My project is basically about a 3 user OCDMA system for 16 QAM, where I have done spectral amplitude coding (SAC) using FBGs. I have used BER test set and the BER I am getting is 0.5 which is bad, and the eye diagram is also horrible. I have used optical amplifier of gain 10, FBGs encoded and decoded using Walsh code (you can check the wavelength and bandwidth values, I have done it by using complementary/balanced detection), laser linewidth of 300 GHZ ( since wavelength = 2.4 nm), and sequence length = 2048 bits. I also changed sequence length to 65,536 bits to support BER test set, still no change in results. All other design parameters have ideal values. However, the M-ary threshold detector values are kept as the default values for 64 QAM. The constellation and eye diagrams are both horrible.
Could anyone please be kind enough to help me locate and solve the problem? Your one tiny help can make things much easier for me here. My thesis work is getting badly hampered due to this. I have been brainstorming since weeks, still no outcome.
Please anyone help me out! Its a sincere request.
Please.