A WDM system project is configured with the 1st to 20th wave LSX. When testing the M40 output port with a spectrum analyzer during commissioning, it is found that the optical power of the 20th wave is significantly lower than the other 19 waves. What are the possible reasons? (Multiple choice)
A . The 20th wave of LSX wavelength division side emission is too small
B . The first 20 wave LSX wavelength shift
C . The insertion loss of the 20th wave channel corresponding to M40 is too large
D . The RX port of the first 20 wave LSX add extra 5dB fixed light attenuation
Answer: ABC