FiberPlex WDM8 - Manual (Page 18)

Video Optimization
The Society of Motion Picture and Television Engineers, or SMPTE, is a leader in the development of standards for film, television, and other
video. The Serial Digital Interface or SDI, was standardized by SMPTE for broadcast quality digital video transmission. Other standards
evolved from this original standard, defining Enhanced, High‐definition (HD), 3G‐SDI (1080p) and Ultra High‐definition (UHD), or 4K video
(2160p).
To help ensure error‐free transmission, the standards include a data scrambler / descrambler to create a high density of transitions in the
serial data, making it easier for the receiver to maintain timing. Where an encoding method such as 8B‐10B ensures a minimal sequential run
of all ones or zeros, it does so at the cost of a 25% increase in bandwidth requirements. The scrambler / descrambler method does not
require this, but as a result there are certain combinations of scrambler state and the next data bits to be scrambled that result in a sequence
of up to twenty consecutive ones or zeros. These sequences are referred to as pathological conditions, and are present in specific shades of
pink or grey.
These pathological conditions may create errors in transmission through typical AC coupled optics, or any other AC coupled interface. Video
Enhanced or SMPTE Compliant optics are designed to accept these pathological conditions, allowing the longer sequences of ones or zeros to
pass without error.
The Fiberplex Technologies WDM16 and WDM8 Active Coarse Wave Division Multiplexer has Video Enhanced optics pre‐installed internally
on every port, ensuring error‐free transmission for all of your video requirements.
SFP MSA Compliance
The SFP Multi‐Source Agreement (MSA) is an agreement that was drafted among competing manufacturers of SFP optical modules. The SFF
Committee was formed to oversee the creation and maintenance of these agreements including the SFP MSA designated as INF‐8074i. This
agreement describes a mutually agreed upon standard for the form and function of SFP modules. However, not all SFPs produced are MSA
compliant. The MSA provides for a transceiver (TX/RX) pinout. Other industries such as broadcast had the need for dual TX and dual RX SFP
for uni‐directional applications such as video. Naturally, a non‐MSA standard was introduced allocating pinout assignments for dual output
and dual input I/O configurations. In addition, the some of the internal serial communication pins were reassigned.
The unique design of the WDM16/8 includes internal multi‐rate, CWDM optical SFPs which handle the wavelength allocation of the CWDM.
These internal modules are MSA compliant, thus the external user accessible SFP modules must also be MSA compatible. For this reason you
cannot use non‐MSA SFPs with the WDM16/8.
Be sure that any SFPs that you wish to use with this unit conform to the pinout in Figure 9.
Figure 9 Pinout of SFP cage on WDM16/8