WDM-Based Passive Optical Network Upstream Transmission at 1.25 Gb/s Using Fabry–PÉrot Laser Diodes Injected With Spectrum-Sliced, Depolarized, Continuous-Wave Supercontinuum Source

We experimentally demonstrate the use of low-cost Fabry–PÉrot laser diodes (FP-LDs) injected with spectrum-sliced beams from our proposed, depolarized, high-power, continuous-wave (CW) supercontinuum (SC) for upstream transmission in a wavelength-division-multiplexed (WDM) passive optical network. A$sim$500-mW CW SC with a$sim$130-nm bandwidth is obtained from a narrowband, amplified spontaneous emission (ASE) seed of a pumped erbium fiber by nonlinear effects such as modulation instability and stimulated Raman scattering in a highly nonlinear optical fiber. Through measurements of relative intensity noise at various wavelengths, it is shown that our spectrum-sliced SC offers the same performance as the spectrum-sliced erbium ASE. Error-free 25-km upstream transmission for six WDM signals generated from the CW SC-injected FP-LDs, is readily achieved at 1.25 Gb/s.     

Supercontinuum Generation in Normal-dispersion Photonic Crystal Fiber Using Picosecond Pulse

Studied is the Super-continuum （SC） generation of a normal-dispersion photonic crystal fiber （PCF） using picosecond pulse excitation. In experimental analyses, a 237 nm broadband infrared continuum was generated pumped at 1 550 nm（normal dispersion regime） by 1.6 ps pulses from an erbium-doped fiber laser. In addition, we conduct the numerical analyses of SC based on generalized nonlinear Schr dionger equation. The results have been applied to investigate the dominant physical processes underlie the generation - of SC. We conclude that dispersion, self-phase modulation （SPM）, four-wave-mixing （FWM） and Raman scattering are determinants of SC generation rather than fission of soliton in normal-dispersion PCF.     

Experimental Study on the Role of Chromatic Dispersion in Continuous-Wave Supercontinuum Generation

The influence of chromatic dispersion on continuous-wave (CW)-pumped supercontinuum (SC) generation in kilometer-long standard fibers is experimentally investigated. We perform our study by means of a tunable, high-power fiber ring laser pumping a dispersion-shifted fiber in the wavelength range of small and medium anomalous dispersion. Our results show that, at low input powers, chromatic dispersion plays a dominant role on nonlinear pump spectral broadening, giving rise to a broader spectrum when pumping just above the zero-dispersion wavelength of the fiber. At higher input powers, however, the width of the generated SC spectrum is mostly due to the Raman effect, hence more independent of the value of the chromatic dispersion coefficient. We show that, in this case, the optimum pumping wavelengths for SC generation are not so close to the zero-dispersion wavelength of the fiber as in the previous case. In these conditions, as the chromatic dispersion grows, we can obtain square-shaped and high-power density spectra, which seem extremely promising for applications in optical coherence tomography.      

Extended-reach WDM-PON based on CW supercontinuum light source for colorless FP-LD based OLT and RSOA-based ONUs

We investigate the benefits of using our proposed continuous-wave supercontinuum (CW SC) as a broadband wavelength-locking source for the implementation of extended-reach, colorless, wavelength division-multiplexed passive optical networks (WDM-PONs). More specifically, first, an extended reach WDM-PON architecture based on both the CW SC and our devised C-/L-band beam combiner is proposed, in which the optical line terminal (OLT) is based on Fabry–Pérot laser diodes (FP-LDs), whereas the optical network units (ONUs) are reflective semiconductor optical amplifiers (RSOAs). Second, a theoretical investigation on the maximum reach achievable with the proposed architecture is carried out considering Rayleigh backscattering noise and injection power limits. Only upstream signal performance is compared for the following four cases: (1) superluminescent diode (SLD) broadband source and FP-LD ONU, (2) SLD and RSOA, (3) CW SC and FP-LD, and (4) CW SC and RSOA. The combination of a CW SC injection source and RSOA-based ONUs is found to allow for the longest distance coverage. Finally, the feasibility of the proposed architecture is experimentally analyzed over a 60-km transmission fiber at 622 Mbit/s.     

A 980-nm Yb-doped fiber MOPA source and its frequency doubling

A continuous-wave (CW) master oscillator-power amplifier (MOPA) fiber source, tunable around 978 nm, was frequency-doubled to 488.7 nm. Both the laser and the amplifier were made with cladding-pumped jacketed air-clad Yb-doped fibers. The MOPA generated up to 2.7 W of power in an output beam with an M/sup 2/ value of 1.8. This was frequency-doubled in a periodically poled potassium titanyl phosphate crystal at room temperature, in a single-pass configuration. The generated blue light had a CW power of 18.1 mW, a nearly Gaussian spatial intensity profile, and an M/sup 2/ value of 1.7.     

Generation of over 140-nm-wide super-continuum from a normaldispersion fiber by using a mode-locked semiconductor laser source

The super-continuum (SC) spectrum flatly broadened over 140-nm 10-dB bandwidth is generated by using a mode-locked semiconductor laser as a pulse source at 1550 nm. In our SC generation system, nearly Fourier-transform limited 0.9-ps pulses obtained through linear and nonlinear pulse compression are incident on a dispersion-flattened fiber having a small normal group-velocity dispersion. While the pulses pass through the normal dispersion fiber, the pulse waveform is adapted to suit the accumulation of a linear chirp, which leads to the flat and wide-band SC spectrum     

10 GHz WDM/OTDM通信多波长光脉冲源

利用色散位移光纤中的复合非线性效应(自相位调制、四波混频、交叉相位调制)得到重复频率10 GHz、谱宽大于50 nm的超连续(SC)光谱,研究了泵浦光功率、波长与生成的SC光谱宽度和平坦度、光脉冲质量的关系.利用AWG从SC谱中滤出4个10 GHz不同波长光脉冲.     

10 GHz再生锁模光纤激光器获得光纤超连续谱的研究

报道了利用10GHz再生锁模光纤环形激光器（RML-FRL）获得波长在1528～1563nm连续可调、脉宽为4．6～5．8ps的短脉冲输出作为高稳定的光纤超连续（SC）谱泵浦源。对RML-FRL输出的脉冲直接放大泵浦4．5km色散位移光纤（DSF）,得到20dB带宽46．08nm的SC谱输出,经阵列波导光栅（AWG）谱切片后,得到间隔100GHz、中心波长符合ITUT标准的30信道输出,脉宽在6．5～7．8ps,示波器显示任意信道的抖动均值小于1．4ps。     

980nm波段连续光纤激光器的研究进展

980nm波段掺镱光纤激光器在高亮度抽运源和蓝绿光源方面具有广泛的应用前景。首先介绍了980nm波段连续光纤激光器的研究价值、研究难点。然后,介绍了国内外研究机构在980nm波段连续光纤激光器和放大器方面的研究进展和存在的问题。最后对980nm波段连续光纤激光器和放大器未来发展方向进行探讨。     

利用10GHz主动锁模光纤激光器在DSF中产生超连续谱

报道利用色散位移光纤 (DSF)中的复合非线性效应得到重复频率 10 GHz,谱宽大于 50 nm的超连续 (SC)光谱 ,研究了抽运光功率、波长与生成的 SC光谱宽度和平坦度、光脉冲质量的关系。     

利用啁啾脉冲传输测量拉曼增益系数的新方法

通过采用二次谐波频率分辨光学门（SHG-FROG）测量啁啾孤子脉冲的时域波形、脉冲宽度和相位等参量,给出一种测量拉曼增益系数的新方法。采用1 450 nm波长连续（CW）激光作泵浦光波,对G.652标准单模光纤（SMF）中啁啾孤子脉冲在1 550 nm波段的拉曼增益系数进行了实验测量,并进行分析计算,得到了CW激光泵浦...     

可调谐全正色散掺镱光纤激光器

利用相位长周期光纤光栅作为光谱滤波器,熔接于全正色散掺镱光纤激光系统中,从而实现了具有波长可调谐的连续激光输出和被动锁模激光脉冲输出,可调谐激光波长范围分别为11.4 nm和10.5 nm.通过调节偏振片改变激光腔内的偏振状态,输出锁模脉冲实现脉冲宽度的可调谐,其调谐范围为3.6~1.2 ns.在530 mW的最大泵浦功率下,得到了重复频率为2.5 MHz、最大单脉冲能量为38.9 nJ的锁模脉冲输出和最大输出功率为124 mW的连续激光输出.     

High-nonlinearity dispersion-shifted lead-silicate holey fibers for efficient 1-/spl mu/m pumped supercontinuum generation

This paper reports on the recent progress in the design and fabrication of high-nonlinearity lead-silicate holey fibers (HFs). First, the fabrication of a fiber designed to offer close to the maximum possible nonlinearity per unit length in this glass type is described. A value of /spl gamma/=1860 W/sup -1//spl middot/km/sup -1/ at a wavelength of 1.55 /spl mu/m is achieved, which is believed to be a record for any fiber at this wavelength. Second, the design and fabrication of a fiber with a slightly reduced nonlinearity but with dispersion-shifted characteristics tailored to enhance broadband supercontinuum (SC) generation when pumped at a wavelength of 1.06 /spl mu/m-a wavelength readily generated using Yb-doped fiber lasers-are described. SC generation spanning more than 1000 nm is observed for modest pulse energies of /spl sim/ 100 pJ using a short length of this fiber. Finally, the results of numerical simulations of the SC process in the proposed fibers are presented, which are in good agreement with the experimental observations and highlight the importance of accurate control of the zero-dispersion wavelength (ZDW) when optimizing such fibers for SC performance.     

Single, Depolarized, CW Supercontinuum-Based Wavelength-Division-Multiplexed Passive Optical Network Architecture With C-Band OLT, L-Band ONU, and U-Band Monitoring

We propose and experimentally demonstrate a novel bidirectional wavelength-division-multiplexed passive optical network architecture that fully utilizes the superior optical properties of an incoherent continuous-wave (CW) supercontinuum (SC) source. The proposed architecture, which incorporates low-cost Fabry-Perot laser diodes that have been wavelength locked by spectrum-sliced beams from a depolarized 130-nm-bandwidth CW SC source, is based on a unique wavelength band allocation scheme of the C-band for an optical line terminal (OLT), the L-band for optical network units (ONUs), and the U-band for channel monitoring. A cost-effective network that features a single broadband source at the OLT, and no additional wavelength- band-selective monitoring beam reflector at each ONU can be readily achieved. The experimental demonstration presented in this paper is carried out at a data rate of 622 Mb/s over a 25-km standard single-mode fiber.     

周期极化钽酸锂倍频窄谱线全光纤连续激光放大器特性

通过准相位匹配技术,采用1μm波段高功率窄谱线连续光纤激光放大器抽运高二次谐波转换效率周期性极化晶体,是实现高光束质量、小型化、高功率连续绿光激光器的一个非常有前途的方向。实验自主研发了高效率主振荡功率放大(MOPA)全光纤保偏放大模块,获得中心波长为1064.25nm,线宽为0.035nm的30 W连续线偏振激光,并以此作为基频光抽运国产周期极化钽酸锂(PPSLT)晶体进行了外腔单通倍频实验。保持PPSLT晶体的控制温度为145.6℃,在抽运光功率为21.5W时得到了2.1W的绿光输出。实验分析了温度、基频光功率密度和Boyd-Kleinman聚焦因子对倍频光转换效率的影响。实验过程中没有出现饱和现象,进一步提高抽运功率有望获得更高功率的绿光。     

High-power supercontinuum generation in a nested linear cavity involving a CW Raman fiber laser

We construct a novel nested linear cavity configuration to generate supercontinuum (SC) under continuous-wave pump. With this structure, stimulated Raman scattering and four-wave mixing can affect the whole region of the SC spectrum while the pump line is removed outside of the continuum, and a symmetrical spectrum can be obtained. The properties of the structure are demonstrated by using 3.5-km single-mode fiber, and an SC centered at 1315 nm with the bandwith of 102 nm and the output power of 1.3 W is achieved. By tuning the feedback fiber Bragg grating, we can easily adjust the spectral shape of SC to fit different requirement.     

基于微结构光纤的10 GHz超过1100信道的平坦超连续谱光源

报道了一种基于微结构光纤的宽带、平坦超连续谱(SC)光源。利用锁模半导体激光器产生的1.6ps,重复率为10GHz的光脉冲,通过一段80m的色散平坦高非线性微结构光纤(HNL-MF),在1.55μm波长区域产生了谱宽超过100nm的平坦超连续谱。实验中采用的微结构光纤的非线性系数约为11W-1·km-1。光纤具有小的正常色散和平坦的色散特性,在1550nm波长处,光纤的色散值约为-0.58ps·nm-1·km-1,而在1500～1650nm波长范围内,光纤的色散值变化小于1.5ps·nm-1·km-1。实验中获得的宽带、平坦超连续谱在1503～1593nm宽达90nm的波长范围内,具有±2.5dB的平坦度。该宽带、平坦超连续谱能同时提供波长间隔为10GHz,超过1100路的多波长载波信道。通过对光谱滤波,获得了速率为10Gbit/s的多波长脉冲序列。这样的超连续谱光源在波分复用(WDM)光通信系统、光波长变换等方面都有重要的应用。     

A Cost-effective Sub-terahertz Continuous Wave Generation Scheme Using a Broadband Optical Source and An Optical Feedback Loop

We have proposed a cost-effective sub-terahertz (THz) continuous wave (CW) generation scheme based on a usual double sideband-suppressed carrier (DSB-SC) scheme. The usual DSB-SC scheme, which consists of a discrete optical source, an optical intensity modulator (OIM), a local oscillator (LO), an optical notch filter, and an erbium doped fiber amplifier (EDFA), is one of well-known photonic-based sub-THz CW generation schemes. As the discrete optical source of the usual DSB-SC scheme is eliminated and an optical feedback loop is incorporated with the usual DSB-SC scheme, our proposed scheme is constructed to decrease implementation costs. Without an optical input, the output of the pump laser of the DC-biased EDFA is inserted to the optical notch filter. Reflected lightwaves with fiber bragg grating wavelengths of the optical notch filter is fed back to the input of the OIM through the optical feedback loop, which is composed of a circulator and a 90:10-coupler. DSB-SC lightwaves have been made by modulating feedbacked lightwaves on the OIM with the frequency of the LO. A sub-THz CW is generated by photomixing them. To verify feasibility of our proposed scheme, we generated and characterized a 120 GHz CW. The measurement results were also compared to those of the usual DSB-SC scheme. Based on our measurement results, we found that characteristics of the generated 120 GHz CW using our proposed scheme are comparable to those using the usual DSB-SC scheme. Consequently, our proposed scheme can be helpful to make a cost-effective sub-THz CW generator based on photonics.     

LD端面抽运掺Yb3+双包层光纤激光器自脉动行为的实验研究

本文对连续波半导体激光器端面抽运的Fabry-Perot腔掺Yb3 双包层光纤激光器的自脉动输出行为进行了研究．发现低Q值腔光纤激光器具有两种形式的自脉动输出，一种是饱和吸收被动调Q产生的自脉冲,另一种是与光纤中的受激Raman散射(SRS)效应相对应的阵发性巨脉冲．通过提高光纤激光器谐振腔的Q值并选择合适的抽运功率，可以有效地减小输出功率的自脉动，获得稳定的连续波激光输出．     

Experimental Investigation of the Role of Four-Wave Mixing in Supercontinuum Generation From a Multimode 975-nm Pumped Fiber Ring Cavity

We demonstrate a broadband supercontinuum (SC) generation that covers an optical spectrum from 1300 to 2000 nm with output power of 1.3 W. The SC generation is realized using a fiber ring cavity that mainly consists of erbium–ytterbium-doped fiber pumped by multimode 975-nm pump lasers, and highly nonlinear fiber (HNLF). Moreover, we investigate the role of four-wave mixing (FWM) in the SC generation by using two different HNLFs, one having normal and the other having anomalous dispersion. It is found that FWM plays a critical role for broadening and flattening of the SC generation in addition to stimulated Raman scattering.