Gigabit single-mode fiber transceiver test method

Posted on by FS.COM

The fiber optic transceiver of the cable on the transmission is through a pair of fiber optic module OXA. I.e. the fiber the emitter (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.

LX, ZX, XD fiber optic module is designed specifically for long-distance fiber optic transmission, the transmitting power of the transmitter compared to multimode module is much higher, XD, ZX, EX more prominent. Connection test of the single-mode fiber and multimode modules differ.

Single-mode fiber transceiver 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.

Usually the attenuator requirements are as follows:
1000LX (10-15KM): 5dm
1000XD (40-50KM): 15dm1000ZX (70-80KM): 28DB
1000EX (100-120KM): 45db
Does not use an attenuator test case, unless the optical module manufacturers reception sensitivity of the reception power of the module design automatic adjustment function, otherwise, might occur receiver receives light saturation 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-ROSA minimum transmit power the minimum received power) the absolute value of – 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 receive it allows the device.

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