Multi-wavelength generation of L-band brillouin/erbium fibre laser

In this paper, the operation of the Brillouin/erbium fibre laser (BEFL) in the long wavelength band (L-band or 1565–1625 nm) is experimentally demonstrated. The Stokes frequency is shifted 10 GHz from its Brillouin pump (BP) from 1598 to 1612 nm for the single wavelength BEFL. Multiple wavelength generation in the BEFL is realised by adding two 3-dB couplers, which are joined in a reverse-S arrangement to take a portion of the generated BEFL signal and re-inject it into the single-mode fibre (SMF) to seed a cascaded BEFL line in the same direction as the first BEFL line. Twenty lines including the anti-Stokes are obtained with a maximum BP and 980-nm pump power of 8.8 and 92 mW, respectively. The L-band BEFL has the potential to be used in future wavelength division multiplexing (WDM) communication system.     

An Enhanced Bismuth-Based Brillouin/Erbium Fiber Laser with Linear Cavity Configuration

A multi-wavelength Brillouin/erbium-doped fiber laser (BEFL) which operates in 1594 nm region is demonstrated using a 215 cm long Bismuth-based EDF and SMF. Two optical circulators were used at the output ends of the system to form a linear cavity to produce a cascaded Brillouin Stokes and anti-Stokes. A stable output laser comb of more than 20 lines was obtained with a spacing of approximately 0.089 nm at a Brillouin pump power of 4 dBm and two 1,480-nm pumps at powers of 100 mW. The number of lines is relatively higher compared with the ring cavity BEFL.     

Multi-wavelength generation using a bismuth-based EDF and Brillouin effect in a linear cavity configuration

The generation of a multiple wavelength source using a bismuth-based erbium-doped fiber (Bi-EDF) in a linear cavity configuration is demonstrated. The configuration uses a pair of optical circulators at the input and output ends of the cavity to form a resonator for multi-wavelength generation in conjunction with optical couplers to inject the Brillouin pump (BP) and to tap the output at the two ends. The Brillouin erbium fiber laser (BEFL) comb with a 2.15 m of Bi-EDF has a wavelength spacing of 0.09 nm and operates in long-wavelength (L-) band region. A stable output laser comb of 50 lines is obtained at a BP of 1568.2 nm and 5 dBm and two 1480 nm pumps at 120 mW. The injected BP wavelength and power as well as the 1480 nm pump powers have a great effect on the number of lines and output power of the BEFL. This configuration is compact due to the use of the significantly shorter Bi-EDF as the linear gain medium, and can be made more compact by replacing the single-mode fiber with highly non-linear fibers such as holey fibers.     

Effects of output coupler reflectivity on the performance of a linear cavity Brillouin/erbium fiber laser

The effect of output coupler reflectivity (or output coupling ratio) on the performance of a linear cavity Brillouin/erbium fiber laser (BEFL) is demonstrated. The operating wavelength, output laser power and number of channels vary with changes in the coupling ratio in the linear cavity system. The optimum BEFL operation is obtained with an output coupling of 40%, i.e., 60% of the laser power is allowed to oscillate in the cavity. A stable laser comb consisting of up to 40 channels with line spacings of approximately 0.09 nm are obtained at the Brillouin pump and 980 nm pump with powers of 2.5 mW and 100 mW, respectively. The linear cavity BEFL has the potential to be used in inexpensive wavelength division multiplexing system.      

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.     

An efficient S-band brillouin erbium fiber laser with additional EDFA

A short wavelength band brillouin–erbium fiber laser (S-band BEFL) with enhanced characteristics is demonstrated using an additional erbium-doped fiber amplifier (EDFA) in the sub-loop of the laser system. Compared with the conventional BEFL without the additional EDFA, the enhanced BEFL has improved the number of channels as well as the flatness of the brillouin Stoke's peak power. By incorporating a double-pass EDFA, a stable output laser comb up to 8 channels was obtained at 1503 nm wavelength region with peak power variation for the first three Stokes is reduced from 30.9 to 5.4 dB. The incorporation of additional EDFA also increases the tuning range of the BEFL, which the maximum tuning range of 1.8 nm was obtained with the single-pass scheme. The S-band BEFL has constant spacing of 0.09 nm or 11 GHz, which has a potential application in dense wavelength division multiplexed system.     

Modeling erbium–thulium-co-doped fiber amplifier for 1400–1650 nm band

We present numerical models of tri-valence erbium ion and thulium ion-co-doped fiber amplifiers pumped by 800-nm and 980-nm lasers. The rate and power propagation equations of the models are numerically solved to analyze the gain as a function of co-doping concentrations, fiber length and signal wavelength. The results reveal that with 800-nm or 980-nm pump, gain competition exists between 1470- and 1530-nm bands, which may arise from the pump absorption competition and complicated energy transfer between the two types of active ions, and the results further show that the gain spectra may cover 305 nm (1375–1680 nm) for 800-nm pump and 160 nm (1400–1560 nm) for 980-nm pump. The doping concentrations and fiber length may be tuned to reduce the ripple of the gain spectra.     

A linear cavity brillouin/bismuth-based erbium-doped fiber laser with enhanced characteristics

A new linear cavity BEFL configuration for increased Stokes-line generation is proposed and demonstrated utilizing a 2 × 2 coupler at the end of the linear cavity. The proposed linear cavity is able to generate up to 33 Stokes lines in the 1590-nm region at a channel spacing of 0.089 nm. The Stokes lines are generated at a BP power of 4 dBm and a 1480-nm pump power of 100 mW. The number of Stokes generated by the proposed BELF is higher compared to conventional BEFL configurations in which the 2 × 2 coupler is placed in the middle of the linear cavity. The number of Stokes lines generated is observed to depend on the 1480-nm pump power as well as the operating wavelength region, which must be as close as possible to the lasing bandwidth of the free-running BEFL. The proposed multiwavelength BEFL is able to operate stably at room temperatures and is also compact due to the use of a 215-cm bismuth-based EDF as the linear gain medium.     

A novel double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror

In the paper, a ring double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror filter is demonstrated, in which the non-linear amplified fiber loop mirror (AFLMF) is used as a filter. At the 980 nm pump power of 10.29 dBm, the tunable laser source center wavelength of 1563 nm and power of −3 dBm, up to 12 even output channels with 0.16 nm spacing are achieved. At the same time, we study the influence of 980 nm pump power, the polarization controller and the tunable laser source center wavelength on the number of Stokes light wave.     

Stable single frequency and single polarization DFB fiber lasers operated at 1053 nm

Stable single-frequency and single-polarization distributed-feedback (DFB) fiber laser was realized by giving a pressure on the phase shift region of the fiber grating. The output wavelength of the DFB fiber laser is 1053 nm. When the pump power of 980 nm laser diode is 100 and 254 mW, the output power can reach 8.3 and 37.1 mW and the polarization extinction ratio was 26 and 20 dB, respectively. After chopped by Acousto-optic modulator (0.3 Hz), the pulse peak value variance is 4.65%(peak to peak) and 1.098% (RMS) for 31 min.     

Tunable single-longitudinal-mode Ytterbium all fiber laser with saturable-absorber-based auto-tracking filter

A broadband tunable, single-longitudinal-mode (SLM) Ytterbium fiber laser with unpumped Ytterbium-doped Sagnac loop is proposed and demonstrated experimentally. The unpumped Ytterbium-doped Sagnac loop is employed as a saturable absorber based auto-tracking filter to ensure single-longitudinal-mode oscillation. And a tunable band pass optical filter with large tuning range is applied to achieve broadband tuning ability. With 1-m Ytterbium-doped fiber as the gain medium, the SLM operation is achieved with over 60-nm wavelength tuning range at 160-mW pump power. The laser is very stable with output power of about 3 dBm and optical signal to noise ratio of higher than 50 dB in all the 60-nm tuning range.     

10-GHz Optical Comb in L-Band Region With Brillouin/Erbium-Doped Fibre Laser

A multiwavelength Brillouin/erbium fibre laser (BEFL) which operates in the long wavelength (L-band) region is demonstrated for potential applications in an L-band wavelength division multiplexing (WDM) communication system. The laser configuration consists of a long erbium-doped fibre to enable L-band amplification where two 3-dB couplers take a portion of the generated BEFL signal and re-inject it into the single mode fibre to seed a cascaded BEFL line in the same direction as the first BEFL line. A stable and strong laser comb of up to five lines with 10-GHz spacing has been obtained with a Brillouin pump (BP) of 9.2 mW and a 980 nm pump of 92 mW. The BEFL has shown a broad tuning range with a tuning characteristic for line #1 which is flat over a range greater than 9.9 nm.     

15波长输出的布里渊掺铒光纤激光器

多波长布里渊掺铒光纤激光器是一种新型的多波长光纤激光器,其原理是利用受激布里渊增益和掺铒光纤的线性增益,可以在常温下得到波长间隔约为0．08nm(～10GHz)的多波长输出。报道的布里渊掺铒光纤激光器,在布里渊抽运功率为1．7mW、980nm抽运功率为300mW的情况下得到稳定的15个波长(间隔～10GHz)的输出,这种激光器用作光传感器、光谱分析仪以及密集波分复用系统的光源。实验发现,输出波长的个数随着980nm抽运功率的增大而增加。另外,布里渊掺铒光纤激光器的信号功率主要来自于掺铒光纤的增益,而布里渊增益对它的影响不大。     

Demonstration of an all-optical switching operation using an optical fiber grating coupler

An optical fiber grating coupler (FGC) is a fused optical fiber coupler with a tapered region in which refractive index-modulated gratings are written. In the FGC, the light with specific wavelength satisfying the Bragg condition of the grating can be dropped to one output port and other lights are transmitted to another output port when lights with various wavelengths are launched into the input port. The FGC can operate as an all-optical switch by controlling the Bragg wavelength of the grating using a third order nonlinear optical effect caused by a control light that are launched with a signal light. In this paper, an all-optical switching operation due to a third order nonlinear optical effect in an FGC is first demonstrated for a signal light with 1.55 μm-wavelength to be changed from one port of the FGC to another one by the 720 W peak of a control light from a Nd:YAG laser with 1.06 μm-wavelength. The switching efficiency obtained was 7%. It was clarified that a longer pulse length of the control light compared to the grating length is required to obtain a large Bragg wavelength shift for the switching. It was also clarified that the Bragg wavelength shift is caused by a third order nonlinear effect and a photothermal effect. A contribution of the photothermal effect was estimated. We also estimated the switching efficiency for pump power in the FGC switch.     

Optimization of Brillouin pump wavelength location on tunable multiwavelength BEFL

Optimization of Brillouin pump (BP) wavelength location on tunable multiwavelength Brillouin-erbium fiber laser (BEFL) with BP pre-amplified technique is experimentally investigated. The tunable multiwavelength BEFL is achieved by utilization a tunable band-pass filter in a laser cavity. The optimum BP power and BP wavelength location within the filter bandwidth is determined in order to obtain the maximum stable output channels. Optimum distance of launching the BP wavelength is found at 0.80 nm shorter from the center wavelength of the filter bandwidth. 15 stable output channels are achieved from the tunable fiber laser system within the optimum range of BP power which is found to be between 5.2 to 5.7 dBm.     

Thermally tunable microfiber knot resonator based erbium-doped fiber laser

A compact and tunable erbium-doped fiber laser is demonstrated using a highly doped fiber and a microfiber knot resonator (MKR) structure which is laid on the surface of a small peltier. The MKR functions as both a reflector and a tunable filter where tunability is achieved by varying the temperature of the resonator by heating the peltier. A stable laser output is achieved at the 1533 nm region with an optical signal to noise ratio (OSNR) of 27 dB using a 65 mW of 980 nm pump power. The operating wavelength of the laser can be tuned from 1532.60 nm to 1533.49 nm as the temperature is increased from the room temperature of 24 to 90 °C. It is observed that the operating wavelength shifts to a longer wavelength as the temperature increases with an efficiency of 12.4 pm/°C. This is due to the thermally induced optical phase shift attributable to the changes in effective refractive index and optical path length of the MKR loop.     

基于受激布里渊散射的波长间隔可变多波长光纤激光器

提出了一个基于自激发受激布里渊散射的波长间隔可变多波长光纤激光器.利用单模光纤中自激发产生的非线性布里渊增益和掺铒光纤的线性增益组成混合增益光纤激光器,从而使光纤激光器在室温下产生稳定的多波长输出.改变双折射光纤环镜滤波器中保偏光纤的长度,可以实现波长间隔可变多波长激光产生,提高了多波长光纤激光器操作的灵活性和实用性.实验实现了波长间隔从0.8 nm至0.076 nm可变的多波长激光产生,波长数随波长间隔减小而增加,间隔为0.08 nm的激光波长数达86.     

高稳定宽频带掺铒光纤超荧光光源

理论研究了双程后向结构掺铒光纤超荧光光源的特性。结果表明 ,在任意反射镜参数下 ,只要选取适当的掺铒光纤长度 ,该结构光源总能实现不依赖于抽运功率的平均波长高稳定性运行 ;在光源高稳定性的前提下 ,反射镜参数优化后的该结构光源具有较宽的频带宽度和较高的抽运效率