A novel frequency quasi-linear swept light source based on multi-frequency time-matched spectrum stitching and recirculating frequency shifter loop (RFSL) is proposed and successfully demonstrated. The seed light with different frequencies enters RFSL in turn through optical delay line to complete the frequency sweep and spectrum stitching of each band. Spectrum stitching can effectively reset the noise, suppress the accumulation of amplified spontaneous emission (ASE) noise and the spectral sideband noise in RFSL, and expand the sweep range several times without affecting the sweep linearity. A swept range of 5.227 nm is experimentally achieved with the noise range of 7.78 dB. Compared with the single-frequency sweep scheme that the noise variation is 9.03 dB, the sweep range is extended by more than three times. The Pearson's correlation coefficients (r) of the output swept signal is higher than -0.99996.

A novel scheme of self-oscillation multicarrier light source based on recirculating frequency shift loop (RFSL) is proposed and experimentally demonstrated in this paper. Compared with conventional RFSL-based multicarrier generation schemes, the radio frequency (RF) signal for driving the modulator in RFSL is generated by an internal self-oscillation of the optical carrier instead of the external commercial RF source device. The self-oscillation method significantly reduces the cost of the light source and decreases the phase noise of RF signal and multicarrier signal. In the experiment, we successfully generate a single-mode oscillation RF signal with the phase noise of −85.10 dBc/Hz at 10 kHz offset frequency. A total of 49 multicarrier optical signals from 1550.59 nm to 1554.44 nm with the power fluctuation as low as 3 dB are obtained. The frequency interval is approximately 10.014 GHz, which is equal to the oscillation frequency of the RF signal.

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