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48 Chapter 2

Lasers

Laser is an acronym for light amplification by stimulated emission of
radiation. Without doubt, lasers produce the best kind of light for
optical communications. The laser is the preferred method of light
generation for higher-speed communications systems and is used
extensively in long-haul telecommunications networks. Table 2-6
summarizes the benefits and operating characteristics of the laser.

Table 2-6
Characteristic Description
Summary of Laser
Single wavelength This is related to the materials used in the manufacturing
Characteristics
process to produce the laser. The light is created in paral-
lel beams and sent along the transmission path.
Better control Lasers can be modulated (controlled) very precisely.
over output
Lenses not The light source is designed for single-mode fiber and
required focuses better into the core of the actual glass.

Higher output Lasers can produce relatively high power. They have out
power put capabilities that are as much as 20 times that of
LEDs.
More light source The light is created in parallel beams, so a stronger light
can be introduced into the fiber. As much as 50 to 80 per-
cent of the created light will make it into the fiber. This is
much greater than with LEDs.

Heat Lasers get hot, so they require additional equipment to
keep them cool; otherwise, they will burn out.

Regulation Rules for using and producing lasers are much more
tightly controlled. Specifications also state the minimum
distances and operations where lasers are allowed.

Higher cost The cost of lasers is significantly higher than the cost of
LEDs, and therefore, lasers are not suitable for localized
communications networks in a corporate environment.
Instead, they are better suited for long-distance networks.

Digital modulation The on and off function is a more direct way to use the
fiber in single-mode and laser combinations.