merenja u telekomunikacijama
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Kratak pregledTRANSCRIPT
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MIHAJLO PRERAD - MERENJA Slide 1
MERENJA U TELEKOMUNIKACIJAMA
Mihajlo Prerad Certified Cable Test Technician Trainer
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MIHAJLO PRERAD - MERENJA Slide 2Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 2
Šta su merenja?
• Pod merenjem se podrazumeva testiranje komunikacione opreme i instalacija, nadzor i održavanje sistema, logička analiza signala, kao i prikupljanje, statistička obrada i ekspertiza podataka o funkcionisanju sistema.
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MIHAJLO PRERAD - MERENJA Slide 3Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 3
Način prenosa signala (fizički sloj)
– Bežične mreže• Prenos signala putem radio talasa• Bez fizičkog povezivanja dve tačke
– Bakarne mreže• Prenos signala putem bakarnog kabla• Različite tehnologije: ADSL, VDSL, SHDSL, Coax, Ethernet...
– Optičke mreže• Prenos signala putem optičkog vlakna• Brzine prenosa 100Gpbs
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MIHAJLO PRERAD - MERENJA Slide 4Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 4
BEŽIČNE MREŽE
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BEŽIČNE MREŽE
• Prenos informacija između dve tačke koje nisu fizički povezane putem radio talasa (vrsta elektromagnetnog zračenja)
• Standardi:– WiFi (802.11a/b/g/n)– Bluetooth– WiMax– VHF, UHF– GSM, UMTS, EDGE
• Frekvencijski opseg:
3Hz – 300GHz
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MIHAJLO PRERAD - MERENJA Slide 6Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 6
Instrumenti za testiranje bežičnih mreža
Analizator spektra (Spectrum Analyzer)
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Dizajn WiFi mreža
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Analiza i monitoring WiFi mreža
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Bakarne mreže -Strukturno kabliranje
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Kategorije i tipovi kablova
Kategorije:• Cat 3 – 16 MHz• Cat 5e – 100 MHz• Cat 6 – 250 MHz• Cat 6a – 500 MHz• Cat 7 – 600 MHz• Cat 7a – 1000 MHz
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UTP
STP
SSTP
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MIHAJLO PRERAD - MERENJA Slide 11Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 11
IZGLED BAKARNIH KABLOVA
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Korak 1: Verifikacija
• Verifikacija omogućuje:– Osnovne funkcije za proveru
konektivnosti kao što su: “wiremap” i dužina kabla
– Jednostavne funkcije za rešavanje problema kao što je nalaženje greške na kablu
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MIHAJLO PRERAD - MERENJA Slide 13Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 13
Korak 2: Kvalifikacija
• Kvalifikacija omogućuje:– Wiremap– Provera brzine prenosa koju kabl
podržava (10/100/1000BaseT)– Dužina kabla i mesto prekida– Crosstalk i Impedance fault– Memorija za čuvanje i štampanje
rezultata
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Šta je sertifikacija?
• “Da li performanse nekog kabla zadovoljavaju parametre propisane prema TIA ili ISO standardu”
• Definicija tih performansi i nivoa koje treba zadovoljiti (“Kategorije ili Klase”) je definisana standardima:
– TIA-568B standard (Cat 5e, Cat 6)– ISO 11801 i IEC 61935 (Class C, D , E i F)
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Parametri sertifikacije
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Greške ožičenja
• Identifikacija fizičke greške instalacije:– Kratak spoj između bilo koje dve
parice– Prekid– Ukrštene parice
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FAIL PASS
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Propagation delay
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• Vreme potrebno da signal poslat sa jednog kraja stigne na drugi kraj• Limit: 555ns
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MIHAJLO PRERAD - MERENJA Slide 18Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 18
Delay skew
• Razlika u propagacionom kašnjenju između najbržih i najsporijih parica
• Limit: 50ns• Idealan <25ns• Uobičajen 25 – 50ns
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Gubitak
Predajnik
signala
Prijemnik
Signala
SLABLJENJE
• Količina izgubljenog signala u prenosnom linku (izraženo u dB)
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Slabljenje - primer
• Proporcionalno raste sa dužinom i frekvencijom
• Za svakih -6dB gubitka, originalni signal slabi za 50% vrednosti
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Ratio Decibel
1/1 0 dB
1/2 -6 dB
1/5 -14 dB
1/10 -20 dB
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Optičke mreže
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#1 – Mreža Nikad neće biti sporija
•Planirajte veće brzine, bolje vreme odziva, smanjeno kašnjenje
#2 - Mreža Nikad neće biti manja
•Planirajte više korisnika, veću količinu saobraćaja, više linkova
#3 - Mreža Nikad neće biti ista
•Planirajte fleksibilnost, izmenljivost i mogućnost brzih promena
Tri zakona mreže:
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Porast korisnika
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Potrošači zahtevaju...
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Potrebe aplikacija
Aplikacija Protok
IP telefonija 0.064 Mbps
Internet 1..10 Mbps
Onlajn video 5 Mbps/ch.
HDTV 9..20 Mbps/ch
MICOM TM INTERNATIONAL | MICOM GROUP MEMBER
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MIHAJLO PRERAD - MERENJA Slide 26Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 26
Potrebe prosečnog korisnika
Data
Voice
Video
AccessNetwork
5..20 Mbps
0.1 Mbps
6..30 Mbps
1..10 Mbps
10 do 30 Mbps
9 – 20 Mbps
0,1 Mbps
1 – 10 Mbps
MICOM TM INTERNATIONAL | MICOM GROUP MEMBER
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Rešenje: postavite optička vlakna!
• Mali gubici• Veliki propusni opseg• Bez uticaja okoline (EMI)• Veoma mali• Lagani
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Infracrvena svetlost Vidljiva svetlost
(VFL)
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Optički kabl
Spoljna izolacija (tzv. “jacket”)
Materijal za učvršćenje (tzv. “cevlar”)
Akrilatna zaštita (tzv. “buffer”)
Primarna izolacija (tzv. “clad”)
Jezgro (tzv. “core”)
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Optički kabl• Koristi svetlosni signal za prenos podataka• Core & Cladding se prave najčešće od specijalne vrste
silikonskog stakla• Tipičan “Cladding” prečnik = 125 µm• Tipičan “Coating” prečnik = 250 µm• Prečnik jezgra (core) definiše tip vlakna
– 9 µm za singlemodna vlakna (varira od 8.3 do 9)– 50 i 62.5 µm za multimodna vlakna
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Tipovi optičkih vlakana
• Monomodna (SM, singlemode)– sva vlakna su monomodna– Talasne dužine: 1310nm i 1550nm (ima i drugih)
• Višemodna (MM, multimode)– sva vlakna su multimodna – Talasne dužine: 850nm i 1300nm
• Hibridni mod– monomodna i multimodna vlakna u okviru jednog kabla
(npr. 4MM i 4SM)
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SC
Tipovi konektora
ST
FCLC
* Popularan je i E2000 konektor (nemam sliku)
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Multimodna vlakna
• Od latinske reči “multi-path”; što znači “višemodni”
• Modovi svetlosti stižu na destinaciju u različito vreme i prouzrokuju širenje/rasipanje signala
125 µm62.5 µm
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Singlemodna vlakna
• Od latinske reči “single-path”; što znači jedan mod (singlemod)
• Postoji samo jedan mod, tako da nema širenja signala.
125 µm9 µm
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Optička merenja
• Optička snaga – merenje apsolutne optičke snage u dBm prema referenci od 1 millivata snage
• Atenuacija (gubitak) – količina svetlosti koja se izgubi u kablu. Meri se u dB.
• Disperzija – širenje pulsa svetlosti tokom vremena prilikom prolaska kroz vlakno.
0 dBm = 1mW (miliwatt)
Gubitak (dB)
Gubitak snage (%)
Primljeni signal (%)
3 50 50
10 90 10
20 99 1
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Uzrok gubitaka
• Različiti tip vlakana (npr. 62.5 i 50 mikrona)
• Razmak između vlakana
• Loše poravnjanje
• Loš ugao
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• Nije poželjno savijanje pod oštrim uglovima
• Singlemodne talasne dužine su osetljivije na savijanje kabla
Savijanje optičkog kabla
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MIHAJLO PRERAD - MERENJA Slide 38Version 2.1a ©2011 Fluke Corporation. All rights reserved. Slide 38
Čišćenje• Za testiranje optičkih vlakana najbitnije je čišćenje
• Bez opreme za čišćenje NE MOŽETE
testirati optička vlakna
• Prašina u kancelariji je tipično između
2.5 µm i 10 µm
• Sva vlakna treba proveriti i očistiti pre
bilo kakvog testiranja ili puštanja u rad
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Izgledi čistih i prljavih vlakana
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Šta radi OTDR (Optical Time Domain Reflectometer)?
OTDR Port
konektor
Processing
& Control
Color
Display
Directional
Coupler
Very Sensitive
Photo
Detector
Two Laser
Diodes
1. Šalje svetlosne impulse
2. Proverava da li se svetlost odbija
3. Što dalje svetlost ode, više mu
vremena treba a se vrati
5. Kada svetlost naiđe na konektor,
deo se reflektuje nazad
4. Što dalje svetlost ode, signal koji
se vrati je verovatno dosta slabiji
(meri dužinu)
(meri gubitke vlakna)
(pronalazi konekcije)
OTDR
Optical Fiber
Electrical
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Tipični OTDR trag
Povratni signal
refleksija
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Krajnji događaj
Kraj vlakna
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Refleksija
Konekcija
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Gubitak
Ne-reflektovani događaj
Splajs ili loša konekcija
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“Gain” tj. Pojačanje
Npr. 50-mikronsko vlakno konektovano na 62.5-mikronsko
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“Ghost“ Efekat
Višestruko presavijeno vlakno
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PITANJA?
HVALA NA PAŽNJI!