Generation of tunable multi-wavelength optical short pulses using self-seeded Fabry-Perot laser diode and tilted multimode fiber Bragg grating

We experimentally demonstrate the simultaneous generation of tunable multi-wavelength picosecond laser pulses using a self-seeding configuration that consists of a gain-switched Fabry-Perot laser diode (FPLD) with an external cavity formed by a tilted multimode fiber Bragg grating.Dualand triple-wavelength pulses are obtained and tuned in a flexible manner by changing the temperature of the FPLD.The side mode suppression ratio larger than 25 dB is achieved at different dualand triple-wavelengths and the typical pulsewidth of the output pulses is ～70 ps.In the experiment,the wavelength separation can be narrowed to 0.57 nm.     

基于高双折射Sagnac环的可调环形腔掺铒光纤激光器理论与实验研究

报道了一种利用偏振控制器（PC）和保偏光纤（PMF）组成的高双折射Sagnac干涉环实现选频和调谐的环形腔掺铒光纤激光器.理论模拟了PMF和PC对波长的控制作用.实验中调节PC得到了单波长、双波长和多波长激光;并验证了滤波间隔随PMF长度的变化规律.实验中得到了斜率效率20%,3 dB线宽0.016 nm,30 dB线宽0.097 nm,边模抑制比（SMSR）40 dB左右的稳定激光输出. 关键词： 光纤激光器 Sagnac干涉环 环形腔 掺铒光纤     

Stable multi-wavelength erbium-doped fiber laser based on dispersion-shifted fiber and Sagnac loop filter

A multi-wavelength erbium-doped fiber laser (MEDFL) with simple line structure is experimentally demonstrated by using a Sagnac interferometer as a comb filter. It is shown that the multi-wavelength lasing is quite stable at room temperature due to the four-wave mixing (FWM) effect among different laser channels in the dispersion-shifted fiber cooperated in the laser cavity.     

Tunable dual-wavelength fiber laser based on a single fiber Bragg grating in a Sagnac loop interferometer

We propose a simple dual-wavelength Er-doped fiber laser configuration based on a dual-wavelength fiber Bragg grating written on the splice joint between two different fibers for wavelength-selective filter in the Sagnac loop interferometer. The wavelength separation between the adjacent lasing wavelengths is 1.12 nm and the side-mode suppression ratio (SMSR) is over 55 dB. The output power variation is less than 0.8 dB over a two-minute period. Moreover, the lasing wavelength can be effectively tuned using the thermal heating method.     

基于二阶保偏光纤Sagnac环光纤激光器的振动检测研究

提出了一种可用于振动检测的新型光纤光栅传感技术. 用偏振控制器和高双折射保偏光纤构建成Sagnac环, 结合掺铒光纤、单模光纤和隔离器, 形成了单波长光纤激光器, 由粘有光纤Bragg光栅的悬臂梁作为传感探头, 并利用Sagnac环本身的线性边缘, 解调振动信号. 阐述了Sagnac环原理及其产生的边缘效应, 并进行了数值模拟计算, 对振动信号进行了检测实验, 检测系统从L₁到L₁+L₂之间对应的周期可调, 灵敏度高达38.2 μ W/nm, 线性度为0.9996, 动态范围在40–70 dB, 可满足振动传感检测的技术参数要求. 关键词： 光纤光学 振动检测 保偏光纤Sagnac环 光纤激光器     

A tunable comb filter using single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop

A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.     

Broadly tunable dual-wavelength erbium-doped ring fiber laser based on a high-birefringence fiber loop mirror

A broadly tunable dual-wavelength erbium-doped ring fiber laser based on a high-birefringence fiber loop mirror (HiBi-FLM) and a polarization controller is demonstrated experimentally. The measured transmission spectrum of HiBi-FLM covers a wide range from 1525 to 1575 nm. The wavelength of proposed laser can be flexibly tunable during this range of ∼50 nm by adjusting the polarization controller. In addition, the spacing of two wavelengths is adjustable by changing the length of HiBi fiber. The dual-wavelength lasers with the HiBi fiber length of 1 and 2 m are experimentally demonstrated and compared. The experimental results show that the proposed laser can stably operate on two wavelengths simultaneously at room temperature, and the output peak power variation is about 0.5 dB during 40 min.     

Multiwavelength self-seeded Brillouin-erbium fiber laser with 45-nm tunable range

We have demonstrated a tunable multiwavelength self-seeded Brillouin-erbium fiber laser (BEFL) without externally Brillouin pumping. In this scheme, the stable multiwavelength comb can be produced within a ∼45-nm wavelength tuning range through adjusting the polarization controllers (PCs) in a high-birefringent Sagnac loop mirror. The generation of ∼200-line Stokes comb has been achieved by adjusting PCs under bidirectional pumping of two laser diodes, which is the largest wavelength number to the best of our knowledge. The effect of 980 nm pump power on the multiwavelength generation was also investigated.     

Electro-optic wavelength-tunable fiber ring laser based on cascaded composite Sagnac loop filters

A continuous wavelength-swept fiber ring laser with a lithium niobate waveguide electro-optic polarization controller in an intracavity fiber Sagnac loop is experimentally demonstrated. Composite fiber Sagnac loop filters are cascaded to demonstrate discrete wavelength switching of a single-wavelength fiber ring laser. Stable single-longitudinal-mode operation is achieved by use of a Sagnac loop saturable-absorber filter.     

A linearly-polarized tunable Yb-doped fiber laser using a polarization dependent fiber loop mirror

A Ytterbium-doped linearly-polarized fiber laser is constructed with a polarization maintaining fiber Sagnac loop mirror. The fiber loop mirror made of polarization maintaining fiber coupler has a polarization dependent reflectivity, which provides the necessary polarization discrimination between the slow and fast axes. With a fiber Bragg grating written in normal polarization maintaining fiber as an output coupler, laser output of up to 5.6 W at 1070 nm is generated with a polarization extinction ratio of > 20 dB and an overall efficiency of 55%. The broadband polarization dependent reflection of the fiber loop mirror offers advantages of easy spectral tuning and simple linearly-polarized laser generation.     

Stable SOA-based multi-wavelength fiber ring laser using Sagnac loop mirror incorporating a high-birefringence photonic crystal fiber

Multi-wavelength fiber laser using semiconductor optical amplifier (SOA) and Sagnac loop mirror (SLM) incorporating a newly designed high-birefringence photonic crystal fiber (HB-PCF) is experimentally demonstrated. The modal birefringence of the fabricated HB-PCF is estimated to be 1.1 × 10⁻³. Mainly, by adjusting a polarization controller in the fiber ring laser, the proposed fiber laser can operate at six lasing wavelengths with 2.7 nm intervals, the signal-to-noise ratio (SNR) of around 30 dB. The output power stability is 0.8 dB. In addition, we obtained near-perfect temperature independence in our multi-wavelength fiber laser system. The temperature dependence of the SLM is around 3 pm/°C.     

Switchable erbium-doped fiber ring laser based on Sagnac loop mirror incorporating few-mode high birefringence fiber

Without the need of any other additional filtering device, a triple-wavelength switchable erbium-doped fiber ring laser based on Sagnac loop mirror incorporating a piece of few-mode high birefringence fiber is newly proposed and experimentally demonstrated. Three potential lasing wavelengths at about 2.0 nm interval with the side mode suppression ratio higher than 40 dB can be switched mainly by adjusting a polarization controller next to the few-mode high birefringence fiber in the Sagnac loop. In addition to the stable single-line lasing operation, simultaneous dual- and triple-line oscillations are also highly stable at room temperature with suppressing the intrinsic homogeneous gain broadening of the erbium-doped fiber.     

基于Sagnac环形镜的高功率多波长线偏振掺镱光纤激光器

设计了基于Sagnac环形镜的哑铃型结构全光纤掺镱激光器,使用976 nm多模激光二极管泵浦,通过调节偏振控制器获得了稳定的多波长线偏振激光输出。泵浦功率为20.4 W时,最高输出功率达到5.13 W,功率波动不大于0.02 W,激光器输出多波长激光线偏振度约为14.19 dB,多波长输出功率平坦度优于3 dB。     

基于Sagnac环形镜的高功率多波长线偏振掺镱光纤激光器

设计了基于Sagnac环形镜的哑铃型结构全光纤掺镱激光器,使用976 nm多模激光二极管泵浦,通过调节偏振控制器获得了稳定的多波长线偏振激光输出。泵浦功率为20.4 W时,最高输出功率达到5.13 W,功率波动不大于0.02 W,激光器输出多波长激光线偏振度约为14.19 dB,多波长输出功率平坦度优于3 dB。     

Curvature measurement by using low-birefringence photonic crystal fiber based Sagnac loop

An optical fiber curvature sensor with low-birefringence photonic crystal fiber (PCF) based Sagnac loop is demonstrated experimentally. The low-birefringence PCF of about 40 cm long is inserted into Sagnac loop, and a section of it about 155 mm is used as the sensing element. The Sagnac output spectra under different curvatures are measured and analyzed. The results show that the wavelength shift of the transmission dip has a linear relationship with the curvature. The sensitivity of the curvature measurement of − 0.337 nm is achieved in the range of 0-9.92 m^− 1. And the temperature effect of the proposed sensor is also analyzed.     

Switchable multi-wavelength erbium-doped fiber ring laser based on cascaded polarization maintaining fiber Bragg gratings in a Sagnac loop interferometer

A switchable multi-wavelength erbium-doped fiber (EDF) ring laser based on cascaded polarization maintaining fiber Bragg gratings (PMFBGs) in a Sagnac loop interferometer as the wavelength-selective filter at room temperature is proposed. Due to the polarization hole burning (PHB) enhanced by the PMFBGs, stable single-, dual-, three- and four-wavelength lasing operations can be obtained. The laser can be switched among the stable single-, dual-, three- and four-wavelength lasing operations by adjusting the polarization controllers (PCs). The optical signal-to-noise ratio (OSNR) is over 50 dB.     

Wavelength-tunable erbium fiber ring laser in single-frequency operation utilizing Fabry-Perot laser with Sagnac cavity

We propose and demonstrate experimentally a stabilized and wavelength-selective erbium-doped fiber ring laser in single-longitudinal-mode operation with Fabry-Perot laser diode (FP-LD) and using a tunable bandpass filter (TBF) inside and outside a Sagnac ring cavity. The side-mode suppression ratios of 21 dB and 36.5 dB and the output power of -3.6 dB m and -8.7 dB m in the wavelengths of 1524.45-1562.35 nm and 1531.07-1562.35 nm with the tuning step of 1.4 nm can be achieved when the TBF outside and inside Sagnac loop, respectively. The output wavelength variation of zero and the output power fluctuation of <0.1 dB are also obtained. Moreover, the transmission efficiency of the ring laser has also been performed experimentally under a 1.25, 2.5 and 10 Gb/s external modulation, respectively.     

Tunable multiwavelength SOA-fiber ring laser based on Sagnac loop mirror incorporating few-mode high birefringence fiber

A tunable multiwavelength fiber ring laser based on a semiconductor optical amplifier and Sagnac loop mirror incorporating a piece of few-mode high birefringence fiber (FM-HBF) is proposed and experimentally demonstrated. It is accomplished by simply adjusting a polarization controller in the Sagnac loop mirror because birefringence of the FM-HBF is polarization dependent. Tunable multiwavelength operation up to 11 oscillating lines at about 2.1 nm interval is stably achieved with an optical side-mode suppression ratio over 35 dB.     

Double-pumped multiwavelength fiber optical parametric oscillator based on a Sagnac loop filter

We propose a double-pumped ring cavity multiwavelength fiber optical parametric oscillator (MW-FOPO) using a highly nonlinear dispersion-shifted fiber (HNL-DSF) as the gain medium and a polarization maintained fiber based Sagnac loop filter as the comblike filter. 22-wavelength lasing of the double-pumped MW-FOPO with a ripple less than ±2.5 dB and a wavelength spacing of about 0.8 nm in a wavelength range from 1541 nm to 1558 nm is experimentally demonstrated. We discussed the power stability of the multiwavelength lasing of the double-pumped MW-FOPO. A comparison of the output spectra between the double-pumped MW-FOPO and single-pumped MW-FOPO is also presented.     

Mutual injection locking of an erbium-doped fiber laser and a fiber-pigtailed Fabry-Perot laser diode

Mutual injection locking of a fiber-pigtailed Fabry-Perot laser diode (FPLD) and a closed-loop erbium-doped fiber-amplifier-based laser (EDFL) system are studied. A single FPLD longitudinal mode can be lasing in the EDFL-FPLD link, with a reduced linewidth of <0.017 nm and an improved sidemode-suppressing ratio of 50 dB. The FPLD's optimized current range is below threshold within 10%, and its required feedback-injecting power is 12.4 microW (corresponding to 0.03% of the EDFL output power). The maximum detuning ranges of the current and temperature of the FPLD that preserve the narrow linewidth and the highest sidemode-suppressing ratio of the EDFL-FPLD link are 2.4 mA and 2.2 degrees C, respectively. The power dissipated by the EDFL-FPLD link is 20% more than that of the free-running EDFL.