Fibre is not new. The first fibre optic link was installed in Chicago in 1976. Since then, the technology and its application have grown so that it is now the transmission backbone of choice for long distance and mass telecommunications. It has reached the price performance point that allows it to be economically viable for communications to, and within, businesses and the home.
Fibre is capable of transmitting both analogue and digital data over large distances, in some cases up to tens of kilometres, as well as over shorter, more manageable distances for use within buildings. Its advantages are well known: immunity to noise and interference, small diameter cables with enormous bandwidth, resistance to tampering and eavesdropping, lack of need for repeaters and boosters and so on.
Early problems with fibre termination have largely been overcome so that application of this technology is much simpler. There are, however, design issues that need to be considered in applications in order to make them successful. Just as with copper wire or radio transmission, the performance of any fibre optic data link can be determined by how well the reconverted electrical signal out of the receiver matches the input to the transmitter. Either too little or too much power will cause high bit error rates. Too much power, and the receiver amplifier saturates, too little and noise becomes a problem as it interferes with the signal. This receiver power depends on two basic factors: how much power is launched into the fibre by the transmitter and how much is lost by attenuation in the optical fibre cable plant that connects the transmitter and receiver.
There are two types of fibre cable; single and multimode. These refer to the light transmission characteristics within the cable itself: the number of propagation modes, or light paths that the light can take along the cable. Multimode, the most commonly used type for smaller industrial, consumer and entertainment applications has the highest attenuation and operates over short distances. The older type, 62.5/125 (the figures refer to the internal/external core diameters in microns), often referred to as OM1 cable and with a limited bandwidth has historically been used in networks with speeds up to 200Mb/s.
More recently, 50/125 cable, OM2 and OM3, is the more widely deployed version offering better performance offering 1G/s rate at 500m and 10Gb/s at 300m. Singlemode cable is used in very high speed links, above 10Gb/s or long distances up to 30Km. In our AV-oriented world, the most likely cable to be used for audio and video transmission is the OM2 variety.
Rainer Stiehl, Vice President of Marketing Europe for Extron: “The increased availability of fibre in buildings will lead to an increase in fibre optic-based A/V system implementations. A fibre optic backbone offers several key advantages for integration today and into the future. It allows for the coexistence of analogue and digital video signals over the same cabling infrastructure, providing a single system solution for accommodating current as well as legacy video formats. Since fibre optics also offers extremely wide bandwidth capability, the same cabling will be capable of handling the ever-increasing resolution requirements for today’s applications and beyond. Furthermore, this fibre-optic backbone can easily be adapted in the future to accommodate new video signals and formats as technologies continue to evolve.”
Jim Hayes, President of The Fibre Optic Association Inc., a body established in 1995 that promotes professionalism in the field of fibre optics and has, so far, trained over 27,000 technicians in the installation and deployment of fibre systems explains its growth: “Fibre benefits from being faster and cheaper. We see more usage in telecom, especially fibre-to-the-home (FTTH) and supporting wireless, and security (surveillance cameras).
"FTTH is probably the fastest growing business in most developed countries. Our schools are teaching FTTH everywhere. Here in the US, many cities are building municipal networks connecting public service groups (government, fire, police), educational facilities (schools, libraries) and building intelligent traffic control systems. Data centres, growing very fast to support increased internet growth, are using more fibre for interconnections since fibre is as cheap as copper for 10Gb/s links and uses significantly less power. For years, the fibre versus copper battleground was in corporate LANs over connections to the desktop.
"But while they were battling each other, WiFi has become so good that users prefer to be mobile with their laptops, iPhones and other web-connected devices. Now corporate LANs are fibre backbones to wireless access points”.
The range of applications is expanding, largely brought about by fibre’s advantages over copper. Resulting in rapid growth in deployment in key areas such as surveillance, control rooms, military and medical environments and high risk areas where electric hazards and harsh operating conditions are prevalent. Reduction in cost has allowed the technology to permeate into areas that were once the domain of copper networks, including conference and sports stadia, retail and transport hubs.
Rainer Stiehl comments on applications: “In hospitals, fibre optic products can be used for local video signal switching in operating rooms. The fact that fibre optic signals are not electrical in nature ensures patient safety. Fibre optic technology can also be used in academic hospitals where video signals from multiple operating rooms need to be routed to the auditorium, where students can view live operations.
"Fibre optic technologies are favoured in military applications, since transmission of content is inherently secure and immune to outside interference. This helps to ensure protection of highly sensitive information and also transmission of uncompressed, high resolution graphics and video with pixel-perfect accuracy. The very long distance transmission capability makes fibre optics ideal for many digital signage applications where end-to-end cable lengths of several kilometres are necessary. Whereas twisted pair transmission distances are limited to a maximum of 450 meters, fibre allows for much longer distances up to 30 km.”
Two factors influence the use of fibre within the AV world. Firstly, IP-based delivery of audio and video that relies on high bandwidth networks that are ideally suited to fibre backbones. Riedel Communications recently launched Mediornet, which utilises fibre signal transport for multi-channel HD/SD video, audio, intercom and data. Accommodating virtually any combination of network topologies, Mediornet is aimed at broadcast, pro-audio, events and sports stadiums. The system uses a carrier frame at 4.25Gb/s, subdivided further to carry any format of audio, video, or data information over single or multi mode fibre links in real time between elements of the system, which may be up to 40Km apart.
Thomas Riedel, Managing Director from Riedel, explains the market need and application: “MediorNet with its new fibre based signal distribution technology with integrated software processing and conversion offers a completely new approach to broadcast, pro-audio and event productions. This will radically change the idea of broadcast production facility design. Furthermore the integration of all technology into one single real time network reduces the effort and costs of installation.”
Secondly the need to transmit full high definition video and high resolution computer images over distances greater than the HDMI-copper limit of 15 metres. In many cases it is simply not possible to distribute video over copper connectors, fibre is allowing an stimulating device development, as Byeong Ho Park, VP, Marketing & Sales at Opticis explains: “The data bandwidth of UXGA, 60Hz, and 24bit colour needs 5Gbps in total, 1.65Gbps per each colour channel. 1080p HDTV has a slightly lower bandwidth. Manufacturers pushes market and at the same time the market pulls higher quality images. In special applications, 3 to 5 million pixels or 30 - 36bits colour depth displays are required which need around 10Gbps data transmission speed”.
Many manufacturers of video extenders are now offering fibre based versions, Extron, Covid, Communications Specialties (CSI), Gefen and others manufacture various fibre extenders for a range of video and computer formats. HDCP and data signalling of EDID information can be accommodated using an additional fibre or in some cases, copper connection between the transmitter and receiver.
Multidyne’s recently-introduced HDMI-ONE is the first claimed to be able to distribute and handle HDCP encrypted signals over one fibre. “HD has already taken over as the standard for broadcast markets and as a result the transport of DVI and HDMI copyright protected material has become more important for the AV, home theatre and permanent installation markets,” says Jim Jachetta, Senior Vice President of Engineering and Product Development. “With the HDMI-ONE, users can now send video from a DVD or Blu-ray player to a monitor or display up to 1000 meters away. Reliable HDCP copyright protection support has not been available over a single multimode fibre until now.”
Multidyne’s recently-introduced HDMI-ONE is the first claimed to be able to distribute and handle HDCP encrypted signals over one fibre. “HD has already taken over as the standard for broadcast markets and as a result the transport of DVI and HDMI copyright protected material has become more important for the AV, home theatre and permanent installation markets,” says Jim Jachetta, senior vice president of engineering and product development. “With the HDMI-ONE, users can now send video from a DVD or Blu-ray player to a monitor or display up to 1000 meters away. Reliable HDCP copyright protection support has not been available over a single multimode fibre until now.”
An adopter of fibre networks must consider the installation process. Derek Miranda, CSI’s Director of Marketing, explains the use of their Fibre Optic Termination Kit: “The kit provides a convenient method of fibre termination. This kit is designed to provide a reliable, quick and easy method to terminate fibre optic cable using Corning UniCam ST or FC type connectors. These connectors have a pre-polished tip with a small piece of fibre inside which eliminates the need for polishing the end of the connector or for using epoxy to secure the fibre cable in the connector. When a prepared fibre cable is inserted into the connector, it mates with the piece of fibre that is already inside.
"A small amount of optical coupling gel is also inside the connector to facilitate the transmission of light from one piece of fibre to the other. Finally, the fibre should be tested for signal attenuation using an optical power meter to assess overall power budgets.”
Whilst the connector assembly of fibre cables can be done in the field with hand tools, highest quality and reliability are only achieved using advanced manufacturing and testing procedures. As Wolfgang Fess, Communications engineer, of Klotz Audio Interface Systems explains: “To comply with a host of complex and exacting International standards it is necessary to use precision manufacturing processes. Our fibre optic cables are manufactured using a multi-stage process of stripping, cleaning, bonding and polishing of the fibre in its ferrule.
"Each cable undergoes stringent tests including 2D and 3D surface analysis and the measurement of optical attenuation according to IEC standards. Attenuation values are recorded and delivered with the cable as a final test report which is a key factor in loss budget analysis when the total attenuation of an entire system is calculated.”
Despite the massive bandwidth available in fibre networks, there is still a drive to squeeze yet more into a cable. Byeong Ho Park: “Current technology is evolving in two directions, one is optical WDM, coupling multiply divided wavelengths into one-fibre and the other is serializing and deserializing (Serdes) the data. The optical WDM requires complicated design and assembly of miniaturized optical components but doesn’t push high-speed transmission. The silicon technology of Serdes requires high-speed logic devices or optical transmission technology, which push up the costs. Other developments allow multiplexing and demultiplexing of control data such as RS232/485 or USB on to the data stream within the fibre cable”.
It is also possible to send light in opposing directions through a fibre cable, although the cost of the components required generally outweigh the cost of an additional fibre for return data.
Fibre opens a wide range of applications, wherever high speed, high bandwidth communications is required. It is well proven, well understood and usable technology that is opening up new vistas and opportunities in the AV world, delivering solutions that are unobtainable without considerable effort and expense using other methods.