Other Considerations
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.
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 unidirectional 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.
Table 6: Pinout Comparison Chart
PIN
Transceiver (MSA)
Transceiver (Non‐MSA)
Dual TX (Non‐MSA)
Dual RX (Non‐MSA)
1
VEE
VEE
VEE
VEE
2
TX_FAULT [VEE]
VEE
NC
Rx2‐
3
TX_DIS
NC
NC
Rx2+
4
MOD_DEF(2) ‐ SDA
VEE
VEE
VEE
5
MOD_DEF(1) ‐ SCL
SCL
SCL
SCL
6
MOD_DEF(0) – PRESENCE [VEE]
SDA
SDA
SDA
7
Rate [NC]
VEE
VEE
VEE
8
LOS
RX1_LOS
Tx2+
NC
9
VEE
NC
Tx2‐
NC
10
VEE
NC
Tx2_DIS
NC
11
VEE
VEE
VEE
VEE
12
RD‐
Rx1‐
NC
Rx1‐
13
RD+
Rx1+
NC
Rx1+
14
VEE
VEE
VEE
VEE
15
VCC
VCC
VCC
VCC
16
VCC
VCC
VCC
VCC
17
VEE
VEE
VEE
VEE
18
TD+
Tx1+
Tx1+
NC
19
TD‐
Tx1‐
Tx1‐
NC
20
VEE
Tx1_DIS
Tx1_DIS
NC
