One of the most desirable transmission medium in a data center environment is the fiber optic cable due to a series of advantages regarding the bandwidth capacity, distance run, immunity to interferences, and security of communication. The general structure of a fiber optic cable.

1. Singlemode vs Multimode Fiber Optic Cable
One of the most desirable transmission medium in a data center environment is the fiber optic
cable due to a series of advantages regarding the bandwidth capacity, distance run, immunity to
interferences and security of communication. General structure of a fiber optic cable.
The Structure
The structure common to all optical fiber cables consist in thin as hair core that conducts light
full of information data. The core is surrounded by an optical material called the “cladding” that
traps the light in the core using an optical technique called “total internal reflection.”
The core and cladding are usually made of ultra-pure glass. The fiber is coated with a protective
plastic covering called the “primary buffer coating” that protects it from moisture and other
damage. More protection is provided by the “cable” which has the fibers and strength members
inside and an outer covering called a “jacket”.
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core glass (9, 50, 62,5 μm)
jacket glass (125 μm)
primary coating mm
secondary coating mm

2. Single-mode Fiber Optic Cable
A Single-mode fiber optic cable has a small diametral core that allows only one mode of light to
propagate. Because of this, the number of light reflections created as the light passes through
the core decreases, lowers attenuation and creates the ability for the signal to travel further.
Multi-mode Fiber Optic Cable
Multi-mode optical fibers have larger cores that guide many modes simultaneously. The larger
core makes it much easier to capture light from a transceiver, allowing source costs to be con-
trolled. Because of this, the number of light reflections created as the light passes through the
core increases, creating the ability for more data to pass through at a given time. Because of the
high dispersion and attenuation rate with this type of fiber, the quality of the signal is reduced
over long distances.
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3. Practical Differences between Single-Mode
and Multi-Mode Cables
Single-mode systems are usually more expensive because of the laser diodes and precise cal-
ibration required to inject light into the cable. The costs of single vs multi-mode cables itself
are negligible, but single-mode devices often cost more. Light travels a longer distance inside
single-mode cables than it does inside of multi-mode cables. How much farther depends on
many factors, but the rule of thumb is, single-mode signals can survive up to 160 kilometers.
The bandwidth (amount of information in the signal) of single-mode is higher than multi-mode.
Since the entrance core of single-mode is so small (9 microns), single-mode connectors must be
kept very, very clean. Even a microscopic particle blocking the pupil can partially or completely
block signal. This tiny core requires precision alignment to inject light from the transceiver into
the core, significantly driving up transceiver costs.
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VS.

4. Cost Difference
The single-mode transceiver optics are more
expensive than Multi-mode based transceiv-
ers, however single-mode is the only fiber that
can justify the term “future-proofed” due to its
massive bandwidth possibilities and extended
reach of many kilometers.
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Design considerations
When specifying equipment for use in a fiber optic connection system the following factors
must be taken into consideration:
• The type of fiber cable being used
• Thickness
• Refractive index
• Absorption spectrum
• Geometry
• The wavelength of light being used
• The characteristics of the light source
• The spectral linewidth (frequency range) of the source
• The characteristics of the receiver devices
• The modulation method
• The method of varying the light to represent data bits

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in this document may be claimed as the property of others.
This document is for informational purposes only and does not set forth any warranty, expressed or implied, concerning any equipment, equipment fea-
tures, or service offered or to be offered by CBO. The publication of information in this data sheet does not imply freedom from patent or other protective
rights of CBO or others. In accordance with the CBO policy of continuous improvement specifications may change without notice.
Contact a CBO sales office for information on feature and product availability.
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