DIPOL Weekly Review – TV and SAT TV, CCTV, WLAN

The world's first quantum network.

Chinese scientists have created the world's first integrated quantum communication network by interconnecting over 700 terrestrial optical fibers and two Earth-satellite links. The network connects locations that are more than 4,600 km apart. Unlike conventional encryption, the quantum communication is considered impossible to corrupt, thus representing the future of secure information transfer for banks and in all other applications with handling of sensitive data involved.

The core of quantum communication is the quantum key distribution (QKD) comprising sequences of zeros and ones generated by quantum states of particles (e.g. photons). Any interference with the transmission or key change is immediately detected. In 2016, China launched the world's first quantum communications satellite, and then created the first QKD network between 2,600 km distant ground stations. Data between stations was transmitted by satellites. In 2017, a fiber optic network measuring over 2,000 km was completed, connecting Beijing with Shanghai. The stage now completed was to integrate and introduce quantum communication all over both networks.

Chinese-made quantum satellite-fiber network connects Shanghai with Beijing and Xinlong with Nanshan

Over the past few years, a team of Chinese scientists led by Jianwei Pan, Yuao Chen, and Chengzhi Peng of the China University of Science and Technology in Hefe, have extensively tested the performance of various parts of the integrated quantum network. For example, with the increased clock frequency and the more efficient QKD protocol, the satellite-ground link now has an average key generation rate of 47.8 kilobits per second, which is 40 times faster than the previous one. The Chinese research team continues this intense research in collaboration with international partners from Austria, Italy, Russia and Canada. As of today, their efforts are aimed at creating compact QKD satellites and terrestrial receivers, as well as satellites in medium and high orbits.

Apartment building monitoring using ColorVu cameras.

The diagram below shows the monitoring of an apartment building based on an NVR and Hikvision IP cameras, belonging to the EasyIP4.0 ColorVu series. The key feature of this series is scene monitoring in color mode around the clock, so the color related information is preserved regardless of the prevailing lighting conditions. The outside area around the building is monitored by eight DS-2CD2047G1-L K03114 compact cameras with 4 MP resolution and 2.8 mm lens with 102° viewing angle. Inside the building, there are four ceiling cameras DS-2CD2347G1-L K00311 with 4 MP resolution, equipped with 2.8 mm lenses with 109° viewing angle. Both models have a white light illuminator with a range of 30 m, which can turn on automatically in low light conditions to ensure a good color image. In most cases, however, when street or staircase lighting is available, the camera works with the illuminator turned off.

Apartment building monitoring with Easy IP 4.0 ColorVu cameras

The distribution of cameras recommended above allows to ensure the accurately identify individuals who attempt to damage the outside of the building (e.g. the walls). The cameras are powered and connected to the DVR via a 16-port PoE switch (N29986). The cameras support H265+, H.265, H.264+, and H.264 standards. With two 4 TB HDDs, such as M89305, H.265 video compression, and continuous recording at 25 fps for all cameras, footage will be stored on HDDs for 14 days.

ImagePerfect in Seagate SkyHawk hard drives, a technology that ensures the integrity of recordings.

The use "ordinary" hard drives in a surveillance system involves the risk of data loss. This is because hard drives used for monitoring purposes operate in different environments than those used in PCs. Data is stored here continuously and accounts for over 90% of the disk load. The need to simultaneously handle multiple data streams generated by individual cameras is also a challenge.

The algorithm of collecting data in the cache and writing to disk after buffer filling

In order to be efficient, large file transfers require not only considerable throughput, but also the availability of error-correction functions that help preserve data coherence during transmission. SkyHawk HDDs rely on a special data correction algorithm that reduces the loss of image frames during write operations. The firmware of the HDD cooperates with the DVR/NVR to ensure the appropriate query handling time, thus minimizing the risk of DVR/NVR buffer overflow and preventing the loss of image frames during playback.

Seagate SkyHawk drives are controlled by special firmware dedicated to CCTV drives. It is based on the multi-level buffering (MTC) technology which ensures high image integrity and simultaneous recording of up to 64 camera streams. The ATA-8 protocol used is optimized for saving recordings in the form of sequences of large data blocks. Data from the NVR is stored in a disk cache buffer. It is written to the non-volatile memory only after that memory is used up. This results in fewer data read/write operations, thus ensuring greater reliability.

Designing TV/SAT systems in multi-family buildings.

DIPOL offers the MR-9xx and MV-9xx TERRA mustiswitches for multi-family buildings, designed in accordance with the requirements of TV/SAT systems, ensuring signal reception from two satellites. The solution offered is quite popular, among others on the Polish, British, German and Australian markets. Advanced TERRA multiswitches have been a still highly recognized a solution for large SMATV systems in Poland since 2004. Quality built, stability of parameters and very low failure rate make these multiswitches a product of choice to even the most demanding customers. DIPOL has been selling TERRA products since 1996. The product warranty extended to 4 years has been on offer from March 2013.

Below, a diagram of an exemplary SMATV system of a multi-family building is shown. It has been saved in various formats: dwg, pdf oraz stn system design software) and it can be easily customised in any form.

A project made in the SatNet program

Project from SatNet program saved in a pdf file

OTDR specifications: dynamic range.

There are a number of features determining its suitability for specific projects to consider when choosing an OTDR. One of the key parameters is the so-called "dynamic range". In general terms, it is the difference, expressed in decibels, between the power level of the backscattered signal at the beginning of the fiber and the noise level. In other words, said parameter determines how long fiber sections with additional attenuating elements (splitters, splices, connectors) can be safely measured (i.e. having a chance to see the end of the line correctly). For example: the dynamic range of 30 dB means that the OTDR will correctly measure the optical path, in which the attenuation will not exceed this value. Although many installers interpret the definition like that, it not an entirely correct understanding and some clarification is required.

The dynamic range depends directly on two parameters configurable by the installer (and the manufacturer), namely the pulse width and light wavelength. The longer (stronger) pulse is introduced into the fiber, the greater will be the dynamic range of the OTDR. Analyzing specifications of an individual device, the standard the manufacturer applied when determining the dynamic range of the OTDR should be considered. These may include popular IEC or Telcordia standards (10 μs pulse, 3 min averaging time, G.652D fiber), or the manufacturer can apply proprietary test inputs, manipulating with the averaging time or extending the pulse length in order to artificially increase the dynamic range in the specification.

The standard adopted or the manufacturer's own test procedure defines not only the pulse parameters used to determine the dynamic range, but also the definition of this parameter alone. As the figure below shows, the dynamic range varies depending on how its lower limit is defined: for the IEC standard it will be SNR = 98% (2% of the signal is noise), for the equally popular Telcordia standard, this limit is set by SNR = 1 (50% of the signal is noise.) The Telcordia standard is clearly less restrictive here. In practice, this translates into a difference of about 1.56 dB in the dynamic range. Therefore, this parameter should be carefully looked at in data sheets.

A - usable measurement range
B - IEC dynamic range
C - Telcordia dynamic range

To meet the expectations of customers, some manufacturers specify the so-called "usable measurement range". This parameter is defined similarly as the OTDR dynamic range, but the lower limit of the backscattered signal is the value below which a 0.5 dB attenuation instance will be undetectable. This parameter tells much more about the real usefulness of an OTDR, than the basic dynamic range, and its value is usually about 8 dB lower (in extreme cases even by 14 dB).

What switch to use when building a network in a warehouse hall?

Industrial switches are dedicated to industrial facilities with harsh environments, including increased dust levels, high or low temperature, or high humidity. Installation of industrial switches is also recommended for overhead cabling on poles or in cable chambers, with the use of sealed enclosures. The switches have Ethernet ports (Fast Ethernet or Gigabit Ethernet depending on the model) for connecting of such devices as IP cameras or PCs. ULTIPOWER industrial switches have IP40 rating (protection against access to hazardous parts, protection against solid foreign objects with a diameter greater than 1 mm). All ports support PoE (the switch has to be powered with 48 VDC). The switches are equipped with an SFP port to convert the transmission medium to optical fiber.

One of the most frequently used industrial switches in such systems is ULTIPOWER 352SFP N299707:

The diagram shows a system in which a single-port switch supplies the camera and transfer data to the switch (installed in a different location, e.g. 2 km away) via optical fiber

Why MJPEG stream in cameras? Video stream encoded in MJPEG format was often used in surveillance systems installed many years ago. It was replaced due to a lower performance than that of the competitive H.264 codec. However, home automation systems or alarm systems often, particularly the legacy ones, support only the MJPEG encoding. To make an IP camera connection possible, proper image stream compression parameters have to be set. In the case of Hikvision IP cameras, this is possible only for the auxiliary stream, i.e. the low resolution one... >>>more

Parameters of a video stream required to run an MJPEG stream (auxiliary stream and the resultant resolution reduction and coding)

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