Optical LANs FDDI FDDI: A High speed network, A.Shah and G.Ramakrishnan, Prentice Hall 1994 Reflective Star RAINBOW TPON R&S first edition contained some material no longer included, see:

FDDI topology Bi-directional ring Data protection

FDDI Tokens Token based network Token is a special frame, only one exists In order to transmit a node must possess the token The token may only be possessed for a limited time Holding times can change as the network runs Special services can be catered for

FDDI Frame FCPASDDASA DATA FCSEDFS Header Content Trailer Maximum Frame Size = 4,500 bytes

FDDI Transmission 100MBits/s data rate Uses 4b5b encoding gives a line rate of 125MBaud Low cost 1.3  m LED source, multimode fibre, pin diode receiver 2 km maximum node separation High performance Laser source, single mode fibre 40km maximum node separation

FDDI line coding 4b5b line code successive 4 bit blocks of data are translated into five bit blocks for transmission code translation is chosen to achieve DC balance e.g. SymbolCode Group

System budget Expressed in dB Minimum transmitter power - Minimum Receiver power gives system budget i.e. How much loss we have to play with also need to account for transmission penalties System Margin safety net built in to allow for aging, typically a few dB

FDDI system budget Minimum transmitter output power -20dBm Minimum receiver input power -31dBm Hence system budget of 11dB Low cost 2km at 2.5dB/km Residual margin 6dB High performance 40km at.2dB/km Residual margin 3dB

(Reflective) Star Topology Star coupler light is distributed from any input to all other outputs Reflective version 1xN coupler with mirror on the single port

8x8 Star Coupler

Single Wavelength Broadcast and select network Equivalent to Ethernet

Multi-Wavelength Free access Equivalent to many Ethernets multiplexed on the same physical infrastructure Negotiated access The network could use one wavelength for control and assign others to specific users Controller

Interconnected Stars c

Wavelength Router

Synchronisation Broadcast networks So far we have assumed that each channel is occupied by one user at any given time Often need to share wavelength resource Use time division multiplexing Synchronisation Different nodes will be at different distances from the coupler

Synchronisation Scheme Star Node Sync The node can measure the round trip delay to the star A transmitter sends out synchronisation pulses The time between sync pulses determines the frame size Transmit a frame beginning one round trip time before the next sync pulse should arrive

RAINBOW Developed by IBM Star topology Maximum 32 wavelengths Physical addressing version I 300 MBit/s/wavelength version II 1GBit/s/wavelength Peer network with connection oriented sessions

Polling Protocol Each node has a single transmitter at a unique wavelength Each node has a single tunable receiver when not currently connected, receivers scan across all the wavelengths looking for a connection request when received the node continuously sends out a connection accept while waiting for a connection confirmation This protocol does not require the nodes to know the physical addresses of other nodes

RAINBOW II

Fibre in the Local Loop Exchange to Customer Hybrid schemes Fibre to the Curb (FTTC) Hybrid Fibre Coax (HFC) All-optical schemes Fibre to the home (FTTH) Fibre to the office (FTTO)

FTTC Exchange Splitter Cabinet MUX Copper delivery to the home

HFC Exchange Splitter Detect and split Coax delivery to the home

FTTH / FTTO Exchange Splitter Fibre delivery to the home

TPON Telephony on a Passive Optical Network designed as an alternative to copper access networks capable of delivering much higher bandwidth to the user deployment so far limited by high installation cost Broadband Passive Optical Network (BPON) much higher bandwidth multimedia capable

Next Lecture Wavelength Routed Networks Wavelength Assignment Wavelength Conversion Cost Implications Network Modeling