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Fiber-optic TV systems
Under EU rules, by 2020 each citizen of the European Union is to have the technical ability to access the Internet with download speed at least 20 Mbps. In this respect, some EU countries introduced regulations aimed at accelerating this process. In some of them, each newly built residential building should be equipped with fiber-optic infrastructure. This type of cabling can be used not only in the implementation of access to high-speed Internet, but also proves to be an excellent medium for other services, including distribution of TV/SAT programming.
Multiswitch systems providing access to digital terrestrial television (DVB-T) and satellite TV platforms are the perfect complement or an alternative to cable TV networks in multifamily buildings. The use of fiber optic solutions for such SMATV systems can have both technical and economical advantages.
Advantages of optical fibers in SMATV systems
  • Possibility of transmitting TV signals over long distances without regeneration (it may depend on the network topology and devices used). The signals can be transmitted over distances of hundreds of meters or even tens of kilometers. A large size of a building or a housing development is not a problem for easy implementation of the system, in contrast with traditional RF technology. SMATV systems based on copper cables can be difficult for implementation when the distances between active devices exceed 100 meters. The application of additional RF amplifiers means additional costs, both at the implementation and operation stage.
Attenuation of a coaxial cable: 10–30 dB / 100 m

Attenuation of a single-mode fiber: 0.25–0.4 dB / km
  • Complete immunity to ground loops, surges and spikes – this often overlooked fact may be in many situations the most important one. SMATV systems, due to antennas located on roofs of buildings are particularly vulnerable to surges resulting from lightning. Despite proper grounding of all system components, some of the equipment of traditional SMATV systems can be irreversibly damaged. Notably, overvoltages can destroy not only the SMATV equipment, but in extreme cases also some consumer devices, such as satellite receivers or televisions. In contrast, fiber optic cable is a perfect insulator. This means that all the surges induced in antennas installed on a roof will not cross the optical transmitter - all other components of the system as well as subscribers' devices are fully protected.
The consequences of lightning surges in SMATV systems can be very expensive.
The use of fiber-optic solutions eliminates this problem.
  • Complete immunity to electromagnetic interference – fiber-optic cables can be without any risk of interference installed together with copper cabling, including AC power lines.
  • Space-saving in installation shafts – one fiber-optic cable with diameter 2–3 mm transmits the same signals as a typical 9-cable multiswitch bus consisting of coaxial cables with 7 mm diameter.
  • Lower cost of cabling – the cost of installing fiber-optic cable instead of a bus composed of 9 coaxial cables can be several or even ten times lower. It is both the result of a competitive price of the optical cable compared with a good quality coaxial cable and the reduction of the number of the cables to the single one.
Advantages of Terra fiber optic SMATV distribution system
The idea of the system consists in converting signals from antennas into optical form and transmitting them via optical bus to optical receiver or group of receivers (with the application of optical splitters), where they undergo reverse conversion into RF signals that are distributed via multiswitches and coaxial cables to the outlets of the users.
  • Excellent signal quality thanks to the use of separate lasers for SAT TV (wavelength of 1310 nm) and terrestrial broadcasts (1550 nm) in the optical transmitter. Other systems, operating at one wavelength, may provide much worse results and can have problems with stability, especially when the input signals are not ideal, e.g. due to unfavorable reception conditions.
  • Application of FC/APC Angled Physical Contact connectors decreases undesired back reflections from the connections of optical fibers. Such reflections can be particularly harmful in fiber SMATV systems due to relatively small distances between the transmitters and receivers.
  • Application of traditional QUATRO LNBs – one of the most important advantages for installers. This means that the dish and LNB can be setup with the use of a traditional SAT TV meter. Competing systems use LNBs with optical output or with N-type output with 50 ohm impedance. In both cases, the installers use in practice a standard single LNB to adjust the dish, then change it to the dedicated one. Apart from the increased workload, such a change always involves the risk of moving the dish or the LNB position. The application of a QUATRO LNB may also be beneficial in the case of a system failure. In this situation, the installer has the ability to verify the problem already by the dish. In other systems, the signals can be measured with a standard satellite meter a lot further, at the output the optical receiver, so the problem cannot be easily localized. To test signal coming out from such special LNBs with optical or 50 ohm outputs, the installer would have to use also some special, expensive equipment.
  • Stable signal levels thanks to AGC in optical transmitter and OLC (Optical Level Control) in optical receiver.
  • Die-cast housings of Terra devices guarantee high screening efficiency, which eliminates an influence of electromagnetic interference in RF segments.
  • Optical power budget of 21 dB – means that the signal from the optical transmitter can be divided by splitters into tens of paths and each of the paths can be connected with a multiswitch or a group of multiswitches. This way, Terra system can cover tens of buildings, located even kilometers away one from another.
Terra system components
Optical transmitter OT501W
The transmitter converts satellite RF signals from a QUATRO LNB and terrestrial DVB-T, DAB and FM signals (previously combined by a triplexer) into optical signals. The built-in WDM multiplexer uses two wave lengths, 1310 nm and 1550 nm, providing excellent signal quality. Each RF input is equipped with automatic gain control (AGC) guarantying stability of the output optical signal (compensation of changes in signal levels associated with different weather conditions).
Optical receiver OR501W
The receiver converts the optical signal transmitted over optical fiber from the OT501W transmitter into electrical form, identical with the original SAT and terrestrial RF signals provided to the transmitter (5 outputs – four pairs of band-polarization SAT TV signals and combined terrestrial signals). So, the receiver can be described as a "virtual QUATRO LNB" (plus terrestrial antenna). The signals should be fed to a multiswitch with the required number of outputs, connected via coaxial cables with subscriber outlets. Of course, it can also be a group of multiswitches providing signals to a large group of users.
Fiber optic cabling
The Terra system has been designed for operation with single mode fibers. The selection of a specific cable depends on the system designer. The system needs only one fiber, however, in the case of deploying a new optical network we recommend to employ cables with 2 or 4 fibers, which will allow for launching other services in the future. When the transmitter is located outside a building (usually close to the master antennas, in a hermetic enclosure or in attic), the cable must belong to the universal group (gel-filled, with jacket resistant to UV radiation). Despite the fact that universal cables have LSOH jackets and can be installed inside buildings, the change of the kind of the optical cable at the entry to a building into an indoor version may be a good idea due to the lack of gel and easier installation.
The change of the kind of optical cable from universal ( L76004) to indoor ( L7102), in Ultimode L5408 box
Connections and fiber splicing
Optical Terra devices are equipped with FC/APC ports, so the fibers should be terminated with the same type of pigtails. Of course, direct connection of an optical line to a device is not a good practice. Optical lines should be terminated on both ends so that subsequent disconnection and connection of the devices (e.g. for maintenance) does not interfere with the structured cabling (other fibers of the optical lines are usually used by other services). So, the fiber should be terminated with a pigtail located in any box with an appropriate adapter. The connection between the adapter and the device is made with a suitable patch cord, terminated on the device's side with FC/APC plug.
The A9872 optical transmitter is connected via FC/APC - FC/ APC L3244 patchcord to FC-SC adapter located in the Ultimode L5302 box. The optical line (Ultimode L7102 cable) is terminated with SC/APC L35522 pigtail. This way, any connection/disconnection operations are performed out of the main line, which protects the structural cabling against accidental damage.
The best method of fiber splicing in to use a fusion splicer. In the examples, the splices were made with the use of EasySplicer L5810. Having the large optical power budget and installing a relatively small distribution network, the installer can also use mechanical splices, like Ultimode L5550. In the case of a large system with great number of splitters, the safety margin becomes narrower and the application of a fiber splicer is highly recommended or just necessary.
Optical splitters and attenuators - power budget
When the optical signal from the transmitter is to be divided into a number of optical channels (paths) e.g. to provide the signal to separate staicases in a building, it is necessary to use an optical splitter. Each of the paths should be terminated with optical receiver that converts the optical signal into RF signals distributed via a multiswitch system.
The number and type of the splitter is determined by optical power budget. In the case of the Terra system, the 21 dB budget is the result of the output power of the transmitter (6 dBm) and the maximum sensitivity of the receiver (-15 dBm). Aside from the single-mode standard, there are no special requirements for the type of the splitter(s). The following table contains information about Ultimode splitters.
 
CodeL36041L36081L36161L36321
NameSO-4-7ASO-8-7ASO-16-7ASO-32-7A
Number of outputs
481632
Attenuation
6.7 dB10.2 dB13.0 dB16.4 dB
The splitters can be connected in cascade, of course taking into account the available power budget.
ULTIMODE SO-4-7A (1:4, G.657A, SC/APC) L36041 splitter mounted in ULTIMODE TB-08B L5408 distribution box. The box can also house the ULTIMODE SP-18M 1x8 MICRO L3608 splitter and additional adapters.
When analyzing the optical power budget, the attenuation of splitters is accumulating with the attenuation of the other system components:
  • optical fiber: 0.4 dB/km
  • fusion splice: 0.1 dB
  • mechanical splice: 0.2...0.5 dB
  • connection (pigtail terminated with adapter/connector): 0.15 dB
  • patchcord: 0.25 dB
In addition, it is necessary take into account a safety margin, at least of 1.5 dB.

In the example above, the total attenuation of a single optical path is equal to: 2 x 0.25 dB (patchcords) + 4 x 0.15 dB (pigtails) + 4 x 0.1 dB (splices) + 6.7 dB (splitter) + 0.4 x 0.4 dB (400 m cable) = 8.36 dB.
Adding the 1.5 margin, we get 9.86 dB, which would be the minimum optical power budget necessary for running the system. Applying Terra devices with 21 dB power budget, we get an immense, additional margin above 11 dB, which guarantees excellent reliability of the system.
In the case of smaller systems, the extremely important issue is the protection of the inputs of the receivers against excessive signal levels. The acceptable range of the optical power at the input of the A9877 receiver is 0...-15 dBm, so the maximum level should not exceed 0 dBm.
Considering the example above, in which the total attenuation of the optical path is about 8.36 dB, and taking into account the output power of the A9872 transmitter at the level of 6 dBm, the input signal level is -2.36 dB, well inside the allowable range. In cases where the total attenuation of an optical path is lower than 6 dB, one should employ a suitable optical attenuator guarantying the input level somewhere in the middle of the allowable range.
Selection of equipment for a specific application
The following example describes implementation of a multiswitch system with fiber-optic bus in a multi-family building with 3 stairwells. The signals to apartments located on 13 stories are provides via 2 risers, and the third riser is located in the part of the building with 4 floors. On each floor there are 4 apartments, each of them should be provided with one RF outlet with FM/DAB/TV/SAT-TV signals.
The layout of the building
Satellite Dish INVERTO IDLB-STCF 120cm (light color)QUATRO LNB: Inverto BLACK Ultra 0.2dBUHF TV Antenna: DIPOL 44/21-60 Tri DigitSingle-mode Patch Cord ULTIMODE PC-544S (1xFC/APC-1xFC/APC, 9/125) - CLEARANCE SALE!Indoor Cable: ULTIMODE ILB-2SM-A (2xG.657A1, limited bending radius)Optical Fiber Termination Box ULTIMODE TB-02HFiber Optic Distribution Box ULTIMODE TB-08B (wall-mounted)Single-mode Patch Cord PC-522S2 (SC/APC-SC/APC, simplex G.657.A2, 1.5m)Fiber Optic Distribution Box ULTIMODE TB-08B (wall-mounted)5/32 Multiswitch: Terra MV-532 (IF gain adjustment, class A)SAT/TV Splitter: Terra SD-504 (class A)5/24 Multiswitch: Terra MV-524 (IF gain adjustment, class A)5/16 Multiswitch: Terra MV-516 (IF gain adjustment, class A)Optical Splitter: ULTIMODE SO-4-7A (1:4, G.657A, SC/APC)
Complete diagram of the SMATV system with optical bus

The master antenna set is located on the roof above the first, high riser. The optical transmitter is installed in the attic, close to the antennas, and connected with them via five coaxial cables. The output optical signal connected via L3244 patch cord and L5302 installation box is then transmitted via L7102 optical cable going down to the technical room located in the basement of the building. The room houses another L5302 box and L5408 box with L36041 optical splitter dividing the signal into 3 paths, each for distributing the signal to optical receivers located in the 3 stairwells.
The 3 links between the technical room and boxes located in the stairwells (each of the boxes protects a pigtail and splice) are made of ULTIMODE L7102 cable with second fiber that can be used for other purposes. The optical paths end at the inputs of the Terra A9877 optical receivers. Thanks to the use of the installation boxes, the optical lines are well protected against accidental damage during any maintenance operations - the active devices are connected via adapters in the boxes, not directly with the lines. The attenuation level of the splitter eliminates the need for application of additional attenuators at the inputs of the receivers.
The optical receivers provide output RF signals distributed in each stairwell via multiswitches with the number of outputs adequate to the needs within the stairwell. In the case of the first and second stairwell, these are MV-524 R70724 and MV-532 R70732, whereas in the third staircase it is the MV-516 R70716 multiswitch. In each stairwell with two multiswitches it is necessary to use the SD-504 R70515 SAT/TV splitter. The outputs of all the multiswitches are connected to subscribers' outlets via a coaxial cable, e.g. Triset-113 E1015.
List of the components of the system:
NameCodeQtyFunction
Satellite dish INVERTO IDLB-STCF 120 cmA96481Master satellite antenna
UHF antenna Dipol 44/21-60 Tri DigitA26701Master DVB-T antenna
Quatro Inverto Black Ultra LNB
A982661QUATRO SAT LNB
Gel-filled coaxial cable TRISET-113 PEE1017->Connections of master antennas with optical transmitter
FO cable ULTIMODE ILB-2SM-A (2xG.657A1)L7102->Optical connections
Single-mode pigtail PG-52S2 1xSC/APCL355228Termination of the fiber of optical lines
Termination box ULTIMODE TB-02HL53028Protection of splices and pigtails
Single-mode patch cord ULTIMODE PC-544S FC/APC - FC/APCL32444Connection of the transmitter and receivers to optical lines
Optical transmitter
Terra OT501W
A98721Signal conversion: RF (copper cables) to optical form (fiber)
Optical receiver
Terra OR501W
A98773Signal conversion: optical (fiber) into RF (copper cables)
Optical splitter
ULTIMODE SO-4-7A
L360411Division of optical signal into 3 paths (stairwells)
Distribution box ULTIMODE TB-08BL54081Wall-mounted distribution box (for optical splitter)
SAT splitter Terra SD-504R705152SAT bus extension
Multiswitch Terra MV-532R707322RF signals for subscribers' outlets
Multiswitch Terra MV-524R707242RF signals for subscribers' outlets
Multiswitch Terra MV-516R707161RF signals for subscribers' outlets
Coaxial cable TRISET-113 PVCE1015->Connections between multiswitches and RF outlets
Compression F-connector MASTER F 113
E80342129Terminations of coaxial cables (RF inputs of transmitter, RF outputs of receivers, multiswitches and splitters)
Subscriber Terminal Outlet Signal R-TV-SATR694100120Outlets in apartments