Question # 1: One of the components that you mention in that paper is the fiber optic receiver consisting of two sections; the detector that coverts the optical signal back into electronic form and the output circuit that reshapes and rebuilds the original signal before passing to the output. This sounds like a particularly critical point in the process. Are there specific specs and other parameters to look for in this receiver between the various manufacturers?
Jim Jachetta: One thing to look for is optical receiver sensitivity. The more sensitive a receiver, the longer distance an optical signal can travel.
In most cases, the information we transport over the fiber has been digitized. There are many fiber manufacturers that digitize video and audio for fiber transport. What makes Multidyne different is the way the video is processed.
We don’t cut any corners. We clamp the video. We low pass filter with a 13 pole elliptical filter. In our Broadcast and Professional Fiber lines we use 12 bit and 9 bit processing, respectively. Most manufactures use 10 or 8 bits for these applications. We use high quality video op amps that cancel high levels of hum and noise. Since there will always be a copper coax cable on the video input, we include an adjustable 1500 foot video cable equalizer and gain control. This eliminated the need for an external video equalizing distribution amplifier.
In short, if the video is not processed, digitized and reconstructed properly, the performance of the fiber optic system will be poor. At Multidyne excellent signal quality from systems end-to-end is our primary goal.
Question # 2: Obviously, a critical part of the maximum transmission distance involves the design and construction of the fiber optic cable itself and this has improved. What has been the most significant improvement in fiber optic cable over the past few years?
Jim Jachetta: In the early days of fiber optic communications, Multimode fiber was widely used due to lower cable costs and lower equipment costs. A big limiting factor to Multimode fiber is distance. You can not transport significant bandwidth over distance with Multimode fiber. Composite video will reach about 4-5 KM and an RGB-HV high resolution video will reach about 800 meters. Multimode fiber has high optical loss per KM, but you actually loose bandwidth over distance first. The fact that a 4 Gbps RGB signal only reaches 800 meters does not have to do with optical attenuation or loss. It has to do with the fact that beyond 800 meters the Bandwidth of a Multimode fiber will not support a 4 Gbps signal.
In the early days Singlemode fiber was more expensive and the equipment was more expensive as well. Due to improvements in fiber cable manufacturing, Singlemode fiber is now less expensive than Multimode. Singlemode fiber theoretically has an almost infinite bandwidth. If an integrator needs to transport High Definition Video or High Resolution Computer Graphics, we always recommend Singlemode fiber. With the wide spread use and demand for HD-SDI, DVI and the new 3Gig HD-SDI, Multimode fiber will not have the needed bandwidth over distance.
If a customer only needs low bandwidth composite video it will work over Multimode fiber, but that system will cost more for the fiber cable and the system will not be future proof.
With that said, our integrators will run into Multimode fiber quite often on building retrofits and upgrades. We had a customer at a large corporation in New York City that needed to move many channels of video, audio, data and SDI over one multimode fiber. Luckily the required run was under 1000 feet. Several manufacturers where brought in and they could not come up with a solution.
The proprietary solution presented by MultiDyne was CWDM over Multimode. CWDM stands for Coarse Wave Division Multiplexing where multiple wavelengths or colors of light are multiplexed onto one fiber. CWDM over Singlemode fiber is very common today. Multidyne is the only fiber vendor offering CWDM over Multimode. Multidyne and the integrator were able to provide the customer a solution for bi-directional video and audio as well as 6 channels of SDI over one Multimode fiber.
Question # 3: How does the wavelength of the signal affect transmission? (wavelength windows)
Jim Jachetta: Depending on the application, the wavelength and can be very important.
In Multimode applications the most common wavelength is 850 nana-meters. For high speed applications a VCSEL or Vertical-Cavity Surface-Emitting Laser is used due to it’s low cost and high speed.
In Singlemode the most common wavelength is 1310 nana-meters. Typically a Fabre Perot laser is used for applications under 15 KM. For longer distances of up to 80 + KM a 1550nm DFB or Distributed Feedback laser is used. Over long distances, dispersion or the spreading of the laser light becomes a factor. A DFB laser typically has a tighter optical spectrum and higher optical power so distances of over 80 KM can be reached.
Since DFB lasers have a tighter spectrum and are much more stable over temperature, they are ideal for CWDM optical multiplexing. Up to 18 DFB lasers in varying wavelengths from 1271 nana-meters up to 1611 nana-meters can be multiplexed with a 20 nana-meter spacing on one fiber. Due to the tight spectrum and temperature stability, the lasers maintain there assigned wavelength and do not bleed into one another.
Question # 4: Lower cost plastic fiber is said to be usable for shorter distances. Suitable for the home theater market?
Jim Jachetta: Plastic fiber is used in many residential home theatre applications. The digital surround sound audio from your cable or satellite receiver uses a TOSLINK plastic fiber optic cable. The wavelength is typically in the 650nm range. The bandwidth is very limited and the distance is only a few feet.
Question # 5: The amount of light that is reflected back into the cable rather than being absorbed in the cladding is an important factor. Please explain the importance of the cladding in an optical fiber?
Jim Jachetta: A fiber optic cable has two distinct parts, the core and the cladding. The core is the inner most part that carries the optical information. The cladding is the outer part that protects the fiber core from shock and damage. The core and cladding have slightly different refractive indexes. That is they have different light reflective properties. It is this different refractive index that keeps the light from bouncing out of the inner core. When light strikes the wall between the core and cladding it is reflected back into the core. The difference in the refractive index is what causes the light to travel down the fiber without escaping.
Question # 6: What are the various ways in which fiber optic cables are classified?
Jim Jachetta: There are many classifications for fiber that have been developed over the years.
The main characteristics of Multimode fiber have to do with the core diameter. There is 50 micron, 62.5 micron and the less common 100 micron Multimode fibers. The most common is 62.5 microns. The core and cladding together typically have a 125 micro diameter. So a 62.5 micron Multimode fiber would have a designation on the jacket of 62.5/125 for 62.5 micron core with 125 micron cladding.
Singlemode fiber is typically 8 microns. The designation found on the fiber cable jacket would be 8/125 for an 8 micron core with a 125 micron cladding.
Question # 7: It seems that the first big commercial application for fiber, back in the late seventies, was telephone service and demand quickly exceeded supply. How is the supply and demand situation now. What’s the price trend on fiber for AV applications now?
Jim Jachetta: The pricing on fiber optic cable and fiber optic components have continually fallen since the telecom and DOT-COM bubble burst. There is ample supply of the common components needed in our fiber optic systems. In most cases, the fiber optic cable is cheaper than the copper equivalent. Copper is in tight supply. There is plenty of silica or sand in the world to make optical fiber.
The cost of the fiber optic equipment is typically on par with the cost of high-end copper or CAT5 equipment. A fiber optic transport system will always provide better performance than a copper or CAT5 solution. In many applications, fiber is the only way to go since copper will not support the bandwidth or the distance requirement. Take DVI for example. DVI will reach 20 to 30 feet over copper. To reach beyond 30 feet, fiber has to be used to transport DVI.
Question # 8: How does it compare to the price trend on copper?
Jim Jachetta: As I mentioned earlier, the cost of fiber has steadily gone down and the cost of copper has gone up. I will give an example. A 6 strand Singlemode fiber cable will cost under $1 per foot in small quantities. A minimum of 6 high resolution UXGA or RGB-HV signals can be transported over this particular fiber cable. If we use CWDM technology more than 100 signals can be transported over this fiber cable.
If we compare this to a CAT5 or UTP solution for just ONE UXGA or RGB-HV signal we would have to use Skew Free CAT5 cable at over $10 per foot. That $10 per foot to move ONE signal.
Question # 9: Of course, there is rapidly increasing demand for high bandwidth residential AV service and the fiber deployment for this represents a huge investment for communication companies. What’s the likelyhood that some future advance in fiber technology might make the currently deployed networks obsolete?
Jim Jachetta: On new installation we always recommend our customers, consultant and integrators to install Singlemode fiber. With Singlemode fiber you will always have the bandwidth for future developments in high resolutions formats such as the new 3 Gig HD-SDI and DVI Dual Link. Optical components are now on the market for 10 Giga bit per second transport. Our R&D department is already working with this technology.
If Singlemode fiber is installed, the chances of obsolescence will be minimal.
Question # 10: Fiber snakes are being marketed now for audio applications involving temporary venue road setups. How durable is fiber for the extremely rough treatment that equipment like this gets?
Jim Jachetta: The connectors are the most likely points of failure and it seems that several manufacturers (like Neutrik) have marketed fiber connectors that closely resemble the good old XLR with a thick, hard shell over it.
Fiber optic snakes are ideal for temporary installations, live performances, concerts, news events as well as field and military applications. Multidyne provides a wide array tactical fiber optic cable assemblies. Typically these assemblies include a ruggedized fiber optic connector with Kevlar re-enforced fiber cable. Break-out or fan-out adapter cables are provided to convert from the tactical connector to the standard ST, SC, FC or LC connectors. These cable systems will be installed in mobile production truck, news gathering vehicles and military hardware. They can withstand the ware and tare of mobile television production and military combat.
Question # 11: It has been said by many that compared to the more familiar copper line, fiber optic cable is more difficult to install and maintain. Is this true?
Jim Jachetta: For installation inside a facility, studio or corporate board room, the standard fiber optic connectors will be used. Connectorizing a fiber cable is very easy. Simple tools and techniques are used similar to those required to connectorize a coax with a BNC.
The first method of connectorizing a big fiber optic cable is to use a Fusion splicer. Each fiber strand is connectorized by taking a short pig tail with a connector already on it and fusion splicing it to the fiber strand. A fusion splicer costs under $5000 or can be rented for a few hundred dollars a day. On large installations, the electrical contractor will handel the fiber installation.
The second method is to use a Quick-connect connector. Several manufactures make epoxy free and polish free connectors. The old school approach was to glue the fiber into a connector, cure it in an oven and then polish the connector. A Quick-connect connector already has a fiber glued in place. The gluing and polished was done at the factory. The installer just strips the fiber cable with simple tools and sticks into the connector. It is that simple.
Question # 12: Advantages of fiber over copper? Noise, ground loops, etc.
Jim Jachetta: Fiber Transport will always give better performance.
There is no noise or ground loops with fiber. There is 100% electrical isolation between each side. This eliminates the danger of lightning strikes and ground differentials between buildings.
Fiber will not pick up electrical interference from HVAC systems and high voltage power lines.
Fiber transport is not limited by distance or bandwidth. A fiber signal can reach over 100KM.
The size of a fiber optic cable is much small than copper or coax. Therefore the installer will have more room in the cable conduits.
Question # 13: How easy is it to splice fiber cable? There are several ways?
Jim Jachetta: There are two types of fiber splicing; mechanical and fusion.
Mechanical splicing uses a simple device to butt splice the two fiber together. Simple tools are used to strip and prep the fiber. The mechanical splice device opens like a clam-shell. The two fibers are positioned in guides to align them properly. The device is locked shut and you have a mechanical butt splice.
In a fusion splice, the two glass ends are actually melted together. Simple tools are used to strip and prep the fiber. The fusion splicer has a door that opens to accept the two fibers. The fiber are placed together. The fusion splicer then automatically aligns and fuses the fiber together with a several thousand degree temperature.
Question # 14: What types of measurements are done to diagnose and evaluate fiber systems? (OTDR) Cleaning, maintaining?
Jim Jachetta: The most basic and important piece of test gear for fiber communications is an optical power meter. An optical meter can help trace an optical signal from the origin or fiber transmitter through patch panels all the way to the receiver. It can help diagnose the point in a system where a fiber signal is lost or interrupted.
An OTDR or optical time domain reflectometer is typically used on very long Telco or telecom fiber runs. An OTDR sends an optical signal down a fiber and measures the back-reflections to determine optical loses, locate fiber faults and dirty optical connectors. An OTDR is not required on most fiber installations.
A fiber connector can be cleaned with a lint free optical wipes with 100% isopropyl alcohol. A can of compressed air is good to blow dirt and dust out of connectors.
Question # 15: Based on the specs you’ve discussed, what advantages does the new DVI-6000 system have to maximize signal quality?
Jim Jachetta: There are several DVI fiber transport systems on the market right now. The DVI–6000 Single & Dual Link, a long–haul fiber optic transport solution for high–quality RGB–HV and DVI–D with a DVI–I interface. Ideal for keeping video and audio communications secure in Command and Control facilities, the DVI–6000 Single Link supports up to 1920×1200 and the Dual Link up to 2560×1600 resolution over a single fiber, and has optional stereo audio and bi–directional data for monitor control. The DVI–6000 transports a pixel–for–pixel image that is 100% transparent with no frame dropping up to WUXGA, 1920×1200, and enables 100% 24–bits for all scan rates with no contouring or bit reduction at a high scan rate.
The DVI–6000 also has a SMPTE 348M option, whereby the data stream between the FTX and FRX is a 2.97GBPS SMPTE 348M SDTI–compliant stream (3G mode). In this mode the DVI video signal is packetized into a proprietary format and then transported via a 3G SMPTE envelope or physical layer signal. Instead of fiber transport, there is an optional 75 ohm coax cable transport feature for 3G mode.
Question # 16: What over innovations in fiber transport has Multidyne offered recently?
Jim Jachetta: We have recently introduced the DTV-4000 4 channel SDI Fiber transport system. The DTV-4000 transports 4 SDI signals over one fiber. Many corporate AV clients are using SDI and HD-SDI for in-house teleconferencing and live news conferences. Many public Fortune 100 clients of Multidyne will have a small production studio with SDI or HD-SDI cameras to broadcast company news to the financial networks live from their board rooms. Several such clients are already using the DTV-4000.
Question # 17: What’s next on the horizon that may overtake and replace fiber technology?
Jim Jachetta: There are some wireless products on the market for video transport. They are limited in bandwidth and distance. A wireless video system will always be highly compressed and limited in transmission distance.
We feel that fiber is here to stay. With virtually infinite bandwidth, fiber will support our information transport needs of today and in the future. Scientists in the fiber optic industry are constantly increasing the useable bandwidth and throughput of fiber optic systems and components.
Question # 18: Question breaking: Please talk about recent Multidyne installations?
Jim Jachetta: We recently provided most of the fiber optic transport gear for an interesting project for the city of Altamonte Springs, Florida. The city wanted to create a multi-use venue located in a rejuvenated area of the city called Cranes Roost Park. The 37 acre venue includes a 900 seat amphitheatre with floating stage. Cranes Roost is at the center of a master-planned business and residential district.
Multidyne fiber gear was used to transport high resolution video for digital signage throughout the park. Video, audio and data interface panels throughout the park give the ability to setup cameras to capture live events on stage or anywhere in the park and re-broadcast on monitors to other locations on site or to local TV stations across Florida.
At the heart of the systems is MultiDyne’s cutting edge optical routing switcher. The scalable EOS-4000 Optical Routing switcher was used to switch RGB-HV, component video, composite video, audio and data. Since the switching is done in the optical domain, only one switch was required for the many video and audio formats required by the project. The EOS-4000 with support up to 4.25 GBps, was the perfect choice for scalability and to future proof the system.
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Ideally suited for sending high-quality, high-resolution digital video, this cutting-edge product addresses the need for solutions with the advanced technology to allow high-resolution image transfer over longer distances. With an impressive operating distance of up to 40KM, the DVI-6000 gives users the freedom of moving a monitor away from a video source. It also easily connects video walls and control rooms with remote video processing equipment while continuing to maintain the highest video quality. Offering true DVI-I signal transport, the product’s unique transcoding capability gives broadcasters the freedom to cross convert signals, allowing an RGB input and DVI output or a DVI input with RGB output.
NEW YORK, OCTOBER 13, 2009 – MultiDyne Video & Fiber Optic Systems, a premier provider of fiber optic-based video and audio transport and routing solutions for broadcast and pro A/V applications, is featuring the openGear compatible HD-4400 four-channel fiber optic transport system at HD World 2009 (Booth 942). The high density, multirate, 3G HD-SDI SMPTE fiber optic transport system with a 4×4 matrix on both the transmitter and receiver was designed as one of MultiDyne’s first offerings as part of the openGear terminal equipment platform group. In addition, MultiDyne will also introduce several new openGear compatible cards in support of the HD-4400, giving users more options and combination choices.
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