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Application Notes

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  Current Sources for Fiber Optic Lasers: A Compendium of Pleasant Current Events &mdash AN90
  PDF, 409 Kb, File published: Apr 1, 2002
  A large group of fiber optic lasers are powered by DC current. Laser drive is supplied by a current source with modulation added to the signal. The current source, although conceptually simple, constitutes an extraordinarily tricky design problem. There are a number of practical requirements for a fiber optic current source and failure to consider them can cause laser and/or optical component destruction. This application note describes ten laser current source circuits with a range of capabilities. High and low current types are presented, along with designs for grounded anode, cathode or floating operation. Each circuit also includes laser protection features. Appended sections cover laser load simulation and current source noise measurement techniques.
  Extract from the document

  Application Note 90
  April 2002
  Current Sources for Fiber Optic Lasers
  A Compendium of Pleasant Current Events
  Jim Williams, Linear Technology Corporation
  INTRODUCTION
  A large group of fiber optic lasers are powered by DC
  current. Laser drive is supplied by a current source with
  modulation added further along the signal path. The
  current source, although conceptually simple, constitutes
  an extraordinarily tricky design problem. There are a
  number of practical requirements for a fiber optic current
  source and failure to consider them can cause laser and/
  or optical component destruction. Protection features must be included to prevent laser and
  optical component damage. The laser, an expensive and
  delicate device, must be protected under all conditions,
  including supply ramp up and down, improper control
  input commands, open or intermittent load connections
  and “hot plugging.”
  Detailed Discussion of Performance Issues Design Criteria for Fiber Optic Laser Current Sources It is useful to expand on the above cursory discussion to
  clarify design goals. As such, each previously called out
  issue is treated in greater detail below. Figure 1 shows a conceptual laser current source. Inputs
  include a current output programming port, an output …

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Manufacturer's Classification

• Monitor, Control and Protection > Surge Stopper, Overvoltage & Overcurrent Protection
• Space & Harsh Environment > Extended Temperature Plastic (H & MP) > Extended Temperature (H & MP) Power Management