Datasheet
Digital video signaling includes a data scrambling algorithm for SDI and HD-SDI that is not easily transported over
a standard optical transport system. This algorithm can produce a signal pattern that causes an error in standard
optical systems. With a certain pattern in the video data, the scrambling algorithm can generate a pathological
signal containing a series of up to 19 bits of the same polarity.
These pathological patterns are not transportable over optical transport systems that employ “off the shelf”
optical components. These components are generally designed to use an AC-balanced signal with a duty cycle of
approximately 50%. That allows the optical transceiver to properly modulate the laser control loop (transmit side)
and lock (PLL circuitry) its receiver.
Until now, the industry has addressed this problem by providing optical components specifically designed for use
with the pathological signaling of digital video: typically DC-coupled optical transceivers. This approach requires
customized transceivers for each combination of distance, wavelength, and fiber type (multi-mode or single-mode)
used. Specialized solutions must also be built for WDM applications. Such designs are purely proprietary, and
therefore tend to be expensive. Unfortunately, DC-coupled transceivers generally have up to 8 dB lower receive
sensitivity than AC-coupled components, and they cannot be amplified in a DWDM application. This sensitivity
loss reduces link range by as much as 35 kilometers.
In contrast to the situation with digital video specialty components, the optical Multi-Source Agreement (MSA) has
led to a ready supply of inexpensive optical interfaces for most applications. However, the specific digital video
solutions cannot use this huge selection of standard and affordable optical components. The general-purpose
type of optical transport platform (multi-rate/multi-protocol transponder or repeater) simply cannot handle digital
video.
Video Extension Over Fiber
Post Production
Facility
Film Studio
Data Direction
Digital Video over Coax
(0-350 m)
SDI SFP
Digital Video over Coax
(0-350 m)
Data Direction
FO SFP
Fiber Optic SDI Link
0-120+ km
Data Direction
FO SFP
The SFP-CXASI-RX, here mounted in a Fiber
Driver EM316DMR3G-3R, receives a
unidirectional SDI signal from a connected
video device. The SDI signal is then
transmitted over fiber via a standard SFP
optical transceiver.
The optical SFP transceiver on the other
side of the fiber link receives the SDI data
signal. The EM316DMR3G-3R (Dual Multi-
rate Transponder) passes the SDI signal to
the SFP-CXASI-TX, and delivers it to the
end point video device.
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MRV [ MRV COMMUNICATIONS, INC. ]
