Fig. 1. (a) Representative PCF structure and (b) its dominant core and cladding eigenmodes. (c) Equivalent two-core fiber and (d) its eigenmodes.

Fig. 2. (a) Real and (b) imaginary parts of n+ and n− as functions of Im(nd)/|G| obtained from the theory (solid lines) and the FEM simulation (dashed lines).

Fig. 3. Eigenvalues of the coupled system n+ (blue) and n− (red) as functions of the wavelength (λ) with Im(nd)/|G| of (a) 0.25 (dashed) and −0.25 (solid), (b) 1 (dashed) and −1 (solid), and (c) 1.5 (dashed) and −1.5 (solid), respectively.

Fig. 4. Transmission spectra obtained by (a), (d) the conventional formulism, (b), (e) the quantum formulism, and (c), (f) the BPM simulation with Im(nd)/|G| of (a)–(c) 0.25 and (d)–(f) 0. Color map scales are independent.

Fig. 5. Transmission spectrum as a function of the propagation length with Im(nd)/|G| of (a) −0.25 and (d) 0.25, (b) −1 and (e) 1, and (c) −1.5 and (f) 1.5, respectively.

Fig. 6. Eigenmode overlap factor at the phase matching point (1.55 μm).

Fig. 7. Phase diagram in a λ versus Im(nd)/|G| plot. The blue region indicates a PT-symmetry phase, and the orange region indicates a PT-symmetry-breaking phase.