单模光纤与多模光纤的耦合.doc

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1、%单模光纤与多模光纤的耦合clearallformatlonga1=52.5e-6;%多模光纤半径aa0=4.1e-6;%单模光纤半径wl=1550e-9;%波长lambdan01=1.4544;n02=1.45;%单模光纤折射率n1=1.4574;n2=1.4420;%多模光纤折射率V0=2*pi*a0/wl*sqrt(n01^2-n02^2);%单模归一化频率w=a0/sqrt(log(2)*(0.65+1.619*V0^-1.5+2.879*V0^-6));%高斯光束半高宽v=1:50;%纤芯模序数V

2、=2*pi*a1/wl*sqrt(n1^2-n2^2);%多模归一化频率uv=(2*v-1/2)*pi/2;wv=sqrt(V^2-uv.^2);up=2*(w/a1)^2*exp(-0.5*w^2/a1*uv.^2);down1=besselj(0,uv).^2+besselj(1,uv).^2;down2=besselk(1,wv).^2./besselk(0,wv).^2;down3=besselj(0,uv).^2;down=down1+(down2-1).*down3;eta=real(up./d

3、own);%{eta=2*(w/a1)^2*exp(-0.5*w^2/a1*((2*v-1/2)*pi/2).^2)./...,(besselj(0,((2*v-0.5)*pi/2)).^2+besselj(1,((2*v-0.5)*pi/2)).^2+...,(besselk(1,sqrt(V^2-((2*v-0.5)*pi/2).^2)).^2./besselk(0,sqrt(V^2-((2*v-0.5)*pi/2).^2)).^2-1).*...,besselj(0,((2*v-0.5)*pi/2))

4、.^2);%}plot(v,eta,'*','markersize',5)