The phase time as a function of the Bragg gratings separation. (a) The phase time as a function of the separation a between two Bragg gratings, for incident λ=1,542 nm, kB=6.1074/μ m, n0=1.452, n1/n0=1.8×10−4, and Lo=8.5 mm. (b, c) The PT is plotted as a function of ω, for a=42 mm. The phase time in (b) is the same as that in (c) but plotted from 0 to 10 ns to compare with Figure 2 in . Arrows indicate the a s in .