forkman Multimode je navržen pro práci při 850 nm a 1310 nm. Nemá dobře definované chování při 1490 nm. Proto pro 1490 nm nenajdete žádné parametry.
"Bidirectional optical transceivers by its definition allows full-duplex optical transmission through one optical fiber. This is achieved with two independent signals which differs from each other with their wavelength 1310nm/1550nm, or 1310nm/1490nm.
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1G BiDi LR (EDGE PN: BIDI-1.25G-SFP-10-AD, 1310nm/1550nm) transceiver connected with OM2 grade multimode cable assured no CRC error free transmission till 300 meters;
1G BiDi LR (EDGE PN: BIDI-1.25G-SFP-10-AD, 1310nm/1550nm) transceiver connected with OM3 grade multimode cable assured no CRC error free transmission till 500 meters;
Additionally 10G BiDi transceiver (EDGE PN: BIDI-10G-SFP-10) connected with OM3 grade multimode cable assured no CRC error free transmission till 200 meters. (OM1 and OM2 should work for much smaller distance, because of fact these fibers are not laser optimized)
So what is happening when we use transceivers destined for “long range” communication in legacy multimode fiber?
Long range transceiver has a 9um laser output diameter. It matches single mode fiber core diameter therefore its signal can be precisely inputted in single mode fiber. But if we connect this transceiver to multimode fiber, the multimode fiber core (50um) is much larger than single mode fiber core (9um). At the signal transmission direction there will be no problem because 9um wide signal will be inserted precisely in the center of 50um fiber core. But problems happen at receiving end. The optical signal when it propagates fiber, it scatters and bounces through all of the 50um core. And at the receiver end, small fraction of signal will be detected by the 9um transceiver detector. Largest signal part will be lost and can be defined as “huge insertion loss”.
Our tests concluded that multimode fiber can be used with BiDi Single mode transceivers, but distance is limited due to multimode fiber construction and factor how many bends cable has. Each cable bend will cause signal more to propagate alongside the cladding, therefore increasing insertion loss at the receiving end (decreasing transmission distance)."