Soliton-like pulse timing jitter in dispersion-managed systems

In this paper, the timing jitter in dispersion-managed soliton-like systems with the Caussian pulse is studied by using two methods. Firstly, the derivation of the dynamic equations for the evolution of soliton-like parameters and the timing jitter expressions for the dispersion-managed soliton-like systems are carried out by the perturbed variational method. By analysing and simulating these timing jitter expressions, one can find that the timing jitter is induced by the amplified spontaneous emission noise and the frequency shift, etc. Nonlinear gain can suppress the timing jitter. The chirp sign and the filters action have also effects on the total timing jitter. Secondly, the timing jitter is calculated and analysed by using the moment method. The results of the two methods prove to be consistent with each other.

Bias-dependent timing jitter of 1-GHz sinusoidally gated InGaAs/InP avalanche photodiode

We characterized the dependence of the timing jitter of an InGaAs/InP single-photon avalanche diode on the excess bias voltage（V（ex）） when operated in 1-GHz sinusoidally gated mode.The single-photon avalanche diode was cooled to-30 degrees Celsius.When the V（ex） is too low（0.2 V-0.8 V） or too high（3 V-4.2 V）,the timing jitter is increased with the V（ex）,particularly at high V（ex）.While at middle V（ex）（1 V-2.8 V）,the timing jitter is reduced.Measurements of the timing jitter of the same avalanche diode with pulsed gating show that this effect is likely related to the increase of both the amplitude of the V（ex） and the width of the gate-on time.For the 1-GHz sinusoidally gated detector,the best jitter of 93 ps is achieved with a photon detection efficiency of 21.4%and a dark count rate of -2.08×10 -5 per gate at the V（ex） of 2.8 V.To evaluate the whole performance of the detector,we calculated the noise equivalent power（NEP） and the afterpulse probability（P（ap））.It is found that both NEP and P（ap） increase quickly when the V（ex） is above 2.8 V.At -2.8-V V（ex）,the NEP and P（ap） are -2.06×10-（16）W/Hz-（1/2） and 7.11%,respectively.Therefore,the detector should be operated with V（ex） of 2.8 V to exploit the fast time response,low NEP and low P（ap）.

Influence of group-delay ripple on timing jitter induced by SPM and IXPM in systems with dispersion compensated by CFBG

An analytical expression was proposed to analyze the influence of group-delay ripple （GDR） on timing jitter induced by self-phase modulation （SPM） and intra-channel cross-phase modulation （IXPM） in pseudolinear transmission systems when dispersion was compensated by chirped fiber Bragg grating （CFBG）. Effects of ripple amplitude, period, and phase on timing jitter were discussed by theoretical and numerical analysis in detail. The results show that the influence of GDR on timing jitter changes linearly with the amplitude of GDR and whether it decreases or increases the timing jitter relies on the ripple period and ripple phase. Timing jitter induced by SPM and IXPM could be suppressed totally by adjusting the relative phase between the center frequency of the pulse and the ripples.

Pulse-Width Jitter Measurement for Laser Diode Pulses

Theoretical analysis and experimental measurement of pulse-width fitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced. The power spectra with and without pulse-width fitter are that the pulse-width jitter will contribute considerably numerically simulated. The simulation results indicate noise to the pulse power spectrum while the product of pulse width and angular frequency is larger than 1. The experimental measurement of pulse-width fitter of a gain-switched Fabry-Perot laser diode with 2.4 GHz repetition rate is also reported. In comparison of the noise power spectra of the first, fourth and seventh harmonics of the pulse repetition rate, 2.3ps pulse-width jitter is obtained.

Residual Phase Noise and Time Jitters of Single-Chip Digital Frequency Dividers

In this paper, we demonstrate the residual phase noise of a few microwave frequency dividers which usually limit the performance of frequency synthesizers. In order to compare these dividers under different operation frequencies, we calculate additional time jitters of these dividers by using the measured phase noise. The time jitters are various from -0.1 fs to 43 fs in a bandwidth from 1 Hz to 100 Hz in dependent of models and operation frequencies. The HMC series frequency dividers exhibit outstanding performance for high operation frequencies, and the time jitters can be sub-fs. The time jitters of SP8401, MC10EP139, and MC100LVEL34 are comparable or even below that of HMC series for low operation frequencies.

Generation and time jitter of the loose soliton bunch in a passively mode-locked fiber laser

Passively mode-locked fiber lasers （PMLFLs） could be not only used as simple and economic ultrashort pulse sources but also as an ideal platform for exploring the nonlinear dynamics of dissipative solitons such as bound solitons, soliton rains, noise-like pulses, sideband-controllable solitons, soliton resonance,

Beam transport design for a 1 MeV prototype dielectric wall accelerator

The beam transport design of a novel proton dielectric wall accelerator is introduced in this paper. The protons will be accelerated from 40 keV to nearly 1 MeV under an accelerating gradient that is as high as 20 MV/m. A consideration of the beam line as well as the transport simulation is presented. The influences of the injection timing jitter and the accelerating pulse timing jitter are also discussed.

Simultaneous clock recovery and demultiplexing of a 320 Gb/s OTDM system using an optoelectronic oscillator based on cascaded MZM and PolM

An improved optoelectronic oscillator scheme for an optical time division multiplexing （OTDM） system based on cascaded Mach-Zehnder modulator （MZM） and polarization modulator （PolM） is experimentally investigated. The system can simultaneously realize clock recovery and demultiplexing. With the MZM working at peak point to generate return-to-zero-33 optical pulses and the PolM working as an equivalent intensity modulator, a high-quality clock signal with 35-fs timing jitter is extracted from the 160-GBaud OTDM-differential quaternary phase-shift keying signal. Narrow short optical switch gates （4 ps） are also generated to demultiplex 160-GBaud signals to 40-GBaud signals. Error-free performance is achieved with 2.4-dB power penalty in the worst case.

Robustness estimation of software-synchronized all-optical sampling for fiber communication systems

The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems. It reveals that the software-synchronized algorithm is sensitive to the signal degradation caused by chromatic dispersion and nonlinearity in optical fibers. The influence of timing jitter and amplitude fluctuation of the sampling pulses is also investigated. It is found that stringent requirements are imposed on the quality of the sampling pulse and the tolerance of 1-dB Q penalty is measured. Considering the practically available optical sampling pulse sources, the results indicate that the amplitude fluctuation of the sampling pulses has the dominant impacts on the software-synchronized method.

Demonstration of a 16×10-Gb/s OTDM system

A 16×10-Gb/s optical time-division-multiplexing （OTDM） system was demonstrated experimentally with a well-designed ultrashort pulse source based on an electro-absorption modulator （EAM） and nonlinear fiber compressor. The obtained 10-GHz stable and pedestal-free pulse train has 2-ps width, high extinction ratio, and low timing jitter. An ultrafast demultiplexer based on a nonlinear optical loop mirror （NOLM） including a commercially available highly nonlinear fiber （HNLF） is employed to demultiplex data signal from 160 to 10 Gb/s. A back-to-back error-free demultiplexing experiment is carried out to verify the system performance.

Demonstration of an 8×10-Gb/s OTDM system

An 8×10 Gb/s optical time-division-multiplexing (OTDM) system was demonstrated with an electroab-sorption modulator (EAM) based short pulse generator followed by a two-stage nonlinear compression scheme which generated stable 10-GHz, 2-ps full-width at half-maximum (FWHM) pulse train, an optoelectronic oscillator (OEO) that extracted 10-GHz clock with a timing jitter of 300 fs from 80-Gb/s OTDM signal and a self cascaded EAM which produced a switching window of about 10 ps. A back-to-back error free demultiplexing experiment with a power penalty of 3.25 dB was carried out to verify the system performance.

Pre-pumped passively Q-switched Nd:YAG/Cr:YAG microchip laser

A pre-pumped passively Q-switched Nd:YAG/Cr: YAG microchip laser is demonstrated with a peak power of 7.5 kW at pulse repetition rate of serveral kilohertzs. The full-width at half-maximum (FWHM) is 734 ps, and the pulse energy is 5.5 μJ with a fundamental spatial mode. In this system, the pre-pumped microchip laser of Nd: YAG/Cr: YAG wafer which is bonded through the thermal-bonding technique has achieved a time jitter value of 12 μs and a Q-switched amplitude instability of 1.26% (1δ) through the pre-pumped modulation technique.

All-optical clock recovery for 40 Gbaud NRZ-QPSK signals using amplified feedback DFB laser diode

An all-optical clock recovery scheme based on monolithic amplified feedback DFB laser （AFL） diode is proposed for nonreturn-to-zero （NRZ） quadrature phase shift keying （QPSK） format signals. By using a preprocessing stage, clock recovery （CR） is successfully demonstrated for 40-Gbaud NRZ-QPSK signals based on this scheme. The dependence of the timing jitter of the recovered clock on the optical power of the injected signal is investigated. A minimum timing jitter of 362.8 fs （integrated within a frequency range from 10 Hz to 10 MHz） is obtained.

100 Gb/s all-optical clock recovery based on a monolithic dual-mode DBR laser

We experimentally demonstrate all-optical clock recovery for 100 Gb/s return-to-zero on-off keying signals based on a monolithic dual-mode distributed Bragg reflector （DBR） laser, which can realize both mode spacing and wavelength tuning. By using a coherent injection locking scheme, a 100 GHz optical clock can be recovered with a timing jitter of 530 fs, which is derived by an optical sampling oscilloscope from both the phase noise and the power fluctuation. Furthermore, for degraded injection signals with an optical signal-to-noise ratio as low as 4.1 dB and a 25 km long distance transmission, good-quality optical clocks are all successfully recovered.

Generation of synchronized femtosecond and picosecond laser pulses in a two-beam-pumped Ti:sapphire laser

Two operating modes, independent self-mode-locking and cross-mode-locking, are presented in a two-beam- pumped double-cavity dual-wavelength femtosecond Ti：sapphire laser. Synchronization of femtosecond and picosecond laser pulses is achieved by properly adjusting the cavity length matching and distributing the pump laser powers in the two laser cavities, and moreover, a timing jitter of 517 fs between femtosecond and picosecond pulses is obtained, with wavelength tuning ranges around 36 and 22 nm in the femtosecond and picosecond cavities, respectivelv.

20-GHz optical pulse source based on cascaded electroabsorption modulators

A high-quality low-timing-jitter 20-GHz optical pulse train is generated by using two cascaded sinusoidally driven electroabsorption modulators （EAMs） at very low bias voltage of -0.8 V in conjunction with atunable distributed feedback （DFB） semiconductor laser. An approximate transform-limited optical pulse, with the pulse width less than 7 ps, the spectral width of 0.3 nm, and the side-mode suppression ratio （SMSR） above 20 dB, is obtained by tuning the optical delay line.

A low-noise PLL design achieved by optimizing the loop bandwidth

This paper describes a low-noise phase-locked loop （PLL） design method to achieve minimum jitter. Based on the phase noise properties extracted from the transistor, and the low-pass or high-pass transfer characteristics of different noise sources to the output, an optimal loop bandwidth design method, derived from a continuous-time PLL model, further improves the jitter characteristics of the PLL. The described method not only finds the optimal loop-bandwidth to minimize the overall PLL jitter, but also achieves optimal loop-bandwidth by changing the value of the resistor or charge pump current. In addition, a phase-domain behavioral model in ADS is presented for accurately predicting improved jitter performance of a PLL at system level. A prototype PLL designed in a 0.18 μm CMOS technology is used to investigate the accuracy of the theoretical predictions. The simulation shows significant performance improvement by using the proposed method. The simulated RMS and peak-to-peak jitter of the PLL at the optimal loop-bandwidth are 10.262 ps and 46.851 ps, respectively.

Spectrum analysis of all parameter noises in repetition-rate laser pulse train

The theoretical investigation of all parameter noises in repetition-rate laser pulse train was presented. The expression of power spectrum of laser pulse trains with all parameter noises was derived, and the power spectra of pulse trains with different noise parameters were numerically simulated. By comparing the power spectra with and without pulse-width jitter, we noted that pulse-width jitter could not be neglected compared with amplitude noise and timing jitter and contributed a great amount of noise into the power spectrum under the condition that the product of pulse width and angular frequency was larger than 1.

Design of cascading two stages of high gain harmonic generation scheme based on Shanghai deep ultraviolet free electron laser

Cascading stages of high gain harmonic generation free electron laser （FEL） seem to be a feasible way to generate short wavelength radiation. With help of the analytical estimates, we design a two-stage cascading scheme to achieve 131 nm DUV radiation on the basis of the Shanghai deep ultraviolet free electron laser test facility. Detailed studies on the FEL performance, the stability and the sensitivity of the output power to parameter variation have been achieved by GENESIS1.3, and design of the lattice structure is presented.