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+//Introduction to Fiber Optics by A. Ghatak and K. Thyagarajan, Cambridge, New Delhi, 1999
+//Example 17.8
+//OS=Windows XP sp3
+//Scilab version 5.5.2
+clc;
+clear;
+//given
+//Since the reflectivity of fiber is 99%,
+R=0.99;//Reflection coefficient of fiber
+lambdaB=1550e-9;//Bragg wavelength in m
+neff=1.45;//Corresponding value of effective index in LP01 mode
+DeltaLambda=1e-9;//Bandwidth of reflection spectrum in m
+I=0.75;//Typical value of transverse overlap integral of modal distribution
+
+//Now, (tanh(k*L))^2=R
+//Rearranging terms, we get:  k*L=atanh(sqrt(R))
+//Let m=k*L
+m=atanh(sqrt(R));
+
+//Rearranging terms of expression DeltaLambda=lambdaB^2/(%pi*neff*L)*sqrt((k*L)^2+(%pi)^2) , we get
+L=lambdaB^2/(%pi*neff*DeltaLambda)*sqrt(m^2+(%pi)^2)//Since m=k*L
+//Length of fiber in m
+mprintf("\n L=%.2f mm",L/1e-3);//Division by 10^(-3) to convert into mm
+
+//Rearranging terms of m=k*L, we get:
+k=m/L;//Corresponding coupling coefficient in m^(-1)
+
+//Rearranging terms of expression k=%pi*Deltan*I/lambdaB
+Deltan=k*lambdaB/(%pi*I);//Change in refractive index
+mprintf("\n Deltan=%.2e",Deltan);//Unitless quantity