10 Gbit/s all-optical clock recovery using three-section DFB laser with optical feedback

All-optical clock recovery using a three-section self-pulsating DFB laser with optical feedback is demonstrated. The feedback of a wavelength-converted clock signal reduces the dependence on the input data signal power, decreases the jitter by up to 2.7 ps, and increases the extinction ratio by 6.5 dB.     

Performance and scalability of an all-optical clock recovery figure eight laser

A novel geometry for all-optical clock recovery using a semiconductor amplifier yields a strong locking mechanism in a short cavity. The recovered clock has a large locking bandwidth, low timing jitter, and fast lock-up time at a 2.5 GHz rate. Preliminary results at a 9 GHz rate also indicate a high quality recovered clock.     

40 Gbit/s all-optical clock recovery using two-section gain-coupledDFB laser and semiconductor optical amplifier

40 Gbit/s wavelength and polarisation insensitive all-optical clock recovery using a two-section distributed feedback (DFB) laser has been demonstrated. The polarisation sensitivity of the two-section DFB laser was solved by converting incoming data onto a local laser through cross-gain modulation using a semiconductor optical amplifier. The scheme has a sensitivity of -13 dBm     

基于放大反馈激光器高速全光时钟提取的研究

为了研究放大反馈激光器全光时钟提取的性能,采用单边带相位噪声功率谱积分的方法,对40Gbit/s无恶化信号和噪声恶化信号分别进行了时钟提取实验,计算了所提取时钟的时间抖动。同时还测量了放大反馈激光器的锁定范围。通过实验取得了恶化前后所提取时钟的时间抖动分别为130fs和150fs,放大反馈激光器的锁定范围为234MHz。结果表明,基于放大反馈激光器的全光时钟提取方案对噪声恶化具有较强的容忍度,而且具有较宽的锁定范围。这一结果对于全光时钟提取技术的进一步发展具有重要意义。     

Dynamics of all-optical clock recovery using two-section index- and gain-coupled DFB lasers

The dynamics of coherent clock recovery (CR) using self-pulsing two-section distributed feedback (TS-DFB) lasers have been investigated. Both simulation and experimental results indicate fast lockup and walk-off of the clock-recovery process on the order of nanoseconds. Phase stability of the recovered clock from a pseudorandom bit sequence (PRBS) signal can be achieved by limiting the detuning between the frequency of free-running self-pulsation and the input bit rate. The simulation results show that all-optical clock recovery using TS-DFB lasers can maintain a better than 5% clock phase stability for large variations in power, bit rate, and optical carrier frequency of the input data and therefore is suitable for applications in optical packet switching.     

基于高精细度F-P滤波器的40Gb/s全光时钟提取

提出了一种基于高精细度Fabry-Perot(F-P)滤波器的全光时钟提取方案,并进行了实验验证。为了实现对信号波长无关的特性,系统利用光纤中交叉相位调制(XPM)效应对输入信号进行正码波长变换,使变换后的波长始终与F-P滤波器的透射峰精确对准。采用精细度为1 012的高精细度F-P滤波器提取时钟,并利用半导体光放大器(SDA)的自增益调制(SGM)效应进一步抑制时钟信号的低频噪声,保证了高质量的时钟输出。实验中,利用这种装置对40 Gb/s归零(RZ)码信号进行了时钟提取,得到了抖动为285 fs的高质量40 GHz时钟信号,验证了方案的可行性。     

采用F-P光纤环滤波器的窄线宽环形腔光纤激光器

提出了一种采用F-P光纤环滤波器的窄线宽环形腔激光器,该激光器采用环形腔结构,两个耦合比为30:70的耦合器和一段2 m长的未泵浦掺铒光纤构成F-P光纤环滤波器,F-P光纤环滤波器产生的梳状谱,可以增大激光模式之间的自由光谱范围（FSR）,在一定程度上减小跳模现象的发生,有利于模式的稳定。研究表明,通过对掺铒光纤的优化和耦合器的选择可以提高F-P光纤环滤波器的精细度,而F-P光纤环中的未泵浦掺铒光纤起到饱和吸收体的作用,使输出激光的线宽得到有效压缩。将保偏光纤光栅和F-P光纤环滤波器共同应用于环形腔掺铒光纤激光器,在室温下得到了3 dB线宽均小于0.07 nm（实验室光谱仪最小分辨率）的窄线宽双波长输出。在2 h的观测时间内,最大峰值功率波动小于0.4 dB,具有良好的稳定性。     

Standard-compliant jitter transfer function of all-optical clock recovery at 40 GHz based on a quantum-dot self-pulsating semiconductor laser

This letter reports on all-optical clock recovery over 40-Gb/s signal using a quantum-dot (QD)-based self-pulsating (SP) laser. In particular, the jitter transfer function from the input signal to the recovered clock is measured for the first time. We clearly demonstrate that, thanks to the narrow spectral linewidth of the free-running SP signal, the QD-based laser allows the suppression of high frequency jitter, and the cutoff frequency is exactly that required by the ITU-T recommendation G825.1 at 40 GHz.     

A tunable dual-wavelength erbium-doped fiber ring laser using a self-seeded Fabry-Perot laser diode

A tunable dual-wavelength erbium-doped fiber ring laser using a self-seeded Fabry-Perot laser diode (FP-LD) is proposed and demonstrated. By adding an FP-LD incorporated with a tunable bandpass filter within the ring cavity, the fiber laser can lase two wavelengths simultaneously because of the self-seeded mechanism. This dual-wavelength output exhibits a good performance having the optical side-mode suppression ratio over 31 dB. The wavelength-tuning range of this tunable dual-wavelength fiber laser can be up to 9 nm.     

基于光纤环镜的被动锁模飞秒脉冲光纤激光器

在当前的高速光通信系统中,光源的选择至关重要。文章分析了光纤环镜的非线性传输特性,论述了利用光纤环激光器锁模产生超短脉冲的原理。     

All-optical clock recovery from RZ-format data by using a two-section gain-coupled DFB laser

High-speed all-optical clock recovery using a two-section gain-coupled distributed feedback laser is demonstrated operating in the coherent and the incoherent modes. It is found that the coherent mode has a much better performance compared with the incoherent mode. The performance of the coherent clock recovery scheme at 12 and 40 Gb/s, including wavelength and polarization insensitivity, timing jitter, and phase noise; power penalty; sensitivity; dynamic range; locking bandwidth; detuning range of the injection wavelength; and lockup time are described in detail. A comparison between the performances of the two modes of operation is also presented.     

160-gb/s optical clock recovery using a regeneratively mode-locked laser diode

Line rate optical clock recovery at 160-Gb/s has been demonstrated based on injection-locking and optical time-division multiplexing of a 40-GHz regeneratively mode-locked laser diode (RML-LD). Injection-locking is achieved by directly coupling the 160-Gb/s data streams to a photodetector in the RML-LD feedback loop. The pulsewidth and root-mean-square timing jitter of the recovered clocks are 2.31 ps and 225 fs (10 Hz-40 MHz), respectively.     

Bit rate and wavelength transparent all-optical clock recovery scheme for NRZ-coded PRBS signals

All-optical clock recovery from 40-Gb/s nonreturn-to-zero (NRZ) pseudorandom binary sequence data streams based on self-pulsating lasers is presented. A compact preprocessing circuit is utilized to convert an NRZ signal to a pseudoreturn-to-zero sequence before injecting into the optical clock. It comprises a semiconductor optical amplifier followed by a periodical wavelength-division-multiplexing demultiplexer filter. A stable sinusoidal clock signal with a root-mean-square jitter below 700 fs is detected at the output of the self-pulsating laser within data dynamic range of more than 8 dB. The performance of the all-optical clock recovery scheme is investigated by varying the bit rates between 39.81 and 43.02 Gb/s as well as for various wavelengths in the C-band.     

Frequency pulling in a Brillouin fiber ring laser

The lasing frequencies of a Brillouin fiber ring laser are shifted slightly from the resonant frequencies of the cold fiber ring resonator due to the optical Kerr effect and the nonlinear phase shift associated with stimulated Brillouin scattering (SBS) used as the gain mechanism in this type of laser. These frequency pulling effects are investigated in detail both theoretically and experimentally. The results of this study are useful in many Brillouin fiber ring laser applications such as Brillouin fiber optic gyroscopes, microwave generators, and frequency shifters. To the authors' knowledge this is the first time the frequency pulling effect caused by the nonlinear phase shift associated with SBS is reported     

L-band tunable erbium doped fiber ring laser using fiber loop mirror filters

We present a novel and efficient L-band wavelength-tunable Er^3＋ doped fiber laser of ring structure. In the cavity two segments of Er^3＋ doped fiber and a fiber Bragg grating are used to improve pump efficiency. Tunable filters based on fiber loop mirrors are also applied inside the cavity to act as both a wavelength selector and a line-width compressor. Using these techniques, a tunable laser with tuning range up to 42 nm, output power larger than 1 mW, power uniformity controlled within 1.75 dB and side mode suppression ratio about 40 dB is achieved.     

Smoothly wavelength-tunable picosecond pulse generation using a harmonically mode-locked fiber ring laser

A simple design of a stable, smoothly wavelength-tunable picosecond pulse generator has been demonstrated using a dispersion-tuned, harmonically mode-locked fiber ring laser with a directly modulated semiconductor optical amplifier (SOA). The SOA functions as both a polarization-insensitive mode locker and a supermode noise suppressor. Near-linearly chirped pulses are generated and compressed to less than 4 ps when the intracavity dispersion is anomalous while 11-ps, near-transform-limited pulses are generated without compression when the dispersion is normal. Smooth wavelength tuning is achieved over more than 11 nm by only tuning the modulation frequency and pulse characteristics are stable over the entire tuning span. A simple numerical model successively simulates the operation principle of the system. The tuning range is determined by both the gain profile and the total intracavity dispersion. The dispersion and the SOA ensure the long-term stability of the system.     

Jitter reduction in self-sustaining monostable clock recovery circuit

A simple circuit modification is presented for reducing the output jitter of the self-sustaining monostable multivibrator clock recovery circuit. Jitter is reduced by preventing the monostable multivibrator from being triggered by pulses that arrive early. Experimental results in a fibre-optic system employing the Petrovic code show that, with this modification, the jitter variance can easily be reduced by a factor of 6.     

基于EAM四波混频效应的光锁相环时钟提取系统

对光锁相环的原理和分类进行了介绍,并提出了一种基于EA调制器四波混频效应的新型光锁相环时钟提取方案,从40/80Gb/s的OTDM光数据信号中提取出同步的10Gb/s时钟信号,是一种具有速率灵活性、宽带特性和高速扩展潜力的时钟提取系统.     

Study of phase-noise properties and timing jitter of 40-GHz all-optical clock recovery using self-pulsating semiconductor lasers

This paper reports on timing-jitter analysis of an all-optical clock-recovery scheme at 40 GHz using self-pulsating (SP) lasers. Based on the analogy with injection locking of oscillators, theoretical investigations on phase-noise properties of the recovered clock lead to the demonstration of a filtering function with slope that is compliant with the International Telecommunications Union (ITU) standards and allow us to underline the dependence of the cutoff frequency of the filtering transfer function on the spectral linewidth of the free running SP laser. From this phase-noise analysis, an analytical expression of the timing jitter of the recovered clock is derived, including the optical signal-to-noise ratio (OSNR) of the injected signal. A set of experiments on all-optical clock recovery at 40 GHz is then presented and demonstrates the crucial role of the spectral linewidth on the timing-jitter-filtering function of the SP laser. In good agreement with theoretical results, the impact of the OSNR degradation of the injected signal on the timing jitter is also demonstrated. Finally, the all-optical clock-recovery operation using a quantum-dot SP laser is shown to be standard compliant in terms of timing jitter, even for highly degraded OSNR.     

Wavelength-switchable erbium-doped fiber ring laser using spectral polarization-dependent loss element

We propose a wavelength-switchable erbium-doped fiber ring laser that uses a spectral polarization-dependent loss element. The element was fabricated by inscribing a long-period grating on a polarization-maintaining fiber. Dual-wavelength switching operation was accomplished by rotating the polarization plane of the fiber laser cavity. The amplitude variation of both laser lines was measured to be less than 1 dB and the signal-to-amplified spontaneous emission ratio was more than /spl sim/40 dB.