convertor extends an Ethernet network connection over a single-mode fiber backbone
