A tunable dual-wavelength erbium-doped fiber ring laser using a self-seeded Fabry-Perot laser diode

A tunable dual-wavelength erbium-doped fiber ring laser using a self-seeded Fabry-Perot laser diode (FP-LD) is proposed and demonstrated. By adding an FP-LD incorporated with a tunable bandpass filter within the ring cavity, the fiber laser can lase two wavelengths simultaneously because of the self-seeded mechanism. This dual-wavelength output exhibits a good performance having the optical side-mode suppression ratio over 31 dB. The wavelength-tuning range of this tunable dual-wavelength fiber laser can be up to 9 nm.     

A tunable S-band erbium-doped fiber ring laser

In this paper, we experimentally investigate and demonstrate an S-band erbium-doped fiber (EDF) ring laser based on an erbium-doped silica fiber and 980-nm pumping laser. Widely tunable range from 1480 to 1522 nm, and the sidemode suppression ratio (SMSR) of >30 dB/0.1 nm and the output power of >-2 dBm in the operating range from 1482 nm to 1517 nm have been achieved for this ring laser. Under the constant power control, the output power variation less than /spl plusmn/0.05 dB can also be accomplished over the tuning range from 1482 to 1517 nm. This S-band EDF ring laser is promising for the future S-band applications.     

A widely tunable narrow-linewidth triple-wavelength erbium-doped fiber ring laser

A widely tunable narrow-linewidth simultaneous triple-wavelength oscillation erbium-doped fiber ring laser (EDFRL) is investigated in detail. The EDFRL can produce double-wavelength oscillations with the same polarization output, as well as another widely tunable wavelength oscillation with orthogonal polarization in both the C-band and the L-band. By preventing two polarization-mode competitions, we have achieved a stable single-longitudinal-mode triple-wavelength lasing output along with a minimum side-mode suppression ratio of 40 dB.     

Switchable and tunable multiwavelength erbium-doped fiber laser with fiber Bragg gratings and photonic crystal fiber

We propose and report on a novel multiwavelength-switchable-tunable erbium-doped fiber laser with excellent stability and uniformity based on four-wave mixing (FWM) in a highly nonlinear photonic crystal fiber. By adjusting the attenuators, the single, dual, or triple wavelengths can be lasing simultaneously. Under the influence of the FWM, the spectrum is stabilized and the uniformity is less than 0.6 dB.     

Switchable multiwavelength erbium-doped fiber ring laser with a multisection high-birefringence fiber loop mirror

We proposed and demonstrated a new concept of switchable multiwavelength erbium-doped fiber ring laser with a multisection high-birefringence fiber loop mirror (HiBi-FLM). The HiBi-FLM results in the laser operating on different allowed wavelengths. The wavelength switching can be achieved by modifying the reflection spectrum of HiBi-FLM through two polarization controllers. The experiment demonstrates the switchable lasing operation within the random combination of three wavelengths, as well as with a large (/spl sim/40 dB) output signal to background noise ratio.     

A stabilized and tunable erbium-doped fiber ring laser with double optical filter

We have proposed and experimentally demonstrated a stabilized and tunable erbium-doped fiber ring laser by using a Fabry-Pe/spl acute/rot laser and a fiber Fabry-Pe/spl acute/rot filter. The sidemode suppression ratio of >30 dB/0.1 nm and the output power of >2.2 dBm can be achieved while this ring laser is tuned from 1528.28 to 1559.64 nm with the step of 1.12 nm. The wavelength variation of less than 0.01 nm and the power fluctuation of /spl les/0.04 dB have also been obtained. When the constant output power is controlled by adjusting the bias current of 980-nm pump laser, the power variation of less than /spl plusmn/0.05 dB can be obtained over the entire tunable range.     

A tunable multiwavelength fiber ring laser for measuring polarization-mode dispersion in optical fibers

We describe and demonstrate a tunable triple-wavelength erbium-doped fiber ring laser along with a method of measuring polarization-mode dispersion (PMD) in optical fibers based on a broad-band orthogonal-pump four-wave mixing in a semiconductor optical amplifier. The measured PMD results for optical fibers are in good agreement with values measured by means of commercial PMD testing equipment.     

Switchable multiwavelength erbium-doped fiber laser with cascadedfiber grating cavities

We propose a new concept to produce switchable multiwavelength oscillations with a cascaded fiber Bragg grating overlapping cavity erbium-doped fiber laser. The laser can be designed to operate in multiwavelength or in wavelength switching modes. The different lines have different thresholds. For three-wavelength oscillation, the output powers are linear or piecewise linear functions of the input pump power. An output with a variation of only 1.5 dB has been achieved with an input pump power of 100 mW. For wavelength switching, three single-wavelength and two dual-wavelength operation regions have been obtained toy adjusting the input pump levels     

Stable multiwavelength dispersion-tuned actively mode-locked erbium-doped fiber ring laser using nonlinear polarization rotation

We demonstrate a stable multiwavelength actively mode-locked erbium-doped fiber laser at 10 GHz based on a dispersion cavity and nonlinear polarization rotation (NPR) effect. The dispersion cavity allows simultaneous multiple wavelengths to satisfy the round-trip condition and smooth wavelength tuning, while the NPR ensures the stable operation and supermode noise suppression. A simple model is developed to explore the optimal setting of the cavity. Simultaneous dual- and five-wavelength operation is experimentally investigated.     

Single-longitudinal-mode multiwavelength fiber ring laser

A single-longitudinal-mode multiwavelength fiber ring laser is proposed and demonstrated. The single-longitudinal-mode operation is realized using a fiber loop mirror with a saturable absorber. The fiber loop mirror acts as a passive self-tracking narrow multiband optical filter. Single-longitudinal-mode multiwavelength lasing is generated by using either a Lyot-Sagnac filter or a fiber grating array.     

多波长掺铒光纤激光放大器的放大特性研究

为了研究多波长掺铒光纤激光放大器的放大特性,在单频放大器的基础上,忽略放大自发辐射,推导了描述多波长掺铒双包层光纤放大器的稳态速率方程组,建立了多波长掺铒光纤放大器的理论模型。利用该模型对单波长放大、双波长放大、四波长放大的特性,进行了数值模拟和理论分析;以四波长的激光信号放大为例,对多波长掺铒光纤放大器的放大特性,均衡增益特性进行了研究。结果表明,在单波长注入情况下,光纤放大器的掺杂光纤存在最佳光纤长度为8m;与小信号放大不同,大功率掺铒光纤放大器在1530nm~1560nm之间增益谱趋于平坦;双波长放大输出功率差随着波长间隔的增加线性增大波长间隔为20nm时,通过调节输入信号功率比可以实现最大功率差6.855W的功率均衡补偿;四波长放大时,通过信号功率配比之后的四波长激光输出功率最大偏差为0.28W,在一定范围内实现了均衡增益。这一结果对于掺铒光纤激光的多波长激光输出以及在激光多普勒测风雷达中的应用具有一定帮助。     

A dual-wavelength erbium-doped fiber laser with widely tunable wavelength spacing

A stable dual-wavelength erbium-doped fiber laser （EDFL） with tunable wavelength spacing and equalized output power is proposed and experimentally demonstrated. The fiber laser uses two fiber Fabry-Perot tunable filters （FFP- TFs） as the wavelength filter. The main cavity is divided into two sub-cavities with imbalance cavity losses through a 30/70 optical coupler. The tunable wavelength spacing can be achieved by changing the center wavelength of the filters and the equalized dual-wavelength output power can be achieved by properly controlling the variable optical attenuator （VOA） inserted in the lower-loss cavity.     

Switchable dual-wavelength erbium-doped fiber laser with tunable wavelength

A switchable dual-wavelength erbium-doped fiber laser (EDFL) with tunable wavelength is demonstrated. The ring cavity consists of two branches with a fiber Bragg grating (FBG) and a spherical-shape structure as fiber filters, respectively. By adjusting the variable optical attenuator (VOA), the laser can be switched between the single-wavelength mode and the dual-wavelength mode. The spherical-shape structure has good sensitivity to the temperature. When the temperature changes from 30 °C to 190 °C, the central wavelength of the EDFL generated by the branch of spherical-shape structure varies from 1 551.6 nm to 1 561.8 nm, which means that the wavelength interval is tunable.     

Strong optical bistability in a simple L-band tunable erbium-doped fiber ring laser

We demonstrate strong optical bistability in a widely tunable L-band erbium-doped fiber ring laser pumped by a 980-nm laser diode. The bistable region is as much as 150-mW wide and can be controlled by the lasing wavelength or the length of erbium-doped fiber. The mechanism for the bistability is not typical cross gain saturation in a two-mode operation, but rather saturable absorption strongly enhanced in the proposed scheme.     

Wavelength-switchable single-frequency erbium-doped fiber ring laser

We demonstrate a single-frequency and wavelength-switchable fiber ring laser obtained by a Lyot filter used in combination with a sampled fiber Bragg grating and a saturable absorber. The operating wavelength of the laser can be tuned, with a constant 0.8-nm step, in the range 1552.6-1555.8 nm. The tuning mechanism works on the rotation of the polarization of Lyot filter input signal. The structure of the laser is very simple regarding its characteristics: an output power of 6 dBm, with a signal-to-noise ratio higher than 60 dB and a spectral linewidth of 8 kHz.     

A widely tunable erbium-doped fiber laser pumped at 532 nm

A tunable erbium-doped fiber laser with a very wide continuous-tuning range (1522-1567 nm) is discussed. The wide tuning range was achieved using an aluminum/erbium-doped fiber; the aluminum codoping is known to broaden the gain spectrum substantially. The tunable fiber laser has a ring laser configuration utilizing an inline tunable etalon as the tuning element. Continuous tuning over 45 nm in the spectral range of 1522-1567 nm was achieved with 80 nW of pumping at 532 nm, using the second harmonic of a Nd:YAG laser as the pump source     

采用可调Mach-Zehnder滤波的波长可切换掺铒光纤激光器

为了实现高稳定性的可调谐激光输出,提出并设计了一种基于马赫-曾德（M-Z）结构和光纤光栅串结合的掺铒光纤激光器,在M-Z干涉结构的一个干涉臂中加入光学延迟线（ODL）,实现对干涉间隔的灵活可调。系统结构设计采用976 nm波长的LD作为泵浦源,长度为6 m的掺铒光纤作为增益介质;采用光栅串将特定波长的光反射回环形腔形成振荡;采用M-Z结构产生梳状滤波用来对光栅串反射回的光进行选择;通过调节ODL来改变腔内损耗,进而实现激光的可调谐输出,并通过在系统中加入可饱和吸收体（SA）和子腔结构来抑制波长的跳变。实验中,在泵浦功率为100 mW时,实现了单波长双波长和三波长的稳定的激光输出。单波长共输出13个,调谐范围为1 570~1 596 nm,调谐间隔为2 nm,边模抑制比均大于50 dB。     

Electrically tunable dual-wavelength switching in a mutually injection-locked erbium-doped fiber ring laser and distributed-feedback laser diode

Wavelength switching in a mutually injection-locked erbium-doped fiber ring laser and distributed-feedback laser diode (DFBLD) is experimentally demonstrated. By adjusting the power and the polarization state of injected light, three stable oscillation regimes were observed: Fabry-Pe/spl acute/rot (FP) mode oscillation, main distributed-feedback (DFB) mode oscillation, and dual-wavelength oscillation. Wavelength switching of 0.8 nm from one of the FP oscillation modes to the main DFB mode of the DFBLD is accomplished when the bias current to the DFBLD is varied from 9 to 14 mA. We also show that these wavelengths can be tuned as much as 2.48 nm when the temperature of the DFBLD is changed by 20/spl deg/C.     

Stable and high-performance multiwavelength erbium-doped fiber laser based on fiber delay interferometer

In this paper, we proposed a novel scheme to realize the multiwavelength erbium-doped fiber lasers. By adding a length of dispersion shifted fiber (DSF) in the ring cavity, we can suppress the cavity mode competition resulting from homogeneous line broadening (HLB) effect. In addition, a comb filter based on fiber delay inter-ferometer (DI) is used for frequency selecting. To enhance the extinction ratio while maintaining the free space range (FSR), the proposed isolator-assisted double-pass DI is utilized into the laser cavity, and a stable 7-wavelength simultaneous lasing spaced at 21.5GHz is accordingly achieved with an extinction ratio of higher than 40 dB. The lasers are stable with a maximum power fluctuation per channel of less than 0.6 dB during an hour test.     

Highly uniform room-temperature multiwavelength unidirectional erbium-doped fibre ring laser without isolators

A high-performance multiwavelength erbium-doped fibre ring laser with sine phase modulator to obtain stable 30 lasing lines in power difference of less than 2 dB is demonstrated. In addition, non-reciprocal loss caused by the proposed cavity structure ensures unidirectional operation when lasing even without optical isolators.