Fig. 1. Schematic diagram of intermodal CW-XPM with the pump modulated under (a) DSB and (b) CS-DSB schemes. Input waves and generated waves are represented by solid arrows and dashed arrows, respectively.

Fig. 2. Experimental setup of direct characterization of the intermodal nonlinear coefficient based on intermodal CW-XPM. TLS, tunable laser source; VOA, variable optical attenuator; MZM, Mach–Zehnder modulator; EDFA, erbium-doped fiber amplifier; BPF, bandpass filter; MMUX, mode multiplexer; PP, phase plate; BS, beam splitter; FMF, few-mode fiber; OSA, optical spectrum analyzer.

Fig. 3. (a) RIGVs and (b) β₂ of the LP₀₁ and LP₁₁ mode groups over the C-band.

Fig. 4. (a)–(b) Optical spectrum of the LP₀₁ mode probe with XPM-induced NPS when the LP₁₁ mode pump is modulated with the (a) DSB or (b) CS-DSB scheme; (c) normalized NPS with respect to the pump power when the LP₁₁ mode pump is modulated with the DSB or CS-DSB scheme.

Fig. 5. XPM-induced NPS versus the wavelength spacing Δλ between the pump and probe when the modulated pump at LP₁₁ mode group is operated at (a) 1552 nm and (b) 1557 nm. The star represents an equal group velocity point for intermodal XPM interaction.

Fig. 6. (a) Intermodal XPM-induced NPS versus the pump power when the wavelength of the pump at LP₁₁ mode group and the probe at LP₀₁ mode group are operated at 1557 and 1552 nm, respectively; (b) number of counts versus κ under various pump modulation frequencies.