The fiber module of the cable on the transmission is through a pair of fiber optic module OXA. i.e. the fiber optic transmitter (TOXA) and fiber optic receiver (ROXA) two partially completed.
The TOSA designed having a maximum emission light power, ROXA design also has a certain sensitivity of the optical signal reception range. Particular signal reception range of ROXA is certain, the signal is too small to detect not too high lead to light-saturated ROXA, devices lossless failure.
Because of LX, ZX, XD fiber module is designed for long cable transmission design, so the launcher of the transmitted power in comparison to multimode module would be much higher, especially XD, ZX, EX are more outstanding. Therefore single-mode fiber connection test and multimode module is different.
Single-mode fiber module using a jumper close (local) tests, are required to pass the increase in the fiber optic line attenuator large enough to ensure proper into finished.
General fiber attenuator requirement as follows:
When do not use fiber attenuator test case, unless the optical module manufacturers to module received power design receiving sensitivity automatic adjustment function, otherwise, may appear receiver receive light full close or critical saturation phenomenon.
In the case of the receiver light-receiving light saturation, the outside of the optical fiber link will exhibit the case of bad connections; hair packet data transmission in the case of light-receiving critical saturation occurs.
The emergence of the above two situations often make the user mistakenly thought fiber module is defective, these two cases are also applicable to the actual cable and fiber supporting the use the cable insertion decay boxing is too small to cause the light receiving signal exceeds the range ROXA received the case.
In the ideal case without considering dispersion, Gigabit fiber module can allow the transmission distance can be obtained by the following formula:
Transmission distance = (TOSAs minimum transmit power-ROSA minimum received power) / (0.25 to 0.35DBM) wherein 0.25 to 0.35dbm of insertion loss per km of fiber optic cable, depending on the quality of cable.
Another direct calculation method of transmission distance:
Module transmission distance = (TOSA minimum transmit power- ROSA minimum received power)of absolute value – fiber optic cable insertion attenuation (dbm)
Select the combination of fiber optic module, we shall consider the receiving end of the light signal received power should not exceed the the ROSA maximum receiver sensitivity!
If the test site were unable to find the light line attenuator, a simple method is to insert module jumper (SC / LC / ST / FC) pulled out a little, until the device port link indicator just lit without exterminate, we can basically confirm ROXA received optical signal is in the range of devices it allows the receiver design.