Facilities Management
Fiber plays video security role
Media conversion connects surveillance networks utilizing copper-based cabling.
by Curt Carlson
Media converters designed specifically for analog video networks can be used in the integration of fiber-optic cabling, allowing physical security and surveillance networks to experience the benefits of extended transmission distances, and protection from noise and interference.
Whether the cabling is
coax for traditional analog cameras or
unshielded twisted pair (UTP) for newer
IP-based cameras, copper cabling poses
several issues that could limit the design
or physical reach of a video security
network. Integrating fiber-optic cabling
into these networks can address many of
these issues.
Whether organizations are
monitoring employees, identifying corporate
visitors, tracking hazardous work areas or
guarding against intruders, theft and
vandalism, most organizations see the
benefits of an effective video security
system. As these networks grow, transmission
distance issues can arise, causing the need
for additional equipment.
Analog-based systems
transmitting video signals over coax cabling
have provided good performance and
acceptable images at distances up to 750
feet. Beyond that distance, equipment such
as signal conditioning and/or signal
amplification and surge protection devices
are needed to prevent the loss of
high-frequency information.
As security professionals
have migrated to the newer IP-based
technology, they have had to face more
challenges. Even though IP-based systems are
growing in popularity, their transmissions
are limited to distances shorter than their
analog equivalents.
IP-based security
networks work within the standards of an
Ethernet network, meaning the maximum
transmission distance on UTP cable is
limited to 100 meters or 328 feet. At that
point, the signal must be regenerated and
retimed with a network device such as an
Ethernet switch. Requirements for these
additional devices in either an analog or an
IP-based network may increase the cost of
the system considerably.
In addition to the
limited transmission distance, both coaxial
and UTP cables are susceptible to noise or
electrical interference caused by high
voltages and ground loop faults, both of
which can lead to quality degradation of the
video signal. Also, the security of the
video network as a whole can be jeopardized
by the ease of tapping into the copper cable
and stealing or copying the video stream.
These
issues have led security professionals to
look for alternative cabling methods.
EASIER INSTALLATION WITH FIBER
Security and surveillance
networks are in a position to take advantage
of the benefits offered by fiber-optic
cabling. These include extended transmission
distances, protection from noise and
interference, higher bandwidth capacity, and
improved reliability and transmission
performance.
Fiber is also smaller in
size and offers stronger tensile strength,
allowing for easier installation.
Transmission distances of an IP video
network on optical fiber cable can be up to
6,562 feet on multimode fiber and even
farther on singlemode fiber, while distances
are only slightly shorter for an analog
video system. Using a fiber infrastructure
in either an analog or IP-based video system
will offer greater transmission distances
than what can be achieved on coax and UTP.
Many corporate LAN
environments will already have fiber in
place in the backbone cabling between
buildings in a campus area network or in the
vertical risers of a multistory office
building. To access this fiber, security
professionals will face new equipment
challenges. Since most analog cameras
support coax cable with a BNC interface and
IP cameras support UTP cable with an RJ-45
interface, how are users expected to connect
fiber-optic cabling to these cameras? The
answer is in the use of media converters.
Media converters are
commonly used in today's LANs to
transparently connect one type of media, or
cabling, to another. Since data travels
differently on copper than it does on fiber,
a media converter changes the electrical
signal coming into the device on UTP cable
to an optical signal that can be transmitted
out of the device over fiber cable.
Media converters are also
available to support a variety of other
communication environments, including analog
video. Most analog video copper-to-fiber
converters are small and can attach directly
to a camera. They do require a source of
power, however, and typically accept the
same power as the cameras (usually 24 VDC),
so there is no requirement for an additional
external power supply.
Specific analog
converters are available for the one-way
video communication of a fixed camera, while
other converters support the two-way
communication of a pan/tilt/zoom (PTZ)
camera. Two-way communication is needed so
the camera can transmit the video signals
and receive serial data from the PTZ
controller.
Generally, media
converters are used in pairs, so another
analog converter would be installed on the
other end of the fiber, providing
connectivity at the central monitoring
location. This element is an essential piece
in any security or surveillance system.
Standard Ethernet media
converters can be used to integrate fiber
into an IP-based video network. Combined
with the emergence of power-over-Ethernet
(PoE) technology, media converters can
provide new methods for powering IP cameras,
even cameras located at the far end of a
fiber run.
THE ROLE OF POE DEVICES
Common PoE devices include PoE injectors, PoE splitters and PoE
Ethernet switches. PoE injectors are
copper-to-copper devices with a data-in port
and a data-out port, which inserts the power
on the UTP cable. A PoE switch acts like a
traditional Ethernet switch, but it will
sense if a port is connected to a
PoE-enabled device and insert power on an
as-needed based.
While PoE is only
supported on UTP cable, devices like PoE
media converters can not only extend the
reach of a network by providing an interface
between copper devices and fiber cable, but
they can also act like a PoE injector.
Locating a PoE converter at the far end of a
fiber run gives a network extended reach,
and this remotely located PoE converter can
also inject power onto the UTP cable.
While the PoE converter
itself needs to be located near a power
source, the IP camera connected to the PoE
media converter can be located and powered
up to 100 meters away from the converter. A
company could locate the PoE converter and
its power source inside a building, while
the IP camera may need to be located outside
the building, far from a power source.
Eliminating the need for an external power
source simplifies the installation of IP
cameras and can be performed by a
low-voltage cable installer or technician,
saving the cost of hiring an electrician to
install new wall outlets in potentially
unique locations.
For those with external
devices like a security camera mounted on
top of a pole in a parking lot, there may be
power at the base of the pole but not at the
top. The PoE media converter could be
located at the base of the pole; the power
source could provide power to the PoE
converter while the converter could send
power up the pole to the camera. In this
application, only the UTP cable would be
routed up the pole. Without PoE, both a
network cable and a power cable would have
to be routed up the pole.
These outdoor applications would also
benefit from industrialized or hardened
media converters. Office-grade media
converters in outdoor installations may have
issues dealing with the wider swing in
operating temperatures experienced in these
applications.
Curt Carlson is product manager at Transition Networks, Minnetonka, Minn.
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