Narrowband phase sensitive fiber parametric amplifier

We describe a widely tunable phase sensitive fiber amplifier, based on narrowband parametric amplification in dispersion shifted fiber. Using a fiber with a zero dispersion wavelength of 1549?nm and a pump wavelength in the range of 1549?nm to 1532?nm, we obtained phase sensitive amplification between 1344?nm and 1781?nm, for an overall wavelength range of 437?nm. The amplifier threshold power is 7?W, and the maximum gain is 50?dB at a pump peak power of 25?W. The variance in gain due to phase sensitivity was measured to be up to 15?dB.     

双泵浦光子晶体光纤参量放大研究

利用光子晶体光纤在不同零色散波长附近具有不同色散的特性,研究了在零色散波长为780 nm和1550 nm附近的双泵浦光子晶体光纤参量放大过程.在780 nm附近,讨论了零色散波长变化对双泵浦光子晶体光纤参量放大的影响.数值模拟结果表明:当零色散波长发生微小的变化时,信号增益谱带宽会发生很大的变化.当两泵浦光之间的波长差值减小时,零色散波长的变化对参量放大的影响在很大程度上可以得到抑制,但是增益带宽会有一定的减小.依据这一原理,在1550 nm附近设计光子晶体光纤中的色散平坦光纤参量放大,在5 m长的光子晶体光纤中,当峰值功率为10 W时,得到了增益为65 dB,带宽达到420 nm且极为平坦的增益谱.     

Broadly tunable femtosecond parametric oscillator using a photonic crystal fiber

Pulses as short as 460 fs and a tuning range as wide as 200 nm around 1 microm have been achieved from a photonic-crystal-fiber-based parametric oscillator. The ring cavity with only 65 cm of photonic crystal fiber is synchronously pumped with a tunable passively mode-locked Yb-doped fiber laser. Widely extended tunability is achieved by using the modulation instability gain in normal dispersion as the result of high-order dispersion in the photonic crystal fiber.     

基于光纤光参量放大的异步双波长全光再生技术研究

本文提出了一种新型的多波长全光再生方案,利用相位时钟光纤光参量放大,并采用相邻信道偏振正交的方法,实现对由异步信源产生的双波长信号全光再生.理论分析了参量放大中的增益饱和现象用于幅度噪声抑制,以及利用相位时钟及后续色散实现对信号定时的机理.在这个基础上,对两个独立信源产生的异步双波长10Gbit/s信号进行再生实验,实验表明该方案有效的抑制了基于多波长3R再生系统中信道间的四波混频与交叉相位调制等非线性干扰.系统在单波长和双波长情况下分别将两路信号信噪比改善了至少6.5dB与4.5dB.误码率测试结果说明,与背对背测试结果相比,无论是在单波长还是双波长条件下,两路波长的信号经过再生后都实现了约2dB的接收机功率代价的改善.     

Widely tunable femtosecond fiber optical parametric oscillator

The phase-matching condition in a fiber is discussed. A balance among the different orders of fiber dispersion can be found to achieve a widely tuning modulation instability gain for pumping around the normal dispersion regime. Three coupled nonlinear wave equations are used to simulate the femtosecond fiber optical parametric oscillator. The numerical results show that, through appropriate choice of dispersion, femtosecond pulses with a 180-nm tunable range can be generated when pump wavelength near a fiber’s zero-dispersion wavelength is tuned only 7 nm. Further tuning is limited by the walk-off between the pump and the signal pulses.     

Raman effects in a highly nonlinear holey fiber: amplification and modulation

We experimentally demonstrate that a short length of highly nonlinear holey fiber (HF) can be used for strong L(+) -band (1610-1640-nm) Raman amplification and ultrafast signal modulation. We use a pure silica HF with an effective area of just 2.85mum(2) at 1550 nm, which yields an effective nonlinearity ~15 times higher than in conventional silica dispersion-shifted fiber. Using a 75-m length of this fiber, we obtained internal Raman gains of more than 42 dB and a noise figure of ~6 dB under a forward single-pump scheme, and the Raman gain coefficient was experimentally estimated to be 7.6 chi 10(-14)m/W . Also, an 11-dB signal extinction ratio in a Raman-induced all-optical modulation experiment was achieved with the same fiber.     

Ytterbium gain band self-induced modulation instability laser

We demonstrate an ytterbium gain band self-induced modulation instability laser. A highly nonlinear holey fiber is used to provide the anomalous dispersion required for bright soliton generation at 1 microm. The all-fiber integrated source yields a 40 GHz train of 4 ps pulses at a wavelength of 1064 nm.     

Noncollinear optical parametric amplification in lithium triborate seeded by a cw Ti:sapphire laser

Experimental investigations of a type-I noncollinear phase-matched optical parametric amplification based on lithium triborate, which was pumped by a 5-ns second-harmonic pulses from a Q-switched Nd:YAG, seeded by a cw Ti:sapphire laser at 800 nm, was presented. The experiments generated 2-ns signal output pulses at 800 nm, the maximum signal output pulse energy reached 19 μJ, the corresponding parametric gain was 44 dB. Furthermore, the experiments demonstrate that the 65 nm-FWHM parametric fluorescence gain spectrum could also be observed. A quantitative account of the ultrabroadband parametric fluorescence gain spectrum was given with our theory. The experimental measurements are in agreement with theoretical calculations.     

Modulational instability and parametric amplification induced by loss dispersion in optical fibers

We show that modulational instability may arise even in the normal group-velocity dispersion regime of an optical fiber when the fiber loss (gain) varies depending on the wavelength. A simple analytical expression for the instability gain is obtained, which reveals that the odd-order terms of the loss dispersion are responsible for this phenomenon. The instability gain is measured experimentally in an optical-parametric-amplification configuration. Large parametric gain is induced in a non-phase-matched regime as we apply narrow band loss at the idler wavelength.     

Experimental realization of a novel dispersion- compensating optical fiber amplifier for simultaneous compensation of positive dispersion and losses

Erbium-doped dispersion-compensating optical fiber (EDCF) has been theoretically simulated and experimentally fabricated using Modified Chemical Vapor Deposition (MCVD) for optimum operation at 5.0km. It is optimized for both gain as well as negative dispersion. The erbium has been doped into the cladding region while the core of the optical fiber is chosen to be narrow so as to have a high negative dispersion. Measured gain of 3.1 dB at 200 m using 100 mW pumping power (980 nm wavelength) at 1550 nm has been obtained and the gain of 32 dB at 5.0 km using same pumping scheme has been predicted. The chromatic dispersion of this EDCF has been also measured to be –43.5 ps/km-nm at 1550 nm and thus, providing the dispersion of –217.5 ps/nm at 5 km. The bend-induced losses are found to be negligible. We are the first to report the experimental realization of EDCF.     

WDM系统中ASE噪声的二阶色散效应

讨论了采用小信号分析法研究脉冲波在色散、非线性光纤中的传输时,放大的自发辐射(ASE)噪声作为功率调制项加入脉冲波的传输方程后所产生的效应.ASE噪声不仅被互相位调制不稳定增益所放大,还受二阶色散成分的影响.其传输函数为COS(1/2β2dzω2),这一函数不能通过色散补偿来消除,会削弱ASE噪声的影响.鉴于此,ASE...     

Influence of the structure parameters on the gain and noise figure in silicon parametric amplifiers based on SOI Rib waveguides

Gain and Noise figure (NF) characteristics in dual-pump parametric amplifier based on silicon on insulator (SOI) Rib waveguides are numerically investigated in the presence of nonlinear losses. The impact of structure parameters of the silicon optical parametric amplifiers (SOPAs) on the gain and the NF are also analyzed. The results show that both the height and the width of the silicon on insulator (SOI) can affect the gain and the NF of SOPAs. 354 nm bandwidth (3 dB) and 8.135 maximum gain can be achieved by tailoring the structure parameters of the SOI rib waveguides. Moreover, the dispersion and the effective mode area of SOI are also analyzed.     

Strong signal suppression in single-pump optical parametric amplifiers

We show that the combined action of parametric gain and Raman scattering can lead to the complete suppression of an input optical signal in a single-pump parametric amplifier. This suppression is due to an interference between the two parametric gain modes. The interference occurs only at a set of discrete combinations of pump power, phase mismatch, and frequency detuning. Experimentally we are able to demonstrate over 95% (13 dB) suppression of an input signal in an amplifier with a peak parametric gain of only 6 dB.     

Theoretical study of gain distortions in dual-pump fiber optical parametric amplifiers

We study analytically and numerically the small signal gain in dual-pump fiber optical parametric amplifiers by including the phase modulation of the pump waves needed for practically increasing the stimulated Brillouin scattering threshold. As for the single-pump case, we show that large signal gain distortions are generated under co-phase modulation, which depend on the rise/fall time of the phase modulation and on the fiber dispersion slope. However, it is clearly confirmed that the counter-phase modulation scheme allows to efficiently suppress these gain distortions over the whole flat gain region. In addition, we demonstrate through realistic numerical simulations that this useful technique overcomes the additional impact of pump-phase modulation to amplitude modulation conversion and zero-dispersion wavelength variations.     

Improved chromatic dispersion monitoring technique

We consider and investigate an improved chromatic dispersion monitoring method using two RF tones with an inserted dispersion offset. This improved technique can be used to monitor both the positive and negative accumulated dispersion caused by optical fibers as well as other optical components in optical networks. We experimentally demonstrate that the monitoring range of the improved technique can be greater than 1150 ps/nm and the monitoring sensitivity better than 0.064 dB/ps/nm by selecting appropriate RF frequencies and dispersion offsets. Our investigations reveal that the RF modulation index should be greater than 10% but less than 20% so as to acquire a large monitoring range with a small power penalty. We also examine the CD monitoring errors caused by polarization mode dispersion (PMD) and self-phase modulation, and show that the use of a dispersion offset can effectively reduce the PMD-induced monitoring errors.     

色散缓变光纤中的调制不稳定性分析

研究了色散缓变光纤中调制不稳定效应,得到了增益谱与光纤纵向色散参量的一般关系式.结果表明,色散缓变光纤较常规光纤具有较宽的增益谱.选取色散级变光纤的色散参量可以获得较大的增益带宽.数值模拟显示,利用色散缓变光纤中的调制不稳定性可以产生高重复率的基本孤子脉冲串.     

Modulation instability of femtosecond pulses in fibres with slowly decreasing dispersion

In this paper,we investigate the modulation instability for generating femtosecond pulses in fibres with slowly decreasing dispersion.Higher-order dispersion and higher-order nonlinear effects are taken into account when the continuous wave or quasi-continuous wave evolves into sub-picosecond and femtosecond pulses by modulation instability in the optical fibres.Our research results show that the gain spectrum of the dispersion-decreasing fibres is much wider than that in conventional fibres.The third-order dispersion effect has no contribution to gain spectrum,while the self-steepening effect reduces the maximum value and gain bandwidth,and the Raman self-scattering effect widens the extent to which the modulation instability occurs.     

Dual-wavelength, two-crystal, continuous-wave optical parametric oscillator

We report a cw optical parametric oscillator (OPO) in a novel architecture comprising two nonlinear crystals in a single cavity, providing two independently tunable pairs of signal and idler wavelengths. Based on a singly resonant oscillator design, the device permits access to arbitrary signal and idler wavelength combinations within the parametric gain bandwidth and reflectivity of the OPO cavity mirrors. Using two identical 30 mm long MgO:sPPLT crystals in a compact four-mirror ring resonator pumped at 532 nm, we generate two pairs of signal and idler wavelengths with arbitrary tuning across 850-1430 nm, and demonstrate a frequency separation in the resonant signal waves down to 0.55 THz. Moreover, near wavelength-matched condition, coherent energy coupling between the resonant signal waves, results in reduced operation threshold and increased output power. A total output power >2.8 W with peak-to-peak power stability of 16% over 2 h is obtained.     

Continuous-wave-pumped Raman-assisted fiber optical parametric amplifier and wavelength converter in conventional dispersion-shifted fiber

We present a continuous-wave-pumped fiber optical parametric amplifier, operating near 1539 nm in conventional dispersion-shifted fiber, with maximum on-off gain and wavelength-conversion efficiency of 13.7 and 13.1 dB, respectively. In addition, we show a novel configuration based on Raman amplification assistance in the parametric gain fiber that further increases the gain and wavelength-conversion efficiencies to 16.7 and 16.2 dB, respectively.     

Amplification of 12 × 10 Gb/s WDM signals with negligible FWM crosstalk in a double-pumped fiber optical parametric amplifier

We report on the amplification of 12 × 10 Gb/s wavelength-division-multiplexed signals by a double-pumped fiber optic parametric amplifier (2P-FOPA). A gain of 10 dB is obtained using a 4.3 km-long conventional dispersion shifted fiber (DSF) as nonlinear medium. Our spectra show negligible generation of spurious FWM products, and we attribute this to the small variations of the zero-dispersion wavelength of the DSF. The 2P-FOPA performance is assessed through Q-factor measurements, and we show that for output powers per channel ranging from −15 to 3 dBm the power penalty is less than 0.5 dB.