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Showing papers on "Fiber laser published in 1998"


Journal ArticleDOI
TL;DR: Single-mode excitation of step-index multimode fibers with light sources with short temporal coherence lengths is demonstrated and designs with reduced microbending-induced mode coupling are described that allow the propagation of the fundamental mode over long lengths with negligible mode coupling even in the presence of tight fiber bends.
Abstract: Single-mode excitation of step-index multimode fibers with light sources with short temporal coherence lengths is demonstrated. Multimode fiber designs with reduced microbending-induced mode coupling are described that allow the propagation of the fundamental mode over long lengths with negligible mode coupling even in the presence of tight fiber bends. At a wavelength of 1.56microm a fiber with a core diameter of 45microm can preserve the fundamental mode for a propagation length of ~20m . Such fibers allow coiling with a coil diameter as small as 7cm.

346 citations


Journal ArticleDOI
TL;DR: A novel application of a wavelength-swept fiber laser to fiber Bragg grating sensor-array interrogation and static-dynamic strain measurements with a resolution of 0.47mu?
Abstract: We demonstrate a novel application of a wavelength-swept fiber laser to fiber Bragg grating sensor-array interrogation. The laser provides high signal powers of >3 mW with <0.1-nm spectral resolution over a 28-nm wavelength span. Using time-interval counting, we demonstrate static-dynamic strain measurements with a resolution of 0.47mu? rms at a sampling rate of 250 Hz.

335 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed strongly pumped fiber laser systems based on a rate equation model and showed that approximate analytical and quasi-analytical expressions are in excellent agreement with the exact numerical solution of the rate equations, and both agree well with recently published experimental data.
Abstract: Strongly pumped fiber lasers are analyzed, based on a rate equation model. Examples include Nd/sup 3+/-doped and Yb/sup 3+/-doped fiber lasers, with distributed Bragg reflector mirrors at either end. Approximate analytical and quasi-analytical expressions are shown to be in excellent agreement with the exact numerical solution of the rate equations, and both agree well with recently published experimental data.

204 citations


Journal ArticleDOI
TL;DR: Two short-coherence-length, rare-earth-doped fiber optical sources for performing optical coherence tomography (OCT) in human tissue are demonstrated and the OCT imaging depth of penetration in in vitro human aorta is compared.
Abstract: We demonstrate two short-coherence-length, rare-earth-doped fiber optical sources for performing optical coherence tomography (OCT) in human tissue. The first source is a stretched-pulse, mode-locked Er-doped fiber laser with a center wavelength of 1.55 μm, a power of 100 mW, and a bandwidth of 80 nm. The second is a Tm-doped silica fiber fluorescent source emitting up to 7 mW of power at 1.81 μm with a bandwidth of 80 nm. The OCT imaging depth of penetration in in vitro human aorta is compared using these sources and conventional 1.3-μm sources. © 1998 Society of Photo-Optical Instrumentation Engineers.

181 citations


Journal ArticleDOI
01 Jun 1998-Nature
TL;DR: In this article, the authors demonstrate that containerless processing, in which a molten sample is levitated by a flow of inert gas, permits sufficient undercooling of molten yttrium aluminium garnet (YAG:Y3Al5O12) to access a viscosity range conducive to fibre-pulling.
Abstract: Optical fibres doped with lanthanide or transition-metal elements can serve as in-line lasers and amplifiers for fibre-optic telecommunications systems. In general, most such fibre lasers use conventional silica-glass fibres doped with erbium or neodymium. But silicon dioxide absorbs strongly in the infrared for wavelengths of greater than 4 µm or so, limiting the infrared range over which such lasers can operate. Some other oxide materials do not absorb significantly until longer wavelengths—the absorption coefficient of crystalline silica at 4 µm is equal to that of yttrium oxide at 7.1 µm and of sapphire (a form of alumina) at 5.1 µm, for example1. Glass fibres made from these materials would therefore expand the range of fibre lasers into the mid-infrared. But molten oxides that do not contain silica typically have a viscosity too low to support fibre-pulling processes. Here we demonstrate that containerless processing, in which a molten sample is levitated by a flow of inert gas, permits sufficient undercooling of molten yttrium aluminium garnet (YAG:Y3Al5O12) to access a viscosity range conducive to fibre-pulling. The process is particularly effective if the molten material of stoichiometric YAG composition is doped with Nd2O3 in place of Y2O3, or with excess Al2O3; and it should also work with other dopants, because molten oxides are good solvents. Fibres could be drawn from a melt doped with Er2O3 in the presence of excess Al2O3. These fibres have the potential to extend the operating range of oxide glass-fibre lasers.

178 citations


Journal ArticleDOI
TL;DR: In this article, a theoretical analysis of the pump-induced temperature change and associated thermal phase shift occurring in a pumped doped fiber is presented, both in the dynamic and steady-state regimes.
Abstract: A theoretical analysis of the pump-induced temperature change and associated thermal phase shift occurring in a pumped doped fiber is presented. Although the primary devices targeted are all-optical switches based on doped fibers, where such effects can be detrimental, this analysis is also applicable to lasers, amplifiers, and other doped fiber devices. The effects of a single pump pulse, multiple pulses and continuous wave (CW) pumping are investigated, both in the dynamic and steady-state regimes. Simple expressions are derived for the thermal relaxation time constant of a fiber, and for its steady-state temperature rise and thermal phase shift under CW pumping. This study predicts that in all-optical fiber switches utilizing a reasonably good dopant the thermal effect due to a single short pulse is negligible in all interferometers, while the steady-state effect can be sizable in a standard fiber Mach-Zehnder but is negligible in a twin-core fiber, a two-mode fiber, and a specially designed Mach-Zehnder interferometer.

175 citations


Journal ArticleDOI
TL;DR: In simulations of a Yb(3+) -doped Fiber laser, ring doping increased the slope efficiency to 62%, up from 13% for a conventional core-doped fiber, and made the laser less sensitive to quenching of the laser-active dopant and to excited-state absorption of the lasing field.
Abstract: We propose and theoretically analyze three-level cladding-pumped fiber lasers in which the laser-active dopant is placed in a ring around a single-mode core. A ring-doped laser can work efficiently at wavelengths with strong small-signal absorption. This is otherwise difficult in a cladding-pumped fiber. Moreover, ring doping makes the laser less sensitive to quenching of the laser-active dopant and to excited-state absorption of the lasing field. In simulations of a Yb3+-doped fiber laser, ring doping increased the slope efficiency to 62%, up from 13% for a conventional core-doped fiber.

168 citations


Journal ArticleDOI
TL;DR: Self-pulsations detected in the output from the double-clad fiber laser may indicate the presence of ion-clustering effects.
Abstract: The operation of a diode-pumped Tm-doped silica fiber laser that uses the cladding-pumping arrangement to produce high-power cw output at wavelengths near 2 µm is reported. We obtained a maximum output power of 5.4 W at a slope efficiency of 31% with respect to the launched pump power at a total optical-to-optical efficiency of 22%. The fiber-laser output wavelength was tuned between 1.880 and 2.033 µm by adjustment of the fiber length, with >4 W of power obtainable from 1.94 to 2.01 µm. Self-pulsations detected in the output from the double-clad fiber laser may indicate the presence of ion-clustering effects.

166 citations


Patent
19 May 1998
TL;DR: In this article, a confocal optical scanning system with a flexible optical emissive fiber or fiber laser and a lasing cavity defined within the fiber is described. And the perturbation created in the cavity by the in-coupling of the signal beam (36) is detected by a transducer (46).
Abstract: A confocal optical scanning system (10) using a flexible optical emissive fiber or fiber laser (11) and having a lasing cavity (12) defined within the fiber. The system in-couples a signal beam (36) produced when a probe beam (32) generated by the fiber laser is reflected from a scanned object (34) back into the lasing cavity. The perturbation created in the cavity by the in-coupling of the signal beam (36) is detected by a transducer (46). Specifically, the perturbation may be the signal beam itself, an oscillation mode of the cavity induced by the in-coupled signal beam or a combination of the signal beam and the probe beam. In a preferred embodiment of the invention the system also has a polarizing assembly (100) for altering a signal polarization of the signal beam and rotate it to either a resonant polarization supported by the cavity or a non-resonant polarization not supported by the cavity.

164 citations


Journal ArticleDOI
TL;DR: In this article, a 5-cm long 1550-nm distributed feedback fiber laser with 4 mW output power is shown to have excellent specifications in terms of optical linewidth, signal-to-noise ratio (SNR), relative intensity noise, sidemode suppression and polarization purity.
Abstract: The device characteristics of Er/sup 3+/,Yb/sup 3+/ single frequency fiber lasers are reported. A 5-cm long 1550-nm distributed feedback fiber laser with 4 mW output power is shown to have excellent specifications in terms of optical linewidth, signal-to-noise ratio (SNR), relative intensity noise, side-mode suppression and polarization purity. For higher power applications, a 1.5 cm single frequency Er/sup 3+/,Yb/sup 3+/ grating-based fiber laser with 60 mW output power and a net efficiency of 12% is demonstrated.

152 citations


Journal ArticleDOI
TL;DR: It is demonstrated that appropriately designed doped multimode fibers provide robust single-mode output when used within a fiber laser cavity, and offers significant scope for extending the range of single- mode output powers and energies that are achievable from fiber-laser-amplifier systems.
Abstract: We demonstrate that appropriately designed doped multimode fibers provide robust single-mode output when used within a fiber laser cavity. Using a novel large-mode-area fiber, we demonstrate what we believe to be record single-mode M2 0.5 mJ from a Q-switched fiber laser and even higher pulse energies (as high as 0.85 mJ) with slightly compromised spatial-mode quality M2<2.0. This approach offers significant scope for extending the range of single-mode output powers and energies that are achievable from fiber-laser–amplifier systems.

Journal ArticleDOI
TL;DR: In this article, the effect of the ytterbium to erbium concentration ratio on the laser characteristics is investigated and some important issues in the fabrication process are discussed.
Abstract: Fabrication process of efficient Yb/sup 3+/,Er/sup 3+/ codoped phosphosilicate fibers by modified chemical vapor deposition (MCVD) combined with the solution doping technique is studied in detail. We show that the process can be adapted to incorporate low viscosity phosphate glass and some important issues in the fabrication process are discussed. These include the sensitive presintering pass. We also report on the fabrication of a low loss all-glass double clad Yb/sup 3+/:Er/sup 3+/ codoped fiber. We explain how we evaluate the fibers and discuss the effect of the ytterbium to erbium concentration ratio on the laser characteristics. Finally, we present results of some investigations into the mechanisms which can affect the efficiency of the lasers, and show that the detrimental up-conversion from the metastable level of the erbium ions is dramatically reduced by the presence of the ytterbium ions.

Journal ArticleDOI
TL;DR: A novel, sensitive, simple, and robust strain interrogation technique is analyzed and experimentally tested, which achieves high dynamic strain sensitivity of 45 picostrain/ radicalHz rms at 3 kHz.
Abstract: A novel, sensitive, simple, and robust strain interrogation technique is analyzed and experimentally tested. By locking a laser wavelength to the midreflection wavelength of a standard fiber Bragg grating and measuring the error signal, we achieve high dynamic strain sensitivity of 45 picostrain/Hz rms at 3 kHz, where the dominant noise in the experiment is the laser frequency noise.

Journal ArticleDOI
TL;DR: A single-longitudinal-mode erbium-doped fiber laser with a passive multiple-ring cavity (MRC) is proposed for the first time to the authors' knowledge and can successfully suppress side-mode frequencies of as much as 1 GHz and provide an output power of 23 mW.
Abstract: A single-longitudinal-mode erbium-doped fiber laser with a passive multiple-ring cavity (MRC) is proposed for the first time to the authors' knowledge. The laser is fundamentally structured by insertion of three different short ring cavities, which serve as mode filters, into the main cavity. When it is combined with a mode-restricting intracavity fiber Bragg grating, the MRC resonator ensures single-longitundinal-mode laser oscillation. The laser can successfully suppress side-mode frequencies of as much as 1 GHz and provide an output power of 23 mW with a side-mode suppression ratio of 51 dB at 1533 nm. The short-term linewidth of the laser output measured is ~2 kHz . The ability of this fiber laser to act as an AM transmitter source is also demonstrated.

Journal ArticleDOI
TL;DR: A novel cladding pumped Nd(3+) fiber laser operating in an enhanced Q-switched regime with a stable repetition rate is described and a peak power of 3.7 kW enhanced by an order of magnitude greater than that of conventional Q- Switched fiber devices is demonstrated.
Abstract: A novel cladding pumped Nd3+ fiber laser operating in an enhanced Q-switched regime with a stable repetition rate is described. By exploiting fiber nonlinearities in the laser cavity, we demonstrated a peak power of 3.7??kW enhanced by an order of magnitude greater than that of conventional Q-switched fiber devices. Pulse durations as short as 2??ns have been achieved.

Patent
26 May 1998
TL;DR: In this article, a laser marking system consisting of a double-clad fiber having a doped core surrounded by an inner pump cladding and providing an optical output for marking is described.
Abstract: A laser marking system comprises a high power fiber laser consisting of a double clad fiber having a doped core surrounded by an inner pump cladding and providing an optical output for marking; a high power laser diode source for pumping the double clad fiber laser via an input into the inner pump cladding; an optical scanner coupled to receive the marking output from the double clad fiber laser to scan the output over a surface of an article to be marked by sweeping the marking output in one, two or three dimensions to form strokes, the completion of which comprises indicia to be marked the article surface; and a controller to control the operation of the scanner in synchronism with the modulation of the laser diode pump source to initiate the marking output and sweep and modulate the marking optical output in one, two or three dimensions to form strokes comprising the indicia. A main advantage of the fiber laser marking system over CO2 and YAG laser marking systems is the ability to provide modulation via the semi-conductor laser diode at the input to the marking laser rather than having to modulate the optical power beam at the output of the marking laser, such as through an acousto-optic modulator, which provides for a pulse of non-uniform stability across the pulse width with a substantially decrease in the amount of power in the modulated beam output. Also disclosed is circuitry to dampen the ON-time rise of a current signal input for operation of the laser diode pump source to improve the ON-time quality of the marking optical output created by the double clad fiber marking laser.

Patent
30 Jun 1998
TL;DR: In this paper, a system and method for photodynamic therapy using a phased array Raman laser amplifier including a beam generator for generating a fundamental laser beam and a Raman seed frequency laser beam, and a fiber optic laser amplifier array for forming a diffraction limited output laser beam at the Ramanseed frequency by amplifying the fundamental beam to a power level corresponding to the Stimulated Raman Scattering (SRS) threshold to thereby pump the SRS process and provide Raman gain.
Abstract: System and method for photodynamic therapy using a phased array Raman laser amplifier including a beam generator for generating a fundamental laser beam and a Raman seed frequency laser beam, and a fiber optic laser amplifier array for forming a diffraction limited output laser beam at the Raman seed frequency by amplifying the fundamental laser beam to a power level corresponding to the Stimulated Raman Scattering (SRS) threshold to thereby pump the SRS process and provide Raman gain to the Raman seed frequency laser beam.

Journal ArticleDOI
TL;DR: In this article, a simple theoretical model has been developed to obtain almost all the dynamical behaviors of erbium-doped fiber-ring laser systems with one polarized mode, as well as the coexistent scenario of the period doubling and intermittently chaotic routes to chaos.
Abstract: In this paper we report studies on the dynamical behaviors of erbium-doped fiber lasers with one polarized mode. The chaotic behaviors, as well as the coexistent scenario of the period doubling and the intermittently chaotic routes to chaos, are observed experimentally in this fiber laser with pump modulation. Optical bistability and a simple bifurcation are also observed in different modulation frequencies. A simple theoretical model has been developed to obtain almost all the dynamical behaviors. Another method to gain chaos in an erbium-doped fiber-ring laser system is a coupled-ring system. Theoretical study shows that chaos occurs in this dual-ring system. Again a bifurcation scenario is found in the marginal region from self-pulsation to chaos. Interestingly enough, a duplicated ring can produce synchronized chaos.

Journal ArticleDOI
TL;DR: In this article, the authors observed laser emission in whispering gallery modes using a microring composed of a semiconducting polymer poly[2,5-bis-(2′-ethylhexyloxy)-p-phenylenevinylene coated on an etched fiber under transient and quasisteady-state pumping conditions.
Abstract: We observed laser emission in whispering gallery modes using a microring composed of a semiconducting polymer poly[2,5-bis-(2′-ethylhexyloxy)-p-phenylenevinylene coated on an etched fiber under transient and quasisteady-state pumping conditions. The threshold for laser oscillation was 1 mJ/cm2 (0.1 MW/cm2) and 30 μJ/cm2 (300 MW/cm2) for nanosecond and femtosecond excitation, respectively. The laser output showed superlinear dependence on the excitation energy above the threshold. The demonstration of lasing under quasisteady-state pumping shows the possibility to develop electrically pumped polymer lasers.

Journal ArticleDOI
TL;DR: In this article, a single-and dual-wavelength tuning and threewavelength operation of an actively mode-locked fiber ring laser generating picosecond pulses were demonstrated by using a cavity with large dispersion.
Abstract: Electrical single- and dual-wavelength tuning and three-wavelength operation of an actively mode-locked fiber ring laser generating picosecond pulses were demonstrated by using a cavity with large dispersion A continuous tuning range up to ∼37 nm of single-wavelength picosecond pulses at ∼1 GHz was achieved by only changing the modulation frequency Continuous wavelength tuning of dual-wavelength (185 nm spacing) 3 GHz picosecond pulses was also demonstrated with a tuning range up to ∼17 nm The tuning ranges were mainly limited by the gain bandwidth of the Er-doped fiber Simultaneous generation of three-wavelength picosecond pulses at ∼2 GHz was also demonstrated by further increasing the cavity dispersion

Journal ArticleDOI
TL;DR: A parametric chirped pulse amplification system in which femtosecond pulses from a mode-locked Er-doped fiber laser system are amplified to 1-mJ energies in a single pass by use of a 5-mm-long periodically poled LiNbO(3) (PPLN) crystal, demonstrating that limitations associated with a low optical-damage threshold for long pump pulses can be overcome.
Abstract: A new type of solid-state femtosecond amplifier is demonstrated that is based on quasi-phase-matched parametric amplification. Such gain media are different from conventional solid-state amplifiers in that their amplification bandwidths and pump and signal wavelengths can be engineered. Furthermore, high gain is characteristic of parametric amplification, permitting extraction of high energies without the need to resort to multiple-pass configurations. We report a parametric chirped pulse amplification system in which femtosecond pulses from a mode-locked Er-doped fiber laser system are amplified to 1-mJ energies in a single pass by use of a 5-mm-long periodically poled LiNbO(3) (PPLN) crystal. This amplifier is pumped by 5-mJ and 0.5-ns pulses at 786 nm, demonstrating that limitations associated with a low optical-damage threshold for long pump pulses can be overcome because of the high nonlinearity of PPLN and that relatively simple Q -switched lasers can be used with such parametric amplifiers.

Journal ArticleDOI
TL;DR: For the first time to the authors' knowledge, an integrated optical distributed Bragg reflector laser with a fixed photorefractive grating in LiNbO(3) is demonstrated.
Abstract: For the first time to the authors' knowledge, an integrated optical distributed Bragg reflector laser with a fixed photorefractive grating in LiNbO(3) is demonstrated. Sample preparation, grating fabrication, and laser characteristics are reported. The device is pumped by a fiber pigtailed laser diode (lambda(p) approximately 1480 nm) through the Bragg grating in a double-pass configuration, yielding an emission in the backward direction at lambda=1531.7 nm . The laser threshold is 40 mW; as much as 5 mW of output power has been obtained at 110 mW of launched pump power in cw operation.

Patent
11 Feb 1998
TL;DR: In this paper, a saturable absorber coupled to one end of a highly-birefringent fiber serving as the laser cavity is introduced to ensure the reliable start-up of modelocking on only the low loss axis.
Abstract: Stable operation of an ultra-compact modelocked fiber laser generating short optical pulses generally without use of any non-fiber, intra-cavity polarization-manipulating elements is obtained by employing a saturable absorber coupled to one end of a highly-birefringent fiber serving as the laser cavity. Once the laser is modelocked in one of the polarization axes of the highly-birefringent fiber, the degeneracy of the polarization axis is eliminated and cw oscillation along the other polarization axis is also prevented. Without a polarization-dependent loss in the cavity, the modelocked polarization axis is indeterminate, i.e., modelocking can occur on either of the polarization axes. However, the introduction of only a small polarization dependent loss is sufficient to ensure the reliable start-up of modelocking on only the low-loss axis. Such a small polarization dependent loss can be introduced by tightly coiling the highly-birefringent fiber, which generates a higher loss along the fast axis; thus, reliable modelocked operation along the slow axis is obtained. Alternatively, single polarization operation is obtained by employing a saturable absorber with a polarization-dependent loss or by introducing polarization-manipulating elements external to the laser cavity.

Journal ArticleDOI
TL;DR: A short-cavity erbium-ytterbium fiber laser that is passively mode locked by a saturable Bragg reflector with a fundamental repetition rate of 235 MHz is demonstrated and a slow gain-recovery model is proposed to explain the pulse-train self-organization.
Abstract: We demonstrate a short-cavity erbium–ytterbium fiber laser that is passively mode locked by a saturable Bragg reflector with a fundamental repetition rate of 235 MHz. The laser operates in the soliton regime and under passive harmonic mode locking with 11 pulses in the cavity and produces output pulse trains at 2.6 GHz with transform-limited 270-fs pulses and 1.6??mW of average power. Within the cavity the multiple pulses form a stable pattern with fixed, nearly equal pulse-to-pulse temporal spacings, causing the output pulse train to have timing offsets of less than 15??ps. A slow gain-recovery model is proposed to explain the pulse-train self-organization.

Patent
24 Apr 1998
TL;DR: In this article, the optical signal produced by a modulated semiconductor laser is passed through a fiber grating optical discriminator to increase the modulation response of the device and decrease the output chirp for transmission through optical fiber.
Abstract: The optical signal produced by a modulated semiconductor laser is passed through a fiber grating optical discriminator to increase the modulation response of the device and decrease the output chirp for transmission through optical fiber.

Journal ArticleDOI
TL;DR: A novel multiwavelength lasing scheme in which a Brillouin erbium-fiber laser with a Sagnac loop mirror and a metal-coated planar mirror were used to generate high-order Stokes and anti-Stokes waves through a four-wave mixing (FWM) process.
Abstract: We have demonstrated a novel multiwavelength lasing scheme in which a Brillouin erbium-fiber laser with a Sagnac loop mirror and a metal-coated planar mirror were used. The Sagnac loop permitted the simultaneous presence of a stimulated Brillouin scattering (SBS) pump and Stokes lines within the loop and thus generated high-order Stokes and anti-Stokes waves through a four-wave mixing (FWM) process. A total of 34 lines of Stokes and anti-Stokes waves with 0.08-nm line spacing was generated through the SBS and FWM processes with 1.5-mW SBS pump power at 1561 nm and 80-mW erbium-doped-fiber pump power.

Journal ArticleDOI
TL;DR: In this article, a secure communication system based on the chaos in erbium-doped fiber lasers is proposed and studied with two schemes: message masking and chaos shift keying.
Abstract: Secure communication systems based on the chaos in erbium-doped fiber lasers are proposed and studied with two schemes: message masking and chaos shift keying. The effect of the parameter mismatch between the transmitter and the receiver on synchronization of chaos is also studied. The synchronization is maintained quite well with mismatches of parameters of 5% or even more by use of a comatching method.

Patent
17 Feb 1998
TL;DR: In this paper, a passive mode-locked linear-resonator fiber laser using polarization-maintaining fibers and a saturable absorber was proposed to produce ultra short pulses and a long-term reliable operation.
Abstract: A passive mode-locked linear-resonator fiber laser using polarization-maintaining fibers and a saturable absorber to produce ultra short pulses and a long-term reliable operation with reduced maintenance. Such a fiber laser can be configured to produce tunable pulse repetition rate and tunable laser wavelength.

Journal ArticleDOI
TL;DR: A compact superfluorescent source based on an Yb-doped double-cladding fiber amplifier is described, which generates 485 mW of broadband emission centered at 1055 nm with a 41-nm FWHM flat power spectrum.
Abstract: A compact superfluorescent source based on an Yb-doped double-cladding fiber amplifier is described. The packaged amplifier is pumped at 975 nm by side-coupling emission from a 2.0-W broad-stripe laser diode through an imbedded V groove. The fiber source generates 485 mW of broadband emission centered at 1055 nm with a 41-nm FWHM flat power spectrum.

Journal ArticleDOI
TL;DR: In this article, an actively mode-locked fiber ring laser with a linearly chirped fiber Bragg grating (FBG) was used for continuous wavelength tuning with a range of 7.2 or 5.8 mm.
Abstract: Electrical wavelength-tunable picosecond laser pulses were demonstrated in an actively mode-locked fiber ring laser with a linearly chirped fiber Bragg grating (FBG). Continuous wavelength tuning with a range of 7.2 or 5.8 mm was achieved by changing the modulation frequency respectively around 2.48 or 6.3 GHz. A pulsewidth of about 20 ps was obtained in the entire tuning range, which was limited mainly by the reflection bandwidth of the FBG.