Tunable Multiwavelength Erbium-doped Fiber Laser Research Articles

Tunable and switchable multiwavelength fiber laser incorporating tapered few-mode fiber Bragg gratings

A tunable and switchable multiwavelength Erbium-doped fiber laser (MWFL) is proposed and demonstrated based on tapered few-mode fiber Bragg gratings (TFMFBG). Optical modes inside TFMFBG have extensive evanescent tails that are sensitive to changes in the external medium. The MWFL can be tuned in the 1.5 µm wavelength region when temperature and refractive index variations are applied to the TFMFBG. The temperature and refractive index sensitivities range from 11.5 pm/⁰C to 14.6 pm/⁰C and 3.10 nm/RIU to 3.93 nm/RIU, respectively. Additionally, due to the polarization dependency of TFMFBG, single-, dual-, and triple-wavelength lasing lines can be switched within the MWFL cavity. The stable triple-wavelength lasing was generated at peak wavelengths of 1533.04 nm, 1532.35 nm, and 1531.71 nm for λ1, λ2, and λ3, respectively. The developed triple-wavelength laser corresponded to a specific guided mode inside the few-mode FBG, including fundamental LP01 mode, higher-order LP11 mode, and mode coupling between LP01 and LP11 (LP01-LP11).

A C-band widely tunable and switchable erbium-doped fiber laser based on a Sagnac-like loop embedded in Lyot filter

In this paper, a new type of widely tunable and switchable multi-wavelength erbium-doped fiber laser based on a Sagnac-like loop embedded in Lyot filter is proposed. The nonlinear polarization rotation effect is obtained by adjusting two polarization controllers (PCs). The polarization-dependent isolator and the Sagnac-like loop are used as the basic structure to realize the wide tuning and wavelength switching in C-band. Compared with the traditional Lyot filter, the Sagnac-like loop is used to replace the segment of polarization-maintaining fiber, and a more uniform comb spectrum can be obtained by this filter. The tunable and switchable wavelengths can be achieved by adjusting the PCs based on the nonlinear effect of the loop. The laser can emit single-, dual-, triple-, quad- and quintuple-wavelengths. The optical signal-to-noise ratios all exceed 43 dB. It can also be adjusted to partial wavelength intervals for quad-wavelength and quintuple-wavelength. The tuning range can reach the full range of the C-band, and the laser efficiency can reach the practical application standard. It can be applied to some precision instruments and equipment.

Tunable and Switchable Multi-Wavelength Erbium-Doped Fiber Laser Based on Composite Structure Filter

A multi-wavelength erbium-doped fiber laser (MW-EDFL) with wide tuning range, switching and adjustable wavelength interval is designed and tested, which is based on a composite filter. The filter consists of a tapered microfiber coupler loop (TMCL) with a nested single mode fiber (SMF)-two mode fiber (TMF)-SMF (STS) structure, which has a comb spectrum with obvious envelope and uniform fluctuation. Our experimental and theoretical results show that the laser can output thirteen wavelengths, when the angles of two polarization controllers (PCs) in the TMCL are accurately set. Moreover, by adjusting the PCs, the tuning range of single- to sextuple-wavelength can reach about 40 nm. Six non-adjacent multi-wavelength outputs can be observed in some specific polarization states. The maximum side-mode suppression ratio (SMSR) of the output laser is 40.6 dB. Compared with other multi-wavelength EDFL, the output characteristics of the laser, such as the adjustability and flexibility of wavelength spacing and the switch-ability of wavelength number, have been improved.

Tunable multiwavelength Erbium-doped fiber laser based on in-fiber Fabry-Perot interferometer fiber Bragg gratings in linear and ring cavity configurations

Multiwavelength Erbium-doped fiber laser (MWEDFL) in the ring and linear cavities operating at 1.5-μm wavelength region was demonstrated. The multiwavelength fiber laser comprises a 3-m Erbium-doped fiber as an active gain medium, an in-fiber Fabry-Perot interferometer Fiber Bragg Gratings (FPI FBG) as a filter, and a 10-km dispersion compensating fiber (DCF) as a nonlinear gain medium. A comparison investigation was conducted. The MWEDFL in the linear cavity generates 12 stable lasing lines, with an optical signal-to-noise ratio (OSNR) of 45 dB. In the case of MWEDFL operated in a ring cavity, 8 stable lasing lines were generated, with an OSNR of 47 dB. The free spectral range (FSR) of 0.08 nm was measured for the FPI FBG in both linear and ring cavities MWEDFL spectrum. Besides, the stability measurement was conducted for 150 min for both MWEDFL cavities. Both lasers had a peak power fluctuation of less than 1.0 dB and negligible wavelength drifts below 0.1 nm. Furthermore, the wavelength tunability of MWEDFL in both configurations was performed by heating the FPI FBG from 28 °C to 100 °C. At the temperature of 100 °C, the MWEDFL shows a wavelength shift of 1.0 nm, and this can be further increased by heating the FPI FBG to its highest temperature limit. This MWEDFL employs in-fiber FPI FBG offers a compact, highly tunable, and simple design applicable for optical communications and optical sensing applications.

Tunable and interval-adjustable multiwavelength Erbium-doped fiber laser based on a compound filter

We propose and experimentally demonstrate a multiwavelength erbium-doped fiber laser (EDFL) based on a compound filter. The compound filter is composed of polarization controllers (PCs), polarizers and a piece of home-made polarization-maintaining photonic crystal fiber (PM-PCF). Due to the high birefringence and few-mode properties of the PM-PCF, Lyot filter and multimode interference filter can be realized simultaneously in the compact structure. Hence, the EDFL can achieve flexible lasing output. By adjusting PCs, the lasing can obtain single-, dual-, triple- and quad-wavelength output, respectively. The tuning range of single-wavelength lasing output can exceed 20 nm with side-mode suppression ratio (SMSR) above 40 dB. For dual-wavelength lasing output, the tuning range with fixed interval can reach 16 nm. Besides, the wavelength interval can be adjusted from 2.5 nm to 17.4 nm. The great interval adjustability is also observed in triple-wavelength output. The wavelength interval can be adjusted from 8.2 nm to 14.7 nm. Compact structure, flexible lasing output, and good stability make our proposed EDFL more convenient and practical to the applications such as sensing and wavelength division multiplexing.

Widely tunable and switchable multiwavelength erbium-doped fiber laser based on a single ring cavity

In this paper, we propose and demonstrate through numerical simulations a novel, to the best of our knowledge, widely tunable and switchable multiwavelength erbium-doped fiber laser (EDFL) operating in the 1524–1650 nm wavelength range covering the C-, L-, and U-bands. The EDFL is based on a single ring cavity and a single forward pump source operating at 980 nm wavelength. The length of the erbium-doped fiber and pumping configuration is optimized, enabling a wide tuning of 126 nm with an average lasing power of 15 dBm. Switchable multiple wavelengths are generated from the EDFL through an intracavity tunable optical filter (TOF) and a specially designed out-of-cavity comb filter (CF). Forty-nine wavelengths having average optical power and linewidth of around −10 dBm and 0.01 nm, respectively, are obtained at the output of the CF. Moreover, the free spectral range among the multiple wavelengths is adjusted easily by simply varying the frequency of sinusoidal radio frequency signal used to modulate the lasing signal obtained by tuning the intracavity TOF at a particular wavelength with the help of a dual-drive Mach–Zehnder modulator. The proposed EDFL is low cost, efficient, and highly stable with an average output power of around 15 dBm for 10% output coupling ratio over a 126 nm wide tuning range covering C-, L- and U-bands.

Tunable and wavelength interval precisely controlled erbium-doped fiber laser by employing the fused taper technology

A tunable multi-wavelength erbium-doped fiber laser with precise wavelength interval control is reported theoretically and experimentally in this paper. It is made up of a Mach–Zehnder interferometer (MZI) filter and a Sagnac filter and supplemented by the four-wave-mixing effect. Compared with other filters, the proposed MZI filter based on the fused taper technology can change the wavelength interval more flexibly. The experiment result shows that wavelength tuning can be achieved, and the tuning range can reach ∼15 nm. Moreover, the variation in the number of wavelengths is also realized. The maximum side-mode suppression ratio can reach 39 dB.

Tunable and interval-adjustable multi-wavelength erbium-doped fiber laser based on cascaded filters with the assistance of NPR

A novel widely tunable and interval-adjustable multi-wavelength erbium-doped fiber laser (EDFL) is experimentally demonstrated in this paper. It is based on the cascaded structure of two-segment Sagnac filter and Lyot filter with the assistance of nonlinear polarization rotation (NPR). By properly adjusting the polarization controllers (PCs) in the laser cavity, the output wavelengths with different flexible lasing states can be obtained, such as tunable single-, dual-, triple-wavelength outputs with a tuning range more than 18 nm. The outputs of quad-, quintuple-, sextuple- and septuple-wavelength can also be tuned, but the step size of the tuning is not fixed due to the intense wavelength competition. In addition, the outputs can achieve changes in wavelength interval. The switchability and tuning range of the laser have been greatly improved, and the wavelength interval adjustment is more flexible. The maximum SMSR of the output laser can up to 47 dB. This EDFL can be used in optical fiber sensing, WDM network and other fields desiring very flexible optical source.

Switchable, Widely Tunable and Interval-Adjustable Multi-Wavelength Erbium-Doped Fiber Laser Based on Cascaded Filters

A novel individually switchable, widely tunable, and interval-adjustable multi-wavelength erbium-doped fiber laser (EDFL) is experimentally demonstrated in this article. It is based on the cascaded structure of SMF-TMF-SMF (STS) filter and Lyot filter with the assistance of nonlinear polarization rotation (NPR). The homemade STS filter is a comb filter that formed by splicing a section of two-mode fiber (TMF) and two segments of single-mode fiber (SMF) with core-offset structures. Compared with other multimode interferences, the spectrum of STS filter is more uniform. When inserted into the laser cavity, this comb filter functions as the wavelength selector with wavelength interval of ∼0.8 nm. The insertion loss of the filter is only ∼0.4 dB. By properly adjusting the polarization controllers (PCs) in the laser cavity, individually switchable wavelengths with different flexible lasing states can be obtained, such as tunable adjacent single-, dual-, triple-, quadruple-, and quintuple-wavelength outputs. The tuning range can up to 30 nm, from 1530 to 1560 nm. When the number of output wavelengths is 1∼3, the tuning process can keep the step size of 0.8 or 1.6 nm. The non-adjacent dual- and triple-wavelength outputs, as well as adjacent sextuple- and septuple-wavelength outputs can also be achieved. The output characteristics, such as flexible switchability and tunability, are difficult to implement by other methods.

Switchable and tunable multi-wavelength fiber laser based on a core-offset aluminum coated Mach-Zehnder interferometer

In this work, a switchable and tunable multi-wavelength erbium-doped fiber laser based on a core-offset aluminum coated Mach-Zehnder interferometer (ACMZI) is presented. The ACMZI is fabricated by core-offset fusion splicing a single-mode fiber segment between two lengths of single mode fiber and then by coating it with aluminum using the thermal evaporation technique. The ACMZI is used as a wavelength selective filter in the proposed ring cavity design. Experimental results show that the laser emission can be switched among a single, double, and triple emission lines by carefully adjusting a polarization controller. Furthermore, the laser lines can be tuned by changing the temperature of the ACMZI. The laser can emit in a single-longitudinal mode and has a single-mode suppression ratio of about 55 dB, a linewidth of 0.05 nm and an efficiency slope of 0.29%. Finally, the laser arrangement is compact, robust, and requires a relatively simple fabrication procedure.

Tunable multiwavelength erbium-doped fiber laser based on BPQDs packaged by poly tetra fluoroethylene and two segments of PMF

Two types of tunable and stable multiwavelength erbium-doped fiber lasers(MWEDFLs) are proposed and experimentally demonstrated, which are based on novel poly tetra fluoroethylene packaging device of black phosphorus quantum dots (PTFEPD-BPQDs) and two sections of polarization maintaining fiber(PMF) in cascade/in parallel. The novel fabrication process uses silica capillaries and PTFE to package BPQDs. The PTFEPD-BPQDs has the function of suppressing the mode competition and stabilizing the multiwavelength output. The channel space and wavelength number of the two types of tunable MWEDFLs can be tuned by adjusting polarization controllers(PCs). In the experiments, for the unpackaged BPQDs device, BPQDs will degrade and lose its function within 48 h, while for the PTFEPD-BPQDs, BPQDs can keep its function for more than 3 weeks. By adjusting the PC, in the cascaded structure, the multiwavelength channel spacing can be tuned among nearly 1.98, 0.67 and 0.43 nm, and the number of multiwavelength output is 4, 9 and 13, respectively.

Switchable, tunable and highly stable multi-wavelength fiber laser based on a spectral filter

In this work, a switchable and tunable multi-wavelength erbium-doped fiber laser based on a spectral filter is presented. Here, the filter is formed by polymer and silicon layers at the tip of an optical fiber. The laser emission wavelengths are mainly determined by the position where the most intense fringes of the reflectivity spectrum of the filter occurs. Moreover, the number of laser emissions are controlled and switched by using a variable optical attenuator inserted into the laser cavity. In this way, single-, dual-, triple-, and quadruple-laser emissions can be obtained within the long operating span from ~1526–~1565 nm. Additionally, the multi-wavelength laser emissions had a side mode suppression ratio ⩾36.48 dBm, a minimum wavelength spacing of ~3.6 nm, and the best peak power difference was 0.45 dB. Besides, the wavelength shift and peak power fluctuation were ⩽0.095 nm and ⩽3.14 dB, respectively, over half an hour. Finally, the emissions of the multi-wavelength laser can be tuned within a tunable range of 2.93 nm by taking advantage of some thermal properties of the Si and polymer layers.

Selectable and stable C-band multi-wavelength ring cavity erbium-doped fiber laser employing Sagnac loop and tunable filter

A tunable C-band multi-wavelength ring cavity erbium-doped fiber laser based on a Sagnac loop and tunable filter was developed and experimentally demonstrated. In this fiber laser, a Sagnac loop fabricated using a 3 × 3 coupler and polarization-maintaining fiber is employed as the comb filter. A 4-m-long C-band and 0.8-m-long L-band erbium-doped fiber serve as the gain medium, and a tunable filter connected to the 3 × 3 coupler is used for laser wavelength adjustment. In the experiment described herein, switchable single-wavelength lasing was realized from 1528.6 nm to 1562.5 nm in 4.9-nm intervals, and the peak power variation was less than 1.12 dB during 10 min of scanning at 26 °C. In addition, switchable double- and triple-wavelength lasing were realized, for which the tunable wavelength scope was 28.6 nm and 19.9 nm, and the power fluctuation was less than 1.14 dB and 1.39 dB, respectively.

Tunable multiwavelength Q-switched erbium-doped fiber laser based on graphene and tapered fiber

A tunable, multiwavelength, Q-switched fiber laser based on a graphene saturable absorber and tapered fiber is shown to solve the problems in existing multiwavelength tunable Q-switched fiber lasers, which are complex, unstable, difficult to tune, and costly. The whole ring cavity includes a main part that is a self-made tuning device with a tapered fiber placed on MgF2 substrate, single-layer graphene, and polydimethyl siloxane film covering the zone of the tapered fiber. It can achieve a stable output and multiple wavelengths, which can be switched into another wavelength by adjusting the parameters of the various changes and polarization controller.

Tunable Multiwavelength Erbium-Doped Fiber Laser Employing PM-FBG and Mach–Zehnder Interferometer with Optical Fiber Delay Line

We propose the use of an erbium-doped fiber laser based on a polarization-maintaining fiber Bragg grating (PM-FBG) and all-fiber Mach–Zehnder interferometer (MZI) to realize a quadruple-wavelength 1.5-μm laser output. In the proposed system configuration, a 1535-nm center wavelength PM-FBG acts as the wavelength selector. The dual-pass MZI is fabricated using two couplers with a 50:50 splitting ratio, and the wavelength spacing of the comb is varied by using a spectrum power-driven optical fiber delay line inserted in MZI. The working threshold in the experiment is 82 mW. Tunable lasers of single-, dual-, triple-, and quadruple-wavelengths can be realized by adjusting the polarization controller. The generated wavelengths are in the range of 1534 to 1534.6 nm, the wavelength space is 0.2 nm, and the 3 dB linewidth is less than 0.05 nm. The power fluctuation is observed to be less than 0.912 dB, and the signal-to-noise ratio (SNR) is larger than 34.9 dB at 26 °C over a scan time of 10 min.

Tunable and stable multi-wavelength erbium-doped fiber laser based on a double Sagnac comb filter with polarization-maintaining fibers

In this paper, a tunable and stable multi-wavelength erbium-doped fiber laser that employs a double polarization-maintaining Sagnac loop comb filter is proposed and experimentally demonstrated. The two nested Sagnac loops are used as the comb filter, which was fabricated using two 3-dB couplers, two polarization controllers (PC), and two sections of polarization-maintaining fibers (PMFs) with lengths of 1.2m and 1.8m, respectively. In the proposed laser, a stable and tunable single-, double-, and triple-wavelength lasing was obtained experimentally in the spectral range of 1528–1564nm, the side mode suppression ratio (SMSR) was higher than 38dB, and the wavelength shifts and power fluctuations were less than 0.04nm and 4.7dB, respectively, for a duration of 10min at a room temperature of 26°C. Furthermore, the laser can emit quadruple-wavelengths through adjustment of the two PCs in the experiment.

Tunable Multiwavelength Er-Doped Fiber Laser With a Two-Stage Lyot Filter

A switchable and tunable multiwavelength erbium-doped fiber laser is proposed and demonstrated based on a two-stage Lyot filter and intensity-dependent loss (IDL) effect induced by a nonlinear optical loop mirror (NOLM). The proposed laser can achieve multi-parameter individually tuning functions, such as adjusting the channel-spacing, number, and spectral-range of lasing line. The channel spacing can be switched via adjusting the beam's polarization in the Lyot filter among 0.53, 0.78, and 1.56 nm. Meanwhile, the number and the spectral range of the multiwavelength lasing line can be independently controlled by IDL modulation through the combination of adjusting pump power and the birefringence in the loop of the NOLM. The individual tuning method of the proposed laser on each specific output characteristic provides more convenience and practicality to the applications.

Tunable multiwavelength erbium-doped fiber laser incorporating single-core comb filter at room temperature

The generation of tunable multiwavelength erbium-doped fiber laser based on an integrated structure of a single-core comb filter and nonlinear polarization rotation (NPR) is proposed and successfully demonstrated at room temperature. The NPR effect effectively induced intensity and wavelength-dependent loss to alleviate mode competition caused by homogeneous gain broadening in erbium-doped fibers. Thirty-two lasing wavelengths in a 3dB flattened spectrum with a tunable wavelength spacing of 0.9nm–1.8nm have been achieved. Good stability of the laser operating at room temperature has been verified by using an optical spectrum analyzer to measure every 10min for an hour.

Tunable multiwavelength erbium-doped fiber laser based on nonlinear optical loop mirror and birefringence fiber filter

A tunable multiwavelength erbium-doped fiber laser (MWEDFL) based on nonlinear optical loop mirror (NOLM) and tunable birefringence fiber filter (BFF) is proposed and demonstrated. By combination of intensity-dependent loss modulation induced by NOLM and pump power adjustment, the proposed laser can achieve independent control over the number of lasing lines, without affecting other important characteristics such as channel spacing and peak location. In addition, the laser allows wavelength tuning with both the peak location and the spectral range of lasing lines controllable. Specifically, the peak location of lasing lines can be controlled to scan the whole spectral range between adjacent channels of comb filter by adjusting the BFF. Moreover, the spectral range of lasing lines can be controlled by adjusting NOLM. This tunable MWEDFL may be useful for fiber-optic communication and fiber-optic sensing.

Multifunctional tunable multiwavelength erbium-doped fiber laser based on tunable comb filter and intensity-dependent loss modulation

A multiwavelength erbium-doped fiber laser based on tunable comb spectral filter and intensity-dependent loss modulation is proposed and experimentally demonstrated. The laser allows fine and multifunctional tunable operations of channel-spacing, peak-location, spectral-range, and wavelength-number. More specifically, channel-spacing switch from 0.4nm to 0.2nm and peak-location adjustment within half of free spectrum range are obtained via controlling the tunable comb filter. The wavelength-number and the spectral-range of the lasing lines can be accurately controlled by intensity-dependent loss modulation in the laser cavity, enabled by a power-symmetric nonlinear optical loop mirror. In addition, fine control over the wavelength-number at fixed spectral-range is realized by simply adjusting the pump power. More important, the tunable operation process for every type of specific parameter is individual, without influences for other output parameters. Such features of this fiber laser make it useful and convenient for the practical application.