Gigabit single-mode fiber optic module

The transmission of the gigabit single-mode fiber optic module on the fiber optic cable is completed by a pair of OXA on the fiber optic module, that is, the fiber optic transmitter (TOXA) and the fiber optic receiver (ROXA). So, how to test the Gigabit single-mode fiber module?

Gigabit single-mode fiber optic module

In design, it has the maximum transmitting optical power, and also has a certain range of optical signal sensitivity receiving. It is especially proposed that the signal receiving range is certain, the signal is too small to be detected, and the signal is too high to cause light saturation, and the device has no loss of efficiency.

Since the optical fiber module is specially designed for long-distance optical cable transmission, the transmitting power of the transmitter is much higher than that of the multimode module. Therefore, the connection test of single-mode fiber is different from that of multimode module.

When the single-mode fiber optic module is used for short-distance (local) testing with jumpers, it must be done correctly by adding a sufficiently large attenuator to the fiber optic line.

General attenuator requirements are as follows:

1000LX (10-15KM): 5dm

1000XD (40-50KM): 15dm

1000ZX (70-80KM): 28DB

1000EX (100-120KM): 45db

In the case of not using the attenuator test, unless the optical module manufacturer has designed the receiving power of the module with the automatic adjustment function of the receiving sensitivity, otherwise, the phenomenon of receiving optical saturation or critical saturation of the receiver may occur.

In the case of receiver optical saturation, the outside of the optical fiber link will show a connection failure; and in the case of critical saturation of optical reception, there will be hairy packets in data transmission.

The appearance of the above two situations will often make users mistakenly believe that the fiber optic module is faulty, and these two situations are also applicable to the situation where the optical cable is too small to receive optical signals beyond the range of ROXA in the actual use of optical cables and optical fibers. .

Under ideal conditions without considering dispersion, the allowable transmission distance of the Gigabit fiber optic module can be obtained by the following formula:

Transmission distance = (TOSA minimum transmit power - ROSA minimum receive power)/(0.25 to 0.35DBM), where 0.25 to 0.35dbm is the insertion attenuation per KM optical cable, depending on the quality of the optical cable.

Another direct calculation method of transmission distance:

Module transmission distance = absolute value of (TOSA minimum transmit power - ROSA minimum receive power) - cable insertion attenuation (dbm)

When choosing a suitable optical fiber module, it must be considered that the maximum received power of the optical signal at the receiving end should not exceed the maximum receiving sensitivity of ROSA!