Dongning Sun

Distribution of high-stability 10 GHz local oscillator over 100 km optical fiber with accurate phase-correction system

We have developed a radio-frequency local oscillator remote distribution system, which transfers a phase-stabilized 10.03 GHz signal over 100 km optical fiber. The phase noise of the remote signal caused by temperature and mechanical stress variations on the fiber is compensated by a high-precision phase-correction system, which is achieved using a single sideband modulator to transfer the phase correction from intermediate frequency to radio frequency, thus enabling accurate phase control of the 10 GHz signal. The residual phase noise of the remote 10.03 GHz signal is measured to be -70  dBc/Hz at 1 Hz offset, and long-term stability of less than 1×10⁻¹⁶ at 10,000 s averaging time is achieved. Phase error is less than ±0.03π.

Distribution of high-stability 100.04 GHz millimeter wave signal over 60 km optical fiber with fast phase-error-correcting capability

We demonstrate a phase-stabilized remote distribution of 100.04 GHz millimeter wave signal over 60 km optical fiber. The phase error of the remote millimeter wave signal induced by fiber transmission delay variations is detected by dual-heterodyne phase error transfer and corrected with a feedback system based on a fast response acousto-optic frequency shifter. The phase noise within the bandwidth of 300 Hz is effectively suppressed; thus, the fast transmission delay variations can be compensated. The residual phase noise of the remote 100.04 GHz signal reaches -56  dBc/Hz at 1 Hz frequency offset from the carrier, and long-term stability of 1.6×10(-16) at 1000 s averaging time is achieved. The fast phase-noise-correcting capability is evaluated by vibrating part of the transmission fiber link.

Photonic radio-frequency dissemination via optical fiber with high-phase stability.

We demonstrate a photonic radio-frequency transmission system via optical fiber. Optical radio-frequency signal is generated utilizing a Mach-Zehnder modulator based on double-side-band with carrier suppression modulation scheme. The phase error induced by optical fiber transmission is transferred to an intermediate frequency signal by the dual-heterodyne phase error transfer scheme, and then canceled by a phase locked loop. With precise phase compensation, a radio frequency with high-phase stability can be obtained at the remote end. We performed 20.07-GHz radio-frequency transfer over 100-km optical fiber, and achieved residual phase noise of -65  dBc/Hz at 1-Hz offset frequency, and the RMS timing jitter in the frequency range from 0.01 Hz to 1 MHz reaches 110 fs. The long-term frequency stability also achieves 8×10(-17) at 10,000 s averaging time.

The distribution of highly stable millimeter-wave signals over different optical fiber links with accurate phase-correction

We have demonstrated an optical generation of highly stable millimeter-wave signal distribution system, which transfers a 300GHz signal to two remote ends over different optical fiber links for signal stability comparison. The transmission delay variations of each fiber link caused by temperature and mechanical perturbations are compensated by high-precise phase-correction system. The residual phase noise between two remote end signals is detected by dual-heterodyne phase error transfer and reaches -46dBc/Hz at 1 Hz frequency offset from the carrier. The relative instability is 8×10-17 at 1000s averaging time.

Photonic generation of linearly chirped millimeter wave based on comb-spacing tunable optical frequency comb

Abstract. We demonstrated a photonic approach to generate a phase-continuous frequency-linear-chirped millimeter-wave (mm-wave) signal with high linearity based on continuous-wave phase modulated optical frequency comb and cascaded interleavers. Through linearly sweeping the frequency of the radio frequency (RF) driving signal, high-order frequency-linear-chirped optical comb lines are generated and then extracted by the cascaded interleavers. By beating the filtered high-order comb lines, center frequency and chirp range multiplied linear-chirp microwave signals are generated. Frequency doubled and quadrupled linear-chirp mm-wave signals of range 48.6 to 52.6 GHz and 97.2 to 105.2 GHz at chirp rates of 133.33 and 266.67  GHz/s are demonstrated with the ±1st and ±2nd optical comb lines, respectively, while the RF driving signal is of chirp range 24.3 to 26.3 GHz and chirp time 30 ms.

Photonic Radio-Frequency Phase Detector based on Radio-Frequency to Intermediate-Frequency Phase Mapping

A photonic radio-frequency phase detector based on radio-frequency (RF) to intermediate-frequency mapping is demonstrated, and the theoretical principle of the design is explained.

Demodulation errors ef fects on f iber-optic current sensor

Harmonic imbalance and phase deviation affect the linearity and sensitivity of fiber-optic current sensor (FOCS). The effects of these two factors are theoretically analyzed. Both the harmonic imbalance and phase deviation must be restricted within a tolerable range of variation. By experimentally optimizing these two factors, the scale factor (SF) error of the current sensor within the range of 0.5% is demonstrated and implemented.