新颖的高功率L-波段掺铒光纤超荧光光源

研究了L-波段超荧光在光纤中的产生机理,设计了一种带光纤圈反射器的双级双程前向输出L-波段光源结构,通过对两级采用掺铒浓度不同的光纤并优化其长度及两级泵浦光功率,实验中获得了功率高达19.86mW(12.98dBm)、中心波长为1577.421nm的L-波段(1555-1620nm)超荧光光源。实现了低浓度掺铒光纤起诱导光及改善光谱的作用,高浓度光纤为主要发光源,采用光纤圈反射器提高了泵浦光的利用效率、光源的平坦度及稳定性。同时分析了结构中各个参量对光源各方面性能的影响,对光源的设计具有指导意义。     

可调谐环形腔掺铒光纤激光器

使用高掺杂掺铒光纤制成了低噪声的环形腔光纤激光器。通过对文献中报道的环形腔结构光纤激光器输出的分析,指出了其存在的问题,并提出了减小其输出背景噪声的改进方案。通过实验验证了改进后的环形腔结构的低噪声特点,从原理上进行了解释。用不同掺铒光纤长度、泵浦功率、光栅波长及光栅反射率进行了实验,得到它们对输出光的性能影响。这种环形腔结构的光纤激光器可实现1525nm~1565nm连续可调谐输出。     

Switchable Q-switched and laser operating mode-locked erbium-doped fiber in the L-band region

We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser （EDFL） operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 #s, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least l0 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.     

Switchable Q-switched and mode-locked erbium-doped fiber laser operating in the L-band region

We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser (EDFL) operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 μs, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least 10 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.     

L波段高掺铒光纤超荧光光源

采用半导体激光二极管泵浦12cm长高掺铒光纤,在双程前向装置中,获得了10.8mW最大超荧光输出功率,斜率效率10.6%,在1553.1~1588.6nm接近36nm的范围内,功率抖动小于0.2dBm。作为比较,在相同实验条件下泵浦10cm长的高掺铒光纤,结果显示输出光谱带宽明显下降,C波段的放大自发辐射远大于L波段的,由此也证明了L波段的放大自发辐射是由C波段的放大自发辐射泵浦产生的。     

Period-doubling of dispersion-managed solitons in an Erbium-doped fiber laser at around zero dispersion

Period-doubling of dispersion-managed solitons in an Erbium-doped fiber ring laser operating at the near zero net cavity group velocity dispersion region was experimentally observed. The generated dispersion-managed solitons of the laser are characterized by their near Gaussian spectral profiles and no sidebands. Numerical simulations verified our experimental observations and showed that the period-doubling could occur both in the positive and negative near zero net cavity group velocity dispersion regions, which suggests that the occurrence of the period-doubling is an intrinsic feature of the mode-locking fiber lasers and independent of the concrete mode-locked pulse profile.     

Switchable dual-wavelength Erbium-doped fiber ring laser with cascaded fiber Bragg gratings

We have experimentally shown wavelength mode switching in a dual-wavelength Erbium-doped single cavity fiber laser where the initial two wavelengths of 1 nm spacing are determined by the cascaded reflection type short-period fiber Bragg gratings having two different centre wavelengths of 1550.5 and 1551.5 nm. The lasing mode depends on the polarization in the ring cavity to migrate from one wavelength to another or operates in both modes in a polarization beam splitter output. To effectively control the polarization in the ring cavity, the polarization controllers were positioned before and after the polarization beam splitter. This method of wavelength switching provides a simple way of mode tuning in dual-wavelength fiber lasers.     

Full L-band coverage of multiwavelength erbium-doped fiber laser

We propose and experimentally demonstrate a dual-pass unbalanced in-line Sagnac interferometer as a novel comb filter for implements in erbium-doped fiber lasers to obtain wide wavebands of multiwavelength radiations with enhancements of signal-to-noise ratios (SNRs). The hybrid combinations of the comb filter with the two schemes of nonlinear polarization rotation and intensity dependent loss have successfully not only enlarged the lasing bandwidth up to 47 nm but also enhanced the SNR up to 40 dB. The simultaneous lasing-wavelengths of 117 channels are also obtained. The multiwavelength lasing spectra with free spectral range of 0.4 nm covering the full L-band are useful for the applications of DWDM and WDM-PON systems.     

L-band erbium-doped fiber laser with polarization-maintaining ring cavity

A new, simple and efficient L-band erbium-doped fiber (EDF) laser with polarization-maintaining ring cavity is proposed and experimentally demonstrated. The laser offers the unique advantage of being a polarization-maintaining lasing, which meets the requirement of external electronic-optical intensity modulation for DWDM communication and interferometric fiber sensors. Theory has been established. Experimental results are given to show that the laser has long-term stability over a couple of hours with 35 dB signal-to-noise ratio at 1598.644 nm and tunable from 1572.167 to 1608.480 nm.     

Erbium-doped fiber laser simultaneously mode locked on more than 24 wavelengths at room temperature

We demonstrate simultaneous mode locking of more than 24 wavelengths at 3 GHz in an actively mode-locked erbium-doped fiber laser operating at room temperature. The multiwavelength operation is achieved when a frequency shifter and an all-fiber 50-GHz periodic filter are inserted into a ring cavity. Active mode locking is performed with an amplitude modulator, and pulses with a FWHM of 30 ps are obtained.     

Passively Q-switched mode-locking Erbium-doped fiber laser with net-normal dispersion using nonlinear polarization rotation technique

We experimentally demonstrate a passively Q-switched mode-locking (QML) operation in an Erbium-doped fiber ring laser with net normal dispersion by using nonlinear polarization rotation technique. A 2 m long section of dispersion compensating fiber (DCF) with extra large positive dispersion was inserted into the cavity to ensure the fiber laser working in the region of net positive dispersion. By carefully adjusting the polarization controller, both uniform dissipative mode-locking pulses with fundamental repetition rate and QML pulse trains with tunable repetition rate from 71.58 to 98.83 kHz are achieved. It is found that the QML operation is caused by the interaction between the polarization state of the pulse and the intracavity polarizer.     

Erbium-doped CW and Q-switched fiber ring laser with fiber grating Michelson interferometer

The band-pass characteristic of fiber grating Michelson interferometer is analyzed, which acts as bothband-pass filter and Q-switch. An erbium-doped fiber ring laser based on fiber grating Michelsoninterferometer is implemented for producing single longitudinal mode CW operation with 5 MHz spectrallinewidth and up to 6 mW output power. In Q-switched operation, stable fiber laser output pulses withrepetition rate of 800 Hz, pulse width of 0.6 μs, average power of 1.8 mW and peak power of 3.4 W aredemonstrated. The peak power and average power of the Q-switched pulses are varied with the repetitionrate.     

C- and L-band tunable fiber ring laser using a two-taper Mach-Zehnder interferometer filter

A stable C- and L-band tunable fiber ring laser, using a two-taper Mach-Zehnder interferometer (MZI) as a filter, is proposed and demonstrated experimentally. One of the two taper waists is mechanically bent to tune the laser wavelength. Being amplified by an L-band erbium-doped fiber amplifier and an erbium-doped fiber, respectively, the fiber ring laser has a full L-band (1564-1605nm) and C-band (1550-1565nm) tuning range with a side-mode suppression ratio as high as 50dB. The laser linewidth and the minimum tuning step are related to the MZI's cavity length. It was also found that thermal annealing relieved the internal stresses of the tapers and greatly improved the laser performance.     

紧凑型窄线宽分布反馈光纤激光器

 在铒/镱共掺杂有源光纤上直接刻蚀光栅,制成一台紧凑型非对称π相移分布反馈光纤激光器。光栅总长度约50 mm,最佳相移位置在29 mm处,最佳耦合系数为150 m^-1。采用980 nm激光二极管同向泵浦,当最大泵浦功率为200 mW时,在1 550.94 nm处实现约10 mW激光输出,线宽小于0.05 nm,阈值约35 mW,斜率效率为6.06%,总光 光转换效率为5%,基本满足长距离光通信系统光源功率实用化的要求。     

L-Band掺铒光纤放大器的优化设计

提出了泵浦分配两段级联,并利用前向ASE推动下一级EDF工作的L-Band放大器的新结构.基于Giles模型并考虑了ASE噪声的影响,运用数值模拟算法系统分析了泵浦光功率分配和铒光纤分配比例对这种EDFA性能的影响.最后优化得到高增益且增益谱平坦的L-Band EDFA,其在输入信号光功率为-20 dBm时,在1571～1608 nm范围内,增益值高达35 dB,增益偏差小于1 dB.     

A narrow-line Erbium-doped fiber laser and its application for testing fiber Bragg gratings

We inspect the spectral features of a diode-pumped Erbium-doped fiber laser (EDFL) with a Fabry-Perot cavity composed of a wavelength-selective coupler in the form of fiber Bragg grating (FBG) and wavelength-insensitive Faraday rotator mirror (FRM). High accuracy for the spectral measurements is provided with the use of an optical heterodyne scheme where the EDFL output is mixed with radiation from a narrow-line semiconductor laser, allowing the detection of the EDFL spectra with a sub-pm resolution. The heterodyne scheme permits precise measurements of the EDFL line-width as a function of the cavity length and pump power. It is worth noticing a narrow-line (a few pm) operation of the EDFL with a short length (<3 m) cavity and low (<5) excess of pump power over the laser threshold. The spectral response of the EDFL to a slow sinusoidal modulation of a physical length of the FBG coupler is analyzed and it is shown that as high as ∼1-nm modulation of the EDFL optical spectrum is attainable at maximal modulation amplitudes. The narrow-line EDFL with a modulated generation wavelength is hereby demonstrated to be a tool for high-resolution measurements of reflection spectra of FBGs, which is to the best of our knowledge a novel application of the EDFL.     

Wavelength tunable erbium-doped fiber ring laser operating in L-band

We describe a novel erbium-doped fiber ring laser utilizing the backward amplified spontaneous emission (ASE) power as a secondary pump source so that it can operate in L-band stably. The output wavelength can be tuned in a wide range of 45 nm, from 1560 to 1605 nm. We also compared this scheme with the condition of not using the ASE as secondary pump source, and found this scheme could improve the performance of the laser when using the same components.     

Observation of 550 MHz passively harmonic mode-locked pulses at L-band in an Er-doped fiber laser using carbon nanotubes film

We demonstrate a passively harmonic mode-locked(PHML) fiber laser operating at the L-band using carbon nanotubes polyvinyl alcohol(CNTs-PVA) film. Under suitable pump power and an appropriate setting of the polarization controller(PC), the 54~(th) harmonic pulses at the L-band are generated with the side mode suppression ratio(SMSR) better than 44 dB and a repetition frequency of 503.37 MHz. Further increasing the pump power leads to a higher frequency of 550 MHz with compromised stability of 38.5 dB SMSR. To the best of our knowledge, this is the first demonstration on the generation of L-band PHML pulses from an Er-doped fiber laser based on CNTs.     

基于FLM的L波段双波长EDFL的双稳态变换

提出和验证了一种L波段双波长掺铒光纤激光器(EDFL)双稳态控制变换和双波长开关切换的方法.将偏振控制器(PC)插入基于3 dB光纤耦合器的光纤环镜(FLM)中，并将该FLM用作L波段双波长级联线形耦合腔EDFL的公共腔镜，结果表明，调节PC可以改变FLM的反射率，实现对EDFL双稳态特性的有效控制，且双稳态特性随FLM反射率呈单调变化.利用这一性质，提出并证实，对于处在FLM最大反射率对应的双稳态第一跃变点和最小反射率对应的双稳态第二跃变点之间的任意固定抽运光功率，调节PC可实现两个稳态之间的相互变换和双波长之间的相互切换.     

Erbium-doped photonic crystal fiber laser with 49 mW

We have demonstrated a continuous-wave (CW) all fiber laser operation at 1558.4 nm of a diode-pumped erbium-doped PCF laser based on 9.6 m erbium-doped PCF. The maximum output power and the threshold of the fiber laser are 49.4 mW and 6.67 mW, respectively. We show that it is possible to achieve a high stability and beam quality laser, which has a great application potential in optical communication field in future.