Victoria Communicaton

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.