I Introduction  
Document Organization  
II Metropolitan Optical Networks  
A. Transmission Systems in Metropolitan Optical Networks (MONs)  
B. Architecture Components  
C. Metropolitan Optical Networks (MON) Topologies  
III Metropolitan Optical Networks (MON) Architectures  
A. Multi-layer Architectures  
B. Single-layer Architectures  
IV Comparative Analysis of Featured Architectures  
A. Features Comparison  
B. Research Themes by Architecture  
C. Future Trends  
V Literature Gaps  
VI Final Considerations