UCLA Extension

Free-Space Laser Communications

A 2-Day Short Course

Laser communication is emerging as an appealing alternative to RF communication for links between satellites as well as other terrestrial applications. Intended for engineers, scientists, managers, or professionals who desire greater technical depth, as well as RF communication engineers who need to assess this competing technology, this course provides an introduction and overview of laser communication principles and technologies for unguided, free-space beam propagation. Special emphasis is on highlighting the differences and similarities to RF communications and other laser systems, and design issues and options relevant to future laser communication terminals for which there currently are no textbook solutions.

Complete Details

Topics include optical/RF comparison, applications, laser sources, link equation, modulation/detection, receivers, advanced spatial acquisition/pointing/tracking techniques from air and space, atmospheric effects, networking, and terrestrial links.

Upon completion, participants should be able to:

  • Identify the fundamental performance advantages of optical (laser) over RF communication
  • Calculate energy propagation using the link equation
  • Summarize laser source and optical detector
  • Compute receiver sensitivity using direct (non-coherent) detection, including associated noise contributions
  • Explain the basic principles of coherent detection
  • Compare basic modulation methods, including direct detection with M-ary pulse position modulation and electro-optic phase/amplitude modulation
  • Evaluate spatial tracking with quadrant detectors and spatial acquisition using quadrant detectors or CCD arrays
  • Estimate degradation due to atmospheric effects, including attenuation, beam spreading, beam wander, and scintillation
  • Compare new systems with selected past and ongoing lasercom programs/ hardware
  • Calculate the receiver performance of direct, heterodyne, and homodyne detection with associated noise contributions
  • Evaluate the trade-offs between silicon APDs and optical pre-amplification for direct detection systems
  • Calculate pointing requirements based on transient burst error effects on communication and potential benefit to pointing performance with inertial stabilization
  • Compare design options for combining subsystems, including spatial acquisition/tracking with CCD arrays or communication/tracking using conical scan

Course Materials

The text, Near-Earth Laser Communications, Hamid Hemmati (editor), CRC Press, 2009, and lecture notes are distributed on the first day of the course. The notes are for participants only and are not for sale.

Coordinator and Lecturer

Hamid Hemmati, PhD, Supervisor, Optical Communications Group and Principal Member of Technical Staff, Jet Propulsion Laboratory, Pasadena, California. Dr. Hemmati’s areas of expertise include planetary communications, free-space optical communications, lasers, and electro-optics system engineering. Prior to joining JPL in 1986, he was with NASA Goddard Space Flight Center and National Institute of Standards and Technology (Boulder). He is a Fellow of SPIE and IEEE, has published over 100 papers, holds seven U.S. patents, and has received nearly 30 NASA Certificates of Recognition. Dr. Hemmati is Chair of the annual SPIE Conference of Free Space Optical Communications, Photonics West, as well as IEEE ICSOC conference on space optics. He is the editor/author of the course textbook as well as two books on laser communications.

Course Program

Introduction

  • Brief historical background
  • Optical/RF comparison
  • Basic block diagram
  • Applications overview

Link Equation

  • Origin
  • Link performance comparison to RF

Laser Transmitter

  • Laser sources for airborne and space-borne applications
  • Modulation methods

Optical Receiver

  • Photo-detectors
  • Electrical pre-amplifier
  • Background light filtering

Detection

  • Channel capacity
  • Poisson photon counting
  • Modulation schemes
  • Detection statistics
  • SNR bit-error probability
  • Optical pre-amplification
  • Advantages/complexities of coherent detection

Acquisition, Tracking, and Pointing

  • Acquisition scenarios, time and probability
  • Acquisition time
  • Combined acquisition/tracking with area array
  • Host platform vibration environment
  • Inertial stabilization
  • Combined communication/tracking with conical scan
  • Soft-mount isolation
  • Fine pointing mechanisms
  • Coarse-pointing mechanisms

Opto-Mechanical

  • Transmit telescope
  • Receive telescope
  • Shared transmit/receive telescope
  • Relay/other optics
  • Thermo-optical-mechanical stability

Laser Transmitter Combining

  • Coherent combiners
  • Spatial combiners
  • Architecture for combining

Atmospheric Effects

  • Attenuation
  • Beam wonder
  • Scintillation/fading
  • Beam spread
  • Turbid (rain, fog, snow)
  • Cloud-free line-of-sight

Link Interoperation and Networking

  • Up/downlink
  • LEO-LEO, GEO-GEO
  • Orbital clusters
  • Future/advanced (e.g., transformational communication)

Eye Safety

  • Regulations, classifications, notices
  • Wavelength dependence

Overview of Lasercomm Programs

  • Past demonstrations
  • Future planned demonstrations
  • Terrestrial commercial hardware

For more information contact the Short Course Program Office:
shortcourses@uclaextension.edu | (310) 825-3344 | fax (310) 206-2815

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