Telecommunications for the future - 2 Rob Parker CERN IT Division

R. Parker - CERN2 Fixed (cabled) links Transmission network “long” distance Transmission network “long” distance users Distribution network “short” distance

R. Parker - CERN3 Fixed (cabled) links Transmission –Modulation –Multiplexing –Cross-connection / switching Distribution the “Local loop” –Distribution to distribution frame –Last “mile”

R. Parker - CERN4 Modulation Frequency Modulation Phase Modulation Amplitude Modulation Pulse Modulation All of these have various versions

R. Parker - CERN5 Multiplexing & Demultiplexing Multiplexing: Combining several different information streams into one Demultiplexing Restoring the multiple information streams from the single one MULTIPLEXORDEMULTIPLEXOR

R. Parker - CERN6 Types of Multiplexing Frequency Division Time Division –PDH (Plesiochronous Digital Hierarchy) –SDH (Synchronous Digital Hierarchy) –ATM (Asynchronous Transfer Mode) Wavelength Division (for optical cables)

R. Parker - CERN7 PDH the data sources are nominally synchronous (to within a few 10s of ppm of the nominal rate) this makes the multiplexing process very complicated because of bit stuffing and stripping….and prone to transmission errors every new data rate in the hierarchy needs a completely new multiplexing definition

R. Parker - CERN8 PDH Hierarchy kbit/ s kbit/s kbit/s 6312 kbit/s 1544 kbit/s 64 kbit/s 2048 kbit/s 8448 kbit/s kbit/s kbit/s kbit/s kbit/s kbit/s x4 x3 x6 x7x5 x3 x30x24 Japan N. America Europe primary rate

R. Parker - CERN9 SDH the data sources are precisely synchronous the multiplexing process is relatively simple lower data rate “tributaries” can be extracted from the data stream without total demultiplexing (and similarly for inserting a tributary) can easily make “self-healing” rings the specification is “future proof”

R. Parker - CERN10 SDH Hierarchy Mbit/s Mbit/s Mbit/s Mbit/s x4 STM-1 STM-4 STM-64 STM-16

R. Parker - CERN11 Two fibre unidirectional line switched ring

R. Parker - CERN12 Two fibre unidirectional path switched ring

R. Parker - CERN13 Wavelength Division Multiplexing uses different wavelengths on the same fibre is totally protocol independent (SDH, ATM, Ethernet…) known as Dense Wavelength Division Multiplex (DWDM) when the wavelengths are close (a few nm.) for DWDM, 40 or more wavelengths can be used on one fibre

R. Parker - CERN14 DWDM principle

R. Parker - CERN15 DWDM system

R. Parker - CERN16 DWDM components Tunable lasers Wavelength adaptors Diffraction gratings Thin film filters Bragg gratings Waveguide gratings

R. Parker - CERN17 SDH & DWDM combined SDH and DWDM are complementary SDH provides: –flexibility –resilience in case of failure DWDM provides: –very high bandwidth CONCLUSION: BANDWIDTH IS NO LONGER A PROBLEM ON LONG-DISTANCE TRANSMISSION LINKS

R. Parker - CERN18 Examples of SDH/DWDM systems TAT-14 (transatlantic cable) –8 fibre, dual bi-directional ring with protection ring –16 wavelengths of STM-64 per fibre pair –2.4 Tbit/s total capacity if fully equipped FA-1: Flag Atlantic 1 (transatlantic cable) –six fibres –40 wavelengths per fibre –10 Gbit/s SDH per wavelength –2.4 Tbit/s total capacity if fully equipped (NB: 2.4 Tbit/s can carry 10,000,000 telephone circuits)

R. Parker - CERN19 Distribution technologies CATV Community Access (or Cable) TV ISDN Integrated Services Digital Network ADSL Asymmetric Digital Subscriber Line Optical fibre

R. Parker - CERN20 CATV –a “cable modem” can provide 10 Mbit/s of bandwidth, BUT: –the medium is shared, so performance is variable

R. Parker - CERN21 ISDN uses existing telephone distribution cabling 2 * 64 kbit/s + 16 kbit /s to the user is widely available worldwide

R. Parker - CERN22 ADSL uses existing telephone distribution cabling “Asymmetric”: the line speed is different to and from the subscriber, because: –data requirements are generally less in the direction “subscriber to network” than the reverse –to reduce crosstalk at the exchange, where many ADSL lines may arrive bundled

R. Parker - CERN23 ADSL principles uses a filter to separate the frequency range 0-4 kHz which leaves the analog telephone connection unchanged uses the frequencies above 4 kHz (to about 1 MHz) to provide digital connection to the telephone exchange at the telephone exchange, connection is made to the ISP

R. Parker - CERN24 ADSL data rates different rates can be used, depending on: –the distance to the telephone exchange –the quality of the cable maximum rate 6 Mbit/s to subscriber, 600 kbit/s to telephone exchange European offerings are generally < 1 Mbit/s

R. Parker - CERN25 Typical distribution cabling “local loop” TELEPHONE EXCHANGE subscribers multi-pair cable single pair cable distribution frame ~ 5 km

R. Parker - CERN26 Fibre in the local loop FTTK Fibre to the kerb –Fibre goes to a distribution frame, at the limit virtually outside the house FTTH Fibre to the home –Fibre goes all the way to the user’s premises

R. Parker - CERN27 Fibre in the Local Loop (FITL) TELEPHONE EXCHANGE subscribers multi-pair cable single pair cable distribution frame ~ 5 km FTTH FTTK