Widely tunable all-optical wavelength converter based on four-wave mixing using two orthogonally polarized pumps

The principle of broad-band orthogonal-pump (BOP) four-wave mixing in semiconductor optical amplifiers is analyzed in theory. The conversion efficiency reduces rapidly as the detuning of wavelength between the signal and pump increase which can be solved by introducing a BOP method. The constant conversion efficiency and signal-to-noise ratio are obtained over a large wavelength detuning range. The wavelength conversion efficiency with variation smaller than 3.88 dB over 52-nm range has been experimentally demonstrated by using BOP, with the 10-GHz output of distributed feedback/electro-absorption modulator as signal. Conventional single-pump scheme is also performed for comparison and the experimental results fit well with the theory.     

A Novel Method for Wavelength Conversion with Dual-pump Four-wave Mixing in a Semiconductor Optical Amplifier

Using a semiconductor-fiber ring laser, a novel method for the all optical wavelength conversion based on dual-pump four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) is demonstrated. For the input signal with different wavelengths, only one external pump is needed. This scheme can simplify the dual-pump FWM in SOA and has nearly constant conversion efficiency and signal-to-noise ratio (SNR) over 50nm range of wavelength shifts.     

FWM conversion with pump suppression for filterless optical packet switching applications

The use of a Pump-Suppressed Four Wave Mixing PS-FWM wavelength converter in a wavelength conversion and selection switching scheme is examined and demonstrated. The scheme requires a single 2 × 1 Mach Zenhder Interferometer (MZI) and offers substantial pump suppression and efficiency improvement in terms of optical signal-to-noise ratio. Performance measurements on the combination of PS-FWM wavelength converter with an Arrayed Waveguide Grating (AWG) for passive routing, shows the potentially successful use of the scheme in an ultra-fast wavelength routed optical packet switching scheme where the use of optical filters for the separation of the converted signal from the pump is avoided.     

Comparative Study of the Signal-to-Noise Ratio and Gain in Photorefractive Materials

We calculate the dependence of the signal-to-noise ratio and gain on the angle α between the pump and signal beams and the beam ratio β in Cu-doped potassium-sodium-strontium-barium niobate (Cu:KNSBN) crystal and compare them with the experimental results available in the literature. We find good qualitative agreement between the calculated and experimental results. Also we study variations of SNR and gain with α and β in BaTiO₃ crystal. Experimental data for this crystal are not available.     

A Novel Method for Wavelength Conversion with Dual-pump Four-wave Mixing in a Semiconductor Optical Amplifier

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All-Optical Wavelength Conversion Based on Four-Wave Mixing in Dispersion-Engineered Silicon Nanowaveguides

We demonstrate experimentally all-optical wavelength conversion based on four-wave mixing in dispersion-engineered silicon nanowaveguides with a picosecond pulse pump. We find that the conversion efficiency is significantly limited by nonlinear losses induced by the two-photon absorption and freecarrier absorption. Using a picosecond pulse pump centered at 1,550 nm, we show that the input continuous-wave signals can efficiently be converted into a broadband idler pulse in silicon waveguides with various dimensions. Conversion efficiencies versus signal wavelengths are different for silicon waveguides with different dimensions due to the variation in the phase mismatch; we obtain a conversion efficiency of – 32 dB in silicon nanowaveguides with a length of 5.8 mm. Such on-chip optical wavelength converters can find important potential applications in highly-integrated optical circuits for all-optical ultrafast signal processing.     

On the polarisation sensitivity and performance optimisation of a dual pump four wave mixing based wavelength converter

This paper presents a detailed investigation of the performance of a wavelength conversion scheme. The converter is based on four wave mixing in semiconductor optical amplifiers using two parallel polarised pumps. Measurements of the conversion efficiency and the signal to background noise ratio of the two replicas of the signal, for the cases of the signal polarisation being either parallel or orthogonal relative to the pump waves have been carried out. These measurements will reveal the polarisation sensitivity of this scheme which appears to be less than 1 dB when the wavelength spacing between the signal and its closest spaced pump is larger than 12 nm. The experimental results are supported in a satisfactory way by theoretical considerations. A simple theoretical expression describing the polarisation sensitivity have been derived and the theoretical results are in good agreement with those experimentally obtained. A performance comparison of the conversion scheme using semiconductor optical amplifiers with different lengths but the same structure is also performed. Through the following study the optimum operational conditions for this wavelength conversion scheme will be determined.     

分布式反向抽运光纤拉曼放大器的功率转换效率分析

为了对反向抽运光纤拉曼放大器的功率转换效率进行研究,由耦合方程出发,采用龙格库塔算法和打靶法相结合的数值模拟方法,详细分析所有物理因素对反向抽运光纤拉曼放大器功率转换效率的影响。结果表明:功率转换效率先随着光纤长度增加而增加,当增加到最大值时保持数值不变;功率转换效率随着初始信号光功率、光纤拉曼增益系数、信号光损耗系数增加而增加,随着光纤有效面积、抽运光损耗系数、抽运光与信号光的频率比增加而减小;功率转换效率和初始抽运光功率呈抛物线曲线关系。所得结论对反向抽运光纤拉曼放大器功率转换效率的进一步研究以及光纤拉曼放大器的其他相关研究有重要参考意义。     

基于信号抽运的光纤光参量放大的全光3R再生系统

本文研究了利用恶化信号作为抽运的光纤光参量放大效应(FOPA)进行全光判决的全光3R(再放大、再整形、再定时) 再生实验方案,理论上分析了在不同的抽运功率条件下时(分别对应"0"和"1"码)参量放大抑制噪声的不同机理,表明选用合理的实验参数可以同时对"0","1"码噪声进行抑制.实验中利用高Q值的法布里-珀罗(F-P)滤波器提取了均方根(RMS)抖动仅为180 fs的40 GHz时钟;完成了对40 bit/s的单波长恶化信号的全光判决实验,将恶化信号的信噪比从4.52改善为11.43.实验验证了理论分析的 关键词： 光纤通信 3R再生 光纤光参量放大 全光判决     

Wavelength conversion by use of four-wave mixing in a novel optical loop configuration

A novel loop configuration for generation of four-wave mixing (FWM) and suppression of input pump wave, signal wave, and amplified spontaneous emission is proposed and experimentally demonstrated. The novel loop configuration is very simple and functions independently of the wavelengths of the pump and the signal waves. By use of the novel loop configuration, nonreturn-to-zero wavelength conversion at 10 Gbits/s is achieved. The FWM-to-pump ratio, the FWM-to-signal ratio, and the signal-to-noise ratio are improved by 17.9, 18.8, and 8.2 dB, respectively. A principle experiment of wavelength conversion of four simultaneous channels is demonstrated.     

20-Gb/s and Higher Bit Rate Optical Wavelength Conversion for RZ-DPSK Signal Based on Four-Wave Mixing in Semiconductor Optical Amplifier

Abstract

We investigate 20 Gb/s wavelength conversion for return-to-zero differential phase-shift keying (RZ-DPSK) signal using four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). We show that the 10-Gb/s RZ-DPSK signal-to-pump ratio increases up to ?0.286 dB with Q factor improvement of 1.663 dB for increasing the cascadeability of optical networks. The effect of variation in bandwidth for an ideal dual-arm Mach-Zehnder interferometer (MZI) is illustrated. For different bit rates, the converted power signal is investigated with increase in signal input power. We show that the quality of converted signal is best before the saturation of SOA. The dependence of four-wave mixing (FWM) efficiency and converted signal power with signal input power is also studied, and it is found that FWM efficiency decreases with increase in signal input power.

The impact of signal-to–pump power ratio, unsaturated amplifier gain, and pump power is further optimized with minimum Q factor penalty for 10-Gb/s and 20-Gb/s bit rate. We show that converted signal power increases up to power saturation level and then starts decreasing. We also show that with higher bit rate, we have a wide range of choices for pump power signal. We further investigate the quality of converted signal at 10 Gb/s, which shows an improvement over signal input power. Finally, the increase in transmission distance after wavelength conversion is investigated.     

Amplitude Regenerative Characteristics of RZ-DPSK Wavelength Converter Based on Four-Wave Mixing in SOA

We investigate the phase-preserving amplitude regenerative characteristics of the return-to-zero （RZ） differential- phase-shift-keying （DPSK） wavelength conversion based on four-wave m/xing （FWM） in a semiconductor optical amplifier （SOA）. The Q-factor and the optical signal-to-noise ratio （OSNR） before and after conversion are experimentally obtained and analysed in different input noise power levels. In both the continuous-wave and synchronous clock pumping cases, we find that there is amplitude clamping in the FWM conversion due to the gain saturation of SOA, which can suppress the amplitude fluctuation of the converted DPSK signal before and after demodulation. We have achieved 2-dB Q penalty improvement in our experiment demonstration of lOGbit/s RZ-DPSK signal with OSNR lower than 19dB.     

Stochastic resonance of bias signal-modulated noise in a single-mode laser＊

Stochastic resonance (SR) for bias signal modulation is studied in a single-mode laser system. By investigating a gain-noise model driven by correlated pump noise and quantum noise, we find that, whether the correlation coefficient between both the noises is positive or negative, SR always appears in the dependence of signal-to-noise ratio (SNR) upon the noise correlation time and the frequency of the modulation signal. However, only when the correlation coefficient between both noises is negative can SR occur in the dependence of SNR upon the quantum noise intensity and pump noise intensity, while when the correlation coefficient between both noises is positive, it shows monotonically.     

一级近似下的双模激光随机共振

将周期信号输入双模激光,对激光光强方程中的乘法噪声项取一级近似,用线性化近似方法计算相关函数和功率谱,结果发现:信噪比随抽运噪声强度、量子噪声强度及信号频率的变化均出现随机共振.     

Parametric amplification of chirped optical pulses under pump depletion

We present simple analytical solutions of coupled wave equations describing chirped pulse parametric amplification under pump depletion. The evolution of the duration and spectrum of amplified pulses in OPA pumped by Gaussian and supergaussian pulses has been investigated both numerically and analytically. Also, the dependence of the energy conversion efficiency from pump to signal was determined for a range of parameter values, and an optimum ratio of signal and pump pulse durations was evaluated.     

20-Gb/s and Higher Bit Rate Optical Wavelength Conversion for RZ-DPSK Signal Based on Four-Wave Mixing in Semiconductor Optical Amplifier

We investigate 20 Gb/s wavelength conversion for return-to-zero differential phase-shift keying (RZ-DPSK) signal using four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). We show that the 10-Gb/s RZ-DPSK signal-to-pump ratio increases up to -0.286 dB with Q factor improvement of 1.663 dB for increasing the cascadeability of optical networks. The effect of variation in bandwidth for an ideal dual-arm Mach-Zehnder interferometer (MZI) is illustrated. For different bit rates, the converted power signal is investigated with increase in signal input power. We show that the quality of converted signal is best before the saturation of SOA. The dependence of four-wave mixing (FWM) efficiency and converted signal power with signal input power is also studied, and it is found that FWM efficiency decreases with increase in signal input power.

The impact of signal-to-pump power ratio, unsaturated amplifier gain, and pump power is further optimized with minimum Q factor penalty for 10-Gb/s and 20-Gb/s bit rate. We show that converted signal power increases up to power saturation level and then starts decreasing. We also show that with higher bit rate, we have a wide range of choices for pump power signal. We further investigate the quality of converted signal at 10 Gb/s, which shows an improvement over signal input power. Finally, the increase in transmission distance after wavelength conversion is investigated.     

Wavelength Converter Using Semiconductor Optical Amplifier Mach-Zehnder Interferometer Based on XPM at 40 Gb/s for Future Transport Networks

Abstract

We have simulated, for the first time, wavelength converter for future broadcast networks at 40 Gb/s using low-cost semiconductor optical amplifiers. The performance analysis is carried out for an all-optical frequency converter based on cross-phase modulation in two semiconductor optical amplifiers arranged in a Mach-Zehnder interferometer configuration to evaluate the efficiency of conversion. The results, evaluated analytically for input, return to zero signal at a bit rate of 40 Gb/s show that conversion is possible over a wavelength separation of 1 nm between the pump and the input wavelength. Increasing the driving current can decrease the cross-phase modulation effect. The cross gain modulation scheme shows extinction ratio degradation for conversion to longer wavelengths.     

双向抽运拉曼光纤放大器性能的研究

对双向抽运拉曼光纤放大器(RFA)的噪声特性、增益饱和及抽运功率转换效率进行了详细研究。结果表明,双向抽运拉曼光纤放大器的噪声特性介于前向抽运与后向抽运之间,但主要取决于前向抽运方式所导致的噪声特性;双向抽运方式的饱和功率低于单向抽运方式的饱和功率,同前向抽运与后向抽运提供的增益比例有关;双向抽运方式的抽运功率转换效率同信号光功率及前、后向抽运提供的增益有关,当信号光功率较低时,增加前向抽运的比例可取得较高的抽运功率转换效率,而信号光功率较高时,增加后向抽运的比例可取得较高的抽运功率转换效率。研究一种配置(情况3)的双向抽运拉曼光纤放大器,可以完全补偿100km传输线路的损耗(包括无源器件的损耗),最低光信噪比为30．21dB。     

Multiwavelength NRZ-to-RZ conversion with significant timing-jitter suppression and SNR improvement

We demonstrate a novel, polarization-insensitive scheme for multiwavelength nonreturn-to-zero to return-to-zero format conversion at 10 Gb/s rate with significant timing-jitter suppression and signal-to-noise ratio improvement. The scheme utilizes a self-starting electroabsorption-modulator based optoelectronic oscillator that simultaneously generates a 10 GHz-rate microwave signal and a train of 15 ps-wide optical pulses with 40 fs timing jitter (100–10 MHz range). Under direct optical injection locking of the oscillator with an incoming data stream, we demonstrate the extraction of a high-quality clock that enables in-line format conversion of multiple, synchronized nonreturn-to-zero channels.     

Experimental demonstration of novel end-pumping method for double-clad fiber devices

We present experimental demonstration of an end-pumping scheme based on splicing the multimode pump and single-mode signal fibers directly to a double-clad fiber with a tailored cross section. The method is used to pump a double-clad, erbium- and ytterbium-doped, fiber ring laser. The efficiency of the end-pumping method is tested by determining the slope efficiencies of the fiber ring laser and the fiber laser in a Fabry-Perot configuration. Comparable slope efficiencies are found when both laser configurations have similar output coupler ratios. The developed pumping scheme and double-clad fiber can find applications in cost-effective power fiber amplifiers and lasers.