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.     

Multiwavelength erbium-doped fiber laser based on nonlinear polarization rotation assisted by four-wave-mixing

We experimentally demonstrate a simple-structure but efficient multiwavelength erbium-doped fiber laser based on nonlinear polarization rotation assisted by four-wave-mixing (FWM). Based on the combination of these two nonlinear mechanisms contributing to intensity-dependent loss to alleviate mode competition, the stable multiwavelength operation at room temperature can be realized in a length of dispersion-shifted fiber. We achieved up to 38-wavelength generation with a spacing of ∼0.4 nm in the laser. In addition, through tuning the birefringence fiber filter, the lasing wavelength can be accurately tuned in the free spectrum range.     

Multiwavelength fiber laser using S-band erbium-doped fiber amplifier and semiconductor optical amplifier

A multiwavelength fiber ring laser that is based on an S-band erbium-doped fiber amplifier (EDFA) and a semiconductor optical amplifier (SOA) is developed. An optical switch is used to switch the multiwavelength fiber laser between S-band and L-band. This fiber laser can stably lase seven wavelengths in the S-band or 28 wavelengths in the L-band. Additionally, the lasing wavelengths with a signal-to-noise ratio of over 33 dB and a wavelength spacing of 100 GHz are demonstrated experimentally. The average powers of the lasing wavelength in the S-band and the L-band are −7.53 and −12.15 dBm, respectively.     

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.     

Simple tunable multiwavelength Brillouin/Erbium fiber laser utilizing short-length photonic crystal fiber

We have demonstrated a simple ring cavity tunable multiwavelength Brillouin/Erbium fiber laser (MWBEFL), in which 70 m highly nonlinear photonic crystal fiber (HNL-PCF) is used as the Brillouin gain medium. The fiber laser utilizes recycling mechanism to enhance stimulated Brillouin scattering (SBS). The configuration that consists of only 3 optical components is easy to be integrated and improves the practicality. At the maximum 1480 nm pump power of 110 mW and the Brillouin pump power of 3 dBm, 10 stable output channels with more than 10 dB optical signal to noise ratio (OSNR) and 0.078 nm channel spacing could achieve 10 nm tuning ranges.     

Hybrid Brillouin/Erbium fibre laser in a linear cavity for multi-wavelength communication systems

A novel technique of producing multiwavelength laser source was described utilising a linear cavity of hybrid Brillouin/Erbium fibre laser (BEFL). Twenty-two stable output lasers with 10.88 GHz line spacing were obtained from this architecture at 1557.5 nm that was at the peak of Erbium gain. The requirement of an internal feedback that is commonly used in a ring configuration to generate cascaded Brillouin Stokes for multiple wavelengths operation was achieved by the proposed linear cavity design.     

Stable room-temperature multi-wavelength lasing oscillations in a Brillouin–Raman fiber ring laser

A stable room-temperature multi-wavelength Brillouin–Raman fiber laser with a ring cavity configuration was proposed and experimentally investigated. An obvious suppressant effect for unstable mode hopping of multi-wavelength lasing oscillations induced by deeply saturated effect was observed in the ring cavity configuration. Stable room-temperature multi-wavelength lasing oscillations with more than 30 lasing lines and wavelength spacing of 0.076 nm were obtained with only 250 mW Raman pump power and a section of high nonlinear fiber with a length of 1.5 km. The lasing output is so stable that the maximum power fluctuations for the foremost three Stokes lines over more than 20 min of observation were less than 0.30 dB. The lasing stability of the laser was also compared with a linear cavity configuration with the same gain components and pump conditions. While using the linear laser cavity configuration, obvious mode hopping was observed. The minimum value of the maximum power fluctuations at all lasing lines over more than 10 min of observation was more than 0.90 dB.     

Switchable triple-wavelength erbium-doped fiber laser using a single fiber Bragg grating in polarization-maintaining fiber

A stable and narrow wavelength spacing multiwavelength erbium-doped fiber laser is proposed and demonstrated. The laser can produce simultaneous dual- and triple-wavelength lasing oscillations with a narrow wavelength spacing of less than 0.1 nm via using a single fiber Bragg gratings written in polarization-maintaining (PM) fiber. By adjusting polarization controller, the wavelength spacing of dual-wavelength lasing oscillations can be tuned to as small as 0.032 nm. The maximum amplitude variation for every lasing wavelength is less than 0.5 dB. The room-temperature operation principle is based on the polarization hole burning and deeply saturated effect in an ordinary erbium-doped fiber ring laser (EDFRL). The laser has the advantages of simple all-fiber configuration, low cost, high stability and operating at room temperature.     

Millimeter wave carrier generation based on Brillouin fiber laser with improved tuning capability

An all-optically generated millimeter wave carrier at 21.7 GHz, 43 GHz and 64.45 GHz are experimentally achieved. These frequencies are realized by generating two consecutively laser wavelengths and are detecting on the 70 GHz high-speed photo detector (HSPD). The initial mixing between the Brillouin pump and the second-order Stokes wavelengths is spaced by 0.178 nm. This spacing, which is doubled from an inherently generated Stokes shift, is accomplished through an isolated circulation of the first order Stokes wave in the double Brillouin Stokes shifter (DSBS) built with 25-km single mode fiber. The generated millimeter carrier is measured at 21.7 GHz, 43 GHz and 64.4 GHz achieved with BP power of 11 mW, 30 mW and 47 mW, respectively.     

Microwave generation using an all polarization-maintaining linear cavity dual-wavelength fiber laser with tunable wavelength spacing

A stable dual-wavelength erbium-doped fiber laser with a linear cavity is formed by a polarization-maintaining uniform fiber Bragg grating (PM-FBG) and a polarization-maintaining linearly chirped fiber Bragg grating (PM-LCFBG), both of which were fabricated on a high-birefringence (Hi-Bi) fiber. Experimental results show stable dual-wavelength lasing operation with a wavelength separation of ∼0.22 nm, which can be tuned down to as small as 0.05 nm and a large optical signal-to-noise ratio (OSNR) of over 40 dB under room-temperature. Microwave signal at frequency of 9.41, 18.03 and 27.46 GHz is achieved by heterodyned the output lasing wavelengths on a photodetector.     

Wideband wavelength tunable fiber ring laser with flattened output power spectrum

A wavelength tunable erbium-doped fiber ring laser with flattened output power spectrum over a broadband is proposed and demonstrated. The power flattening is achieved using a high-birefringence fiber loop mirror, in which a number of high-birefringence fiber sections and polarization controllers are used to get a reflection spectrum that can compensate for the output power spectrum. The wavelength tuning is realized by compressing or stretching the FBGs in the laser cavity. A 1×3 switchable fiber Bragg grating array is incorporated into the fiber ring to get a wideband tuning range of 38 nm, from 1527 to 1565 nm. Within this range, the output power uniformity is controlled within ±0.8 dB. The total output power is about 4 dBm, the 3-dB linewidth is 0.01 nm, and the side mode suppression ratio is more than 48 dB.     

0.16 nm spaced multi-wavelength Brillouin fiber laser in a figure-of-eight configuration

A stable and compact multi-wavelength Brillouin fiber laser (BFL) operating at room temperature is experimentally demonstrated using a 100 m long photonic crystal fiber (PCF) in conjunction with a figure-of-eight configuration. At a Brillouin pump (BP) level of 15.3 dBm, 7 simultaneous lines with 20 GHz or 0.16 nm line spacing is achieved by removing the odd-order Stokes lines. The anti-Stokes lines are also generated via four wave mixing process in the laser cavity. Compared with the Erbium-based multi-wavelength laser, this BFL has advantages in term of channel spacing and flexibility in the choice of operating wavelength. The output spectrum of the proposed BFL can be tuned by 80 nm, dependent on the availability of an appropriate BP source. The multi-wavelength BFL shows a good stability with power fluctuations of less than 0.5 dB over more than 3 h.     

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.     

间隔0.173nm的可调谐多波长布里渊掺铒光纤激光器

使用四端口环行器和可调谐滤波器,设计了一种间隔为双倍布里渊频移的多波长布里渊掺铒光纤激光器.该光纤激光器中使用的四端口环形器可以限制奇次阶斯托克斯光在腔内循环并耦合输出初始泵浦光和偶次阶斯托克斯光,而可调滤波器抑制环形腔所形成的自激振荡模,增加了激发多波长激光的功率,从而增加多波长输出个数及其调谐范围.在布里渊泵浦功率为8dBm、980nm泵浦功率为279mW时,实验获得波长间隔为0.173nm的6个波长的激光输出,输出激光的可调谐范围为28nm.     

C-band continuously tunable lasers using tunable fiber Bragg gratings

We report the development of a ring tunable fiber laser based on tunable fiber Bragg gratings (TFBG) integrated with an optical circulator. The TFBG is embedded inside a 3-piont bending device for wavelength tuning. The tunable laser operating in the C-band has power variation, tuning resolution, tuning range and laser line width of ±0.5 dB, 0.5 nm, 25.0 nm and less than 0.05 nm, respectively. As 40 mW of pump power is used, the ring tunable laser has a side mode suppression ratio of 60 dB and a power conversion efficiency of 25%. These specifications ensure the high-quality operation of a tunable laser.     

A widely tunable dual-wavelength erbium-doped fiber ring laser operating in single longitudinal mode

A new mechanism to induce polarization hole burning effect in Er-doped fiber ring lasers is presented. By using this effect, incorporating with the counter-propagation of the two light beams, the inhomogeneous in the gain medium broadening was significantly increased, and thus a stable dual-frequency Er-doped fiber ring laser operating in single longitudinal mode and single-frequency was demonstrated. Frequency spacing was tunable from 0.47 GHz to THz.     

Multiwavelength erbium-doped fiber laser employing a nonlinear optical loop mirror

A stable and broad bandwidth multiwavelength erbium-doped fiber laser is proposed and demonstrated successfully. A nonlinear optical loop mirror which induces wavelength-dependent cavity loss and behaves as an amplitude equalizer is employed to ensure stable room-temperature multiwavelength operation. Up to 50 wavelengths lasing oscillations with wavelength spacing of 0.8 nm within a 3-dB spectral range of 1562-1605 nm has been achieved. The measured power fluctuation of each wavelength is about 0.1 dB within a 2-h period.     

Optimization of erbium-doped fiber MOPA laser

An erbium-doped fiber laser (EDFL) constructed in a master oscillator and power amplifier (MOPA) configuration is analyzed. The pump powers for the fiber cavity laser and the booster amplifier stages are managed properly to achieve maximal pump conversion efficiency. Our design achieves a pump conversion efficiency of 91.4%, corresponding to a quantum efficiency of 96.6%, for a 1565.8 nm MOPA laser pumped by a total power of 300 mW at 1480 nm. The optimized MOPA laser shows a 25% enhancement in the pump conversion efficiency, compared to a non-MOPA fiber laser. A side lobe suppression ratio of 48 dB for the optimized MOPA laser is observed.     

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.      

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.