Compensation Of Power Fading Research Articles

Photonic generation and transmission for an X-band dual-chirp waveform with frequency multiplication and power-fading compensation.

The generation of an X-band dual-chirp waveform, which is capable of pulse compression, plays an important role in radar, electric warfare, and satellite communication systems. With the development of applications such as multi-static radar, transmission over long distances has attracted considerable attention. In this paper, a photonic system for X-band dual-chirp waveform generation and transmission based on frequency multiplication and power-fading compensation is put forward and experimentally carried out. Based on a compact dual-parallel Mach-Zehnder modulator (DPMZM), the dual-chirp waveforms of 8.6-9.6GHz and 9.6-10.6GHz are generated by an RF carrier of 4.8GHz and transmitted through a 40km single-mode fiber (SMF) spool. The dispersion-induced power fading of the chirp waveform is compensated for by about 13dB. The full width at half maximum (FWHM) and the peak-to-sidelobe ratio (PSR) of the compressed pulses are 1ns and 11.5dB, respectively. Moreover, the compensation of power fading in the entire X-band is verified to demonstrate the applicability of our system. By flexibly adjusting the bias voltage of the built-in phase shifter, the system can be applied in more scenarios.

Microwave photonic dispersion immune self-interference cancellation scheme for a radio over fiber based in-band full duplex communication link

A microwave photonic scheme for multi-functional radio over fiber based in-band full duplex communication links to realize deep self-interference cancellation, long range transmission, and efficient signal recovery is proposed. In the proposed scheme, double sideband modulation helps avoid applying electrical couplers or optical filters and is beneficial to improve the frequency conversion efficiency. By virtue of the intermediate frequency signal amplitude regulation mechanism induced by fiber dispersion, the conditions of dispersion induced power fading compensation, amplitude matching, and phase reversion between self-interference and reference signals can be satisfied through joint DC bias tuning. The high precision delay matching in the optical domain is advantageous to the deep self-interference cancellation performance in a wide frequency range compared to its electrical counterparts. Furthermore, the deterioration of signal quality and self-interference cancellation performance caused by fiber dispersion is avoided. Experimental analyses show that a single tone signal in a wide frequency range of 2–20 GHz can be cancelled over 60 dB. A broadband signal with bandwidth of 50 MHz in the C-band, X-band, and K-band can be cancelled over 35 dB. Furthermore, the recovery performance of the signal of interest with different modulation formats and different signal to interference ratios is investigated, showing high quality signal transmission and efficient signal recovery. The capability of dispersion induced power fading compensation is also verified, and the spurious-free dynamic range is measured to be 88.47dB⋅Hz2/3.

Photonics-Assisted Ultrawideband RF Self-Interference Cancellation With Signal of Interest Recovery and Fiber Transmission

Self-interference and chromatic dispersion are two main limiting factors that influence the recovery of the signal of interest (SOI) in in-band full-duplex (IBFD) radio-over-fiber (RoF) links. An ultrawideband photonic-assisted approach to radio-frequency (RF) self-interference cancellation (SIC) with high-speed SOI recovery and fiber transmission capability is proposed. The key to achieve the above optimum performances in a compact system is the combined use of fiber dispersion induced RF time delay and optical carrier phase-shifted double sideband (CPS-DSB) modulation. A high precision and tunable time delay matching between the reference signal and the SI signal can be achieved by dispersion induced RF time delay. Meanwhile, the equal amplitude, phase reversal, and dispersion-induced SOI power fading compensation conditions are satisfied simultaneously by manipulating the optical carrier phase of the CPS-DSB signal. For 25 km fiber transmission, 30 dB cancellation depth over 2.7 GHz bandwidth, 160 Mbit/s 16-quadrature amplitude modulation (16-QAM) SOI recovery, and good immunity to fiber dispersion are experimentally demonstrated. In addition, the proposed scheme facilitates multipath SIC by implementing an array of tunable lasers (TLs) with a shared electro-optic modulator at the reference branch.

Linearized Photonic Microwave and mm-Wave Mixer With Dispersion-Induced Power Fading Compensation

A novel photonic microwave and millimeter-wave (mm-wave) mixer with simultaneous third-order intermodulation distortion (IMD3) suppression and dispersion-induced power fading compensation is proposed and experimentally demonstrated. In our proposed scheme, a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator is used to modulate RF/IF and LO signals. The bias voltages of the main modulators are adjusted to compensate dispersion-induced power fading. When the polarization state of the modulated signal and the attenuation of the RF signal are properly adjusted, IMD3 distortion can be suppressed. In the experiment, relatively flat microwave and mm-wave signals from 11 to 35 GHz are obtained through 4and 50-km fiber transmission, while the measured spurious free dynamic range (SFDR) is 112.9 dB·Hz4/5. In addition, an upconverted 16 quadrature amplitude modulation (16 QAM) vector signal with a carrier frequency of 19.3 GHz is obtained and the measured constellation diagrams and error vector magnitudes are given after transmission over different fiber lengths (back to back, 4 and 50 km).

An analog photonic down-conversion link with simultaneous IMD3 distortion suppression and dispersion-induced power fading compensation

A novel analog photonic down-conversion link based on a polarization modulator and a phase modulator with simultaneous linear optimization and chromatic dispersion-induced power fading compensation is proposed and experimentally demonstrated. By introducing an appropriate phase shift to the optical sidebands, chromatic dispersion-induced power fading is compensated, and third-order intermodulation distortion terms are eliminated in the same time. The scheme exhibits wide operating frequency range due to its no use of filters and frequency-dependent electrical or optical devices. The scheme is robust, as the operation of the polarization modulator and the phase modulator are independent of signal amplitude and bias voltage. Experimental results show that, for a 25-km transmission link, an improvement of more than 15.5 dB in spurious-free dynamic range is achieved and the dispersion-induced power fading is compensated at the same time. In addition, benefiting from the power compensation and significant suppression of IMD3, a 16QAM vector signal is demonstrated to have a good demodulation performance.

Photonic Microwave Up-Conversion Link With Compensation of Chromatic Dispersion-Induced Power Fading

An effective scheme of frequency doubling up-conversion is proposed and demonstrated, which achieves the generation of high-frequency microwave signal and the compensation of chromatic dispersion-induced power fading (CDIPF). The system structure is based on a cascading of a Sagnac loop and a Mach–Zehnder modulator (MZM), where a phase modulator is used in the Sagnac loop. In the loop, only the clockwise propagating light wave is modulated by a small local oscillator signal, leaving the counter-clockwise propagating light wave unmodulated because of the velocity mismatch. The output signal is divided into two parts, one traveling into an MZM and the other entering an optical phase shifter. The intermediate frequency signal is supplied to the MZM, which is biased at its minimum point and then the carrier-suppressed double sideband is achieved. With the adjustment of the optical phase shift, the CDIPF can be compensated at any frequency. In the simulation, by comparing the frequency responses of the proposed link with and without dispersion compensation, we successfully demonstrate the performance of power fading compensation for 60- and 80-km link. Consequently, the spurious-free dynamic range is effectively improved by 13.54 dB at 22.6 GHz for 60-km link.

Compensation of dispersion-induced power fading with adjustment-free operation

A scheme for compensation of dispersion-induced power fading is proposed and experimentally demonstrated. The system transmits two modulated laser lights via a wavelength division multiplexer and a wavelength division demultiplexer. By optimizing the power ratio and the phase difference between the two modulated signals, the dispersion-induced power fading can be adequately compensated. A key significance of our approach is that no adjustments are required when the input radio frequency signal scans over a broad bandwidth of 1 to 12 GHz. We successfully demonstrate the compensation of the power fading for both 20- and 30-km fiber links. An improvement of spurious-free dynamic range is also achieved.

Compensation of Dispersion-Induced Power Fading in Analog Photonic Links by Gain-Transparent SBS

We demonstrate an analog photonic link with compensation of dispersion-induced power fading based on gain-transparent stimulated Brillouin scattering (SBS) induced carrier processing. Gain-transparent SBS introduces a phase shift selectively to the optical carrier. By properly adjusting the phase shift, the frequency response of the analog photonic link is shifted. The dispersion-induced power fading can thus be compensated at any working frequency. We demonstrated dynamic compensation of the power fading in photonic links over two transmission distances of 25 and 40 km in standard single mode fibers (SMFs). With gain-transparent SBS, the linearity of the analog photonic link is also improved. The spurious-free dynamic ranges of the proposed links over 25 and 40 km SMFs are measured to be 106.14 dB·Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> and 105.34 dB·Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> and are improved by 35.15 dB · Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> and 35.86 dB · Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> , respectively. The transmission of 2 Gb/s 4-QAM and 4 Gb/s 16-QAM discrete multitone signals at 18 and 14 GHz microwave carrier frequencies are experimentally demonstrated with the lowest EVM of 12%.

Broadband Dispersion-Induced Power Fading Compensation in Long-Haul Analog Optical Link Based on 2-Ch Phase Modulator

A broadband dispersion compensation scheme based on a 2-Ch phase modulator (2-Ch PM) is proposed and experimentally demonstrated in the long-haul analog optical link. Benefiting from the complementary power fading function for the phase and intensity modulated link, which are simultaneously obtained by using the 2-Ch PM, the broadband and long-reach dispersion compensation is implemented. The experimental results show that the dispersion-induced power fading is greatly mitigated for the radio frequency (RF) signal with a bandwidth up to 18 GHz over 24.45-km single-mode fiber (SMF) transmission. Meanwhile, the system spurious-free dynamic range (SFDR) is improved with a maximum value of 24 at the frequency of 17.5 GHz; the vector signal transmission performance has also been improved.

Distance-independent microwave and millimeter-wave power fading compensation using a phase diversity configuration

We use a nonlinearly chirped fiber Bragg grating in a phase diversity configuration to achieve distance-independent microwave and millimeter-wave dispersion-induced power fading compensation for double-sideband subcarrier-multiplexed systems. We demonstrate compensation for power fading over 150 km at 8 and 12 GHz, with received subcarrier power in all cases uniform to within 1 dB.