1. Fiber-Optic Communications
James N. Downing

2. Optical Signals and Networks
Chapter 8
Optical Signals and Networks

3. 8.1 Optical Signal Characteristics
Electrical-to-Optical Signal Conversion
The electron is converted to a photo—preserving information that is coded
Optical source
LED
Laser Diode
Regenerated and retimed by clock recovery circuit

4. 8.1 Optical Signal Characteristics
Optical Signal Formats
OOK
Uses two signal levels—one and zero
Two line codes—return-to-zero and non-return-to-zero
Return to zero code has twice the bandwidth but less dispersion
Non-return-to-zero code more commonly used because of the simplicity but clock recovery is more difficult

5. 8.2 Wavelength Division Multiplexing
WDM assigns a unique wavelength to each channel and allows more than one wavelength to be transmitted in the same fiber.

6. 8.2 Wavelength Division Multiplexing
Dense Wavelength Division Multiplexing
Developed for the C and L bands
Consist of 100 channels from 186 THz to THz
Somewhat expensive
Practical for long-haul high capacity applications

7. 8.2 Wavelength Division Multiplexing
Coarse Wavelength Division Multiplexing
Allows multiplexing with wider wavelength spacing
Lower cost
Easier installation
Requires no precision laser diodes
Requires no sophisticated filters
Choice for metro markets

8. 8.3 Optical Networks Fiber in the Network
Characteristics are optimized over the long, straight runs with few interruptions
Optical Network Transport Protocols
Fiber Distributed Data Interface (FDDI)
Provides dual counter rotational ring for CAN and MAN
Primarily used for storage

9. 8.3 Optical Networks Optical Network Transport Protocols Fibre Channel
Used for connections of servers to shared storage devices over short distances
Enterprise system connector ESCON
Interconnects the S/390 mainframe to storage
FICON
Connects mainframe to storage—8 times faster than ESCON

10. 8.4 SONET Synchronous Optical Network What is SONET?
Provides a standard optical transport
Operates at the physical layer for framing and transporting data over fiber optics
Four layers: path, line, section, and photonic layer

11. 8.4 SONET
What is SONET?
Path layer: Defines and controls the end-to-end communications on the network
Line layer: Synchronization and automatic protection switching (APS)
Section layer: Details procedures between optical repeaters such as framing, scrambling, and error monitoring
Photonic layer: Controls the optical-to-electronic conversion

12. 8.4 SONET The STS-1 Frame and Data Formats 9 by 90 matrix of 810 bytes
Transport Overhead
Contains the section and path overheads for a total of 27 bytes
Synchronous Payload Envelope
Contains the matrix of information to be transmitted (783 bytes)

13. 8.4 SONET The STS-1 Frame and Data Formats
4% of available payload is used for operations, administration and management.
First two bytes of the line overhead are pointers, which specify the offset to the first SPE byte that is allowed to float inside the allotted space.
Timing is via a precise stratum 3 reference.

14. 8.4 SONET Advantages Standardization and synchronization
More efficient multiplexing and depmultiplexing
More reliable, flexible, and expandable
Less equipment is required
Reconfigurable network with centralized management
Ring type topologies

15. 8.4 SONET
Disadvantages
Rigid rate hierarchy and convergence requirements
Inefficient use of bandwidths
Current rate hierarchy is not suitable for Ethernet transport
Limited node network management functions
Lack of storage area network

16. 8.4 SONET Evolving Network Transport Services Packet over SONNET (PoS)
Link Access Procedure (LAPS)
IP over LAPS
Ethernet over LAPS
Generic Multi-Protocol Label Switching (GMPLS)
Resilient Packet Rings (RPR)
Multiservice Provisioning Platforms (MSPP)

17. 8.4 SONET Next Generation SONET (NG-SONET)
Generic Framing Procedure (GFP)
Virtual Concatenation (VC)
Link Capacity Adjustment Scheme (LCAS)
Smart DWDM

18. 8.4 SONET Alternative and Hybrid Transport Systems
Carrier Class Ethernet
LAN PHY
WAN PHY
RPR