Switchable Erbium-doped Fiber Laser Research Articles

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.

Spatial mode and wavelength switchable erbium-doped fiber laser based on a fiber beam shaper.

A fiber-based beam shaper to adjust the distribution of spatial modes in a few-mode fiber (FMF) is theoretically and experimentally investigated in this work. A compact and robust device, composed with a single mode fiber-graded index multimode fiber-few mode fiber (SMF-GIMF-FMF), is fabricated by simply fusion splicing of the fibers. Switchable spatial modes and multi-wavelength comb are obtained by the combination of the beam shaper and the few-mode fiber Bragg grating (FM-FBG). This combination acts as a filter to select the wavelength and spatial mode in the laser. A spatial mode switchable fiber laser with high mode purity is extended among LP01, LP11 and cylindrical vector beam (CVB) by adjusting the pressure applied on the beam shaper. Five-discrete wavelengths and their free combination wavelength comb are emitted with a slope efficiency higher than 10%. The fiber laser can be used in the spatial- and wavelength-division multiplexing (SWDM) fiber communication networks requiring particular structure light field.

Tunable and switchable erbium-doped fiber laser based on the parallel filter of the FBGs embedded in Sagnac ring and the in-line MZI

A tunable and switchable erbium-doped fiber laser (EDFL) based on the parallel filter is proposed and experimentally verified. The parallel filter is composed of two branches. One branch is double fiber Bragg gratings (FBGs) embedded in Sagnac ring filter, which can realize the selection of two wavelengths; the other branch is an in-line Mach Zehnder interferometer (MZI) filter, which is composed of a 10 cm polarization-maintaining fiber (PMF) fused in the middle of single mode fibers (SMFs) with spheres at both ends, which can realize the selection of five wavelengths. When the parallel filter is inserted into the fiber laser cavity and the polarization controllers (PCs) are adjusted, the laser excitation from single-wavelength to quadruple-wavelength can be realized, including 7 different single-wavelength laser states, 16 different dual-wavelength laser states, 11 different triple-wavelength laser states and 2 different quadruple-wavelength laser states. In addition, the intervals of the dual-wavelength laser states are relatively regular, and the dual-wavelength laser intervals are obtained every ∼ 2 nm from 7 nm to 18 nm. And the optical signal-to-noise ratios (OSNRs) are more than 43 dB, and the highest OSNR is 60 dB. Finally, by changing the temperature applied to the FBG, tunability of dual-wavelength intervals can be achieved with a range of 1.1 nm. Due to the variety of lasing laser states of the fiber laser, easy switching, and regular intervals between the dual-wavelength laser states, the fiber laser proposed can be better applied to wavelength division multiplexing (WDM)system.

Tunable and Switchable Dual-Wavelength SLM Narrow-Linewidth Fiber Laser with a PMFBG-FP Filter Cascaded by Multi-Ring Cavity

A single longitudinal mode (SLM) dual-wavelength switchable erbium-doped fiber laser (DW-EDFL) based on polarization-maintaining fiber Bragg grating Fabry–Perot cavity (PMFBG-FP) cascaded multiple sub-ring cavities (MSCs) is proposed. A PMFBG-FP with a narrow-band transmission peak and MSCs was implemented as an optical filter to achieve stable dual-wavelength laser output and guaranteed SLM status. By stretching the PMFBG, a highly stable dual-wavelength tunable output could be achieved with a maximum tuning interval of 0.17 nm. The optical signal-to-noise-ratio (OSNR) at dual-wavelength lasing was higher than 57 dB, and the optimal wavelength and power fluctuations within 0.5 h were 0.01 nm and 0.79 dB, respectively. Meanwhile, the measured linewidths of each wavelength were 1.55 kHz and 1.65 kHz, respectively. The measured polarization states of the two laser wavelengths were linear and orthogonal, with a degree of polarization (DOP) of nearly 100%.

Erbium-doped fiber laser with switchable wavelength generation based on tunable filter and dual-pass mach-zehnder filter incorporated with fiber delay line

A wavelength switchable erbium-doped fiber laser incorporated with a tunable filter and dual-pass Mach–Zehnder interferometer (MZI) was designed and experimentally demonstrated. The erbium-doped fiber was used as the gain medium for the fiber laser and the laser working threshold was 92 mW. The dual-pass MZI was fabricated using three optical couplers (OCs) and the variable fiber delay line. A tunable filter was used for laser tuning and it was combined with two OCs to construct a subsidiary cavity. A tunable and stable single- and dual-wavelength laser output was obtained in the experiment. In the case of single-wavelength laser output, the tuning span was in the range of 1527.6–1562.4 nm with an interval of 1.2 nm. Additionally, the side-mode suppression ratio (SMSR) was greater than 37.45 dB. In the case of dual-wavelength laser emission, the lasers were tuned from 1540.7 and 1541.6 nm to 1560.8 and 1561.2 nm, respectively. The stability of the single-, dual-and triple-wavelength laser output was evaluated and the power fluctuation was less than 1.36, 1.34, and 1.37 dB, respectively. Finally, quadruple- and quintuple-wavelength laser outputs were achieved by adjusting the loss of the intra-cavity.

Multiwavelength switchable fiber laser employing a DMD as tuning element and variable optical attenuator

Multiwavelength switchable erbium-doped fiber laser is demonstrated by using a digital micromirror device (DMD) as an optical filter and wavelength-dependent variable optical attenuator. The spectrum can be switched from single to multiwavelength lasing output by simple adjustment of the DMD reflection pattern. The mode competition in a fiber ring is efficiently suppressed by finely modulating the reflection column to balance the diffraction loss and EDF gain on each wavelength. The results show the 3 dB-bandwidth of multiwavelength lasing signal is less than 0.06 nm and the side mode suppression ratio is greater than 35 dB. The peak power fluctuation is less than 0.8 dB, and the wavelength drift is less than 0.06 nm over 50 min. The multiwavelength generation from the DMD-based tunable fiber laser is stable, flexible and fast.

All-fiber Mach–Zehnder comb filter based on tapered fibers for wavelength switchable erbium-doped fiber lasers

A wavelength switchable erbium-doped fiber laser was constructed based on an all-fiber Mach–Zehnder interferometer (MZI) comb filter. The MZI consisted of a fiber with two tapers. An L-band erbium-doped fiber was used as the gain medium, and 1557.92, 1563.2, and 1568.06 nm single-wavelength and dual-wavelength switchable lasers at 1558, 1563.7, and 1570.2 nm were realized by adjusting the polarization controller. During scanning, the maxmin power fluctuations of single- and dual-wavelength lasing were 0.604 and 2.482 dB, respectively. The signal-to-noise ratio was >24.46 dB and the laser’s 3 dB linewidth was <0.39 nm.

Multi-wavelength switchable erbium-doped fiber laser based on a hybrid filter incorporating a bi-tapered Mach–Zehnder interferometer and Sagnac loop

A multi-wavelength switchable C-band erbium-doped fiber laser based on a hybrid comb filter composed of a Sagnac loop and Mach–Zehnder interferometer (MZI) is designed and experimentally demonstrated. In the designed ring cavity fiber laser, the MZI is composed of bi-tapered single-mode fiber fabricated by etching with hydrofluoric acid. In the experiment, the wavelength intervals in the comb spectra of the Sagnac loop and MZI are 3.4 and 18.8 nm, respectively, and by combining the Sagnac loop and MZI, measurements of the hybrid comb spectrum are obtained. When the pump power is 91 mW, lasing occurs at 1529.2 nm. Adjustment of the variable attenuator (VA) can provide 1541.9 and 1558.6 nm single-wavelength switchable lasers, for which the maximum peak power difference is less than 3.59 dB, the signal-to-noise ratio (SNR) exceeds 19.25 dB, and the peak power fluctuation is less than 0.34 dB over a 30 min scan time at 26 °C. For dual-wavelength switchable laser emission, four different sets of wavelengths can be realized, and the SNR exceeds 15.57 dB with power fluctuations of less than 1.6 dB, under the same monitoring conditions. By further adjusting the VA, stable and tunable triple-wavelength lasing is also realizable; under these conditions, the SNR exceeds 15.02 dB and the power fluctuation is less than 0.91 dB. Furthermore, four- and five-wavelength lasing can also be achieved by adjusting the VA again, with SNRs exceeding 19.05 and 14.98 dB, respectively.

Switchable erbium-doped fiber laser (EDFL) using non-adiabatic microfiber

Abstract We have investigated the operation principle of the switchable EDFL which stands for the erbium-doped fiber laser, where a non-adiabatic microfiber has been fabricated and used. Utilizing the flame-brushing technique, the optical microfiber has been fabricated and afterward, it has been inserted into the EDFL cavity, therefore by proposing the setup configuration, the single and multi-wavelength laser could be generated. By applying the different filtering effects of the microfiber, the results of a single wavelength laser (one set), dual-wavelength laser (three sets) and triple wavelength laser (two sets) could be generated over a wavelength range of 1560–1565 nm. The signal to noise ratio (SNR) of 42–50 dB is obtained from the experiment with acceptable wavelength and power fluctuation over the test period of 30 min. Proposed switchable EDFL shows tunable and stable single and multi-wavelength laser generation in C band region.

Wavelength-switchable erbium-doped fiber laser based on femtosecond FBG inscribed on fiber core and cladding through the coating

Wavelength-switchable and multiple-wavelength outputs from fiber laser systems have many potential applications but, at present, methods for their generation are quite complex. Here we propose a simple approach, demonstrating a dual-wavelength switchable erbium-doped fiber laser that incorporates a single fiber Bragg grating (FBG), fabricated by a femtosecond laser in a plane-by-plane inscription method through a fiber coating, for a switchable 1564.66 and 1562.87 nm dual-wavelength laser operation. An 800 nm femtosecond pulsed laser acts as the inscription laser, focused by a 63× oil lens, fabricating a first-order FBG with an interval of 541 nm directly, on both the fiber core and cladding, through the polyimide coating. A 4 m-long erbium-doped fiber was selected as the gain medium. A lasing threshold of 66 mW was used in the experiment, and a switchable laser with stable single- and dual-wavelength outputs was achieved by adjusting a polarization controller. We were able to generate two different single-wavelength lasers with power fluctuations lower than 0.09 dB when measured over 40 min. In addition, dual-wavelength laser output could be obtained with power shifts of less than 0.9 dB at 26 °C.

Actively manipulation of operation states in passively pulsed fiber lasers by using graphene saturable absorber on microfiber

We experimentally demonstrate an operation switchable Erbium-doped fiber laser by employing graphene saturable absorber (GSA) on microfiber. With the introducing of a polydimethylsiloxane layer, a graphene can be considered as a parallel plate on microfiber and induces different propagation losses to TE and TM modes. By the use of such polarization sensitive GSA on microfiber, Erbium doped fiber laser with switchable operation states such as continuous wave, stable Q-switching, Q-switched mode-locking, and continuous-wave mode-locking, can be achieved by simply tuning the polarization states in the laser cavity. Our results show that covering graphene on microfibers could be a promising method for fabricating all fiber SA, and may have high potential in wide applications.

Polarization controlled multiwavelength switchable erbium-doped fiber laser based on high birefringence few-mode fiber loop mirror

A multiwavelength switchable erbium-doped fiber laser with linear cavity is proposed and experimentally demonstrated. It is based on a fiber loop mirror incorporating a piece of high birefringence few-mode fiber and polarization controller. Due to dependence of its reflection properties on the polarization controllers, the fiber laser can operate in the random combination of three wavelengths by only adjusting the polarization controllers in the linear cavity. The wavelengths involved in the switching operation are determined by the merged Sagnac and intermodal interferences elicited in the fiber loop mirror. The optical signal to noise extinction ratio of every oscillation line is higher than 40 dB and power fluctuation less than 0.5 dB.

Single- and dual-wavelength switchable erbium-doped fiber ring laser based on intracavity polarization selective tilted fiber gratings

We propose and demonstrate a single- and dual-wavelength switchable erbium-doped fiber laser (EDFL) by utilizing intracavity polarization selective filters based on tilted fiber gratings (TFGs). In the cavity, one 45 degrees TFG functions as an in-fiber polarizer and the other 77 degrees TFG is used as a fiber polarization dependent loss (PDL) filter. The combined polarization effect from these two TFGs enables the laser to switch between the single- and the dual-wavelength operation with a single-polarization state at room temperature. The laser output at each wavelength shows an optical signal-to-noise ratio (OSNR) of >60 dB, a side mode suppression ratio (SMSR) of >50 dB, and a polarization extinction ratio of approximately 35 dB. The proposed EDFL can give stable output under laboratory conditions.

Wavelength switchable L-band erbium-doped fiber laser employing C-band EDFA as gain medium

A new structure for the L-band multiwavelength switchable erbium-doped fiber laser is proposed. Overlapping laser cavities are formed by cascading fiber Bragg gratings as reflectors in a ring structure with a C-band EDFA as a common gain medium. The proposed laser is made to be wavelength-switchable by individually adjusting the loss of each overlapping cavity. Instead of using an L-band EDFA as the gain medium in the L-band fiber laser, we have experimentally demonstrated that by tailoring the gain of the C-band EDFA to have a significant gain tilt in the L-band, a lasing power efficiency of 26% can be achieved over a wide range of switchable lasing wavelengths. Following this optimal design, the side-mode suppression ratio and the minimal separation between two switchable lasing wavelengths were found to be over 42 dB and 0.33 nm, respectively.

Triple-wavelength switchable Erbium doped fiber laser with cascaded asymmetric exposure long-period fiber gratings

The cascaded asymmetric exposure long-period fiber gratings are fabricated by CO(2) laser, which provide multi-wavelength filters with anisotropic transmission spectrum under different states of polarization. Inserting this device in the ring cavity of an erbium-doped fiber laser, a triple-wavelength switchable lasing laser with equal spacing of 2.6 nm has been obtained. Owing to the polarization dependent loss of the new cascaded long-period fiber grating, the wavelength switching of random combination of C(1) (3), C (2) (3), and C(3) (3) is demonstrated through the polarization controlling. We derive the wavelength switch to the polarization characteristic of cascaded asymmetric exposure long-period fiber gratings.