Yuancheng Zhang

20 ps Transition Time All-Optical SOA-Based Flip-Flop Used for Photonic 10 Gb/s Switching Operation Without Any Bit Loss

A novel scheme for integrable ultrafast all-optical flip- flop is demonstrated. Transition times as low as 20 ps with a contrast ratio higher than 17.5 dB have been experimentally measured. All-optical switching operation in a 2times2 spatial and wavelength preserving switch is reported with a power penalty of about 1 dB. The proposed solution exploits the fast falling edge provided by a semiconductor optical amplifier (SOA) based optical flip-flop. Numerical investigations already demonstrated high extinction ratios (>40 dB) and low switching energies (15.6 fj) for integrated optical flip-flop. On the other hand, slow rising times, due to the cavity length, intrinsically limit such configurations. By using SOA-based logic gates, two flip-flop outputs are combined in a new bistable signal. Both the new rising and falling edges are related to the primary flip-flop falling edge. This way it is possible to eliminate the intrinsic slow rising time that limits the flip-flop configuration based on the coupled ring lasers, without excessively increasing the complexity of the structure and maintaining a reasonably high contrast ratio. Furthermore, the noise on the high level has been improved due to the regenerative properties of the logic gates based on cross-gain modulation and cross-phase modulation in a single nonlinear SOA. Finally, flip-flop output has been used to drive a 2times2 all-optical spatial and wavelength preserving switch based on SOAs. For cross/bar switch configurations, 10 Gb/s error-free operation has been obtained without bit loss.

Photonic Digital-to-Analog Converter Based on Summing of Serial Weighted Multiwavelength Pulses

A novel photonic digital-to-analog converter (PDAC) scheme based on summing of serial weighted multiwavelength pulses is proposed and experimentally demonstrated. The weighted multiwavelength pulses are delayed and summed in time domain through dispersion, and each weighted pulse with specific wavelength corresponds to a bit of input digital data. Regardless of the resolution, this scheme only requires one electrooptic modulator (EOM). In the experiment, a 3-bit PDAC with a sample rate of 2.5 GS/s is realized, and the input digital signal is mapped to an analog output linearly by a transfer function. This simple and compact setup could reduce the system complexity and avoid the synchronization of multiple EOMs.

Experimental Demonstration of All-Optical Analog-to-Digital Conversion With Balanced Detection Threshold Scheme

A novel balanced detection threshold scheme for all-optical analog-to-digital conversion is experimentally demonstrated. A 4-bit 10-GSamples/s all-optical analog-to-digital converter based on phase-shifted optical quantization and a balanced detection threshold scheme is realized to quantize a 9.9-GHz sinusoidal electrical signal, achieving a spur-free dynamic range of 24.2 dB. Compared with single-ended detection, the quantization result is improved with the balanced threshold scheme due to reducing the influence of the power fluctuation and improving the receiver sensitivity.

Single-SOA optical memory based on coupled fiber ring lasers

A compact optical memory with single SOA is demonstrated by exploiting two coupled fiber ring lasers. Without necessity of feedback, the memory shows bi-stability over a large wavelength range. Dynamic flip-flop operation is also investigated.

Improvement of all optical ADC based on phase-shifted optical quantization by using a polarization modulator

A novel scheme of OADC using PolM is proposed in this paper and ENOB of 3.18 bits under a sampling rate of 10Gs/s is obtained in the experiment.

Three-State Optical Memory Based on Coupled Ring Lasers

A three-state optical memory is demonstrated, with a compact configuration and low switching power. It is presented that the memory has an extinction ratio of 40 dB and a large wavelength range of set pulses.

SOA Fiber Ring Laser-Based Three-State Optical Memory

By exploiting three coupled semiconductor optical amplifier (SOA) fiber ring lasers, a compact, integratable, and polarization-independent three-state all-optical memory is demonstrated, with 40-dB extinction ratio for each state. Dynamic flip-flop operation between states is also demonstrated with switching pulse energy of 13.6 nJ. Due to the broad bandwidth of SOA gain spectrum, the wavelength range of set pulses is large. Finally, the transition behavior of state switching is investigated.

Phase-shifting optical quantization for high-speed microwave signals

This paper firstly briefly introduces and reviews the recent developments in phase-shifting optical quantization for high-speed microwave signals, which is one promising branch in all-optical analog-to-digital conversion. After that, a phase-shifting optical quantization system with a sampling rate of 40GS/s and a theoretical read-out-bits of 4-bit is built, and practical considerations for further improvements of both sampling rate and resolution are discussed.

A novel proposal of all-optical analog-to-digital conversion with unbalanced MZM and filter array

A novel phase-shifted optical analog-to-digital conversion proposal is presented and analyzed. Using an unbalanced MZM and specifically designed filter array, the desired phase shift between adjacent quantization channels can be realized. Comparing with existing schemes, the main advantage of this scheme is only one EOM and two wavelengths needed, regardless of the quantization resolution. Utilizing commercial products, analysis indicated that the number of bits as high as 8-bit and sampling rate up to 40GS/s can be realized.

A Photonic Digital-to-Analog Conversion Based on Multi-wavelength Sampling

A novel digital-to-analog converter based on multi-wavelength pulse source is proposed and primarily demonstrated by experiment. The multi-wavelength pulse train which has been pretreated is separated in time domain through dispersion. The pulse of different wavelength corresponds to the input digital data. Only one electro-optical modulator is needed in the scheme. In the primary experiment, a 3-bit photonic digital-to-analog converter with a sample rate of 2.5 Gb/s is realized. The scheme is simple and compact compared with the scheme using multiple electro-optical modulators.