A multiwavelength CW source based on longitudinal mode-carving of supercontinuum generated in fibers and noise performance

We experimentally demonstrate novel multiple wavelength continuous wave (CW) sources based on longitudinal mode-carving of supercontinuum (SC) generated in optical fibers. We show that by longitudinal mode-carving of the SC we can generate >600 wavelength channels with 10-GHz precise channel spacing and -6-dBm/ch power level at the >48-nm flat region (±0.5-dB spectral uniformity) of the SC. By full utilization of the generated SC, the channel count exceeding 1600 can be accomplished. Moreover, we study the noise performance of the carved CW signals experimentally and theoretically. Experimentally, we measure the relative intensity noise (RIN) to characterize the noise performance of the generated CW signals. An average RIN value of -107 dB/Hz is obtained. Compared with the CW sources carved directly from the pump laser, a 4-dB/Hz RIN degradation is measured. The two main reasons behind the high RIN values are determined to be the frequency instability and the low side-mode suppression ratio of the pump laser. Experimentally, we confirm that the combined effect of the frequency instability and the low side-mode suppression ratio of the pump laser can degrade the RIN as much as ∼30 dB/Hz. Theoretically, we estimate the lowest achievable RIN values as -160-dB/Hz and -144-dB/Hz RIN after the erbium-doped fiber amplifier (EDFA) and the SC fiber, respectively. These results indicate that, starting with a stable pump laser, CW lasers with <-140-dB/Hz RIN can be achieved.