EE 4392 Introduction To Optical Systems Instructor: Dr Mohammed Zamshed Ali Distributed Networks Fal

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WELCOME
EE 4392Introduction To Optical
SystemsInstructor Dr Mohammed Zamshed
AliDistributed Networks Fall 2007Department
of Electrical EngineeringUniversity of Texas at
Dallas
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Distributed Networks

• Distribution Networks
• Tee Networks
• Star Networks
• Ring Networks

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Distributed Networks
Fiber Networks Point-to-Point One-way
transmission. One transmitter and one
receiver. Ex. Telephone network Distributed M
any transmitters and receivers and shared
transmission line (fiber). Ex. Local-area
networks (LAN) Cable TV
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Distributed Networks
The four-port directional coupler (DC) is
important in distribution networks.
1
2
P2
Input
P1
DC
P3
3
4
P4
For our definitions (to follow), we assume and
the input power is at port 1.
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Distributed Networks
1. Throughput Loss LTHP - 10 log (P2 /P1
) (9-1) The reduction in power from port 1 to
port 2. 2. Tap Loss LTAP - 10 log (P3 /P1
) (9-2) The reduction in power from port 1 to
port 3.
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Distributed Networks
3. Directionality LD - 10 log (P4 /P1
) (9-3) In the ideal case P4 0, so that
LD infinite Typically, LD gt 40 dB 4. Excess
Loss LE - 10 log (P2 P3) /P1 (9-4) In
the ideal case, P2 P3 P1, so that LE 0
dB Typically, LE is a few tenths dB
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Distributed Networks
In practice, due to undesirable losses
(e.g.,scattering, imperfect construction) (P2
P3 ) lt P1 LE represents these losses 5.
Splitting Ratio SR (P2 /P3 ) Couplers are
often described (named) by their splitting ratio
or their tap loss.
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Distributed Networks
Given the tap loss for an ideal coupler (LE 0,
LD infinite ), produce a table showing the
splitting ratio and the throughput loss. The
result is LTAP(dB) (P3 /P1 ) SR
(P2 /P3 ) LTHP (dB) 3 1/2 11 1 3 6 1/4 3
1 3 1.25 10 1/10 91 9 0.46
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Distributed Networks
Duplexing Network Duplexing means simultaneous
transmission in both directions through the
fiber.
T
T
DC 1
DC 2
1
Fiber
2
2
1
3
4
3
4
R
R
Ex. Compute the transmission loss assuming ideal
3-dB couplers
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Distributed Networks

• Total Loss
• L 3 3 6 dB
• Ex. Compute the loss assuming
• Excess loss 1.5 dB
• 3 dB couplers
• 1 dB loss per connector , 4 connectors
• 2 dB fiber loss
• L (3 1.5) (3 1.5) 4 2
• DC1 DC2 connectors fiber
• L 15 dB

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Tee Networks
Tee Network
3
N-1
2
1
N
DC
DC
R T
T R
Fiber Bus
TEE Couplers
The directional couplers (DC) permit duplex
operation for the end terminals(1 and N). This is
an N - terminal network. Each terminal has a
transmitter and a receiver.
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Tee Networks
The TEE coupler looks like
2
1
DC1
3
4
2
3
DC2
4
1
R
T
Terminal
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Tee Networks
Notes on this system

• The terminal shown can transmit and receive in
  both directions.
• Only one terminal in the network can transmit at
  any one time.
• The TEE is a broadcast network.

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Star Networks
Star Network A star network has N terminals.
Each terminal has a transmitter and a receiver,
so there are N transmitters and N receivers in
the star network. There are a total of 2N ports
on the star coupler.
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Star Networks
4 Terminal Star Network (4 x 4 star coupler)
1
Star Coupler
Dual Fiber Cable
2
4
Dual Fiber Cable
Terminal
3
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Star Networks
An ideal star coupler divides all the input power
equally to all output (receiver) ports. The
couplers insertion loss is then LIN - 10 log
(1/N) (9-9) If we include the couplers excess
loss (LE) and connector loss (LC) the total
star coupler insertion loss is L - 10
log (1 / N) LE 2LC (9-10) Compare with the
tee network where L (N - 1) LTHP
LTAP 2NLC (9-8)
The star losses increase much more slowly than
those of the tee network.
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Star Insertion Loss
LE 0.2 dB, Lc 2 dB
Loss (dB)
1
Ideal
N (number of terminals)
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Star Networks

• For N gt 5 (more than 5 terminals in the network),
  the star is generally preferred over the TEE.
• A star network uses more fiber than a TEE.

1
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Ring Networks
Station
Nodes
3
2
4
1
N
5
Fiber
Station
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Ring Networks

• The ring is made up of a series connection of
  point-to-point fiber links.
• Each node is a regenerator which detects the
  message and regenerates it for transmission to
  the next node.
• Each node also delivers the message to the
  attached station located at that node.
• Since there are no distribution losses, a large
  number of terminals (stations) can be linked.

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Ring Networks
Disadvantages of the Ring Network Reliability If
any node or fiber becomes inoperable, the system
is shut down. Solution Redundancy 1. Add a
second, counter rotating ring. 2. Add bypass
switches.
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Ring Networks
Dual Fiber Cable
R T
2
T R
Primary Path
T R
T R
3
1
R T
R T
Secondary Path
R T
4
T R
Counter-Rotating Ring Network Secondary path used
only with failure of a node or fiber (see next
page).
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Ring Networks
Ex. Suppose node 3 fails. The reconfigured
transmission path is
R
2
T
T R
1
R T
R
4
T
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Ring Networks

• Application of the Counter-Rotating (Dual) Ring
• Fiber Distributed Data Interface (FDDI) LAN.
• Properties of FDDI
• Baud rate 125 Mbps
• Token passing ring
• Maximum ring circumference 100 km
• Maximum number of nodes 500
• Fiber multimode GRIN fiber
• Duplex cables

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Ring Networks

• Properties (continued)
• Light source LED
• Wavelength 1300 nm
• Maximum station-to-station distance 2 km