Understanding Fiber Optics
P l a s t i c c o a t i n g C l a d d i n g
p ca
r yp
Optical Fiber Types Main type
Charac teristic s
Singlemode e mode
C o r e
Typical dimensions
8µm - Low atten attenuatio uation n to 12µm - 1260 to 1640 nm transmission wavelengths - Access/medium/long haul networks (>200km) - Nearly infinite bandwidth
125µm
50µm 62.5µm
125µm
Multimode - High attenuation (graded index) - 850 to 1300 nm transmission wavelengths - Local networks (<2 km) - Limited bandwidth
Index Profile
Lightwavve ep propa ropagation
250to 900µm
n1 1.457 ≈
Fiber Optic Transmission Windows
Visible
lilig ht
Windows
Wavelength (nm)
ssion 700
n2 1.471 ≈
n ows
n1 1.540 ≈
250to 900µm
Optical Connectors nnector Optical Connector
Fib er tr tra n sm ission wa wave len g th ra ra ng e (IR - Inf rared) rared)
800
635
900
1000
1100
1200
850
1300
1400
1300 /1310 138 1383
1500
Connector types*
1600
1490 1 550
Name
1625
Applications
FC-PC / FC-APC
Datacom, Telecommunication, CATV
SC-PC / SC-APC
Datacom, Telecommunication, CATV,LAN
E2000-PC / E2000-APC (Ferrule diameter :1.25mm)
Telecommunication, Datacom,CATV,LAN
LC-PC / LC-APC (Ferrule diameter :1.25mm)
High density interconnection, Datacom, telecommunication,CATV
ST-PC
Inter-/Intra-building, Security,Navy, Datacom, LAN
MU-PC / MU-APC
Datacom, Telecommunication, CATV
MT-RJ (Ribbon fiber)
Tatacom, LAN
Biconic
LAN,Datacom, Medical instrumentation,Remote, sensing,Telemetry, CATV
DIN-PC / DIN-APC
Datacom, Telecommunication, CATV
Attenuation (dB /km)
n2 1.540 to 1.562 ≈
10
Refractiveindex:
A measureof measureof thespeedoflightin amaterial. n1and n2aretherespectiverefractiveindex n2aretherespectiverefractiveindex ofthecladdingand thecore. n1
1st
ITU Fiber Standard
Description
Applications
G.651
Characteristics of a 50/125 mm multimode graded index optical fibre cable.
Video and Datacom in premises networks. Up to 10 GigE transmission in local area networks (up to 300 m). Wavelength coverage: 850 to 1300 nm
G.652 Class A/B G.652 Class C/D
Characteristics of singlemode optical fiber and cable
From access to long haul networks. Supports high bit rate transmission (10 Gb/s and +, 10 GigE…). Suitable for DWDM and CWDM systems. Wavelength coverage: 1260 to 1625 nm.
Characteristics of non-zero dispersion shifted singlemode optical fiber and cable.
Transmission applications at high bit rates for STM-64/OC-192(10 Gb/s) overlonger distances. Suitable for STM-256/OC-568 (40 Gb/s). Supports DWDM transmission applications in the C+L bands. Wavelength coverage: 1550 to 1625 nm.
Characteristics of bending loss insensitive singlemode optical fiber and cable for the access network.
Support optimized access network installation with very short bending radii applied in fiber management systems and particularly for in- and outdoor installation, specialy in FTTx network. Wavelength coverage: 1260 to 1625 nm.
G.655 Class C G.655 Class D G.655 Class E
G.657 Class A G.657 Class B
Window
Water peaks
2nd/3rd Window
NS WP Single mode Fiber
O
E
S C L
U
LWP Single mode Fiber 1 Rayleigh scattering IR absorption
0.1
Wavelength (nm) 80 0
Typical fiber cables b e t u
d e
I n les ( I nd o o
b a b c a
o r
)
Thermoplastic jacket
Outer jacket
e b u t
Overallpolyester barrier Water-prooftape
Possiblefillers
t door ) o o u
( e s
l e l b
a c
r
f e f
u b
t
h
g
i
T
10 00
Aramid yarn
e
s
Floodedcore
o o
L
Thermoplastic jacket
f i i b n f
o b b
i R
er c ab l e l e
s
Outer jacket Dielectric strength members
Band
Description
Wavelength Ra Range
O
Original (2nd Window)
1260 to 1360 nm
E
Extended
1360 to 1460 nm
1 400
16 00
Bloisture blockinggel
S
Short Wavelengths
C
Conventional ( erbium window )
1530 to 1565 nm
L
Longwavelenghts
1565 to 1625 nm
U
Ultralongwavelengths
1625 to 1675 nm
1460 to 1530 nm
FRP strength member
Central member
Multiple250 microns fibers
900micronstightbufferedfibers
Applications:Computerrooms, telecommunications central offices,tunnel and confined areas,riser shafts.
Applications:Buildinginterconnections,telecommunications and,data trunk, longhaul networks, ducts between buildings.
Typical applications:equipment interconnect, high speed datatransfer,premise network…
Tight buffered tubecablecan hold from 1to 12 fibers per tube(upto 200fibers in onecable).
Applications requiringmoistureand weather resistant.Loose tubecable can holdfrom 1to 12fibers per tube(upto 200 fibers in onecable).
Ribbon cables can hold 204 fibers in a 0.5-inch cable. This pictureshows a 3000fiber undergroundcable.
"
"
Optical Transmission Transmission
Optical Transmission
ical Transmission
0 to to -1 0 dB dBm
FWHM 100nm
specifications must be considered.One of the ma jor parameters requiring measurement is optical loss budget, or end-to-end optical link loss. loss. When calculating the optical loss budget of a fiber link ,the , the source source,, detector,and optical transmission line must be considered.
Optical loss budget should tak e into account both lin k loss loss and system power margins.These power margins cover allowances for the effect s Splice loss of environment,aging and eventual repairs. In order to calculate lin k loss loss budgets,typical values of the different component are used.
FWHM 3nm
Splice gain
An example of a typical singlemode system could be: (1) Average Transmitter (Tx) output optical power: 0 dBm Minimum Receiver (Rx) sensitivity: -20 dBm (2) 20 dB (1) – (2) Maximum optical loss budget:
A Total Total connector connector Loss = 0.5 dB x Number of connector pairs
1300 LED
1300 FP laserdiode (MLM laser)
<<1nm
B Total f iber iber Loss = loss per k m x fiber distance 1550 nm
0.2 dB/km
≈
Photodetectorsspectralresponse S y (A/W )
InGaAs
1.0
Rx
Ge(23°C)
Si
C Total Total splice splice Loss= 0, 1 dB x Number of splices Network (Link Loss)
1300 (nm) DFBlaserdiode (SLMlaser) y
Thetype offiber used and thecharacteristics ofthe sourceimpose limits onsystem performance.Thenarrower thespectral bandwidth ofthe sourcediode, thehigher thepossible frequency bandwidth/bit rateof thesystem. -LED: Short-haul andlaw bitrate(LANnetwor k s) s) systems thatusemulti-mode fibers. -Laser diode:Long-haul andhigh bitratesystems thatuse singlemode fibers. Multi-Longitudinal Mode(MLM) lasers,also k nown nown as Fabry-Perot (FP) lasers and Single Longitudinal Mode(SLM) or Distributed Feedback (DFB) (DFB) lasers areused for these applications.
1310 nm ≈ 0.35 dB/km
G e(0 °C)
Total other D Total other components loss = loss x Number of components Mechanical splice ≈ 0.5dB ≈ 3.5 dB 7 dB ≈ 1 1:32 splitter 17
0.5
1:2 splitter
850
Before Bef ore cleaning e aning
After Aft er cleanin cleaning g
Optical Connection Inspection It is very important to clean connectors. A dirty connector will dramatically increase the power loss ! Inspect your connector before and after cleaning using a videoscope.
PhysicalContact (PC) C Con onne nect ctor or
Angl An gled ed Ph Phys ysic ical al Co Cont ntac actt (APC) Connector
Measurement units : Watts, dB or dBm
≈
8°
+5 to to -10 dB dBm
Optical Loss Budget
When installing a fiber networ k ,networ , network topology topology and equipment
N N on velist on e x hausti hausti v e list
*
is scattered in all directions causing loss. ei gh Rayl ei gh scattering: light energ y is NSWP : N on on Suppressed W ater ater P eak. eak. LWP : Low W ater ater P eak eak ( e x :G :G .652.D fiber ).
LED and Laser diode power spectra -15to -25dBm
Attenuation is the result o f a a variety of scattering scattering and absorption mechanisms,and is wavelength dependent. Since singlemode optical fibers are designed to to operate over a wide range range of wavelengths, wavelengths, the attenuation measurement measurement is performed as a function of wavelength,typically between 1200 nm and 1625 nm. Fiber optic transmission mak es es use of the three optical windows (850,1300,1550 nm) that are given by the attenuation characteristics of the silica fibers. Also,635 nm light is used for visible fault fault location. For remote fiber testing testing a wavelength of 1625nm or above is used used to not disturb disturb the traffic.
Buffer tube Ribbon
Aramid strengthelement
Tx
120 0
A cable is an assembly of optical fibers with materials providing mechanical and environmental protection of the optical fibers Outer jacket
1300
1550
Si:Silicon,applications in thevisible light range(400 to 1000nm) Ge: Germanium,applications in optical windows (750to 1600 nm) InGaAs:Induim Galium Arsenide,application in optical windows (>1000nm)
y
Absolute Power (mW)
Absolute Power (dBm)
1000 100 10 5 1 0,5 0,1 0,01 0,001 0,0001
+30 +20 +10 +7 0 -3 -10 -20 -30 -40
Loss (dB)
Power (%)
- 0,10 - 0,20 - 0,35 -1 -3 -6 - 10 - 20
2 5 8 20 50 75 90 99
Insertion Loss:0 to 0.5 dB Optical Return Loss:>40 dB
Insertion Loss:0 to 0.5 dB Optical Return Loss:>60 dB
InsertionLoss(IL): o nLoss(IL): Lossin transmitted ansmitted signalpower resultingfrom theinsertion ofa componentin anoptical fiber link. Opti calR c alR et urnLoss( ORL): Ratioofthereflected power totheincidentpower from afiber opticlink or y sy stem stem ,
ve v alue. e x pressed asa positi v alue.
Connector Mating Plug pair
Plug pair
Hybrid mating adapter
K ey ey
M at at in in ga da da pt pt er er
F er er ru ru le
K ey ey
(nm)
dB: quantify dB: quantify gain gain or or loss P 1 dB = 10 log (P1 and P2 expressed in Watts) P 2
dBm: specify dBm: specify absolute power levels P 1 dBm) = 10 log (P1 expressed in mW ) P( dB 1mW
Understanding
Fiber Optics