Waldemar:
Typically, the output power level of an optical transmitter is not settable by the user. The TX range is where the actual output power of the device may fall given the laser manufacturer's tolerances. The reason it is important is the optical receiver also has a specified operating range. You need to verify that the minimum link budget (using the data sheets minimum TX output power and the receiver's sensativity) for the TX/RX pair is greater than the loss of the fiber cable "jumper" that will interconnect the TX to the RX. Once you receive the
optical card, you can measure the TX value and add attenuators (as necessary) to meet the RX's operating range.
