Yanfei Xing

Optical Nyquist pulse generation using a time lens with spectral slicing

Optical Nyquist pulse generation based on a time lens with subsequent optical filtering is proposed. A nearly chirp-free 10-GHz 8.1-ps Nyquist pulse generator is experimentally demonstrated. By inserting group velocity dispersion (GVD) between cascaded phase and amplitude modulators, 11 tones ultraflat optical frequency comb (OFC) of 10-GHz frequency spacing within 0.9 dB power variation is obtained. The quasi-rectangular shape spectrum is then filtered out with a tunable rectangular-shaped optical band-pass filter (OBPF) and the quasi-linear chirp is compensated by a segment of standard single mode fiber (SSMF). By changing the wavelength of the continuous wave (CW) light, nearly chirp-free Nyquist pulses over C band are obtained. Furthermore, simultaneous dual-wavelength pulse generation is also demonstrated.

Gaussian-like dual-wavelength prescaled clock recovery with simultaneous frequency-doubled clock recovery using an optoelectronic oscillator

A novel multifunctional frequency-doubling optoelectronic oscillator (FD-OEO) mainly based on a Mach-Zehnder modulator (MZM) cascaded with a phase modulator (PM) and a subsequent optical bandpass filter (OBPF) is proposed. We experimentally demonstrate simultaneous operations of frequency-doubled optical clock (FD-OC) recovery, low-duty-cycle dual-wavelength prescaled OC recovery and error-free fourfold time division demultiplexing with the proposed OEO injected with a 4 × 25-Gb/s optical time-division-multiplexing (OTDM) signal. We show that the proposed FD-OEO operates well for both the differential phase shift keying (DPSK) and on-off keying (OOK) modulation formats. The extracted dual-wavelength prescaled OC is proved to be nearly transform-limited with Gaussian-like shape. Furthermore, all four 25-Gb/s tributaries can be selectively demultiplexed by adjusting the phase shifters in the OEO loop. The power penalty at a bit error rate (BER) of 10(-9) is measured to be 2.4 dB, 1.2 dB for the best channel for DPSK signal and to be 2.5 dB, 1.1 dB for the best channel for OOK signal. In addition, as an extra benefit of the OEO, low-phase-noise prescaled electrical clock (EC) is also extracted.

Cost-effective Optical Nyquist Pulse Generator with Ultra-flat Optical Spectrum Using Dual-parallel Mach-Zehnder Modulators

Rectangular-shaped optical frequency comb generation with Nyquist temporal waveforms using dual-parallel Mach-Zehnder modulators is proposed. Nyquist pulse with 3.66% duty cycle and 25-tone frequency combs with flatness within 0.5 dB is generated.

Effective optical clock recovery and simultaneous fourfold demultiplexing of OTDM signal using an optoelectonic oscillator.

We propose and demonstrate a novel scheme for clock recovery and simultaneous fourfold optical time-division demultiplexing using a dual-parallel Mach-Zehnder modulator based optoelectronic oscillator. 25-GHz prescaled optical clock with a 23% duty cycle and a 22-dB extinction ratio is successfully extracted from both 100-Gb/s on-off keying (OOK) and differential phase-shift keying (DPSK) optical time-division-multiplexing (OTDM) signal. The timing jitters (100 Hz to 10 MHz) are measured to be 195.9 fs and 125.6 fs for the optical clock extracted from the 100-Gb/s OOK and DPSK signal, respectively. Error-free optical time-division demultiplexing is also achieved simultaneously with clock recovery. By adjusting the phase shifter in the OEO loop, all four channels can be selectively demultiplexed. The power penalties at a bit error rate (BER) of 10⁻⁹ for the four demultiplexed channels are measured to be between 0.8 dB and 1.2 dB for the OOK signal and between 0.9 dB and 1.5 dB for the DPSK signal.

Optical Time-Division Demultiplexing Using a Time-Lens-Assisted Mach–Zehnder Modulator

We propose to use a diverging time lens to equivalently minimize the time window of a LiNbO3 Mach-Zehnder modulator (MZM) and promote its capability in optical time-division demultiplexing applications. A single MZM is demonstrated experimentally for fourfold 100-Gb/s tributary demultiplexing assisted with a phase modulator based diverging time lens. Error-free detection is achieved for all four channels and the power penalty at a bit-error-rate of 10-9 is 2.4 dB, 1.1 dB for the best channel.

Low-Phase-Noise Clock Recovery From NRZ Signal and Simultaneous NRZ-to-RZ Format Conversion

We propose and demonstrate an improved optoelectronic oscillator based on a dual-parallel Mach-Zehnder modulator for simultaneous low-duty-cycle and low-phase-noise clock recovery from NRZ signal and wavelength-preserved NRZ-to-RZ format conversion. A 25-GHz optical clock with a 25% duty cycle and a 22.5-dB extinction ratio is successfully extracted from the incident 25-Gb/s NRZ signal. Benefiting from the intrinsic property of the optoelectronic oscillator, an electrical clock with a 174-fs root-mean-square timing jitter (100 Hz-10 MHz) is also achieved. Simultaneously, error-free wavelength-preserved NRZ-to-RZ format conversion with a -2-dB power penalty at a bit error rate of 10-9 is demonstrated.

Optical Gaussian pulse generator using phase modulator based spectral slicing and compression

A 25-GHz 3-ps optical Gaussian pulse generator using phase modulators is experimentally demonstrated with wavelength tunability over C-band. Error-free 100-km transmission of 100-Gb/s OTDM signal is achieved with it.

Optical time-division multiplexing signal processing using electro-optic modulators

We present some optical signal processing methods for optical time-division multiplexing, based on electro-optic modulators. Dual-parallel Mach–Zehnder modulator and time-lens-based signal processing for optical frequency comb generation, optical Nyquist pulse generation and time-domain demultiplexing are realized. Multifunctional optoelectronic oscillators which are capable of performing simultaneous electrical clock recovery, optical clock recovery and demultiplexing are demonstrated with modulators embedded as the key components.

Modulator-based high-speed optical signal processing for optical time-division multiplexing

We present a summary of our recent progress in high-speed optical signal processing for optical time-division multiplexing, based on electro-optic modulators. Optical frequency-comb generation, optical Nyquist pulse generation, equivalent switching window expansion for demultiplexing, and simultaneously clock recovery and demultiplexing are realized by structures with modulators embedded as the key components.

Dual-wavelength clock recovery with simultaneous fourfold demultiplexing using an optoelectronic oscillator

Dual-wavelength Gaussian-like optical clock recovery with simultaneous error-free fourfold demultiplexing of a 100-Gb/s OTDM-DPSK signal are demonstrated with an improved optoelectronic oscillator. Frequency-doubled clock recovery is also achieved.