Patent name: A method for testing the cost of optical channels

Technical field: The present invention relates to the field of optical communication technology, in particular to a method for testing the cost of optical channels Background technology: The optical channel cost is a significant decrease in receiver sensitivity caused by the distortion of the signal waveform during channel transmission. It manifests as the BER (bit error rate) curve of the system shifting towards higher input power levels. This is equivalent to a positive channel cost. In some cases, there may be negative channel costs, but the likelihood is low. (A negative channel cost indicates that the channel related distortion actually improves the transmitter eye image that is worse than the perfect eye image.) Ideally, the BER curve will only be moved, but shape changes are not uncommon and will indicate an increase in the BER base. Because the channel cost changes with receiver sensitivity, it should be tested with BER of 10-12. The necessity of testing channel costs is due to the overall degradation caused by reflection, inter symbol interference, mode allocation noise, and laser chirping, which needs to be standardized using optical channel costs. For low dispersion systems, the maximum channel cost allows for ldB, while for high dispersion systems, the maximum channel cost allows for 2dB. There are basically two methods used to test the cost of optical channels nowadays