Wavelength-selection erbium fiber laser with single-mode operation using simple ring design

In this demonstration, we propose and experimentally investigate a wavelength-selection erbium-doped fiber (EDF) laser in single-longitudinal-mode (SLM) by using simple fiber ring scheme design. We use a tunable bandpass filter (TBF) inside the gain cavity to restrict the lasing frequency. The proposed ring cavities can also serve as the mode filters for side mode suppression. Based on the simple ring cavity design, the mode hopping can be avoided to achieve SLM output. The TBF inside the laser scheme also obtains the wavelength tuning in the range of 1520.02 to 1562.02 nm. In addition, the output performance of the proposed fiber laser has also been discussed.     

Stable single-longitudinal-mode fiber laser using PM FBG F-P etalon and PM fiber saturable absorber

we present a stable and high efficiency single-longitudinal-mode (SLM) fiber ring laser by using polarization-maintaining fiber Bragg grating Fabry-Perot (PM FBG F-P) etalon combining PM fiber saturable absorber. The PM FBG F-P etalon, which is directly fabricated in hydrogen-loaded PM fiber, is used as reflector and mode-selecting component to reduce the longitudinal-mode density greatly. Meanwhile, a segment un-pumped PM Er³⁺-doped fiber (EDF) serves as saturable absorber to suppress mode hopping and ensure the stable SLM operation. Stable SLM laser output at 1550.4 nm with linewidth of 2.0 kHz is observed. Laser output power is 43.7 mW for a pump power of 148 mW, optical-optical efficiency is 29.5% and signal-to-noise ratio (SNR) is larger than 55 dB.     

Single-longitudinal-mode erbium-doped fiber laser based on a fiber Bragg grating Fabry-Perot filter

A novel single-longitudinal-mode (SLM) erbium-doped fiber laser with a simple linear cavity based on a fiber Bragg grating Fabry-Perot filter (FBG-FPF) and a narrowband (～0.06 nm) FBG is proposed and demonstrated experimentally. Two uniform FBGs form the FBG-FPF, which has two ultranarrow transmission bands with a bandwidth of 0.12 pm and a wavelength spacing of 0.095 nm. By slightly tuning the central wavelength of the narrowband FBG, SLM lasing at 1549.658 or 1549.563 nm (corresponding to the two transmission peaks of the FBG-FPF) is achieved with a laser output power of ～4 mW, when the pump power is ～75 mW.     

Single-longitudinal-mode fiber ring laser using fiber grating-based Fabry-Perot filters and variable saturable absorbers

A single-longitudinal-mode (SLM) fiber ring laser is demonstrated by incorporating a fiber Bragg grating (FBG)-based Fabry-Perot (F-P) filter and a variable saturable absorber in a fiber ring cavity. An ultra-narrow bandpass filter is established by the combined mode filtering of the FBG-based F-P filter and the variable saturable absorber. No accurate control for cavity length is required, and stable single longitudinal-mode operation without mode hopping is conveniently achieved.     

Stable single longitudinal mode erbium-doped silica fiber laser based on asymmetric linear three-cavity structure

We present a stable linear-cavity single longitudinal mode (SLM) erbium-doped silica fiber laser. It consists of four fiber Bragg gratings (FBGs) directly written in a section of photosensitive erbium-doped fiber (EDF) to form asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio (OSNR) of about 60 dB is verified experimentally. In laboratory condition, the performance of power fluctuation of less than 0.05 dB observed from the power meter for 6 h and wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer (OSA) for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.     

Stable single longitudinal mode fiber ring laser based on polarization maintaining erbium doped fiber

A stable single longitudinal mode (SLM) fiber ring laser that incorporates polarization maintaining erbium doped fiber (PM EDF) acting as gain medium and saturable absorber is proposed and demonstrated. Both theoretical deviation and experimental result prove that optical intensity is time invariant when the laser operates in single longitudinal mode, the SLM operation can be approximately verified by optical intensity analysis, which is practical to analyze longitudinal mode in the application of engineering. The linewidth of the fiber ring laser is measured by the delayed self-heterodyne interferometery, and an acousto-optic frequency shifter is employed to shift the lasing frequency and eliminate zero frequency interfere. The SLM operation is verified by the scanning Fabry–Perot interferometer, whereas the lasing frequency drift slowly during a period of 2 h, PM EDF is proved to be effective on suppressing mode hopping and selecting longitudinal mode.     

Stable single longitudinal mode erbium-doped silica fiber laser based on an asymmetric linear three-cavity structure

We present a stable linear-cavity single longitudinal mode (SLM) erbium-doped silica fiber laser. It consists of four fiber Bragg gratings (FBGs) directly written in a section of photosensitive erbium-doped fiber (EDF) to form an asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio (OSNR) of about 60 dB is verified experimentally. Under laboratory conditions, the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer (OSA) for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.     

Quasi-distributed fiber Bragg grating sensor system based on a Fourier domain mode locking fiber laser

A novel quasi-distributed fiber Bragg grating (FBG) sensor system based on Fourier domain mode locking (FDML) fiber laser is proposed and demonstrated. The low reflectivity FBGs with the same Bragg wavelength are connected cascaded in a long fiber working as the sensing elements of the sensor system as well as the wavelength and cavity length selecting elements of the FDML laser. By adjusting the driving frequency of the FDML fiber laser, lasing with different selected cavity lengths will be achieved correspondingly. When the wavelength of the working FBG shifts which includes the sensing information, FBG interrogation can be realized both in wavelength and time domain.     

Single-longitudinal-mode operation of a grating-based fiber-ring laser using self-injection feedback

A fiber Bragg grating- (FBG-) based fiber-ring laser that utilizes the transmitted light of the FBG as self-injection feedback for single-longitudinal-mode (SLM) oscillation is proposed and demonstrated. This laser is simply constructed by means of feeding back the transmitted light of the FBG and is coupled into the main ring cavity through an optical coupler. The self-injection feedback is the key to ensuring SLM laser oscillation. The SLM operation principle is discussed in detail, and a SLM laser with output power of 6.6 dBm, an optical signal-to-noise ratio of 57 dB at 1549.19 nm, and a short-term linewidth of 3.5 kHz is reported.     

Tunable erbium-doped fiber ring laser with signal-averaging function for fiber-optic sensing applications

This work proposes a novel erbium-doped fiber ring laser as a sensing control center (CC) for long-haul fiber Bragg grating (FBG) sensor systems. The tunable erbium-doped fiber laser with signal averaging functionality not only provides intense and stable laser light, but also suppresses the effect of noise on the system performance. A sample 30/60 km FBG sensor array is connected to the fiber ring laser to demonstrate experimentally the feasibility and effectiveness of the laser as a CC. The experimental results indicate that the signal averaging operation inside the proposed setup increases the system signal-to-noise ratio (SNR).     

基于线型腔掺铒光纤激光器的光纤光栅传感实验研究

提出了一种基于线型腔掺铒光纤激光器的光纤布拉格光栅传感解调系统,并进行了理论分析和实验验证。此传感系统具有稳定性好、信噪比高、结构简单等特点。实验结果表明:在常温下光纤光栅传感解调系统能很好的实现光纤光栅传感信号的传感和检测;15m掺铒光纤用作增益介质可以产生较大信噪比的稳定激光输出,系统在4nm范围内的解调精度为0.04nm。     

Stable single frequency Er-doped all-fiber ring laser with fiber Bragg grating Fabry-Perot filter

Using a fiber Bragg grating (FBG) and a Fabry-Perot cavity composed of two fiber Bragg gratings (FBGFP) as its frequency-selective components, a type of single frequency all-fiber ring laser permits oscillation only on one longitudinal mode of the main cavity without modehopping while the cavity length can be up to tens of meters. The salient feature is due to the single narrowband resonance of the FBGFP filter. Such a fiber ring laser is achieved experimentally, and the laser mode is limited inside the single resonance of the FBGFP.     

Dual-wavelength S-band erbium-doped fiber double-ring laser

We propose and demonstrate an S-band CW dual-wavelength erbium-doped fiber (EDF) dual-ring laser using a compound-ring filter (CRF) with various coupling losses inside the gain cavity. Employing a ring filter combined within the cavity, the fiber laser can lase a dual wavelength without any filter inside the ring loop. The dual-wavelength output exhibits a good performance having optical side-mode suppression ratios (SMSRs) of 31.6 and 31.8 dB and output powers of ?9.6 and ?9.3 dBm at 1505.58 and 1506.43 nm, respectively, when the coupling loss is 30% inside the cavity. In addition, the output stabilities of the dual-wavelength laser have also been analyzed.     

Single-longitudinal-mode erbium-doped fiber laser with the fiber-Bragg-grating-based asymmetric two-cavity structure

We present a simple and stable single-longitudinal-mode (SLM) erbium-doped fiber linear-type laser. It consists of three FBGs directly written in a photosensitive erbium-doped fiber (PEDF) to form asymmetric two cavities with different cavity lengths, which can effectively increase the longitudinal mode spacing and suppress mode hopping, experimentally compared with symmetric two cavities and single-cavity structures. The stable SLM operation is conveniently achieved without accurate control of cavity length, and the laser linewidth of less than 5 kHz is acquired.     

Tunable single-longitudinal-mode SOA-based fiber laser based on the spectral narrowing effect in a dispersion-shifted fiber

A tunable single-longitudinal-mode(SLM) semiconductor optical amplifier(SOA)-based fiber laser based on a dispersion-shifted fiber(DSF) is proposed and successfully demonstrated. SLM operation is obtained due to the spectral narrowing effect resulting from inverse four-wave mixing in a DSF. A tunable optical filter performs wavelength selection function. By inserting a length of DSF in the laser cavity, SLM lasing can possibly be obtained when laser oscillation is stably established after traveling through the DSF many roundtrips. Stable tunable SLM oscillation with a signal-to-noise ratio as high as 65 dB over a wavelength range of about 35 nm is achieved experimentally, and each spectral linewidth is less than 6.5 kHz.     

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.     

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.     

Multiple fiber Bragg grating interrogation based on a spectrum-limited Fourier domain mode-locking fiber laser

A novel fiber Bragg grating (FBG) sensing system based on a spectrum-limited Fourier domain mode-locking (SL-FDML) fiber laser is proposed. Multiple FBGs cascaded in a long fiber are utilized as both the sensors in the system and the wavelength-selected components in the SL-FDML fiber laser. Both wavelength-division multiplexing and spatial-division multiplexing techniques are demonstrated for interrogation of multiple FBGs by mapping the wavelength measurement to the time measurement and by adjusting the driving frequency of the SL-FDML fiber laser. The proposed FBG sensing system, employing techniques of the wavelength- and spatial-domain interrogation of multiple FBGs, can be used in remote and quasi-distributed multipoint sensing.     

Single-longitudinal-mode Brillouin fiber laser incorporating an unpumped erbium-doped fiber loop

A long-cavity single-longitudinal-mode (SLM) Brillouin fiber laser is firstly demonstrated by utilizing an unpumped Erbium-doped fiber (EDF) loop. The utilized EDF enables to form a self-induced ultra-narrow grating filter, and thus guarantees the SLM operation.     

Pressure sensing utilizing linear cavity erbium-doped fiber laser

In this paper, we report a fiber laser pressure sensor based on linear cavity erbium-doped fiber laser. The fiber laser structure comprises of an erbium-doped fiber amplifier, a circulator, an optical coupler and a fiber Bragg grating (FBG) which acts simultaneously as a lasing wavelength selecting components as well as a pressure sensor. The FBG is fitted to the shock tube where the pressure is applied. The fiber laser pressure sensor has a low threshold power of 7 mW, an output power of 2.28 mW and an optical signal to noise ratio over 55 dB. The proposed fiber laser sensor is expected to be an attractive choice for long-distance pressure monitoring.