Guangcan Chen

A microwave frequency comb (MFC) generator based on an integrated mutually coupled (IMC) distributed feedback (DFB) laser is demonstrated. The proposed MFC generator is simple and compact, only consisting of an IMC laser, a microwave signal generator, and a photodetector. By adjusting the bias currents of the three sections of the IMC laser and the modulation parameters, the bandwidth of the MFC can be significantly enhanced compared to the case adopting a solitary DFB laser. The characteristics of the MFC with the tuning current and the modulation parameters were investigated experimentally to determine the optimum operating condition. A broadband MFC with 40 GHz bandwidth within a 15 dB amplitude variation was achieved under a modulation frequency of 2 GHz.

An Indium-phosphide-based monolithically integrated photonic chip comprising of an amplified feedback laser (AFL) and a photodetector was designed and fabricated for on-chip photonic and microwave generation. Various waveforms including single tone, multi-tone, and chaotic signal generation were demonstrated by simply adjusting the injection currents applied to the controlling electrodes. The evolution dynamics of the photonic chip was characterized. Photonic microwave with frequency separation tunable from 26.3 GHz to 34 GHz, chaotic signal with standard bandwidth of 12 GHz were obtained. An optoelectronic oscillator (OEO) based on the integrated photonic chip was demonstrated without using any external electrical filter and photodetector. Tunable microwave outputs ranging from 25.5 to 26.4 GHz with single sideband (SSB) phase noise less than −90 dBc/Hz at a 10-kHz offset from the carrier frequency were realized.

A wavelength-tunable chaotic optical signal generation and on-chip O/E conversion scheme based on an integrated laser-photodiode chip subject to filtered optical feedback is proposed and experimentally demonstrated. The integrated chip consists of a Fabry-Perot (FP) gain section and a photodiode, which was fabricated on an n-InP substrate with the same active material. By applying a filtered feedback signal to the FP gain section, wavelength-tunable chaotic carrier ranging from 1576 to 1587 nm was achieved. On-chip microwave chaotic signal generation with a standard bandwidth over 5.5 GHz was obtained using the integrated photonic chip.

In this paper, a method of temperature sensing based on microwave signal generation with fiber Bragg grating (FBG) as a frequency discriminator is proposed and experimentally demonstrated. According to the proposed approach, the optical carrier frequency is placed at the slope of the phase response of the FBG. The measure and to the phase of microwave signal generated by the frequency discriminator is mapped through an electrical spectrum analyzer. The proposal can describe the change in the flat area of the amplitude response, which improves the sensing resolution of the temperature near the center wavelength. Higher precision can be distinguished from the slope of the phase response. A result that the sensor responds to temperature with a sensitivity of 5.2dB/°C is achieved.

A structure in photonic integrated circuit with a microring serially connected by an optical attenuator is proposed to generate the non-reciprocity by the nonlinear optical effect in microring. We find that when the information of the transmission spectra of both forward and backward directions is utilized for sensing, the precision of sensing can be enhanced. We calculate the non-reciprocity ratio of our proposed structure, and utilize this spectrum for sensing. Simulation shows the non-reciprocal spectrum varies with the attenuation value of the attenuator. The slope of 4.34dB/GHz can be achieved by utilizing 10dB attenuator, and the sensing frequency range is 7.35GHz. These results benefit its application in sensing.

Synchronized dual-wavelength narrow-linewidth lasers and a wideband frequency-tunable optoelectronic oscillator (OEO) are simultaneously realized using mutual-injection-locked distributed feedback (DFB) lasers. The two laser modes serve as the seeding light and a microwave photonic filter for optoelectronic oscillation. Mutual-injection locking between the two DFB lasers through a delay fiber loop results in synchronized narrow-linewidth operation. Microwave tuning from 19 to 41 GHz has been obtained through thermal-tuning of the DFB lasers, with the single-sideband phase noises below -100 dBc/Hz at a 10-kHz frequency offset from the carrier. Laser linewidth has been reduced from several-MHz to kHz with a linewidth reduction factor over 104.

A simple dual-frequency laser Doppler velocimeter using a monolithically integrated dual-mode amplified feedback laser as the dual-frequency light source is proposed and experimentally demonstrated. A preliminary result of a longitudinal velocity 327.9 μm/s was measured.

We report data transmissions using a packaged two-section distributed Bragg reflector (DBR) laser which has InGaAlAs multi-quantum wells (MQWs) as the gain material. The tunable DBR laser has a wavelength tuning range of 11.44 nm. The DBR laser has uniform 3-dB direct modulation bandwidth (over 12GHz) within the over 11 nm wavelength tuning range. 10 Gb/s data transmissions are performed at up to 25-km distance and different wavelength emissions at 25 °C and 50 °C.

A simple frequency-tunable optoelectronic oscillator based on a distributed-feedback (DFB) laser under optical feedback at period-one (P1) oscillation is proposed and experimentally demonstrated. The directly modulated DFB laser functions as an active tunable microwave photonic filter and a high-efficiency modulator due to the high-efficiency response at the P1 oscillation frequency, eliminating the needs of the narrowband electrical bandpass filter and high-gain RF amplifier. By tuning the optical feedback ratio, tunable microwaves ranging from 8.6 to 15.2 GHz with single sideband phase noise below −110.88 dBc/Hz at a 10-kHz offset from the carrier were realized.

Synchronized dual-wavelength narrow-linewidth laser and high-quality microwave signal generation is demonstrated using mutual-injection-locked DFB lasers with optoelectronic feedback. Two synchronized lasers with linewidth down to kHz and beating frequency of 23.3 GHz is realized.