We propose silicon micro-ring modulator (MRM) based W-band transmitter for next generation wireless communication. 14 Gb/s non-return-to-zero (NRZ) communication at 80 GHz carrier frequency have been experimentally demonstrated by utilizing off-chip electro-optic comb or two free running lasers and on-chip high-speed narrow-band micro-ring modulators. Error free wireless transmission without W-band amplifier can be achieved by using linear equalizers with 40-tap feed forward equalization (FFE).
A novel scheme for the generation of full-duty-cycle triangular pulses based on an optoelectronic oscillator (OEO) was proposed and experimentally demonstrated. With the employment of the Chirped Fiber Bragg Grating, the "Vernier effect" was realized, which can effectively improve the side mode suppression ratio. The triangular pulses train with repetition of 6 GHz respectively was obtained successfully in experiment.
Whispering gallery mode (WGM) microcavities can confine photons within a microscale volume for long periods of time, strongly enhancing light-matter interactions, making it an important platform in optical science and applications. However, current research on microcavity system relays on precise mechanical coupling with microscope monitoring, and its resonance characteristics are highly sensitive to external environmental factors such as vibration, temperature and humidity changes, which greatly limits the practical application of microcavity devices. Therefore, we propose an ultra-stable packaging method with air/water tightness and constant temperature characteristics. A variety of fixatives with different Young's modulus gradients and low coefficient of thermal expansion were used to design a package structure with overall vibration isolation and buffering effect, in order to ensure the stability of coupling mode and improve the robustness of the microcavity module. Hopefully, our research work will pave the way for the application of optical microcavity devices in high-speed optical communication, nonlinear optics, narrow linewidth lasers and ultra-high sensitivity sensors.
A high performance marine towing cable system based on ultra-sensitive fiber-optic distributed acoustic sensing (uDAS) is demonstrated and tested in field. The towing cable is specially designed with 15 sensing units arranged at equal intervals of 0.6 m. The sensitivity of the sensing unit is greatly enhanced to -130 dB re rad/μPa at frequency from 4 Hz to 700 Hz. For the first time, sea trial is carried out to test the flow noise, underwater acoustic signal capture and beamforming capacity. The proposed towing cable system with high sensitivity, a simple structure and light weight, opens up a new way for light-weighting unmanned towing applications
Due to the Lambertian radiation profile of lighting grade of light emitting diodes (LEDs), the visible light communication (VLC) performance is not uniform and varies dramatically for a small change in the receiver’s position. A practical VLC system demands uniform performance over a significant coverage area to allow users’ movement. In this paper, a top-hat engineered diffuser is used to distribute the optical signal equally over a large area. The signal to noise ratio (SNR) varies a little over a large coverage area. Due to a sharp fall in the diffuser’s intensity distribution, the interference from neighbouring transmitters is reduced and as a result, the coverage area is further improved. In a 5m ×5m ×3m room, employing four LED transmitters with the proposed top-hat diffuser, the coverage probability has been improved from 31.91% to 67.55% when compared to the situation without the diffusers.
We have experimentally demonstrated a long-cavity large-normal-dispersion erbium-doped fiber laser utilizing an optical integrated module (OIM) and nonlinear polarization rotation technique to realize dissipative soliton resonance (DSR) in a concise way.
The improvement of acousto-optic modulation performance is closely dependent on the design and fabrication of on-chip optical waveguide and interdigital transducer. In this work, the waveguide width of 1.6 μm and the relative distance of 11.4 μm are delicately optimized to obtain better modulation efficiency based on our proposed nonsuspended heterogeneous-integration acoustic-optic modulator.
Fiber lasers with narrow linewidth are essential light sources for many prospects in advanced scientific fields. In this article, we propose a scheme of self-injection locked single-frequency fiber laser based on a hybrid cavity configuration and a novel type of nanoparticles doped fiber to achieve narrow linewidth output. Experimental study and measurement analysis of key performance parameters have been carried out, including linewidth, optical spectral and noise characteristics. The single frequency performance has been verified with > 60 dB side mode suppression ratio. A 556 Hz 3dB linewidth has been achieved, with better frequency noise performance compared with a typically high quality commercial laser source.
Highly stable and widely wavelength-tunable optical frequency comb generation from an active and harmonic mode-locked short-cavity laser employing a bismuth-oxide- based nonlinear erbium-doped fiber is demonstrated. Flat 10- GHz-spaced optical frequency comb with a frequency bandwidth of 240GHz is produced.
A hot-wire anemometer based on a cladding-etched optical fiber Bragg grating (FBG) coated with a layer of silver film and optically heated by a laser diode is demonstrated, which shows a high sensitivity.
We proposed a low-complexity NN-equalizer based on spectrum segmentation and a modified loss function to mitigate the nonlinear distortion in high-speed UVLC system. Experiments demonstrate that the proposed scheme achieves similar performance compared with classical NN-equalizer, and with a 43.1% network complexity reduction.
Stimulated Brillouin scattering (SBS) is explored in integrated optoelectronic systems to demonstrate microwave photonic filters, microwave sources, non-reciprocal devices, narrow-linewidth lasers, etc. Suspended structures and phononic crystals are applied to boost the SBS gain. However, the Brillouin gain coefficient is related to multiple factors such as electrostrictive force, radiation pressure, and the distribution of acoustic and optical modes. It is challenging to obtain the optimal SBS gain coefficient via simple parameter sweeps. In this contribution, we use the genetic algorithm to optimize the suspended phononic crystal Brillouin optical waveguide. The variations of mechanical quality factors and the optical modes are considered to optimize the forward SBS gain. Using this method, we can obtain the optimized waveguide design more simply and accurately. Compared to the previous approaches, the optimized parameters have a 10 percent improvement in the calculated Brillouin gain coefficient.
A tunable high-Q Mach-Zehnder interferometer (MZI) coupled micro-ring resonator (MRR) with a large free-spectra range (FSR) is demonstrated by introducing multimode waveguides assisted with modified Euler curve, both phase and coupling coefficient can be tuned. Utilization of the silicon micro-ring enables a microwave photonic band-pass filter with a 3-dB bandwidth tuned from 150 MHz to 2 GHz, and central frequency thermally tuned from 500 MHz to 40 GHz.
Interleaved frequency division multiple access (IFDMA) is considered as a promising candidate for next-generation optical access networks. In this paper, we proposed a bidirectional long short-term memory (BiLSTM)-based detection method for IFDMA-PON. The performance of the BiLSTM-based method was evaluated with varying modulation formats and laser linewidths. The results showed that BiLSTM could detect system impairments more effectively with higher tolerance for nonlinear distortion of the transmitter than traditional least square-based methods.
A photonics-based microwave frequency measurement system with broadband signal generation and processing is demonstrated. A microwave frequency measurement range from 1 to 39 GHz is experimentally achieved with a measurement error below ±50 MHz.
Sparse code multiple access (SCMA) is a promising technology for long-reach passive optical networks (LR-PONs). The design of SCMA codebooks is crucial to system capacity and transmission performance. In this paper, a novel design of SCMA codebooks over fiber channel is proposed, including a low-complexity design criterion based on error probability minimization for independent resource elements and a new labelling rule. The simulation results show that the presented low-complexity SCMA codebook design exhibits good transmission performance, especially in the low optical signal-to-noise ratio (SNR) regions. The codebook design is applicable to LR optical access networks.
In this paper, we consider service provisioning in a wavelength selective switch (WSS) based all-optical data center network with spine-leaf topology. Its related routing, wavelength, time-slot assignment (RWTA) problem is modelled and solved in the context of two WSS reconfiguration scenarios. Specifically, for the all-stop (AS) WSS reconfiguration scenario, an integer linear programming (ILP) model is formulated and an efficient heuristic algorithm is developed. For the not-all-stop (NAS) WSS reconfiguration scenario, an efficient heuristic algorithm is developed. Simulation results show that the proposed schemes are efficient to significantly reduce the overall task completion time (TCT) compared with a benchmark scheme. Also, the NAS scenario can significantly reduce the overall TCT compared with the AS scenario since the former can maximally eliminate the WSS reconfiguration time.
We experimentally demonstrate an optical polarization sensor method in real-time coherent optical communication system. Based on the adaptive equalization in receiver digital signal processing, the polarization rapid rotation event can be located in the bidirectional communication links.
