Tunable Multiwavelength Fiber Laser Research Articles

Tunable and switchable multi-wavelength mode-locked fiber lasers induced by an optimized hybrid mode-locked composite filtering effect

A multi-wavelength mode-locked fiber laser can generate different wavelengths from a single laser cavity, offering potential as a dual-frequency comb and serving as an ideal light source for terahertz wave generation. We present an optimized hybrid mode-locked Er-doped fiber laser with flexible outputs: switchable and tunable dual-wavelength mode-locking, along with stable tri-wavelength mode-locking, which is achieved by introducing 0.69 m polarization-maintaining fiber and bent 200 m single-mode fiber to enhance intra-cavity birefringence and nonlinear effect to optimize the hybrid mode-locking effect, that is, build the composite filter effect. The dual-wavelength mode-locking not only covers a tunable wavelength range of 5 nm but also provides tunable wavelength intervals of 4-26 nm due to the composite filter effect. The formation dynamics of the tri-wavelength mode-locking can be switched either pair-by-pair or one-by-one. This approach enables the realization of wavelength interval tunable dual-wavelength mode-locking in mode-locked fiber lasers simply by introducing fiber without additional actions. Such a simple, compact fiber laser with tunable wavelength capabilities holds significant potential for diverse applications.

Michelson interferometer-based tunable multiwavelength thulium-doped fluoride fiber laser in S-band for 5 G networks

This work reported a multiwavelength thulium-doped fluoride fiber laser (TDFFL) for the S-band region using the Michelson interferometer as an optical filter. Michelson interferometer was utilized as a comb-like filter, whereas dispersion-compensated fiber (DCF) of 10 km length was used to increase the number of lasing lines and reduce mode competition. Approximately 61 lasing lines were achieved with a signal-to-noise ratio (SNR) of 40 dB in the wavelength region from 1501.36 to 1505.52 nm within 10 dB of maximum power. The stability of the multiwavelength fiber laser was also recorded for the time duration of two hours, and it was found that all lasing lines were stable and equally spaced at the free spectral range (FSR) of 0.07 nm. The variation in optical power was less than 0.5 dB; however, the wavelength shift was about 0.01 nm. Tunability of multiwavelength laser has also been observed up to the broader transmission span of 57 nm by incorporating the tunable band pass filter (TBPF). Moreover, FSR was observed to be tunable within the range of 0.02 to 0.14 nm by using the optical delay line (ODL) with a Michelson interferometer. Additionally, the proposed laser can generate frequency signals from 2.65 GHz to 18.54 GHz according to the obtained range of FSR.

High-order tunable multi-wavelength random Raman fiber laser based on few-mode fiber filter

In recent years, multi-wavelength fiber lasers have become one of the research hotspots and have been extensively applied in optical fiber communication systems. However, the presented multi-wavelength fiber lasers mainly operate in the 1.5 μm band. In this paper, a few-mode fiber filter-based cascaded high-order tunable multi-wavelength random Raman fiber laser (MWRRFL) is demonstrated, for the first time, in which a tuning range covers the 1.1–1.5 μm band. In the half-open MWRRFL, a few-mode fiber-based intermodal interferometer filter is inserted in the point reflector as a wavelength selector. The synergetic effect including high Raman gain and Rayleigh backscattering intensity in the hybrid of dispersion-shifted fiber and standard single-mode fiber is employed. It presents the capability for flat multi-wavelength random lasing stimulation. As a result, the wavelength channel number of the 6th-order random lasing is 6, with a maximum power variation of 4.66 dB and good temporal stability. The proposed cascaded tunable MWRRFL could provide a versatile source for optical fiber communication, optical fiber sensing, spectrum analysis, etc.

L-band of ∼ 1.6 μm tunable multi-wavelength mode-locked Er-doped fiber laser with an MMF- FMF based structure

1.6 μm tunable mode-locked fiber laser are mainly used in the biomedical field, laser processing, and other aspects, have excellent application prospects. We propose a novel MMF-FMF-based device, which acts both as a saturable absorber and a wavelength selection filter. The reduction of insertion loss caused by FMF affects the laser gain competition process, leading to changes in gain allocation and bandwidth allocation. The laser generated stable mode-locked pulses with a repetition frequency of 23.23 MHz at pump powers exceeding 51 mW. By adjusting the angle of the fiber optic squeezer with the PC, successfully achieved switchable single-, dual-, and triple-wavelength lasing outputs, as well as tunable single- and dual-wavelength lasing outputs. The wavelength-tuning ranges for the single- and dual-wavelength lasing outputs were 31 nm (1570 nm-1601 nm) and 24 nm, respectively. The accurately adjustable L-band novel mode-locked fiber laser exhibits enormous potential for application.

Tunable and switchable multi-wavelength random fiber laser based on random distributed feedback and improved Lyot filter

Tunable and switchable multi-wavelength random fiber laser based on random distributed feedback and improved Lyot filter

O-band tunable multiwavelength Brillouin-Raman fiber laser based on a wavelength-agile Raman pump.

Multiwavelength Brillouin-Raman fiber laser (MBRFL) features broadband multiwavelength generation with flat-amplitude and high optical signal to noise ratio (OSNR), which has great potential in optical fiber communication applications. Till now, the spectral regions of MBRFLs are mostly concentrated at conventional C- and L-band and the tunability of MBRFL is limited by using the Raman pump with fixed wavelength. Here, by utilizing wavelength-agile random fiber laser which can emit tunable lasing at 1.2 µm band as the Raman pump, we experimentally demonstrate the tunable MBRFL in the O-band for the first time, to the best of our knowledge. At Raman and Brillouin pump powers of 920 mW and -3 dBm, respectively, up to 90 Stokes lines with 0.13 nm wavelength spacing and >13 dB OSNR can be obtained when the Raman and Brillouin pump wavelength are set at 1231 nm and 1300 nm, respectively. Moreover, by tuning the wavelength of Brillouin pump from 1295 nm to 1330 nm, tunable MBRFL can be achieved with similar multiwavelength generation bandwidth by simultaneously tuning the Raman pump wavelength, and the number of Stokes lines are beyond 85 across the tuning range. The bandwidth of the demonstrated O-band MBRFL is also the widest wavelength span ever reported for multiwavelength Brillouin fiber lasers at 1.3 µm band. Our work indicates that the use of wavelength-agile random fiber laser as Raman pump in MBRFL can provide an effective way to extend the spectral regions of MBRFL and also improve the tunability performance of MBRFL.

Tunable spectrally-flat multi-wavelength cylindrical vector beam fiber laser by using a re-circulating frequency shifter loop with two external injections

We experimentally demonstrate a tunable spectrally -flat multi-wavelength cylindrical vector beam (CVB) fiber laser based on a two-mode long-period fiber grating (TM-LPFG) and a re-circulating frequency shifter loop with two external injections. The TM-LPFG is utilized as a mode converter in the re-circulating frequency shifter loop to excite the LP11 mode in the two-mode fiber. By adjusting the wavelength interval of the two injected seed signals, the power of the injected seed signals, and the pump power can produce a flat intensity envelope between the two injected wavelengths. Multi-wavelength CVBs of 12, 18, or 30 channels with a peak-to-peak power variation lower than 2 dB between the two injected wavelengths are obtained with a wavelength spacing of approximately 0.08 nm. The wavelength spacing can be adjusted by changing the frequency of the radio frequency signal. Multi-wavelength CVBs of 14 channels with a peak-to-peak power variation lower than 2 dB between the two injected wavelengths are obtained with a wavelength spacing of approximately 0.2 nm. The purity of the generated multi-wavelength CVBs is higher than 98%. Due to the absence of interference-type filter elements, the multi-wavelength CVB fiber laser exhibits excellent stability. The maximum wavelength deviation of each channel is less than 6.5 pm, and the maximum intensity fluctuation is less than 0.7 dB over a period of one hour.

Tunable Single and Multi-Wavelength Er-Doped Mode-Locked Fiber Laser Based on GIMF-PCF-GIMF

Tunable Single and Multi-Wavelength Er-Doped Mode-Locked Fiber Laser Based on GIMF-PCF-GIMF

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).

Tunable and switchable multi-wavelength pulsed fiber laser based on a nonlinear optical loop mirror and an improved Sagnac filter.

We propose and experimentally demonstrate a tunable and switchable multi-wavelength erbium-doped fiber ring pulsed laser based on a nonlinear optical loop mirror (NOLM) and an improved Sagnac filter. To achieve multi-wavelength pulsed laser output, we adopt a NOLM as a quasi-saturable absorber and an improved Sagnac loop as a wavelength selected filter. The constructed laser has a maximum output wavelength number of five with a pulse repetition frequency of 40.45kHz and pulse duration of 108ns. The laser can output single-wavelength and dual-wavelength pulsed lasers within a certain wavelength tuning range and a five-wavelength pulsed laser with a constant wavelength interval of 3nm by adjusting the polarization controller. Dual-wavelength, three-wavelength, and four-wavelength pulsed lasers with various wavelength intervals are also obtained. The output performance of the constructed laser is tested with a maximum average output power of 127.45µW and minimum pulse duration of 52ns, and the stability of the laser output is also tested with a maximum power fluctuation of 0.62dB and minimum wavelength drift of 0.51nm with pump power of 350mW.

Tunable Multiwavelength SOA-Based Fiber Laser

Tunable multiwavelength fiber lasers based on semiconductor optical amplifiers (SOA) have received attracting interest due to their wide prospective applications in dense division multiplexing (DWDM) systems and optical sensing. Using an SOA in a nonlinear optical loop mirror (NOLM), we demonstrate up to 13 lasing peaks by controlling the pump current and the polarization controller. At maximum pump current (450 mA), the emitted multiwavelength is between 1550 nm and 1572 nm with a wavelength spacing of 1.87 nm and 3 dB output linewidth of 0.8 nm with an output power of −7 dBm and 27 dB optical signal-to-noise ratio (OSNR). The multiwavelength output power and multiwavelength peak stability are investigated, and it was found that the power fluctuation of each multiwavelength line is less than 0.2 dB. In addition, by adjusting the polarization controllers (PCs) and SOA temperature, we obtained a tunable multiwavelength emission. The proposed fiber laser offers advantages such as simple structure, low loss, and long-time stable and multiwavelength emission.

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 Brillouin-Raman multi-wavelength fiber laser with a linear cavity configuration

A tunable Brillouin-Raman multi-wavelength fiber laser has been proposed and demonstrated in a linear cavity configuration, where stimulated Raman scattering and stimulated Brillouin scattering occur simultaneously in the dispersion compensation fiber. The influence of Brillouin pump (BP) and Raman pump (RP) power on the obtained Brillouin Stokes lines has been investigated in detail. The experimental results show that when BP wavelength is 1545 nm, 63 orders of Stokes lines can be obtained at most, and the interval between adjacent lines is about 0.08 nm. Moreover, there are two opposite relations between the number of the generated Stokes lines and the BP power within the whole tunable range of 1520–1575 nm (55 nm), depending on the Raman gain. The proposed laser featuring simple structure will enable promising potentials in optical communications and optical sensor systems.

Switchable multi-wavelength thulium-doped fiber laser using a two-taper fiber filter

An individually switchable and tunable multiwavelength thulium-doped fiber laser (TDFL) is proposed and experimentally demonstrated. The key component of the laser is a comb filter composed of two fiber tapers separated by a short middle section. A nonlinear loop mirror (NOLM) is inserted into the laser cavity to suppress the intense gain competition. By properly adjusting the polarization controllers (PCs) in the cavity, the laser can operate in at most sextuple wavelength state. In addition to these laser output characteristics, the experiment result also shows that single wavelength tuning can be achieved, and the tuning range is 1952.06 nm to 1975.62 nm. This multi-wavelength TDFL may be useful in optical fiber sensing or other fields desiring flexible optical source.

Tunable and narrow linewidth multi-wavelength Brillouin-erbium fiber laser using dual-wavelength pumping

Tunable and narrow linewidth multi-wavelength Brillouin-erbium fiber laser using dual-wavelength pumping

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.

Tunable multi-wavelength SBS Q-switched random fiber laser based on SMF

Tunable multi-wavelength SBS Q-switched random fiber laser based on SMF

Ultralong wavelength operation of a tunable multiwavelength Brillouin-Raman fiber laser in 1.65 μm band

A tunable multiwavelength Brillouin-Raman fiber laser (MW-BRFL) operated at an ultralong wavelength band (U-band) is presented in this work. The MW-BRFL was configured in a full-open linear cavity consisting of 11.2 km long dispersion compensating fiber that functioned as a Brillouin frequency shifter and Raman amplification gain medium. At Raman and Brillouin pump powers of 930 mW and 11.8 dBm, respectively, a stable multiwavelength generation with wavelength spacing of 0.17 nm was generated over a wavelength span of 53 nm. The generated channels covered a spectral range of 1630–1683 nm corresponding to 314 channels. The channels could also be tuned over 10 nm with an average optical signal-to-noise ratio greater than 26 dB. The laser system exhibited power fluctuation of less than 0.25 dB over 3 h. In a nutshell, the proposed MW-BRFL is promising with respect to its performance, simplicity and flexibility.