Tunable Erbium-doped Fiber Ring Laser Research Articles

Tunable narrow linewidth erbium-doped fiber ring laser based on saturable absorber and self-injection feedback

Tunable narrow linewidth erbium-doped fiber ring laser based on saturable absorber and self-injection feedback

Tunable and stable single-frequency fiber laser by applying Rayleigh feedback light and saturable absorber filter

In this study, a stable and tunable erbium-doped fiber (EDF) ring laser architecture is demonstrated. To filter the dense longitudinal-mode noises and achieve the single-longitudinal-mode (SLM) performance, the Rayleigh backscattering (RB) feedback injection and unpumped EDF saturable absorber (SA) induced filter is applied inside the ring cavity. Here, an effective wavelength-selection scale of the EDF laser is achieved between 1528.0 and 1576.0 nm, when C-band EDF based gain-medium is utilized. Additionally, the wavelength linewidth, optical signal to noise ratio (OSNR), output power and output stability of the fiber laser are also discussed over the available wavelength range in the measurement.

Switchable and tunable multi-wavelength erbium-doped fiber ring laser based on single STS filter

A novel switchable and tunable multi-wavelength erbium-doped fiber ring laser (EDFL) is proposed and experimentally demonstrated by using a single SMF-TMF-SMF (STS) structure filter. The STS filter, based on mode interference, is fabricated by sandwiching a section of two-mode fiber (TMF) between single mode fibers (SMF) through core-offset splicing, which has a comb spectrum with obvious envelope and uniform fluctuation. The transmission characteristics of the STS filter can be changed by adjusting the polarization controller (PC) wrapped on the TMF. Based on the cooperation of the STS filter and polarization dependent loss (PDL), the fiber laser can be individually switchable and widely tunable. By adjusting the PC, the outputs can be switched from single-wavelength to adjacent eight-wavelength and can be tuned in the range of 1528 ∼ 1561 nm. Furthermore, non-adjacent dual-, three- and four-wavelength with different intervals can also be achieved by appropriately adjusting the PC. With the assistance of four wave mixing (FWM) effect, the fiber laser has a stable output. The tuning and switching of the proposed multi-wavelength EDFL is simple and flexible.

Broadly Tunable Erbium-Doped Fiber Ring Laser Based on Tapered Polarization Maintaining Fiber

A broadly tunable erbium-doped fiber ring laser is proposed and demonstrated based on the tapered polarization maintaining fiber (PMF) Sagnac interferometer, in which the Sagnac and intermodal interferences are superimposed to generate one localized peak over a wide wavelength range in its transmission spectrum. By heating the tapered PMF, the localized peak may be discretely tuned with the temperature at the step, depending on the intermodal interference. Tunability may become continuous when additional stress is exerted longitudinally on the tapered PMF. The tapered PMF Sagnac interferometer is inserted into the laser cavity to achieve broadly and continuously tunable output. Specifically, by optimizing the PMF length and its tapering section to obtain proper channel intervals of the Sagnac and intermodal interference, the lasing wavelength is continuously tuned over 60 nm covering from 1565.1 nm to 1625.2 nm with sidemode suppression ratio higher than 50 dB and power uniformity better than 1 dB. The tuning responses to temperature and axial stress are both linear with sensitivity of −1.1 nm/°C and −29.4 pm/μϵ. Most importantly, the temperature and axial stress affect the Sagnac and intermodal interferences, respectively, which makes it convenient to set the lasing wavelength beforehand during operation.

Narrow spectral linewidth and tunable erbium-doped fiber ring laser using a MZI based on CHCF

In this paper, a narrow spectral linewidth and wavelength-tunable erbium-doped fiber laser based on a Mach-Zehnder interferometer (MZI) as a filter is proposed and experimentally demonstrated. The filter is fabricated by splicing a short length of capillary hollow-core fiber (CHCF) between two small sections of multimode fibers (MMF). The interference pattern generated by the filter has a free spectral range of 10.5 nm and a maximum extinction ratio of 36 dB at 1560 nm. Then, by incorporating the filter inside a ring cavity laser, a single laser emission centered at 1566.46 nm with a spectral width around 0.03 nm and a high SNR of 66 dB (also has a SMSR of 53 dB) is obtained. By changing the temperature of the filter, the wavelength emission of the laser can be tuned from 1566.46 to 1570.09 nm. Considering that the fabrication process of the filter is relatively simple and can be easily implemented in an EDFL, we strongly believe that it can have a great deal of interest in telecom applications.

Fiber Bragg Grating Sensor Interrogation Using Tunable Erbium-Doped Fiber Ring Laser Source

Fiber Bragg gratings (FBG) are ideal sensors for temperature, strain or vibration sensing applications with their advantages over conventional electronics sensor systems. In this paper, two different FBG sensor interrogation schemes based on broadband ASE source and tunable EDFRL source are demonstrated and compared. With both interrogator configurations, the response of the FBG sensor to temperature change is found to be linear and the sensitivities are measured as 11 pm/°C and 10.5 pm/°C, respectively. The experimental results have revealed that the optical power reflected from the FBG sensor is almost 20 dB higher with tunable EDFRL source than broadband ASE source. Thus, an interrogation method with tunable EDFRL can be suitable for remote, quasi-distributed sensor applications requiring high output power and OSNR.

Loss-Modulation-Based Wavelength-Range Shifting of Tunable EDF Ring Laser with Cascaded-Chirped Long-Period Fiber Grating for Temperature Measurement.

A novel tunable Erbium-doped fiber ring laser (EDFRL) with a cascaded-chirped long-period fiber grating (C-CLPG) as a wavelength selection filter is proposed from the viewpoint of the sensor use, in which a variable optical attenuator (VOA) is employed as an intracavity loss modulator to change the oscillation wavelength region so that the resultant tuning wavelength range is widened. In the demonstrative experiment for temperature measurements, oscillation over the wavelength range of 12.85 nm (1557.62~1570.47 nm), which is more than three times range of the previously presented laser and is equivalent to 64 °C in terms of temperature change, was achieved, while a single-wavelength oscillation was maintained. In addition, a practical technique for realizing a temperature measurement by combining with the VOA control is also discussed.

EDF ring laser using cascaded-chirped long period fiber grating for temperature measurement.

A novel tunable erbium-doped fiber ring laser (EDFRL) using a cascaded-chirped long period fiber grating (C-CLPG) as a wavelength selection element is proposed. The oscillation wavelength is determined by the one of the spectral peaks of the C-CLPG used, and the oscillation output provides a high signal to noise (S/N) ratio detection and a highly sensitive measurement of the temperature due to its high power and narrow spectral output. In the experiment, it is confirmed that the wavelength of the output shifts in accordance with the temperature-induced spectral shift of the C-CLPG transmittance spectrum and the temperature sensitivity is obtained to be ∼-0.2 nm/°C within the wavelength range of 1567.30 ∼ 1575.78 nm. The oscillation wavelength range is to be limited depending on the fringe spacing of the channeled spectrum of C-CLPG, which limits the temperature measurement range, but a data processing approach to solve this problem is additionally proposed and its availability is also presented.

Tunable single-wavelength erbium-doped fiber ring laser using a large-core fiber

In this paper, a tunable single-wavelength erbium-doped fiber ring laser is proposed. A novel fiber filter based on a large-core fiber is developed for suppressing the mode competition in erbium-doped fiber lasers (EDFLs). Under the pump power of 250 mW, single-wavelength lasing output is implemented with a side mode suppression ratio (SMSR) higher than 55 dB. By adjusting the curvature applied on the large-core fiber, stably tunable single-wavelength lasing output within the wavelength range from 1552.4 nm to 1563.2 nm is obtained with a 3 dB linewidth of 0.2 nm. Furthermore, the wavelength shift and peak power fluctuation are controlled within 0.02 nm and 0.5 dB by monitoring the lasing output with an interval of 6 min in one hour, respectively. A contrast experiment of a laser without tapering LCF is carried out to examine the importance of the taper in LCF-based filter. Experimental results demonstrate that the side modes of the lasing output can be effectively suppressed and thus SMSR can be improved from 41 dB to 58 dB by using a taper.

Compound comb filter based on Sagnac interferometer and phase shifted fiber Bragg grating using for tunable and switchable fiber ring laser

A kind of stable, switchable and tunable erbium-doped fiber ring laser based on a Sagnac interferometer (SI) is presented and experimentally demonstrated. The SI is composed of a section of an elliptical-core spun fiber sandwiched between two polarization controllers (PCs) in a Sagnac loop. The proposed compound comb filter, which consists of an SI cascaded with a phase shifted fiber Bragg grating, is developed to suppress the mode competition in the laser oscillation. By adjusting the PCs, a stable and tunable single-wavelength lasing output can be achieved. The optical signal-to-noise ratio (OSNR) is better than 40 dB, and the 3 dB linewidth is less than 15 pm. Furthermore, stable dual-wavelength lasing outputs with different wavelength intervals of 0.132 nm, 0.336 nm and 0.418 nm can also be obtained by carefully adjusting the PCs. The power difference between the two lasing peaks is less than 2 dB, and the OSNR is about 50 dB.

Tunable multi-wavelength EDF laser based on Sagnac interferometer with weakly-coupled FMF delay line

A simply manufactured and broadly tunable multi-wavelength Erbium-doped fiber (EDF) ring laser based on Sagnac interferometer with weakly-coupled few-mode fiber (FMF) delay line is proposed and experimentally demonstrated. The incorporation of FMF is realized with all-fiber mode multiplexer/demultiplexer (MUX/DEMUX) consisted of mode-selective couplers (MSC). The FMF and the mode MUX can simultaneously generate higher-order modes and fundamental mode. Single-, dual- and triple-wavelength lasing are obtained with broad tuning over 30-nm and smallest tuning step of 0.52-nm by adjusting polarization controller (PC) in the Sagnac interferometer. Optical signal-to-noise ratio (OSNR) higher than 30-dB and stability in 30-min are also measured.

Tunable single wavelength erbium-doped fiber ring laser based on in-line Mach-Zehnder strain

A tunable single-wavelength of an erbium-doped fiber ring laser is proposed and demonstrated. The laser integrates a tapered in-line Mach-Zehnder interferometer (IMZI) in its ring loop as an intracavity filter. The light spectrum is adjusted by changing an axial strain of the interferometer in a 60μm range. As a result, a total tuning range of 6.19nm that covers the wavelength from 1552.94nm to 1559.13nm is observed, and the sensitivity of 103.5pm/μm is recorded. This high sensitivity lasing behavior is useful for high selectivity and fine tuning for narrow wavelength applications.

A widely tunable fiber ring laser with closed loop control based on high-precision stepper motor

A tunable single-longitudinal mode erbium-doped fiber ring laser based on stepper motor and closed loop control is proposed and demonstrated. The system consists of an erbium-doped fiber (EDF), a tunable fiber Bragg grating (FBG) filter and a wavelength detector. The characteristics of output laser, such as output power, power stability and 3-dB linewidth, are investigated in the operation range of 1 531—1 569 nm. The repeated experimental results of the fiber laser show that the 3-dB linewidth is less than 17 ps, the side-mode suppression ratio (SMSR) is up to 60 dB, the output power is up to 1.37 dBm, and the power variation is less than 0.61 dB.

Selectable dual-wavelength erbium-doped fiber laser with stable single-longitudinal-mode utilizing eye-type compound-ring configuration

In this paper, a tunable dual-wavelength erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) under a tuning range of 1530.0–1560.0nm is proposed and demonstrated. Here, the mode spacing of lasing dual-wavelength from 1.0 to 30.0nm can be selected arbitrarily in any wavelength position. To accomplish the SLM output, the eye-type compound-ring scheme is proposed inside ring cavity for suppressing the multi-longitudinal-mode (MLM) highly. The entire measured output power and optical signal to noise ratio (OSNR) of each dual-wavelength are larger than −13.3dBm and 60dB respectively. In addition, the output stability measurement of proposed EDF laser is also performed and analyzed.

Photonic crystal fiber long-period grating absorption gas sensor based on a tunable erbium-doped fiber ring laser

It has been a persistent challenge to quantify gas emissions from industrial byproducts and warfare agents for environmental protection purposes, especially to detect multiple gas species using one device with high sensitivity and selectivity. To overcome this issue, a photonic crystal fiber (PCF)-based spectroscopic absorption sensing platform is proposed. We combine the PCF and long-period grating (LPG), two fundamental elements of fiber optics, into one functional unit to investigate the coupling properties of various PCF cladding modes. Further, we synchronize the PCF–LPG with a tunable Er-doped fiber ring laser into a thermo-stable and compact absorption spectroscopic sensor as a proof-of-concept for gas sensing. Because the Er-doped fiber ring laser can be tuned within the C-band wavelength, multiple gases can be recorded with the absorption spectra in one sensing operation. As a demonstration, the sensor was tested in NH3 with multiple gases combined, a sensitivity up to 17.3nW/ppm was achieved. The PCF–LPG-based gas sensors are easy-to-fabricate, cost-effective, and can be used in various applications where conventional fiber-optic sensors are not applicable.

Use of fiber Bragg grating (FBG) for stable and tunable erbium-doped fiber ring laser with single-longitudinal-mode (SLM) output

In this demonstration, we propose and investigate a stable C-band erbium-doped fiber (EDF) laser with compound-ring cavity. To achieve wavelength tunability with single-longitudinal-mode (SML) output, the sub-ring scheme and fiber Bragg grating (FBG) are used inside the ring cavity. Here, different lasing wavelengths can be selected by employing different Bragg wavelengths of FBGs. In this experiment, the obtained optical signal to noise ratios (OSNRs) and output powers are larger than 44.5 dB and 8.0 dBm respectively in the tuning range of 1531.70–1547.88 nm. Moreover, the output wavelength and power fluctuations of the proposed EDF laser are less than 0.02 nm and 0.1 dB in an observation time of 30 min, respectively.

Tunable erbium-doped fiber ring laser based on thermo-optic polymer waveguide Bragg grating

A tunable erbium-doped fiber ring laser incorporating a tunable thermo-optic polymer waveguide Bragg grating is proposed. Nano-imprinting technique was used to fabricate the polymer waveguide Bragg grating whose reflectivity and 3dB bandwidth are 25dB and 0.8nm, respectively. The polymer waveguide Bragg grating was used as wavelength selective element in the ring laser system and the center wavelength can be tuned by controlling the electrical power on the micro-heater. The fabricated tunable laser exhibits an output of 4.1dBm, side-mode suppression ratio of 55dB, 3dB bandwidth less than 16pm, and wavelength tuning range of 8.4nm.

Random spaced index modulation for a narrow linewidth tunable fiber laser with low intensity noise.

A tunable random feedback fiber laser with low intensity noise is proposed and experimentally demonstrated. The random feedback is effectively achieved by multiple reflections from 100 randomly spaced refractive index modulation regions over 10 cm SMF in both longitudinal and transverse directions. A tunable erbium-doped fiber ring laser with narrow linewidth of 2.4 kHz and a high side-mode suppression ratio of 59 dB is achieved over a 0.5 nm tuning range. The proposed fiber laser exhibits low relative intensity noise (<-120 dB/Hz) and low frequency fluctuation of ∼3.41×10(-11) over 5 s.

Tunable and switchable six-wavelength erbium-doped fiber ring laser

A tunable and switchable six-wavelength erbium-doped fiber ring laser based on a fiber Bragg grating based FP filter (FBG-FPF) and a polarization-maintaining fiber Sagnac loop (PMFSL) is proposed and demonstrated experimentally at room temperature. The FBG-FPF with low insertion loss is used to generate dense multiwavelength output. The PMFSL acts as a comb filter and frequency stabilizer. Through adjusting the squeezed fiber polarization controllers, six kinds of single-wavelength with the tunable range of 11 nm, eleven kinds of dual-wavelength, three kinds of triple-wavelength and one kind of six-wavelength can be obtained and switched with one another. All lasing lines with 3 dB linewidth of less than 0.29 nm and optical signal-to-noise ratio of more than 22 dB locate in the range of C- and L-bands of the optical communication waveband.

An L-band widely tunable erbium-doped fiber laser with all-fiber structure

We report on a widely tunable L-band erbium-doped fiber ring laser with the exploitation of an all-fiber Lyot fiber. The all-fiber Lyot filter is constructed from a polarizer, a short section of polarization-maintaining fiber and polarization controllers. Theoretical analysis shows that the laser oscillating wavelength can be tuned by changing the polarization rotation angle. By adjusting the polarization controllers, the laser can be tuned continuously over the full L band (1559.84–1603.19 nm) with a tunability of 43 nm, a side-mode suppression ratio over 44 dB, and power uniformity better than 1.2 dB. The simple and efficient tuning mechanism allows the building of inexpensive widely tunable fiber lasers with all-fiber structure.