Abstract
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.
Highlights
T HE generation and the application of multicarrier light source have attracted attentions within recent years [1]–[3]
Because of the advantages of precise frequency interval and uniform power spectrum, multicarrier light source has been widely used in many areas, such as optical arbitrary waveform generation [4], microwave photonics [5], dense wavelength-division multiplexing (DWDM) [6], orthogonal frequency division multiplexing (OFDM) in optical communication system [7] and optical frequency reference for either measurement or optical signal processing [8], [9]
The conversion of optical-to-radio frequency (RF) signal was realized by the balanced photodetector (BPD)
Summary
T HE generation and the application of multicarrier light source have attracted attentions within recent years [1]–[3]. The frequency interval of multicarrier is equal to the frequency of the driven RF signal, so it can be tunned flexibly External modulation, such as cascaded EOMs [12] and EOM driven by optoelectronic oscillator [13], [14], can generate multicarrier through only one optical modulation of seed light, but the number of subcarriers depends on the power of RF signal. Different from the conventional RFSL-based multicarrier generation scheme, the most prominent feature of our scheme is that the RF signal driving the EOM is generated by an optical-electrical-optical self-oscillation loop instead of external commercial RF source. In the process of self-oscillation, the output optical signal of RFSL is converted into electrical signal by a balanced photodetector (BPD) and the electrical signal that is selected and amplified in the electrical domain is fed back to drive the EOM to generate optical signal By repeating this process, the RF signal gradually acquires the center frequency of the electrical filter and approaches the oscillation condition. The subcarriers number is 49 and the frequency interval between adjacent subcarriers is approximately equal to the RF signal frequency
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