Powerpoints Fiber Flashcards
What’s the preferred media for long haul transmission?
Fiber
OSP (Outside plant fiber):
Designed to go outdoors - burial, aerial, submarine. Ruggedized for the environment.
singlemode-
Premises Fiber:
Shorter in length than OSP, part of the LAN. Installed where other media isn’t appropriate.
Fiber is immune to:
EMI/RFI
Signal path for fiber ranges from ___ to
8mm to 62.5mm
Dirt:
Enemy #1 - everything must be cleaned constantly.
Fiber construction:
Jacket = covering Buffer = color coded plastic covering Cladding = glass Core = hollow path for the signal
Connector:
Non-permanent device for interconnection. ST, SC, LC, Duplex multimode.
MTP-prefabricated cabling systems
Types of splicing (2) and define:
Splices are considered permanent joints
Fusion - lowest loss and least reflectance,welding two fibers together using special machine.
Mechanical - temporary restoration for most multimode,two fibers locked together manually.
Optical Power:
Absolute measurement of signal strength.
Optical Loss:
Loss of power along a path, measure in dB.
Decibal (dB):
Ratio of power to loss
Scattering:
Loss due to signal hitting impurities in fiber.
Tools:
Cleaver = used to “cut” bear fiber, uses splices (fusion/mechanical) and can lock connections (unicam and others).
Fiber stripper = strips the buffer and coatings off the fiber for terminations.
Fusion splicer = fuses two fiber ends together, making them one piece of glass.
Anaerobic Connector Stuff (?)
Polishing film, polishing puck, scribe
Visual Fault Locator:
visible light source(LED or flashlight) that allows visual checking of continuity and tracing for correct connections, such as duplex connector polarity
OTDR (Optical Time Domain Reflectometer)
uses backscattered light to take a snapshot of fiber,measures lenght,splice loss, or fiber attenuation, as well as for fault location in fiber from only one end of the cable
Macrobending/Microbending:
Macro = attenuation from bending fiber, overbending the fiber Micro = attenuation increase caused by high frequency small radius bends along length of fiber. compression bending of fiber
Transceivers:
Send and receive data. Short for TRANSmitter and reCEIVER. Electrical signal (sending) converted to “light”, sent over the fiber, and turned back into electrical signal (receiving).
Signal Sources (signal generators):
LED - cheap, low power used in LAN’s with MM fiber.
Lazers - $$ varies with type and power. VCSEL is the cheapest with the lowest power, FP - middle; DFB is the most expensive and powerful used for long haul.
Repeaters:
Boost the signals
Signal Detectors:
Detect optical signal and turns it back into an electrical one. Have a minimum signal level they can detect, and if the signal below that level in a run, a repeater must be used.
Multimode:
Multiple signals (modes are signals).
uses step or graded index
OM3 uses lazers
Graded/Step Index
Graded - has many cores within the core
Step - single boundary for reflection (single mode)
Single Mode:
Supports only one mode with a smaller core and longer runs than a multimode, and almost always uses step index.
lower loss and and virtually infinate bandwith
Types of Attentuation:
Absorption: Loss from signal being converted to heat.
Scattering - Loss from signal hitting molecules wrong, then redirected.
Model Dispersion:
Effects only multimode - modes travel at different speeds thru the media.
Chromatic Dispersion:
Effects multimode and single mode and caused by widening of the signal. If it widens too much, detector may not be able to detect the number of pulses.
big problem with LED sources in multimode
Classify the three types of fiber:
Media type (single/multimode) Cable construction Where it's designed to be installed.
Cable construction:
Tight buffered, loose tube and ribbon
125mm diameter / 250mm protective coating.
Tight buffered - 8 - 62.5mm core, 125mm cladding, 250mm coating; 900mm buffer. All together makes one tight buffered strand.
Loose Tube - 8 - 62.5mm core, 125mm cladding, 250mm coating. Multiple strands packed into each tube and may be many tubes in the cable.
Ribbon - 8 - 62.5mm core, 125mm cladding, 250mm coating;2-12 strands packed together in a ribbon, many ribbons in a cable. Very high density in a single cable.
NEC Article 770:
NEC is only concerned with fire and electrical hazards.
OFN is non-conductive - - no conductive material in the cable.
OFC is conductive; cable may become energized is a fault condition.
Cable must be suitable for the environment.
Connectors vs. splice:
Connectors are used when changes are often made, panels where equipment changes, and the fiber run itself is occasionally altered.
Splices are used when no changes are expected, to extend a fiber run, and repair a damaged fiber run.
Hybrid
Composite
H-contains 2 types of fiber
C-contains fiber and electrical conductors
pulling tensions
under tension during pulling 20x the diameter of cable
not under tension minimum long term bend 10x diameter of cable
Reflectance
fresnel reflection,optical,return loss, or backrelection
amount of light that is relected back up the fiber toward source light in the connector, primary problem in connectors
Ferel
white tip at end of connector
3 methods for terminating connectors
glue and finish-uses anaerobics and hotglue
cam lock-unicam and others
fusion splice to pigtail
