High-power high-performance radio-over-fiber link for minimalist wireless base station.

Broadband minimalist wireless base stations without energy-consuming electrical power amplifiers are the rosy scenario of the next-generation wireless communication systems. High-power radio-over-fiber (RoF) links, which are featured by large operation bandwidths, are regarded as the supporting technology for realizing such a vision. Nevertheless, the severe signal-to-noise ratio (SNR) deterioration induced by the second Brillouin scattering in high-power and long-distance RoF links must be first solved.

Suppression of Brillouin scattering-induced noise in long-haul high-power RoF links via non-uniformly distributed four-tone phase modulation.

An approach to suppressing Brillouin scattering-induced noise in long-haul high-power radio-over-fiber (RoF) links is proposed via non-uniformly distributed four-tone phase modulation. Four single-tone signals with uneven frequency intervals are utilized to phase modulate the optical signal before transmission. The power transferring from the optical carrier to the non-uniformly distributed modulation sidebands largely suppresses the Brillouin scattering-induced relative intensity noise (RIN).

Time-delay signature suppression of the chaotic signal in a semiconductor laser based on optoelectronic hybrid feedback.

An approach to generating chaotic signals with low time-delay signatures (TDSs) from a semiconductor laser (SCL) is proposed and demonstrated based on optoelectronic hybrid feedback. Through using a chirped fiber Bragg grating (CFBG) to provide distributed feedback, a chaotic signal with a low TDS is generated from the SCL. With the assistance of the nonlinear optoelectronic feedback provided by a microwave photonic link, the relaxation oscillation effect in the SCL is effectively suppressed, and the periodicity of the oscillation is greatly weakened.

Characterization of high-speed electro-optic phase modulators based on heterodyne carrier mapping at a fixed low-frequency.

A self-referenced method based on heterodyne carrier mapping is proposed to characterize the modulation efficiency of high-speed electro-optic phase modulators (EOPMs). The heterodyne carrier mapping replicates the optical carrier after phase modulation to an electrical replica, which enables observing the power variation of the optical carrier at a fixed low-frequency in the electrical domain. The modulation depths and half-wave voltages within the frequency range of up to 40 GHz are determined by measuring the amplitude ratio of the mapped low-frequency component at 80 MHz in the cases of on and off single-tone modulation of the EOPM.

Flexible ultra-wide frequency microwave down-conversion based on re-circulating four-wave mixing in a semiconductor optical amplifier.

A flexible ultra-wide frequency photonic-assisted method is proposed for microwave harmonic down-conversion based on re-circulating four-wave mixing (RFWM) in a semiconductor optical amplifier (SOA). The proposed down-converter consists of a RF-driven electro-optic modulator (EOM) and a RFWM-intensified optical local oscillator (LO) located in a ring-assisted Mach-Zehnder interferometer (R-MZI). In the optical LO, the optical carrier is first modulated by a low-frequency electrical LO through an EOM for triggering high-order harmonics sideband generation in the optical domain through the FWM effect in the SOA, and the generated harmonics sidebands are further intensified by re-circulating the FWM products back to the EOM and the SOA successively with an amplified ring loop.

Cross-referenced deadband-free microwave frequency measurement with cascaded-four-wave-mixing-based photonic harmonic down-conversion.

A cross-referenced and deadband-free method with photonic harmonic down-conversion is proposed for microwave frequency measurement based on cascaded-four-wave-mixing (CFWM) in semiconductor optical amplifiers. The proposed method enables ultra-wide and accurate frequency measurement with low-frequency spectrum detection, and at the same time achieves deadband-free and multi-tone frequency measurement by cross-referenced frequency discrimination. For a proof of concept, microwave signal measurement is experimentally demonstrated up to the 40 GHz frequency range with an 0.

Multipulse dynamics under dissipative soliton resonance conditions.

The stable multipulse emission from an erbium-doped mode-locked fiber laser in dissipative soliton resonance (DSR) regime is numerically and experimentally investigated. It shows that in the multipulse operation of DSR, all pulses have identical characteristics. The number of these pulses is determined by the initial conditions, and keeps constant with the growth of pump power.

Calibration-free measurement of high-speed Mach-Zehnder modulator based on low-frequency detection.

A calibration-free electrical method is demonstrated for measuring the frequency response of high-speed Mach-Zehnder modulators (MZMs) based on low-frequency detection. The method achieves the high-frequency modulation index and half-wave voltage measurement of MZMs by the low-frequency electrical spectrum analysis of the two-tone and bias-modulated optical signal. Moreover, it eliminates the need for correcting the responsivity fluctuation in the photodetector through setting a specific frequency relationship between the two-tone and bias modulation.

Calibration-free absolute frequency response measurement of directly modulated lasers based on additional modulation.

A calibration-free electrical method is proposed for measuring the absolute frequency response of directly modulated semiconductor lasers based on additional modulation. The method achieves the electrical domain measurement of the modulation index of directly modulated lasers without the need for correcting the responsivity fluctuation in the photodetection. Moreover, it doubles measuring frequency range by setting a specific frequency relationship between the direct and additional modulation.

Extinction-ratio-independent electrical method for measuring chirp parameters of Mach-Zehnder modulators using frequency-shifted heterodyne.

An extinction-ratio-independent electrical method is proposed for measuring chirp parameters of Mach-Zehnder electric-optic intensity modulators based on frequency-shifted optical heterodyne. The method utilizes the electrical spectrum analysis of the heterodyne products between the intensity modulated optical signal and the frequency-shifted optical carrier, and achieves the intrinsic chirp parameters measurement at microwave region with high-frequency resolution and wide-frequency range for the Mach-Zehnder modulator with a finite extinction ratio. Moreover, the proposed method avoids calibrating the responsivity fluctuation of the photodiode in spite of the involved photodetection.

Self-calibrating measurement of high-speed electro-optic phase modulators based on two-tone modulation.

We propose a self-calibrating method for high-frequency response measurement of electro-optic phase modulators based on two-tone modulation. The method utilizes the electrical domain measurement of heterodyning spectrum between the two-tone modulation optical signal and the frequency-shifted optical carrier, and eliminates the need to correct the responsivity fluctuation in the photodetection. High-frequency modulation depth and half-wave voltages are measured and compared to those with the traditional optical spectrum analysis method in the experimental demonstration.