1. Problem We need more bandwidth
Data traffic doubles every 4 (up to 12) months
More users connect to the Internet …
And stay connected for longer times …
And have better connection speeds (56kbps modem DSL & Cable modem)
New applications (e.g. NAPSTER, GNUTELLA) require more bandwidth
And we can expect numerous other bandwidth intensive applications
Data traffic >> Voice traffic
11/7/2000
EE228A Lecture

2. Solution Optical Networking High speed transmission
Enormous bandwidth made available
WDM makes ~160 channels/wavelengths possible in a fiber
Each wavelength carries about 10 Gbps
Hence Tbps speeds become a reality
Low bit error rates
10-9 as compared to 10-5 for copper wires
High speed transmission
Transparent to bit rates and modulation schemes
Reconfigurability
Made possible due to developments in hardware
11/7/2000
EE228A Lecture

3. Hardware Fiber Lasers Amplifiers (as opposed to regenerators)
reduced dispersion, non linearity and attenuation loss
Lasers
reduced noise (both phase and intensity)
2.5 Gbps, 10 Gbps , tunability emerging
made from semiconductor or fiber
Amplifiers (as opposed to regenerators)
make possible long distance transmissions
erbium-doped fiber amplifiers
transparent to bit rate and signal format
have large gain bandwidths (useful in WDM systems)
expensive (~$50K)
11/7/2000
EE228A Lecture

4. Hardware Filters Optical Add-Drop Multiplexor (OADM)
with narrower spacing, wider ranges and tunability
Optical Add-Drop Multiplexor (OADM)
OADM 1 2 3
’3
Optical cross-connects (OXC)
route a channel from any I/P port to any O/P port
can be fixed, rearrangeable, and also with  converters
11/7/2000
EE228A Lecture

5. Hardware … … Rigid OXC Rearrangeable OXC I/P port N I/P port 1
O/P port 1
O/P port N … 1 M
I/P port N
I/P port 1 …
O/P port 1
O/P port N 1 M
Rigid OXC
Rearrangeable OXC
11/7/2000
EE228A Lecture

6. Hardware Wavelength () converters (WC)
improve utilization of available wavelengths on links
needed at boundaries of different networks
all-optical WCs being developed
greatly reduce blocking probabilities 3 3 2 2 WC 1 1
New request
1 3
New request
1 3
No Wavelength converters
With Wavelength converters
11/7/2000
EE228A Lecture

7. Earlier Optical Networks
SONET/SDH, ATM, FDDI …
fiber as transmission medium
switching, processing and routing electronically
require O/E/O conversions
use one wavelength only
Primarily for voice traffic
lots of redundancy, overhead, protection
New networks should optimize for data (IP traffic)
IP over WDM is emerging as the new architecture
11/7/2000
EE228A Lecture

8. 11/7/2000
EE228A Lecture