#In order to force a constant effective index, set the group index and effective index to the same value
#In order to enter optical length simply set effective index/group index to '1'

#The center frequency for the waveguide propagation properties

f0 = 193.1e12;
ng = 8.05894;
neff = ng;
FSR = 120e9;
lambda = c / f0;

#Parameters to generate 
#Optical Half-Band Filters
#K. Jinguji and M. Oguma, "Optical Half-Band Filters"
#J. Lightwave Technol. 18, 252- (2000)

#The wavegude length
deltal = c / FSR  / ng;


#From table III (page 258)
#IIR elliptic half-band filter
#circuit parameters (x*pi)

teta1  = 0.25;
teta2  = 0.25;
teta11 = 0.2820;
teta12 = 0.4456;

#Phase shift multiplier

phi = 0.0;
phi11 = 1.0;
phi12 = 1.0;

#The wavegude length

deltal11 = 2 * deltal;
deltal12 = 2 * deltal;

#constant phase shift
#shift = 2 * pi * f0 / c * deltal * ( neff - ng )
#estimate neff from phase shift multiplier
#effective index required to cause phin*pi phase shift:

neff = phi * c / 2.0 / f0 / deltal + ng;
neff11 = phi11 * c / 2.0 / f0 / deltal11 + ng;
neff12 = phi12 * c / 2.0 / f0 / deltal12 + ng;

#Coupling coefficients
r1 = sin( teta1 * pi ) ^ 2;
r2 = sin( teta2 * pi ) ^ 2;
r11 = sin( teta11 * pi ) ^ 2;
r12 = sin( teta12 * pi ) ^ 2;

switchtodesign;

setnamed("WC1","coupling coefficient 1",r1);

setnamed("SBR11","frequency",f0);
setnamed("SBR11","length",deltal11);
setnamed("SBR11","group index 1",ng);
setnamed("SBR11","effective index 1",neff11);
setnamed("SBR11","coupling coefficient 1",r11);

setnamed("SW","frequency",f0);
setnamed("SW","length",deltal);
setnamed("SW","group index 1",ng);
setnamed("SW","effective index 1",neff);

setnamed("SBR12","frequency",f0);
setnamed("SBR12","length",deltal12);
setnamed("SBR12","group index 1",ng);
setnamed("SBR12","effective index 1",neff12);
setnamed("SBR12","coupling coefficient 1",r12);

setnamed("WC2","coupling coefficient 1",r2);