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

Film Studio

Post Production

Facility

Digital Video over Coax

(0-350 m)

Digital Video over Coax

(0-350 m)

Fiber Optic SDI Link

0-120+ km

Data Direction

Data Direction

SDI SFP

Data Direction

FO SFP

FO SFP

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.

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.

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