How to choose the appropriate cable for monitoring systems such as CCTV and ip camera (part of the security system). fiber optic cable, coaxial cable, or twisted pair(cat5e/cat6.)？

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1. What is a video surveillance system? What is the relationship between the video surveillance system and the security system? And what are the categories of the video surveillance system?

1.1What is a security system?

A security & Protection System (SPS) is an electronic system or network that uses security prevention products and other related products. Some people call it a loss prevention system, loss prevention is the task of the security industry.

The system is roughly constituted of an Alarm system, monitoring system, patrol system, attendance and access control, broadcasting system, building intercom system, power environment monitoring system, parking lot management system.

1.2What is a video surveillance system?

CCTV Monitoring System CCTV (Closed Circuit Television) The application of optical fiber, coaxial cable, and microwave in its closed-loop transmission of TV signal and from the camera to the image display constitutes an independent and complete TV system. It can create real-time images, genuinely reflect the object being monitored, and not only significantly extend the observation distance of the human eye but also expand the function of the human eye. It can replace artificial monitoring in a harsh environment for a long time so that people can see all the actual situations of the monitored scene and recorded through video. The CCTV video surveillance system is a part of the security system, and here we discuss the application of the optical cable, the coaxial cable, and the twisted wire in the CCTV video surveillance system.

2. The application of the optical fiber, coaxial, and twisted wire in the video surveillance system, the advantages, and disadvantages of each.

2.1 Introduction of coaxial cable and its application in video surveillance.

Coaxial cable is a kind of wire and signals transmission line is generally caused by four layers of material: the innermost is a conductive copper wire, outside of the conductor is one layer of the dielectric insulator made of plastic, outside of the insulator layer is a thin layer of mesh conductive wrap (generally copper or alloy), and then an outermost layer of insulation material as a skin for protection.

Advantages: good anti-interference ability, stable data transmission, and low price.

Disadvantages:

A: Signal attenuation is severe. To ensure the image quality, the transmission length is limited. When the signal is transmitted in the coaxial cable, its attenuation is related to the transmission distance and the frequency of the sign itself. Generally speaking, the higher the signal frequency, the greater the attenuation. The bandwidth of the video signal is enormous, reaching 6MHz, and the color part of the image is modulated at the high end of the frequency. In this way, not only the overall amplitude of the video signal is attenuated during transmission in the coaxial cable, and the attenuation of each frequency component attenuated significantly, especially the color part, is the most serious. Therefore, the coaxial cable is only suitable for the close transmission of the image signal. When the transmission distance is over 200 meters, the image quality will be significantly affected, especially if the color becomes dim and distorted. In an actual project, a coaxial amplifier is used to amplify the video signal to extend the transmission distance. It can compensate different frequency components in various sizes to balance and to make the video signal output received by the receiver as accurate as possible. However, coaxial amplifiers cannot be installed without limit. Generally, in a point-to-point system, they can only be installed at most for two to three; otherwise, the video transmission quality cannot be guaranteed, and it is not easy to adjust. Therefore, when using the coaxial cable in the monitoring system, the transmission distance range is generally limited to about 400 or 500 meters to ensure good image quality.B. Coaxial cable itself is greatly affected by climate change, and the image quality is affected by climate.

C. Coaxial cable is thick, which is not convenient to wire in intensive monitoring applications;

D. Coaxial cable generally can only transmit video signals. If the system needs to transmit control data, audio, and other signals at the same time, it needs additional wiring;

E. Coaxial cable has limited anti-interference ability， and cannot be applied to a strong interference environment;

F. Coaxial amplifiers have the disadvantage of difficult adjustment.

2.2 Introduction of twisted pair and its application in video surveillance

There are 3 types of lines that are widely used, CAT5& CAT5E/CAT6&CAT6E/CAT7. The former has a thin line diameter, and the latter is thicker.

A. CAT5: This type of cable increases the twine density and coats a high-quality insulation material, with a transmission rate of 100MHz, used for voice transmission and the maximum transmission rate of 100Mbps, mainly for 100BASE-T and 10BASE-T networks. This is the most commonly used Ethernet cable.

B.CAT5E: super 5 class has a small attenuation, less crosstalk, and has a higher attenuation and crosstalk ratio (ACR) and signal-to-noise ratio (Structural Return Loss), and a minor time delay difference. The performance is greatly improved. The maximum transmission rate of the super-class 5 lines is 250Mbps.

C. CAT6: the transmission frequency of this type of cable is 1MHz~250MHz, and the comprehensive attenuation crosstalk ratio (PS-ACR) of the six types of wiring system at 200MHz should have a large margin, which provides 2 times the bandwidth of more than CAT5E. An essential difference between CAT6 and CAT5E is that: the performance of crosstalk and echo loss is improved. For the new generation of full-duplex high-speed network applications, excellent echo loss performance is essential. The essential link model is eliminated in CAT6. The wiring standard adopts the topology of the star shape. The required wiring distance is: the permanent link length should not exceed 90m, and the channel length should not exceed 100m.

D. CAT6E: Super six line is an improved version of the six lines, which is also an unshielded twisted pair cable specified in ANSI / EIA / TIA-568B.2 and ISO 6 / E standards is mainly used in gigabit networks. In terms of transmission frequency, like the six types of lines, it is also 200~250 MHz, and the maximum transmission speed can also reach 1 000 Mbps, but it is greatly improved in crosstalk, decay, and signal-to-noise ratio.

E. CAT7: This line is the latest twisted pair line in the ISO 7 class / F class standard, mainly designed to adapt to the application and development of ten gigabit Ethernet technology. But it is no longer an unshielded twisted pair but a shielded one so that it can transmit at least 500 MHz, more than twice the six and super six lines, with a transmission rate of up to 10 Gbps.

The use of twisted pairs has a long history, and telephone transmission is using it. Many industrial control systems, significant interference places, and long-distance transmission have used twisted pairs. Today our widely used LAN is using twisted pair as well. The twisted pair is widely used because it has many advantages, such as strong anti-interference ability, long transmission distance, easy wiring, and low price. Because of the significant attenuation of the signal, when the transmission distance is long, the frequency of signs can not be too high, while in high-speed signals such as Ethernet, there is a limit for twisted pairs to 100m.

When the bandwidth reaches 6MHz, if transmitted directly in the twisted pair line, the attenuation will be excellent for video signals. To achieve long-distance transmission in a twisted pair line， the signals must be amplified and compensated for video signals. The twisted pair line video transmission equipment is to complete this function. With a pair of additional twisted pair video transceivers, the image can be transmitted to 1 to 2km. Twisted pair and twisted pair video transmission equipment are very cheap. Not only did it not increase the system cost, but the cost decreased significantly when the distance increased compared with the coaxial cable. Therefore, the monitoring system with twisted pair transmission is more advantageous than coaxial cable.

1.3 Optical fiber introduction and application in video surveillance

The optical fiber (Fiber Optic Cable) transmits signals through light pulse, so the material is also mainly glass or plexiglass. It consists of a fiber core, a cladding, and a protective sleeve.

The fiber structure is similar to the coaxial cable, a central optical fiber made of glass or transparent plastic, surrounded by protective materials. It can be combined into one cable as needed. According to the different modes of optical signal occurrence, optical fiber can be divided into the single-mode optical fiber and multimode optical fiber.

A "mold" is a beam of light that enters the optical fiber at a certain Angle). Multimode fiber is generally used for network connections within the same office building or in relatively close areas. Single-mode optical fiber delivers data with higher quality and longer transmission distance and is often used to connect between office buildings or to more geographically dispersed networks. Suppose you use optical fiber and cable as a network transmission medium. In that case, you also need to add optical terminal transceivers and other equipment, so the cost is more and less used in typical applications.

single mode optic fiber

multimode optic fibre

The most important characteristic of optical fiber is that the transmission is the light signal, so it is not affected by the interference of external electromagnetic signals. Signal attenuation speed is plodding, so the signal transmission distance is far more than the above electrical signal transmission and is especially suitable for the electromagnetic environment of harsh places. Due to the optical reflection characteristics, several signals can be transmitted simultaneously. Thus the transmission speed of optical fiber can be very high. Currently, 1Gbps 1000Mbps optical fiber network has become the mainstream high-speed network. Theoretically, the optical fiber network can reach the highest speed of 50,000 Gbps and 50Tbps. However, using optical fiber as a network transmission medium requires specific professional knowledge, an optical transceiver, and other special equipment, so the cost is high.

3. Who is the big winner of optical fiber and coaxial cable?

There are two different monitoring methods in HD video surveillance: IP HD and SDI HD; in SDI HD transmission, most transmission media is optical fiber cable. For the HD video surveillance system, both the IP network architecture and the traditional analog fiber transmission architecture are important future development directions, especially for the classic analog fiber transmission architecture, users and engineers do not have to adapt to the IP architecture.

Both fiber-optic cable and coaxial cable belong to a network cable. Although both can be used in the monitoring field, there are apparent differences. First, the coaxial cable's appearance is thicker than the optical fiber cable. From the structure, the coaxial cable comprises layers of insulation materials that wrap the central copper conductor; optical fiber is composed of much hair-like glass fiber wrapped by an insulation sleeve.

Secondly, the data transmission speed, anti-interference ability, and price of optical fiber and coaxial cable are also different. In most domestic or civil markets, coaxial cable is more widely used, which is because of the low price advantage of coaxial cable. In data transmission, take the general standard definition image. For example, the coaxial cable also meets data transmission needs in data stability and size.

3.1 Optical fiber and coaxial cable stand at the same starting line

Again, for the HD development of video surveillance system, 1080p image occupies much bandwidth, so in particular areas, optical fiber transmission is slightly better; optic fiber relies on visual information, strong anti-interference, and good confidentiality; some people say that coaxial cable is affected by bandwidth, 1080p image occupies much bandwidth, with the current data flow, it is difficult to achieve high-quality image transmission.

3.2 Different materials have different engineering wiring 

Images and data transmission is also mentioned above, so what will happen for practical applications? Today, monitoring is not just sold as equipment but by engineering systems. What problems do you encounter in the network wiring?

Optical fiber is a fragile object in engineering wiring that needs special attention. Especially for the angle turning places, optical fiber cable can not be folded into a dead corner, and delicate optical fiber will be broken, can not achieve transmission; coaxial cable is the most common household network cable in the monitoring system with BNC joint, do not need special care, the use is very casual.

3.3 Cost is very different in the application fields

Let's take a look at the difference in their application field. Due to the different cost of the two cables, their application field is different. Coaxial cable cost is relatively low and suitable for home network monitoring systems; optical fiber cost is high and more used for safe city and other projects. In particular, the development of video surveillance HD has become a real-time situation, but in the current market application situation, both can be applied in the HD monitoring system; the imaging effect also depends on the storage system and display equipment, so bandwidth is not the only standard to determine the "HD" picture quality.

3.4 Develop a diversified monitoring market

Monitoring equipment due to the different transmission media will form different monitoring systems. It will also vary for other devices in the design. These two various transmission media lead to the diversification of monitoring systems.

IP network monitoring system based on coaxial cable is an open monitoring platform. A network monitoring camera corresponds to an IP address, its security is worrying, but for peripheral equipment, NVR, network video servers, and other products are derivatives of IP network monitoring, which is the future development direction of network HD monitoring.

The traditional simulation network monitoring system, which is based on optical fiber cable, is a relatively closed circuit monitoring environment, especially the use of optical fiber transmission speed and prominent data characteristics, while in a time simulation monitoring market is nearly dead, pull it back from the edge of death, especially for HD-SDI products: HD-SDI HD camera, HD-SDI optical terminal equipment, with optical fiber transmission, you can enjoy 1080p high picture quality.

Comments:

Two different transmission media let us see the diversified development direction of the video surveillance system, whether the developed IP network monitoring or the traditional CCTV closed-circuit monitoring system. In this critical period of connecting the past and the next, the monitoring and transmission provide more development space for the security market.

Optical fiber transmission drives the development of the high-end monitoring market and is the most significant backup force of SDI monitoring products; coaxial cable transmission drives the Ethernet monitoring market, make the video surveillance field closer to civilian life, is the best guardian of people's food, clothing, housing, and transportation. From the construction of a safe city to family monitoring, the diversified development of the monitoring market is the pride of the whole industry. In the face of future market development opportunities, the two stand on the same starting line, who win and who lose? Can you decide?