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The authors experimentally demonstrated the generation of mode‐locked pulses from all‐fibre erbium‐doped fibre laser cavity by using organic material, Alq3, as a saturable absorber (SA). The SA film was integrated into a ring fibre laser cavity to act as a mode‐locker. A mode‐locking operation was achieved in three different experiments with pulse width/repetition rate of 1.26 ps/3.36 MHz, 970 fs/3.36 MHz and 820 fs/4.9 MHz by using cavity length/optical coupler (OC) of 61.5 m/80:20 OC, 61.5 m /95:5 OC and 42 m/80:20 OC, respectively. All the experiments produced a soliton and a very stable mode‐locking operation at central wavelength of ∼1561 nm. The experiments confirmed that organic material can readily be used as SA for a mode‐locked operation in the 1.5 μm region. This demonstration might shed new insights into the potentials and techniques for developing ultrafast fibre lasers by using organic materials as SAs. [ABSTRACT FROM AUTHOR]

Q‐switched and mode‐locked fibre lasers have been successfully demonstrated in ytterbium‐doped fibre laser cavity by taking an advantage of the optical absorption of antimony telluride (Sb2 Te3) material. The Sb2 Te3 was embedded into polyvinyl alcohol to function as a saturable absorber (SA). A Q‐switching pulses train was obtained by incorporating the SA into the laser ring cavity configured with 3 dB coupler. The Q‐switching pulse repetition rate increases from 24.4 to 55 kHz as the pump power is increased from the threshold of 75.4–96.2 mW. The maximum pulse energy of 252.6 nJ is obtained at 82.3 mW pump power. On the other hand, by changing the output coupler to 10 dB coupler, a stable self‐started mode‐locking operation was then generated at pump power range from 47.8 to 89.4 mW with a fixed repetition rate of 24.2 MHz. At 89.4 mW pump power, the maximum output power and pulse energy are obtained to be around 18.6 mW and 0.8 nJ, respectively. The authors results display that the Sb2 Te3 material could also be developed as an effective SA for both Q‐switched and mode‐locked fibre lasers. [ABSTRACT FROM AUTHOR]

An evaluation of the amplitude jitter and timing jitter for a regeneratively mode‐locked fibre laser via the use of the harmonic analysis approach is presented. The RF power spectrum of four harmonics derived from a 10 GHz mode‐locked pulse train was measured with high resolution. From a detailed analysis of the noise pedestal present in these harmonics, an amplitude jitter of ∼0.3% and an absolute timing jitter of ∼41 fs are obtained. [ABSTRACT FROM AUTHOR]

We demonstrate a passively Q-switched erbium-doped fiber laser (EDFL) based on few-layer MoS2 as a saturable absorber (SA). Few-layer MoS2 is prepared by the chemical vapor deposition method. The prepared MoS2 is transferred onto the end face of a fiber connector to form a fiber-compatible MoS2-based SA. The saturation intensity and modulation depth of the MoS2 SA are measured to be 0.43 MW/cm2 and 33.2%, respectively. The Q-switched EDFL has an all-fiber linear cavity with two fiber Bragg gratings as the end mirrors. By inserting the MoS2 SA into the laser cavity, stable Q-switched operation is achieved at 1.55 μm. The laser has a pump threshold of 20.4 mW, a pulse repetition rate tunable from 10.6 to 173.1 kHz, and a minimum pulse duration of 1.66 μs. Our results show that few-layer MoS2 is a promising SA for Q-switching laser operation. [ABSTRACT FROM PUBLISHER]

Cross-phase modulation instability (XPMI) is experimentally observed in a fiber ring cavity with net normal dispersion and mode-locked by long fiber taper. The taper is deposited with reduced graphene oxide, which can decrease the threshold of XPMI due to the enhanced nonlinearity realized by 8-mm evanescent field interaction length and strong mode confinement. Experimental results indicate that the phase matching conditions in two polarization directions are different, and sidebands with different intensities are generated. This phase matching condition can be satisfied even the polarization state of the laser varies greatly under different pump strengths. [ABSTRACT FROM PUBLISHER]

A single-longitudinal-mode (SLM) fiber ring laser based on topological insulator (TI) Bi2Te3 saturable absorber (SA) had been experimentally demonstrated. The TI: Bi2Te3 nanosheets, which were fabricated through the bottom-up approach, were coated onto the microfiber as an efficient saturable absorber device to ensure the SLM operation. Combined with fiber Bragg grating, the output wavelength can be continuously tuned about 1 nm. Without any accurate cavity control, stable SLM operation without mode hopping had been conveniently achieved. Based on the Lorentzian fitting, the line-width was measured to be less than 10 kHz. The output power of SLM fiber laser can reach up to 23 mW, indicating that the proposed TI-based SA may be suitable for high-optical power SLM operation in the future. [ABSTRACT FROM PUBLISHER]

Square nanosecond mode-locking was demonstrated in a short-cavity polarization-maintaining (PM) fiber laser with a nonlinear amplifying loop mirror (NALM). Nonlinear phase shifts in the NALM enforced peak-power clamping and accordingly, the output pulse duration varied with the NALM gain. Gain competition of multipulse mode-locking was observed with short NALM loops. Such NALM-based mode-locking exhibited long-term stability against environmental disturbance. [ABSTRACT FROM PUBLISHER]

An Yb3+, Ho3+ codoped all-fiber laser oscillating at ~2.05 μm in continuous-wave, employing a novel pump version, 1.064 μm, is reported. Low threshold (~0.8 W) and moderate slope efficiency (~15.6%) of lasing are obtained in the simplest nonoptimized Fabry-Perot cavity, composed of a couple of spectrally adjusted fiber Bragg gratings. High brightness of ~2.05-μm output is an attractive laser's feature, stemming from spatially single-mode operation and narrow optical spectrum (~70 pm at a 3-dB level), in the whole pumps' range. The laser demonstrates high stability: during uninterrupted few-hours-perday operation its output power fluctuates within a 3% range. [ABSTRACT FROM PUBLISHER]

A novel tunable dual-wavelength thulium-doped fiber laser is demonstrated experimentally. The wavelength-tuning by employing a high birefringence fiber Bragg grating is proposed in 2-μm band lasing for the first time. By adjusting the polarization controller, stable dual-wavelength operation at the wavelengths of 1941.40 and 1942.21 nm is obtained. The optical signal-to-noise ratio is better than 48 dB. A 15.5% slope efficiency is achieved using a 90% output coupling ratio for laser extracting. The wavelength-tuning range in dual-wavelength operation is as wide as 6.93 nm. [ABSTRACT FROM PUBLISHER]

We report an environmentally stable nanotube mode-locked fiber laser producing linearly-polarized, nanosecond pulses. A simple all-polarization-maintaining fiber ring cavity is used, including 300 m of highly nonlinear fiber to elongate the cavity and increase intracavity dispersion and nonlinearity. The laser generates scalar pulses with a duration of 1.23 ns at a center wavelength of 1042 nm, with 1.3-nm bandwidth and at 641-kHz repetition rate. Despite the long cavity, the output characteristics show no significant variation when the cavity is perturbed, and the degree of polarization remains at 97%. [ABSTRACT FROM PUBLISHER]

We proposed and demonstrated a stable multiwavelength erbium-doped fiber laser by using a microfiber knot resonator (MKR)-based comb filter. By properly rotating the polarization controller, up to 11 lasing lines in a 3-dB bandwidth with 0.184-nm channel spacing were obtained. In addition, the lasing locations can be flexibly tuned by virtue of spectral filtering effect induced by the polarization-dependent isolator and the intracavity birefringence. The results demonstrated that the MKR could be employed as a high performance comb filter to realize a compact multiwavelength fiber laser. [ABSTRACT FROM PUBLISHER]

A switchable single-polarization dual-wavelength single-longitudinal mode (SLM) erbium-doped fiber (EDF) ring laser is proposed and demonstrated. For the first time, the structured polarization-maintaining chirped fiber Bragg grating (PM-CFBG) filter, which has ultranarrow transmission band is created by tapering directly on the PM-CFBG. Then, the stable SLM operation of the fiber laser is guaranteed by the structured PM-CFBG filter and 20-cm unpumped EDF acting as a saturable absorber. Meanwhile, the stable dual-wavelength fiber laser with a wavelength spacing of ~0.41 nm and stable single polarization state is experimentally realized. The measured linewidth of the fiber laser for each wavelength is <;8 kHz with a 20-dB linewidth. [ABSTRACT FROM PUBLISHER]

We have demonstrated a switchable dual wavelength fiber ring laser with a high degree of polarization output by using an intracavity 3-stage all fiber Lyot filter. The filter is formed by concatenating four 45° tilted fiber gratings separated by polarization maintaining fibers with a length ratio of 1:2:4 (20, 40, and 80 cm), giving a compact integrated configuration with reduced bandwidth. Switchable dual wavelength or single wavelength output at 1533.5 and 1563.3 nm has been achieved. The output lasing is considerably stable owing to the in-phase mode-selecting function of the multistage Lyot filter, and has a very high degree of polarization higher than 99.9%. [ABSTRACT FROM PUBLISHER]

We demonstrated a stable passively Q-switched Er-doped fiber laser around the optical communication band with a microfiber-based topological insulator (TI) Bi2Te3 saturable absorber. The saturable absorber was fabricated by the optical deposition method and its nonlinear transmission ~1568 nm was characterized. By virtue of the TI saturable absorber, stable Q-switched pulses can be formed with pulse repetition rate increasing from 2.6 to 12 kHz, and pulse duration decreasing from 50 μs to 9.5 μs through altering the pump strength. Our results evidently show the effectiveness of Bi2Te3-based saturable absorber and its potential applications for pulsed laser generation. [ABSTRACT FROM PUBLISHER]

A novel configuration for a dual-wavelength fiber ring laser with improved lasing stability realized through the use of an injection-coupled optoelectronic oscillator (OEO) is proposed and demonstrated, and its application to transverse load sensing is studied. The OEO-coupled dual-wavelength laser has two mutually coupled loops: the fiber ring loop and the OEO loop. In the fiber ring loop, a polarization-maintaining phase-shifted fiber Bragg grating is incorporated to generate two optical wavelengths with the wavelength spacing determined by the birefringence of the polarization-maintaining (PM) fiber. In the OEO loop, a microwave signal with its frequency also determined by the birefringence of the PM fiber is generated, which is fed into the fiber ring loop to injection lock the dual wavelengths. Due to the injection locking, a very stable dual-wavelength operation is established. The use of the dual wavelengths for high-resolution and high-speed transverse load sensing is then implemented. The sensitivity of the transverse load sensor is measured as high as +9.7573 and -9.7350 GHz/(N/mm), along the fast and slow axes, respectively. The high frequency purity and stability of the generated microwave signal permits very reliable and high accuracy measurement and the microwave frequency interrogation allows the system to operate at an ultra-high speed. [ABSTRACT FROM PUBLISHER]

A novel double-pumped ring cavity multiwavelength fiber optical parametric oscillator (MW-FOPO) with tunable wavelength spacing is proposed. In the MW-FOPO, we utilize a highly nonlinear dispersion-shifted fiber as the gain medium and a Mach-Zehnder interferometer as the comb-like filter. Twenty-four-wavelength lasing of the double-pumped MW-FOPO with a ripple less than ±4.3 dB and a wavelength spacing of about 0.8 nm in a wavelength range from 1541 to 1558 nm is experimentally demonstrated. The wavelength spacing can be continuously tuned and multiwavelength lasings with wavelength spacings of 0.08, 0.2, 0.4, and 0.8 nm are demonstrated, respectively. We discussed the power stability of the multiwavelength lasing of the double-pumped MW-FOPO. A comparison of the output spectra among the double-pumped MW-FOPO, the single-pumped MW-FOPO, and the multiwavelength erbium-doped fiber laser is also presented. [ABSTRACT FROM PUBLISHER]

A 10 GHz mode‐locked fibre laser has been treated to improve its stability and the quality of generated pulses. An unpumped 3 m erbium‐doped fibre (EDF) is incorporated outside the cavity at the output of the mode‐locked laser and a setup is designed so as to form the strong standing waves inside the EDF that leads to spatial hole burning effect. This reduces the phase noise of the mode‐locked laser, resulting in the timing jitter reduction from 260 to 130 fs. [ABSTRACT FROM AUTHOR]

A stabilized and tunable single-longitudinal-mode erbium-doped fiber ring laser has been proposed and experimentally demonstrated. The laser is structured by combining the compound cavity with a fiber Fabry-Peacuterot tunable filter. An injection-locking technique has been used to stabilize the wavelength and output power of the laser. One of the longitudinal modes is stimulated by the injected continuous wave so that this mode is able to win the competition to stabilize the system. A minimum output power of 0.6 dBm and a signal-to-noise ratio of over 43 dB within the tuning range of 1527-1562 nm can be achieved with the proposed technique. A wavelength variation of less than 0.01 nm, a power fluctuation of less than 0.02 dB, and a short-term linewidth of about 1.4 kHz have also been obtained [ABSTRACT FROM PUBLISHER]

This paper describes the design and operation of a stable narrow-linewidth linearly polarized fiber ring laser using a polarization-maintaining (PM) erbium-doped fiber as a saturable absorber. The effect of the PM fiber on suppressing mode hopping is experimentally demonstrated and optimum conditions for single-mode operation are identified. Laser output power is ∼ 4.7 mW at 1535 nm for a pump power of 94 mW, the polarization extinction ratio is 24.8 dB, the SNR is larger than 45 dB, the relative intensity noise is below -104 dB/Hz at frequencies above 150 kHz, and the linewidth is less than 1.5 kHz. Potential applications of the fiber laser for interferometric or spectroscopic fiber sensors are briefly discussed. [ABSTRACT FROM PUBLISHER]

A theoretical and experimental study of a multiwavelength fiber-ring laser that incorporates a semiconductor optical amplifier (SOA) in the laser cavity as a phase modulator to suppress the homogeneous line broadening is presented. The analysis reveals that the phase shift introduced by the SOA-based phase modulator is more significant than that formed using a LiNbO3 phase modulator, which leads to a better suppression of the homogeneous line broadening. Multiwavelength lasing with small wavelength spacing and improved stability at room temperature is achieved. A fiber-ring laser based on the proposed approach is implemented. Stable multiwavelength operation with up to 26 wavelengths and wavelength spacing as small as 0.19 nm at room temperature is demonstrated. [ABSTRACT FROM PUBLISHER]

This paper investigates rational harmonically mode-locked fiber ring lasers generating amplitude-stabilized fourth-order optical pulse trains at 13.91 GHz using a modulation signal frequency of 3.477 GHz. Pulse amplitude stabilization in terms of both amplitude equality and low amplitude noise is realized by using the nonlinear characteristics of a Mach-Zehnder intensity modulator in conjunction with intracavity optical filtering. The generated optical pulse trains are investigated for their amplitude equalization, amplitude noise, supermode noise suppression, and pulse timing jitter. It is shown that the pulses remained close to transform-limited over an operating wavelength range of 1535-1565 nm. [ABSTRACT FROM PUBLISHER]

A simple design of a stable, smoothly wavelength-tunable picosecond pulse generator has been demonstrated using a dispersion-tuned, harmonically mode-locked fiber ring laser with a directly modulated semiconductor optical amplifier (SOA). The SOA functions as both a polarization-insensitive mode locker and a supermode noise suppressor. Near-linearly chirped pulses are generated and compressed to less than 4 ps when the intracavity dispersion is anomalous while 11-ps, near-transform-limited pulses are generated without compression when the dispersion is normal. Smooth wavelength tuning is achieved over more than 11 nm by only tuning the modulation frequency and pulse characteristics are stable over the entire tuning span. A simple numerical model successively simulates the operation principle of the system. The tuning range is determined by both the gain profile and the total intracavity dispersion. The dispersion and the SOA ensure the long-term stability of the system. [ABSTRACT FROM PUBLISHER]

This paper investigated injection locking characteristics of a fiber distributed feedback (DFB) laser operating in dual polarizations, and found that it could operate in a single polarization by injection locking. The locking bandwidth was less than 10 MHz, much narrower than DFB laser diodes as a consequence of longer cavity length and resulting longer photon lifetime. As a more practical method to realize single-polarization operation of the fiber DFB laser, we proposed self-injection locking with a polarization-selective optical feedback composed of a mirror and a polarizer, and demonstrated a stable single-polarization operation [ABSTRACT FROM PUBLISHER]

We report an environmentally stable and ultracompact dissipative soliton mode-locked fiber laser with a semiconductor-saturable absorber mirror (SESAM). A polarization-maintaining fiber loop mirror is used as the linear cavity end mirror, which also serves other purposes, such as a laser output coupler, a polarizer, and a pulse-shaping bandpass filter. Self-starting stable mode-locking operation with 2-nJ pulse energy and 24-ps pulsewidth is achieved. The laser emission shows high polarization extinction ratio of over 22 dB, with excellent stability. [ABSTRACT FROM PUBLISHER]

We demonstrate the mode-locking operation in an all-polarization-maintaining (all-PM) erbium-doped fiber laser by exploiting graphene oxide saturable absorber for the first time. The self-started, environmentally stable laser directly generates linearly polarized soliton pulses of 502 fs duration at a repetition rate of 48.2 MHz with an extinction ratio of 21.3 dB. The optical spectrum centered at 1555.92 nm has 3-dB bandwidth of 6 nm. This unique combination of the all-PM configuration and the novel graphene oxide saturable absorber offers an ideal approach to fabricate a compact single-polarization femtosecond source with high environmental stability. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate an all-fiber, polarization maintaining (PM) ultrafast fiber laser using a hybrid mode-locking mechanism consisting of a nonlinear amplifying loop mirror and carbon nanotube saturable absorber (CNT-SA). By incorporating the CNT-SA, the threshold for mode-locked operation is reduced by approximately a factor of 3, from 330 to 120 mW. Moreover, the all-PM fiber design provides excellent stability and turnkey operation. [ABSTRACT FROM PUBLISHER]

A stable narrow bandwidth semiconductor saturable absorber mirror mode-locked Yb-doped fiber laser was demonstrated in a short linear cavity with fundamental repetition rate up to 843 MHz. At the fundamental repetition rate of 490 MHz, the maximum output power was 17 mW at ~ 300-mW incident pump power. The center wavelength and the spectral bandwidth were 1064.1 and 0.13 nm, respectively, imposed by a narrow bandwidth fiber Bragg grating. The pulsewidth was measured to be 21 ps, and the time-bandwidth product of the laser pulse was 0.72. [ABSTRACT FROM PUBLISHER]

A stably and widely tunable single-longitudinal-mode dual-wavelength erbium-doped fiber (EDF) laser is investigated for the generation of a tunable optical beat frequency. The lasing wavelength spacing is widely controlled in a range from 3.46 to 13.2 nm, which means that the tunable optical beat frequency in a range from 0.43 to 1.66 THz can be achieved. Nonlinear polarization rotation effect is implemented to stabilize and equalize outputs of the tunable dual-wavelength EDF laser. Since the dual-wavelength fiber laser has a single-longitudinal mode, the proposed dual-wavelength fiber laser is stable. [ABSTRACT FROM PUBLISHER]

We report a high energy, high peak power, all-flber-based single-frequency ~15-ns pulsed laser source at ~1918.4 nm in master oscillator-power amplifier configuration. The pulsed fiber laser seed was achieved by directly modulating a continuous- wave single-frequency fiber laser using an electro-optic modulator driven by an arbitrary waveform generator to pre-shape the pulses before amplification to mitigate pulse steepening and dynamic gain saturation. One piece of large (25-μm) core, polarization-maintaining highly thulium-doped germanate glass fiber was used in the power amplifier stage to boost the energy and the peak power of the 15-ns pulses to >;0.5 mj and >;33 kW without any nonlinearities. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate an all-fiber scheme to generate a precisely tunable microwave signal by heterodyning the two cascaded single-frequency Brillouin fiber lasers (BFLs). The generated microwave frequency is equivalent to the offset between the first- and the second-order Stokes frequencies. The ~10 GHz generated signal exhibits high stability with a linewidth of 2.8 KHz. By controlling elastic strain to the fiber in the BFL, the microwave frequency can be tuned up to 270 MHz. Owing to frequency pulling effect (FPE) in BFL, the signal frequency can be continuously tuned in a range of 9.6 MHz within one free-spectral range (FSR) of 19.8 MHz, and the tuning accuracy is 100 KHz. [ABSTRACT FROM PUBLISHER]

We exploit the anomalous dispersion generated by an index-guided photonic crystal fiber (PCF) for dispersion compensation in an ytterbium fiber laser passively mode-locked with a semiconductor saturable absorber. A PCF, reasonably compatible with standard fiber, and a Faraday rotator in the cavity allow for robust all-fiber subpicosecond operation at 1 m, insensitive to environmental disturbance. [ABSTRACT FROM PUBLISHER]

We report a polarization-maintaining lambda/4-shifted distributed feedback (DFB) Er-doped fiber laser with a ring cavity configuration. The ring cavity suppressed the self-pulsation of the stand-alone Er-doped DFB fiber laser. The laser with a 57-m-long ring cavity achieved single-longitudinal-mode operation, a linewidth as narrow as 6 kHz, and relaxation-oscillation-free noise characteristics. [ABSTRACT FROM PUBLISHER]

A novel grating structure is proposed and demonstrated to obtain stable dual-wavelength (DW) distributed-feedback (DFB) fiber lasers at room temperature. The proposed grating is based on a symmetrical structure, where one half is periodically sampled by "0"-to-"pi" period and the other half is done by "pi"-to-"0" period. This structure can create two separated resonance cavities and hence achieve the stable DW lasing operation. By fabricating the proposed grating on a piece of Er : Yb-codoped fiber, we experimentally obtain a stable DW-DFB fiber laser with wavelength spacing of ~440 pm at room temperature [ABSTRACT FROM PUBLISHER]

Noise characteristics are studied for a self-stabilized laser utilizing the interplay between the intracavity dispersion and the optical frequency shift. The noise suppression bandwidth of this scheme is from 0 to ~100 KHz and showed the reduction of residual timing jitter (integrated from 0.9 Hz to 1 MHz) from 2.2fs to 660 attosecond which represents, to our knowledge, the lowest timing jitter reported for an actively mode-locked laser [ABSTRACT FROM PUBLISHER]

We realized the repetition rate multiplication in a phase-modulated soliton fiber laser with the rational harmonic mode-locking method. A modified pulse phase-locking method is used to stabilize the fiber laser at 10-GHz repetition rate with the rational harmonic order up to five (limited by the component performance). The laser showed an excellent stabilization performance in a long-term bit-error-rate test [ABSTRACT FROM PUBLISHER]

We report the observation of a stable output power of 204 mW in a Tm3+ : ZBLAN upconversion blue fiber laser, which we believe to be the highest reported to date as being stable in the long term. For the first time, we also present results of the dynamics of a real-time photobleaching of the color centers by an external laser source during laser oscillation. The dependence of the photoinduced absorption on the photobleaching power is also investigated. The total average photoinduced absorption was estimated at 2.7 dB/m [ABSTRACT FROM PUBLISHER]

A single-longitudinal-mode dual-wavelength distributed feedback fiber laser with a wavelength spacing of 0.312 nm is proposed and demonstrated. Based on two spatially separated resonant cavities in a single fiber Bragg grating made by a simple method, stable dual-wavelength lasing is established. Then, a 38.67-GHz microwave signal generated by beating the two lasing wavelengths is obtained with a 3-dB bandwidth of ~6 kHz and a frequency drift <5 MHz without any feedback mechanism. As a potential application of this device, a tunable microwave source ranging from 18.67 to 58.67 GHz (with a small discontinuity) is proposed and partially demonstrated [ABSTRACT FROM PUBLISHER]

A stable 50-pm-spaced triple-wavelength fiber ring laser with nearly equal output power at each lasing line is achieved experimentally by incorporating a triple-transmission-band fiber Bragg grating filter in the fiber ring cavity. Such a laser will be very useful in applications requiring closely spaced multiwavelength components [ABSTRACT FROM PUBLISHER]

Four pi-phase shifts are introduced in a uniform fiber Bragg grating (FBG) structure to realize a quadruple-transmission-band filter with ultranarrow 40-pm wavelength spacing. Four separate single-wavelength lasings at 1552.60, 1552.63, 1552.67, and 1552.71 nm, and three pairs of dual-wavelength lasings among above four wavelengths, are achieved stably by incorporating the quadruple-transmission-band FBG filter in a fiber ring cavity with a tunable uniform FBG acting as coarse frequency selection. This new kind of laser will be very useful in applications requiring closely spaced and tunable single- or dual-wavelength components [ABSTRACT FROM PUBLISHER]

A chirped phase-shifted structure is demonstrated for compact multiwavelength distributed feedback (DFB) fiber laser at room temperature for the first time. The chirped structure provides separated resonance cavities and then the stable multiwavelength operation. The equivalent phase shift method is demonstrated to realize the desired chirp and phase shifts simply and flexibly. A 44-pm-spaced dual-wavelength DFB fiber laser is then achieved experimentally, which is the narrowest spacing ever reported for a compact multiwavelength fiber laser [ABSTRACT FROM PUBLISHER]

We demonstrate an all-fiber high-power single-frequency Brillouin fiber ring laser with maximum power of 100 mW at 1.55 mum, which is actively stabilized by using the Pound-Drever-Hall frequency-locking scheme. Significant reduction (~20dB) of both relative intensity noise and frequency noise was observed in the Brillouin Stokes radiation as compared with those noises of its pump source, a narrow-linewidth Er-doped fiber laser. Ultranarrow spectral linewidth of the Brillouin fiber lasers was investigated by both delayed self-heterodyne technique and heterodyne beat technique between two independent Brillouin fiber lasers [ABSTRACT FROM PUBLISHER]

Stable continuous-wave lasing of two longitudinal modes of a distributed Bragg reflector fiber laser is reported. Intensity noise and coupling between the modes was characterized for both 0.8- and 0.2-nm mode separations [ABSTRACT FROM PUBLISHER]

We demonstrate a stable multiwavelength actively mode-locked erbium-doped fiber laser at 10 GHz based on a dispersion cavity and nonlinear polarization rotation (NPR) effect. The dispersion cavity allows simultaneous multiple wavelengths to satisfy the round-trip condition and smooth wavelength tuning, while the NPR ensures the stable operation and supermode noise suppression. A simple model is developed to explore the optimal setting of the cavity. Simultaneous dual- and five-wavelength operation is experimentally investigated [ABSTRACT FROM PUBLISHER]

We investigate experimentally and theoretically the linewidth of an Er-Yb-doped distributed feedback fiber laser. We find that two noise sources are mainly responsible for the observed behavior, fundamental thermal noise at low pump power levels and temperature fluctuations induced by pump intensity noise at higher powers. Potential techniques to overcome these limitations are discussed. [ABSTRACT FROM PUBLISHER]

A simple design of a stable multiwavelength pulse generator was demonstrated using a dispersion-tuned actively mode-locked erbium-doped fiber (EDF) ring laser with distributed dispersion cavity. The distributed dispersion cavity in the fiber laser successfully reduced the cross-gain saturation in EDF, and thus, enabled multiwavelength operation. Simultaneous generation of wavelength-tunable 10-GHz pulses up to four different wavelengths was achieved with the same wavelength space of 2.94 nm. The extinction ratio of all wavelengths was above 30 dB. In addition, smooth wavelength tuning was achieved over more than 41 nm when the laser was working at dual-wavelength mode. The super mode noise was ~60 dB below the signal level at both wavelengths. The laser state was found to be very stable [ABSTRACT FROM PUBLISHER]

Self-stabilizing effect of four-wave mixing (FWM) is analyzed and proven in this letter by using the undepleted approximation and the perturbation method. Multiwavelength erbium-doped fiber lasers with excellent stability and uniformity are demonstrated experimentally at room temperature. The novel fiber lasers are stabilized and equalized as a result of the balance between the self-stabilizing function of FWM and the mode competition effect of erbium-doped fiber. [ABSTRACT FROM PUBLISHER]

A stable and broad bandwidth multiwavelength fiber ring laser suitable for use in dense wavelength-division-multiplexing systems is demonstrated. A highly nonlinear photonic crystal fiber is inserted in the ring cavity to stabilize the power fluctuation and broaden the output spectrum. A thin-film Fabry-Pe´rot etalon filter is used to get stable wavelength lasing. A Sagnac filter is employed to achieve uniform power distribution at each wavelength at the laser output. A laser with a power fluctuation about 0.1 dB in each wavelength within 20 min and with wavelength shift of less than 0.016 nm within 10 min is achieved. A stable 24-wavelength lasing operation with wavelength spacing of 0.8 nm within the 3-dB spectral range of 1573-1594 nm and signal-to-noise ratio better than 48 dB is observed experimentally. [ABSTRACT FROM PUBLISHER]

A dual-mode external cavity laser employing two spatially separated fiber Bragg gratings has been investigated. We experimentally demonstrated that, without utilizing polarization separation techniques, a closely spaced (∼0.3 nm) dual-mode emission can be stabilized if a specific in-phase relation between the external feedbacks and the gain chip facet residual feedback is satisfied at both lasing wavelengths. The radio-frequency (RF) beat signal generated by the dual-mode optical signal had a typical extinction ratio of 25 dB above the noise floor and a 3-dB linewidth of approximately 2 MHz. The RF beat signal had a frequency tuning range of 200 MHz, where the dual-single-mode spectrum can be maintained. [ABSTRACT FROM PUBLISHER]

In this work, an optical short pulse generator is designed consisting of a pulse compressor and cascaded notch filter type repetition rate doublers. The performance characteristics such as pulsewidth and peak power as a function of design parameters are studied. The pulse compressor is optimized based on the simulation results. The 6-ps-wide pulses at 20-GHz repetition rate directly generated from mode-locked fiber laser are compressed to 1.25-ps-wide pulses. Using a set of polarization-maintaining fiber loop mirrors, the repetition rate is quadrupled and stable 1.45-ps-wide pulses at 80 GHz are achieved. [ABSTRACT FROM PUBLISHER]

A novel single-longitudinal-mode (SLM) fiber ring laser that incorporates an equivalent phase-shifted fiber Bragg grating acting as an ultra-narrow bandpass filter in the laser cavity is proposed. The equivalent phase-shifted fiber Bragg grating has an ultra-narrow transmission bandwidth which ensures an SLM lasing. Stable SLM operation without mode hopping is demonstrated. [ABSTRACT FROM PUBLISHER]