* An Add-drop filter

* Circuit parameters
.assign lambda0 = 1.55e-6

* Circuit definition
;cwsrc1 in wl=1.55e-6 power=1
vlsrc1 in values=[[0.5e-9,1,{lambda0}],[2e-9,0,{lambda0}]]

coupler1 in 1 out 2 k=0.15
coupler2 add 3 drop 4 k=0.15

wg_ring_l 4 1 length=300e-6 neff=3.999
wg_ring_r 2 3 length=300e-6 neff=3.999

probe1 out
probe2 drop
probe3 in

* Simulator options
.options abstol=1e-6 reltol=1e-8 timescale=-12 traceall=1

* Analysis parameter
.assign dlambda = 1e-12

* Analysis
;.dc /cwsrc1/WL 1549.9e-9 1550.1e-9 {dlambda}
.tran 3e-9