Model 922-MES
– User Manual
Focal Technologies Corporation
Page 7-1
A Moog Inc. Company
Document No. 922-0662-00, Rev 1.0
7.0
Optical Interface
7.1 Optical Transceivers and Wavelength
The Model 922-MES card communicates optically using one or two small form-factor pluggable (SFP)
transceivers per card. The device can be ordered with a wide selection of qualified SFPs, depending on the
application distance, optical budget, and fiber count requirements. Depending on the SFPs selected, the card is
able to function on one (1) to four (4) fibers. The MES supports SFPs with 100 Mb/s and 1 Gb/s optical data
rates. In general, lower optical data rates have higher optical power budget and longer range.
Standard, API qualified, SFPs utilize two separate fibers, typically one transmitting in each direction at 1310 nm
for shorter links (< 50 km), or 1550 nm for longer links, up to 200 km at 100 Mb/s.
Bidirectional SFPs, or “Bidis”, are available with integrated wavelength division multiplexing (WDM) optical
components, providing bidirectional operation using two wavelengths on a single fiber (e.g. 1550/1490 nm or
1310/1550 nm). Bidi SFPs are typically limited to a range of 50 km.
SFP transceivers with CWDM wavelengths (1471 nm to 1611 nm) may be used to combine up to four sets of
modems (i.e. 8 CWDM wavelengths) on the same fiber. CWDM systems require additional optical modules that
may include power splitters, for redundancy, and/or CWDM couplers for combining or separating wavelengths.
Optical modules are available from the factory in a variety of packaging options. Note that the combination of
multiple wavelengths on a single fiber may cause the combined optical power levels to exceed Class I power
limits.
Typical 1 Gb/s SFP options include a Bidi version (1550/1490 nm) with 50 km range and a CWDM version
(1551 nm) with 100 km range. Contact the factory for qualified SFP options and for instructions on installation.
7.2 Optical Fiber
The card communicates using up to two SFP transceivers per card, which requires up to four fibers. The fiber
must be singlemode, such as SMF-
28e (9/125 μm) or equivalent. For links over 100 km, dispersion shifted
singlemode fiber (SMF-DS), should be considered to minimize dispersion on the 1550 nm wavelength.
Bend-insensitive jumpers with reduced boot-lengths may be used to allow for fiber routing to the card within
confined spaces, such as in subsea pressure housings. These jumpers are available from the factory or third
party vendors. Regardless of the fiber types used, the following handling guidelines should be followed:
Observe the bend radius of fiber optic cables at all times
When mounting, disassembling, or reassembling the cards, ensure that no fibers are subjected to bends in
excess of those held by the natural routing of the fibers. The minimum bend radius of standard singlemode
SMF-28e fibers should generally be no less than 25 mm, though single loops may be less than this
– as low
as 15 mm
– without damaging the fibers. Keep in mind that allowable values are dependent on the type of
fiber and the environment, and cable manufacturers typically specify the minimum bend radius. Avoid even
temporary bends with a radius less than 15 mm, which may induce cracks that affect long-term reliability of
the fibers. Use bend insensitive fibers where tight bends are expected during installation or operation.
Ensure fiber optic components are of the same type
All jumpers, cables, connectors, couplers, and Fiber Optic Rotary Joints (FORJs) used in the external
optical system connecting the card must use the same type of fiber, i.e. all components in the fiber link
should be singlemode. A single mismatched jumper in the system may cause intermittent or persistent
optical link errors. Do not rely on cable jacket or connector colors alone to determine the type of optical
fiber.
