Technology - Infrastructure - Last Mile 11 - Free Space Optical

Synopsis

Free Space Optical laser links between buildings over short distances provide very high data rates at low costs relative to a fibre link. We discuss the FSO technologies, backup systems operating at 2.5, 5 and 60GHz, security, problems of rain, fog, sunshine, scintillation, eye safety and other practical considerations of siting optical equipment on the top of buildings and between buildings via windows.

Table of Contents

• 1. Synopsis
• 2. Free Space Optical communications
  • 2.1 Infra-red and 60GHz propagation
    • 2.1.1 Infra-red wavelengths
    • 2.1.2 Fog and rain attenuation
    • 2.1.3 60GHz 5mm microwave
    • 2.1.4 Switching of redundant paths
    • 2.1.5 10µm infra-red
    • 2.1.6 Scintillation
    • 2.1.7 Interference and security
    • 2.1.8 Sunlight
  • 2.2 Practical FSO devices
  • 2.3 Novel FSO technologies
    • 2.3.1 3G base stations and WLAN APs
    • 2.3.2 Mesh
    • 2.3.3 Adaptive optics
    • 2.3.4 Direct fibre to the rooftop
    • 2.3.5 Plasma paths through fog
    • 2.3.6 High power 1550nm lasers
    • 2.3.7 Novel receive telescope design
    • 2.3.8 Wavelength Division Multiplexing (WDM)
  • 2.4 FSO practicality
    • 2.4.1 FSO manufacturers
• 3. Related reports