Fiber optic transceivers have points which launch, which receive?

in the use of fiber optic transceivers, there are a lot of friends will have such doubt:

1, optical transceiver must be used in pairs?

2, fiber optic transceivers have points is a closed one is hair? Or just as long as it is of two optical transceiver can pair used?

3, if the optical transceiver must be used in pairs, one pair of words must be the same brand and model? Or feel free to sign can be combined?

there are some friends in our group asked three questions above, a lot of friends in the process of project USES are likely to have the question, which is really about?

a: optical transceiver used as photoelectric conversion equipment is usually in pairs, but also can appear optical transceiver and fiber optic switches, optical transceiver SFP transceivers with matching use also is very normal, in principle, as long as the optical transmission wavelength is the same, signal encapsulation format is the same and is supported by some sort of agreement of optical fiber communication can be realized.

general single mode fiber (double Normal communication need two root fiber) Transceiver is regardless of the transmitting terminal and receiving end, as long as can be used in pairs.

only single fiber transceiver ( Normal communication need a fine) Can be transmitter and receiver.

double fiber transceiver or single fiber transceiver used in pairs, different brands can be compatible with each other. But you need to rate, wavelength, mode is the same.

means different rate ( Correlates with gigabit) , different wavelengths ( 1310 nm to 1300 nm) Are you can't communicate, in addition to this, even the same brand of single fiber transceiver with double fiber double fiber is composed of a pair can't each other.