Dong Jian-Ji

All-Optical Temporal Differentiator Using a High Resolution Optical Arbitrary Waveform Shaper

We experimentally demonstrate an all-optical temporal differentiator using a high resolution optical arbitrary waveform shaper, which is based on liquid crystal on silicon switching elements, and both amplitude and phase of the spectrum are programmable. By designing specific transfer functions with the optical waveform shaper, we obtain first-, second-, and third-order differentiators for periodic pulses with small average errors. We also theoretically analyze the bandwidth limitation of optical waveform shaper on the differentiator.

Diversity of photonic differentiators based on flexible demodulation of phase signals

We theoretically propose a multifunctional photonic differentiation (DIFF) scheme based on phase demodulation using two cascaded linear filters. The photonic DIFF has a diversity of output forms, such as the 1st order intensity DIFF, the 1st order field DIFF and its inversion, and the 2nd-order field DIFF, depending on the relative shift between the optical carrier and the filters resonant notches. As a proof, we also experimentally demonstrate the DIFF diversity using a phase modulator and two delay interferometers (DIs). The calculated average deviation is less than 7% for all DIFF waveforms. Our schemes show the advantages of flexible DIFF functions and forms, which may have different optical applications. For example, high order field differentiators can be used to generate complex temporal waveforms, and intensity differentiators are useful for the ultra-wideband pulse generation.

Reconfigurable all-optical dual-directional half-subtractor for high-speed differential phase shift keying signal based on semiconductor optical amplifiers

All-optical digital logic elementary circuits are the building blocks of many important computational operations in future high-speed all-optical networks and computing systems. Multifunctional and reconfigurable logic units are essential in this respect. Employing the demodulation properties of delay interferometers for input differential phase shift keying signals and the gain saturation effect in two parallel semiconductor optical amplifiers, a novel design of 40 Gbit/s reconfigurable all-optical dual-directional half-subtractor is proposed and demonstrated. All output logic results show that the scheme achieves over 11=dB extinction ratio, clear and wide open eye diagram, as well as low polarization dependence (< 1 dB), without using any additional input light beam. The scheme may provide a promising candidate for future ultrafast all-optical signal processing applications.

A 40-Gbit/s 1-to-2 Photonic Data Distributor Employing a Single Semiconductor Optical Amplifier

A simple design of l-to-2 photonic data distributor is proposed. A proof-of-concept experiment is performed at 40 Gbit/s employing four-wave mixing and cross gain modulation in a single semiconductor optical amplifier. Correct output logic signals with high extinction ratios (over 11 dB) and clear open eyes are obtained, without using any additional input light beam. The scheme would be a promising candidate for future ultrafast all-optical signal processing applications.

Microwave photonic filter with a continuously tunable central frequency using an SOI high-Q microdisk resonator

Utilizing a high-Q microdisk resonator (MDR) on a single silicon-on-insulator (SOI) chip, a compact microwave photonic filter (MPF) with a continuously tunable central frequency is proposed and experimentally demonstrated. Assisted by the optical single side-band (OSSB) modulation, the optical frequency response of the MDR is mapped to the microwave frequency response to form an MPF with a continuously tunable central frequency and a narrow 3-dB bandwidth. In the experiment, using an MDR with a compact size of 20×20 μm2 and a high Q factor of 1.07×105, we obtain a compact MPF with a high rejection ratio of about 40 dB, a 3-dB bandwidth of about 2 GHz, and a frequency tuning range larger than 12 GHz. Our approach may allow the implementation of very compact, low-cost, low-consumption, and integrated notch MPF in a silicon chip.

All-Optical Clock Recovery from NRZ-DPSK Signals at Flexible Bit Rates

We propose and demonstrate all-optical clock recovery (CR) from nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signals at different bit rates theoretically and experimentally. By pre-processing with a single optical filter, clock component can be enhanced significantly and thus clock signal can be extracted from the preprocessed signals, by cascading a CR unit with a semiconductor optical amplifier based fibre ring laser. Compared with the previous preprocessing schemes, the single filter is simple and suitable for different bit rates. The clock signals can be achieved with extinction ratio over 10 dB and rms timing jitter of 0.86 and 0.9 at 10 and 20 Gb/s, respectively. The output performances related to the bandwidth and the detuning of the filter are analysed. By simply using a filter with larger bandwidth, much higher operation can be achieved easily.

On-chip optical pulse shaper for arbitrary waveform generation

We propose and demonstrate a silicon-on-insulator (SOI) on-chip optical pulse shaper based on four-tap finite impulse response. Due to different width designs in phase region of each tap, the phase differences for all taps are controlled by an external thermal source, resulting in an optical pulse shaper. We further demonstrate optical arbitrary waveform generation based on the optical pulse shaper assisted by an optical frequency comb injection. Four different optical waveforms are generated when setting the central wavelengths at 1533.78 nm and 1547.1 nm and setting the thermal source temperatures at 23 °C and 33 °C, respectively. Our scheme has distinct advantages of compactness, capability for integrating with electronics since the integrated silicon waveguide is employed.

Photonic generation of power-efficient FCC-compliant ultra-wideband waveforms using semiconductor optical amplifier (SOA): theoretical analysis and experiment verification

We theoretically design a power-efficient ultra-wideband pulse generator by combining three monocycle pulses with different weights. We also experimentally demonstrate a feasible scheme to generate such power-efficient ultra-wideband waveforms using cross-phase modulation in a single semiconductor optical amplifier. The designed ultra-wideband pulse fully satisfies the requirements for the spectral mask specified by the Federal Communications Commission with high power efficiency. In the experiment, a power-efficient ultra-wideband waveform with a pulse duration of 310 ps is achieved, and the power efficiency is greatly improved compared with that of a single monocycle pulse or a mixture of two monocycles.

Optical pulse shaper with integrated slab waveguide for arbitrary waveform generation using optical gradient force

Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach—Zehnder interferometer (MZI) to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo—optic effect or electro—optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip, which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator (SOI) wafer, which has a top silicon layer of about 220 nm in thickness.

Photonic multi-shape UWB pulse generation using a semiconductor optical amplifier-based nonlinear optical loop mirror

We propose and demonstrate a scheme to implement photonic multi-shape ultra-wideband (UWB) signal generation using a semiconductor optical amplifier (SOA) based nonlinear optical loop mirror (NOLM). By employing the cross phase modulation (XPM) effect, cross gain modulation (XGM), or both, multi-shape UWB waveforms are generated including monocycle, doublet, triplet, and quadruplet pulses. Both the shapes and polarities of the generated pulses are flexible to adjust, which may be very useful in UWB pulse shape modulation and pulse polarity modulation.