Application Specific Fibre Optic Modem Information Guide


KBC’s ASFOM (Application Specific Fibre Optic Modem) range offers integrators and end users true flexibility and choice. Rather than having to change a system specification to accommodate the limitations of the transmission equipment, ASFOM gives you a unique opportunity to develop a transmission system that meets your own requirements. Instead of being limited by the set increments of channels and the mix of signal types offered by most manufacturers, the ASFOM range allows analog video, data, analog audio, contact closure, telephone, Ethernet, DVI, SDI and USB to be combined in the exact quantity and order that is needed. Solutions can be as simple as a single contact closure link or extend to a system requiring 128 real time video signals - all supported on a single fibre. Both point-to-point and bus topologies can be configured.

With applications in security and surveillance; access control; building management and industrial control to name but a few, ASFOM’s incredible flexibility allows virtually any requirement to be met using a standard, off-the-shelf product. To add to this, the ASFOM range is fully-ruggedized, with a temperature range of -40°C to +70°C, ensuring that the equipment operates in the harshest of environments.

ASFOM allows customers to:

  • Minimize installed fibre infrastructure usage and therefore maximise the infrastructure’s revenue potential
  • Reduce third party infrastructure rental costs (where applicable)
  • Recover fibre if the infrastructure is fully loaded
  • Ensure that system design is not dictated by equipment limitations
  • Minimize communication room rack space requirements
  • Reduce air conditioning and power costs

Electrical Modules

To reduce product lead times, ASFOM electrical interfaces are built as modules and then connected to a motherboard within the unit that carries out the processing and transmission operations. All KBC Networks audio, data and contact closure interfaces feature screw block terminal connectors. They are provided in this format to make installation as quick and easy as possible. In the field, these signals will typically be offered to the fibre transmission interfaces as copper cable. RJ45 and “D” shell connectors housing multiple interfaces, on the other hand, often create problems on-site as specialist break out cables need to be manufactured to enable the connection to be made. The electrical modules available are:

ASFOM composite videoAnalog composite video (single or dual channel)
ASFOM video channels are transmitted in an uncompressed digital format, providing high quality, real-time video images through the link. Interfaces can be configured for either 8 or 10 bit digital resolution providing medium haul or short haul performance specifications respectively. ASFOM links can be configured with anything from 1 up to 128 video channels on a single fibre. Units are not built in set increments of 4 or 8 channels; instead, the exact number of video channels can be specified. The video interface presentation is a 75Ω BNC.

ASFOM Analog AudioAnalog audio
Designed to transmit a line level audio signal, the interface utilizes AES3 24bit encoding providing excellent audio performance. The interface will accept balanced or unbalanced signals and has a standard impedance setting of 600Ω, (other impedances can be specified if required). Using the Configurator, simplex or duplex audio can be specified - along with the direction required if simplex is chosen. Presentation of the electrical audio interface is a 6-way screw block connector. In one module it is possible to have up to 2 simplex audio channels or 1 full duplex channel.


Designed to transmit RS232, RS422 or RS485 (2 wire & 4 wire), the data interface is a fully field selectable, user configurable module. To cope with system manufacturers’ data rates, it has a bandwidth in excess of 250 kbps - far greater than its competitors can offer - and is transparent to data encoding schemes. Presented as a 4-way screw block connector, dip switches configure the interface for the required data standard. Again, to improve usability and make installation as easy as possible, switchable 120Ω termination impedance and biasing is provided. The switchable termination removes the need for the installer to try and insert a resistor into a connector that was not designed to accept it. The ability to remove the KBC biasing enables connection to most third party data interfaces without compromising the data transfer.

ASFOM Contact Closure

Contact Closure
Using the Configurator, simplex or duplex contact closure can be specified - along with the direction required if simplex is chosen. The contact closure interface is an 8-way screw block terminal that can take up to 4 simplex or 2 duplex circuits.



ASFOM TelephoneTelephone
This module provides a single telephone interface with dip switches to determine which end of the telephone link the unit is connected to. The link can also be configured as an emergency interface (lift one end the other end rings) by setting the switches in a certain format. This setting can also be used in an engineering capacity providing an end-to-end voice link during configuration of any attached system. An RJ11 presentation is provided.

ASFOM Ethernet

This module provides an Industry standard 10/100 auto sensing interface with RJ45 presentation. The Ethernet traffic is transferred at wire speed through the ASFOM system, providing true 100 Mbps data rate.



Using a pair of 75Ω coaxial connectors as the interface, this module supports a G703 standard, 2.048 Mbps E1 interface.



A DVI 1.0 interface, supporting display resolutions for DVI of 1920 x 1200 @ 60Hz, or full 1080p for television, is supported through the ASFOM channel. The DDC line, passing the EDID information from monitor to graphics adapter, is transmitted across the fibre, although the ‘loop-through’ connector provided at the transmitter can also be used to provide the EDID information from a locally connected monitor. Due to electrical bandwidths, multimode ASFOM transmission distance is limited to 2km, with 30km distances achievable with singlemode. The DVI interface requires 2 ASFOM slots in any physical configuration and will need 4 dedicated wavelengths when combined with other signals.

The 3G-SDI module supports SMPTE 259M, 292M and 424M signal levels along with embedded audio and data through the ASFOM system. A ‘loop-through’ connection is provided on the transmitter module. Due to electrical bandwidths, multimode ASFOM transmission distance is limited to 2km, with 80km distances achievable with singlemode.


The HD-SDI module supports SMPTE 259M and 292M signal levels along with embedded audio and data through the ASFOM system. A ‘loop-through’ connection is provided on the transmitter module. Due to electrical bandwidths, multimode ASFOM transmission distance is limited to 2km, with 120km distances achievable with singlemode.


Supporting USB 2.0 and 1.1 standards, the interface provides extension of the USB (Universal Serial Bus) through the ASFOM system, with data rates up to 480Mbps (High Speed) and 500mA port power supported. The host end (upstream) is a single type B connection, with four Type A connections provided at the remote (downstream) end.


Physical Configuration

ASFOM products are available in variety of physical formats to suit the environmental requirements of any project. The physical format will be initially dictated by the number of electrical modules required.

ASFOM Wall-mount


Where a limited number of electrical interfaces are needed, or the units are to be located in a remote location with no 19” rack, wallmount box options are available. The wall-mount unit is available in either the ‘thin’ three module version, or the ‘thick’ version which can accommodate up to 6 electrical modules in the dual height unit.


ASFOM 19 Rack-mount


19” Rack-mount
The rack-mount module has an internal power supply and can be configured with a redundant power option if required. Up to 9 electrical modules can be housed in the 1U variant and up to 18 modules in the 2U format. In both the wall-mount and 19” rack-mount units the module bays coloured in grey cannot be used to house the dual video interface.

ASFOM 19 Chassis19” Chassis

KBC offers both 3U and 4U chassis for ASFOM card modules. The 3U chassis can be used for configurations of one or two electrical modules and allows basic ASFOM units to locate in the same chassis as KBC Digital Standard units. For larger channel requirements or in situations where there are multiple links coming back to a centralized control room, the 4U 19” chassis is recommended. It has an integral power supply and can hold up to 14 single slot cards or various configurations depending on the individual product permutation. The ability to mount various interfaces in a chassis presents significant space savings when compared to the competition’s offerings. In a single slot, the KBC unit can have up to 6 video channels or a configuration such as 4 video channels and a fully field-configurable data channel. Dual redundant power supply options are available for the 3U and 4U chassis, utilizing either a second AC or a DC input. KBC chassis are shipped with blanking panels across all slots so that unused slots are protected and integrity of the chassis is maintained. No forced air cooling is required in the rack module or the 19” chassis, which means that fan filters don’t have to be changed on site; this reduces ongoing maintenance costs. KBC believes in designing products to run cool which reduces stress on components and increases the operational lifetime of the product.

Possible Applications:

ASFOM Chassis applications

ASFOM can be configured to provide either optical point-to-point or bus architecture solutions.

ASFOM Optical Configuration 1 schematic

Point-to-Point Systems
Depending on the solution required, ASFOM point-to-point systems will use single wavelength, WDM (Wavelength Division Multiplexing) or CWDM (Coarse Wavelength Division Multiplexing) optical components. The optical package used depends on the quantity and mix of electrical interfaces. The analog video interface, for example, requires more bandwidth than the other interfaces, and if video is required in the ASFOM, it will also dictate the optics used. Up to eight video signals can be transported on one  wavelength, therefore; a system requiring four video signals only, would use a single wavelength LASER transmitter. An eight-channel multiplexer would also use a single wavelength and require optics with a data rate of 1.2 Gbps. This data rate  (bandwidth) will limit the multimode transmission distance due to modal dispersion, to approximately 2km. If the system requires twelve video signals only, a WDM optic would be used to combine two wavelengths together in one fibre. This would be configured by putting eight video signals on one wavelength and the other four video signals on the second wavelength. The two wavelengths would then be multiplexed together. This can be thought of as two different colours of light in the same fibre that do not interfere with each other. The WDM would also be used in situations where duplex signals are required  on a single fibre. In this case, the wavelengths travel in opposite directions. This could be a solution for say four video signals with a duplex data channel, where, as shown, λ1 (wavelength 1) would carry the four video and one half of the data channel, and λ2 would carry the other half of the data channel.

ASFOM Optical Configuration 2 schematicWhen the system becomes more complex, a CWDM is used. This device is able to multiplex up to sixteen different wavelengths together, enabling them to pass through a single fibre. Each  wavelength is spaced 20nm apart and unique optical transmitters and receivers are used to generate and see each particular wavelength. As each wavelength is spaced close together, the optical components are more expensive than standard optics. As a result, CWDM-based system costs are much greater than standard optic system costs. For example, rather than being twice the cost of a sixteen channel multiplexer, a thirty two channel video only multiplexer could be up to three times the price simply because of the optics required. The direction of information flow at a particular wavelength is dictated by the location of the transmitter optic, associated with the particular wavelength. Another reason for using a CWDM device in a point-to-point system could be for expansion. If a CWDM system is specified data delivered at day one, future expansion can be accommodated by putting signals on unused CWDM wavelengths and then passing them across the already-installed fibre. As all KBC’s products are serial numbered, this is simply a process of checking records and identifying the available wavelengths.

ASFOM Optical Configuration 3 schematicBus Systems
By utilizing the features of CWDM and CWDM OADM (Optical Add Drop Multiplexer) technology, ASFOM products can be configured as a bus network on a single optical fibre. Due to the CWDM technology, KBC would advise that bus systems are configured on singlemode fibre only. The CWDM module combines up to sixteen different optical wavelengths (colours of light) onto one fibre, allowing the bandwidth potential of the fibre to be realized and minimizing the requirements on the installed infrastructure. The system is configured by having a CWDM at the head-end and then using CWDM-OADM units at the remote points. The CWDM-OADM allows unused  wavelengths to be added in and used wavelengths to be dropped off where required. The number of wavelengths added in or dropped off will depend on the system requirements at a particular location. The system cannot use more than sixteen wavelengths due to the CWDM.

Expanding a Bus System
Bus systems can also be added to in the future, expanding as the system requirement does. This will have major benefits for the end user as the existing infrastructure can be used and no additional fibre is required. As long as there are unused CWDM wavelengths, additional modules can be added that utilize those wavelengths.

Designing a Bus System
As with point-to-point systems, the maximum number of video signals that can be transmitted at one wavelength is eight. Therefore if ten videos are required at a certain location, two wavelengths are required. If return signals, such as audio or data, are required at the same location, they will also need an optical wavelength. For example, imagine a railway line with five stations, all monitored from a control room at one end of the line. At each station there are ten PTZ (pan-tilt-zoom) cameras that need to viewed and controlled from the control room. The control room also needs a telephone connection to each remote station. This system will require four ASFOM systems that have ten video, one data and one telephone circuit. Each system will require three optical wavelengths, which equates to twelve out of the sixteen available wavelengths being used. All the ASFOM systems that are at the stations will be classified as transmitter units and their corresponding receivers will be located at the control room. The example below shows four remote stations (nodes) where each station has four video input signals; a bi-directional data channel and a single Ethernet channel. Due to the electrical signals, each location will require two optical wavelengths to carry the information. At the head-end, all signals are presented to the user.

ASFOM Optical Configuration 4 schematic