Owner's manual

GigaBit Media Converter
5
Connecting to the Network
When installing the GigaBit Media Converter, care must be taken in choosing
the appropriate cabling to avoid Differential Mode Delay (DMD) effects.
DMD is caused by singlemode, (1310 nanometer) laser point sources
launching into multimode cable. Optical power is concentrated in the center of
the ber core, propagating in less than 5% of possible modal paths. This can
result in reduced bandwidth and/or the appearance of individual data pulses,
refracting into multiple, overlapping, light pulses at the receiver end, causing
CRC errors.
The connection requires a Mode Conditioning patch cable to provide
the Conditioned Launch necessary to prevent (DMD) effects. Mode
Conditioning patch cables are not used with short wave length (850 nano-
meter) lasers. Note that ber cable is typically certied for a particular
bandwidth using light emitting diodes (LEDs) that provide the “Overlled
Launch” condition i.e. illuminate all possible modes and bers.
For additional details see the Restricted Launch Specication dened by the
Telecommunications Industry Association. The TIA FO-2.2.1 Committee
has released two standards: (1) FOTP-203: Launched Power Distribution
Measurement Procedure for Graded-Index Multimode Fiber Transmitters, and
(2) FOTP-204: Measurement of Bandwidth on Multimode Fiber.