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資料番号: SA1004501000

This investigation demonstrates a stable multiwavelength fiber ring laser with ultra-narrow wavelength spacing using a semiconductor optical amplifier (SOA). A delay interferometer and a mirror are used as a double-pass interferometer to improve the signal-to-noise ratio in this experiment. Up to 181 stable lasing wavelengths with a wavelength spacing of 10.7 GHz and a signal-to-noise ratio of over 24 dB are produced at room temperature.

A tunable multiwavelength fiber ring laser based on a semiconductor optical amplifier and Sagnac loop mirror incorporating a piece of few-mode high birefringence fiber (FM-HBF) is proposed and experimentally demonstrated. It is accomplished by simply adjusting a polarization controller in the Sagnac loop mirror because birefringence of the FM-HBF is polarization dependent. Tunable multiwavelength operation up to 11 oscillating lines at about 2.1 nm interval is stably achieved with an optical side-mode suppression ratio over 35 dB.

We propose and demonstrate an efficient and simple wavelength switchable dual-wavelength passively mode-locked fiber ring laser based on a semiconductor saturable absorber mirror (SESAM) and a cascaded sequence of fiber Bragg gratings (FBGs). The efficient self-starting mode-locked operation was realized with a SESAM. Dual-wavelength pulses with a wavelength spacing of 12.49 nm were obtained which was determined by the reflection peaks of the FBGs used in the experiment. In addition, by rotating the polarization controllers (PCs), the switchable dual-wavelength operation was simply achieved via exploiting wavelength-dependent loss mechanism.

We investigate the evolvement of the periodic intensity variations of the pulse-train in a fiber ring laser mode-locked by the nonlinear polarization rotation technique. It is found that the phenomenon of such intensity fluctuations is related to the orientation of the polarization controllers when the pump power is fixed. The numerical results show that the mechanism of the periodic intensity variations is caused by the interaction of the nonlinear polarization rotation and the passive polarizer in the cavity.

A kind of stable, switchable and tunable erbium-doped fiber ring laser based on a Sagnac interferometer (SI) is presented and experimentally demonstrated. The SI is composed of a section of an elliptical-core spun fiber sandwiched between two polarization controllers (PCs) in a Sagnac loop. The proposed compound comb filter, which consists of an SI cascaded with a phase shifted fiber Bragg grating, is developed to suppress the mode competition in the laser oscillation. By adjusting the PCs, a stable and tunable single-wavelength lasing output can be achieved. The optical signal-to-noise ratio (OSNR) is better than 40 dB, and the 3 dB linewidth is less than 15 pm. Furthermore, stable dual-wavelength lasing outputs with different wavelength intervals of 0.132 nm, 0.336 nm and 0.418 nm can also be obtained by carefully adjusting the PCs. The power difference between the two lasing peaks is less than 2 dB, and the OSNR is about 50 dB.

In this paper, we propose and experimentally demonstrate a mode locked fiber ring laser with the implementation of a photonic crystal fiber (PCF) to generate pulse train at high speed. This fiber ring laser combines rational harmonic mode locking based on a Lithium Niobate Mach-Zehnder modulator and nonlinear polarization rotation from a highly nonlinear PCF. By fine tuning of the modulation frequency and the polarization controllers in the cavity, a 30 GHz pulse train with pulse width 1.9 ps is generated. Without the PCF, the pulse width at 30 GHz from the rational harmonic mode locking is 5.8 ps. We also conduct numerical simulations of the pulse evolution, which shows good agreements of the experimental results.

In this article, the output power stability of several different highly erbiumdoped fiber ring lasers, as a function of the laser parameters, is experimentally investigated. The study is focused on the optimization of several key parameters (erbium-doped fiber length, pump power, and different laser configurations) without changing the basic scheme. The results obtained show that the laser configuration plays an important role in achieving stable multi-wavelength lasing at room temperature in the erbium-doped fiber ring lasers. For an optimized configuration, these power fluctuations are lower than 0.08 dB, showing a notable improvement compared with previously presented work where the output power variations were about 0.2 dB. These lasers have the advantage of a simple all-fiber configuration, low cost, high stability, and operability at room temperature. The authors would like to thank the European COST action-299 for funding the STSM grant to one of the authors.

We report a dual-wavelength amplitude-equalized rational harmonic mode-locked fiber laser operating at up to 40 GHz based on the technique of nonlinear polarization rotation (NPR) in a highly nonlinear fiber. A theoretical simulation shows that NPR structure can introduce a self-feedback mechanism to stabilize the two simultaneously lasing wavelengths. By carefully adjusting the polarization controllers (PCs) in the cavity, amplitude-equalized pulses at two different wavelengths have been obtained.

We propose and demonstrate a novel switchable quadruple-wavelength erbium-doped fiber ring laser (EDFL) based on two-segment Lyot–Sagnac filter which is used as the wavelength-selective filter. Due to the deeply saturated spectral hole-burning (SHB) effect in an ordinary erbium-doped fiber, the laser realizes stable single-wavelength, dual-wavelength, triple-wavelength, and quadruple-wavelength output by controlling two polarization controllers (PCs) appropriately. The optical signal-to-noise ratio (OSNR) is over 30 dB. The peak fluctuation is less than ~2 dB over 1.5 h at room temperature.

An erbium-doped fiber ring laser with embedded Mach–Zehnder interferometer (MZI) is constructed and experimentally demonstrated for strain and refractive index (RI) measurement. The MZI consists of a segment of thin-core fiber sandwiched between two single-mode fibers and acts as both the sensing component as well as a bandpass filter to select the lasing wavelength. The strain sensitivity of ∼-0.97 pm/μϵ and RI sensitivity of ∼44.88 nm/RIU are obtained in the range of 0 to 1750 μϵ and 1.3300 to 1.3537, respectively. The high-optical signal-to-noise ratio of >50 dB and narrow 3-dB bandwidth of

This paper reports the periodic power variation of the pulse-train in a passively mode-locked soliton fiber ring laser. It can obtain either the uniform or nonuniform pulse-train output by simply rotating the polarization controllers. The experimental results show that the pulse-train nonuniformity is caused by the interaction between the nonuniform polarization states of the soliton pulses and the passive polarizer in the cavity.

A multiwavelength fiber ring laser comprising of a Lyot filter and hybrid gain medium is presented. A wavelength channel spacing of 100 GHz is achieved by appropriate tuning of the Lyot filter length. Four wavelength channels are simultaneously mode-locked at 10 GHz using an electroabsorption modulator. We highlight how the intra-cavity modulator can affect the stability of the mode-locked laser spectrum when used in conjunction with a Lyot filter. We show that, due its reduced polarization sensitivity, an electroabsorption modulator significantly improves the stability of the mode-locked laser spectrum when compared to using a Mach–Zehnder modulator.

A novel actively and passively mode-locked semiconductor optical amplifier fiber ring laser was presented, where semiconductor optical amplifier provided cavity gain and introduced nonlinear polarization rotation, whereas, intensity modulator not only acted as modulator but also polarizer. The pulses with duration below 3 ps (FWHM) and peak power about 16 mW at a repetition rate of 10 GHz can be obtained in our system and the system stability may be enhanced. To investigate system parameters effects on mode-locked pulses, a theoretical model was developed.

We numerically study a stable multiple-pulse operation of passively modelocked stretched pulse fiber ring laser. The simulation results show that multiple pulses are formed with being triggered by radiation from a single pulse in a restricted parameter range. In order to obtain a better understanding of the effect of gain bandwidth and nonlinear gain on harmonic modelocking process of multiple-pulse operation, we analyze those effects in detail.

We present a tunable narrow-linewidth dual pump-probe optical source based on modified Brillouin ring laser technology aimed at Brillouin-based sensing. The developed source exhibits a narrow linewidth and allows for a large tuning range, attaining

Different polarization dynamic states in an unidirectional, vector, Yb-doped fiber ring laser have been observed. A rich variety of dynamic states, including group velocity locked polarization domains and their splitting into regularly distributed multiple domains, polarization locked square pulses and their harmonic mode locking counterparts, and dissipative soliton resonances have all been observed with different operating parameters. We have also shown experimentally details of the conditions under which polarization-domain-wall dark pulses and bright square pulses form.

Whispering Gallery Modes (WGMs) microresonators continue to receive an even greater interest for investigation in many fundamental processes (e.g.: quantum electrodynamics or non–linear optics) and in more applied fields of photonics (e.g.: filters, microlasers and chemical/biological sensing), due to their high Q—factors, small mode volumes and long photon storage times. Here we present an overview on the main results obtained in our Labs about the implementation of these optical microcavities as suitable platform for sensing and biosensing applications.

We demonstrate a cascaded Raman fiber ring laser delivering a pulsed fourth-order Stokes component. Periodic emission of subnanosecond pulses is achieved from the interplay between nonlinear polarization evolution and Raman cascade process.

We report on the generation of high power superbroad spectrum bunched noise-like pulses from a passively mode-locked erbium-doped fiber ring laser without using the stretched-pulse technique. The maximum 3-dB spectral bandwidth of the noise-like pulses is about 93 nm with an energy of about 15 nJ. We further show numerically that the superbroad spectrum of the pulses is caused by the transform-limited feature of the pulses together with the Raman self-frequency shift effect.

In this demonstration, we propose and experimentally investigate a widely C + L band wavelengthtunable fiber ring laser in continuous-wave (CW) tuning based on a hybrid semiconductor optical amplifier (SOA) and erbium-doped fiber amplifier (EDFA) in a serial scheme. When a hybrid first-stage

Tunable all-optical wavelength converters have been regarded as key opto-electronic devices in intelligent next-generation optical networks. A novel scheme for tunable wavelength conversion, based on cross-gain modulation(XGM) in a semiconductor optical amplifier (SOA)-based fiber-ring laser, is proposed. Then, theoretical model for this novel scheme is established. Conversion output characteristics are calculated theoretically and measured experimentally under different conditions. The experimental results coincide with the theoretical resalts. Tunable wavelength conversion at 2.5 and 10 Gb/s with a 40-nm tuning range are demonstrated experimentally. Experimental and theoretical studies show that this novel scheme is worthy of further investigation.

Optical clock recovery and clock division is demonstrated from a pseudo-data pattern at 20 Gb/s, using a semiconductor optical amplifier fibre ring laser. The ring laser is capable of generating 4.7 ps pulses at 20 GHz repetition rate and less than 3 ps pulses at the divided clock frequencies of 10 and 5 GHz, over a 16 nm tuning range. The effect of the input data pattern on the recovered clock signal is investigated. The extinction ratio of the recovered clock signal to the clock sub-harmonics was found to be as high as 40 dB despite the long series of consecutive zeros of input pattern.

Clock recovery from degraded signals at 10, 20, and 40 Gb/s data rates was achieved using a two-ring injection mode-locked fiber-ring laser based on 10-GHz bandwidth components. No pattern effect was observed in these experiments. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 273–276, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10892

A novel clock recovery scheme using two-ring injection mode-locked fiber ring laser based on all 10 GHz bandwidth components was demonstrated. With this scheme, the clock with low timing jitter was obtained from a degraded 10 Gb/s optical data stream. Optical clock recovery was also achieved from a degraded 20 Gb/s optical data train when the clock division technique in the opto-electronic oscillator (OEO) and the rational harmonic mode-locking technique in the fiber ring laser were applied. No pattern effect was observed in the experiments.

The reason of pulse amplitude unequalization at repetition rate multiplying via Fabry-Perot (F-P) filter is analyzed. Several original methods of suppressing the amplitude unequalization are proposed. Their suppressing effects and tolerance to the F-P instability are compared and investigated.

We report self-starting mode-locking of a diode-pumped super-stretched unidirectional ring laser based on a 26 m cladding-pumped Yb3+-fiber and an internal grating dispersion compensation. The long fiber resulted in an extremely high pulse stretching ratio inside the cavity of about 500 which is more than one order of magnitude above previously demonstrated laser systems. This system was passively mode-locked by nonlinear polarization rotation and generated pulses with 40 nm bandwidth at 1095 nm, a pulse energy of about 9.5 nJ and an output power of 630 mW.

A theoretical study of active mode-locking fiber loop laser using semiconductor optical amplifier (SOA) was presented in this paper. The effects of linewidth broadening factor of SOA on active mode-locking were investigated originally. The relations between parameters of output pulse series and the critical parameters of SOA and other elements in fiber loop were obtained.

A humidity sensor based on the intracavity sensing of a fiber ring laser is proposed and experimentally demonstrated. In the fiber ring laser, a humidity-sensitive fiber-optic multimode interferometer (MMI), fabricated by the single-mode-no-core-single-mode (SNCS) fiber coated with Agarose, works as the wavelength-selective filter for intracavity wavelength-modulated humidity sensing. The experiment shows that the lasing wavelength of the fiber laser has a good linear response to ambient humidity from 35%RH to 95%RH. The humidity sensitivity of pm/%RH is obtained with a narrow 3 dB bandwidth less than 0.09 nm and a high signal-to-noise ratio (SNR) ~60 dB. The time response of the sensor has been measured to be as fast as 93 ms. The proposed sensor possesses a good stability and low temperature cross-sensitivity.

Magnesium diboride (MgB2) is a well-known superconductor at temperatures below 39 K. At higher temperatures, it behaves as a lossy material. In this paper, we examine the performance of MgB2 nano-particles as saturable absorber in a ytterbium-doped fiber ring laser at room temperature: we show that the nano-particles can produce pulses between 200 and 1700 ns. The dynamics of the saturable absorber are both examined as a stand-alone saturable absorber and in combination with an acousto-optic modulator. We believe, to the best of our knowledge, that this is the first time that MgB2 is used as a saturable absorber in a Q-switched laser.

A tunable continuous-wave thulium-doped fiber ring laser near 2 μm has been studied numerically and experimentally under in-band pumping at 1.6 μm and a tunable range > 30 nm has been demonstrated under cavity-loss variation.

We present a 1.65-pm passive harmonically mode-locked Raman fiber laser based on nonlinear polarization rotation. The pulse-energy at fundamental mode-locking up to 290.7-nJ, and the highest repetition rate of 587.2 MHz can be achieved.

A passively mode-locked soliton fiber ring laser was successfully demonstrated, and bound soliton pulses with an FWHM pulsewidth of 326 fs and fixed separation of 938 fs were first observed. The number of bound soliton pairs in the cavity can be controlled under lower pump power. The transmission effects were investigated by injecting bound soliton pulses into a single mode fiber.

An experimental and theoretical study of a high repetition rate laser source operating on a novel mode-locking technique is presented. This technique relies on the fast saturation and recovery of a semiconductor optical amplifier induced by an external optical pulse and has been used to obtain 4.3 ps pulses at 20 GHz. A complete mathematical model of the fiber ring laser is presented describing the mode-locking process in the laser oscillator and providing solutions for the steady-state mode-locked pulse profile. The critical parameters of the system are defined and analyzed and their impact on the formation of the mode-locked pulses is examined. The comparison between the theoretical results and the experimental data reveals very good agreement and has allowed the optimization of the performance of the system in terms of its critical parameters.

We characterize optical pulses generated using a regeneratively mode-locked fiber ring laser (RML-FRL) in terms of pulsewidth and pulse noise. These results are then compared with pulses obtained from a conventional active harmonically mode-locked fiber ring laser (ML-FRL). We establish that under the same operating conditions, optical pulses from the RML-FRL are shorter by more than 8% and exhibit a 15-dB improvement in phase noise compared to those obtained from ML-FRL. In addition, over a frequency range 100 Hz–100 kHz, a reduced amplitude noise of 0.3% and rms timing jitter of 0.26 ps have been estimated for the RML-FRL pulses compared to 0.6% and 0.38 ps, respectively, for the pulses in the ML-FRL. Relaxation oscillations are also completely eliminated in the RML-FRL.

We propose and experimentally demonstrate a triple-wavelength fiber ring laser using a semiconductor optical amplifier (SOA) in conjunction with an array waveguide grating (AWG). The experimental results show three lasing lines with an adjustable wavelength separation and a large optical signal-to-noise ratio under room temperature. The three channels operate at 1531.5 nm, 1532.3 nm and 1533.1 nm with a peak power above -23 dBm and optical signal to noise ratio above 30 dB at SOA drive current of 350 mA. By changing the ports of the AWG, the center wavelengths of the tri- ple lasing lines can be changed and the wavelength separation between the lasing lines can also be changed. The proposed laser configuration has the advantages of a simple and compact structure, quad-wavelength operation and the system can be upgraded to generate more wavelengths.

We proposed and demonstrated a room-temperature multiwavelength Yb-doped fiber ring laser with high stability based on a Mach-Zehnder interferometer by exploiting spatial hole burning and polarization hole burning effects, from which stable eight lasing wavelengths is obtained. The number of the lasing wavelengths (eight) is the most to our knowledge, and the wavelength spacing is 1.1 nm. Triple-, and dual-wavelength operation with the wavelength spacing of 1.1 nm or its integral multiples have been obtained by adjusting the intracavity polarization controllers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 723–725, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23206

An Ytterbium-doped mode-locked fiber laser using the polarization sensitive isolator and polarization controllers (PC) is reported. In the normal dispersion, the fiber laser can oscillate at the multi-pulse states by adjusting the position of the PC. On the condition that the polarization state isn’t changed, the outputs of Ytterbium-doped mode-locked fiber laser change from single pulse to multi-pulse by increasing the pump power. The fiber laser can achieve different multi-pulse output by adjusting the PC1 and PC2 carefully.

We present a dual longitudinal mode narrow linewidth, injection-seeded, Q-switched fiber ring laser. Deeply modulated pulses near 1.55 μm with a modulation frequency that can be tuned continuously from DC to a demonstrated 25 GHz have been achieved. High peak powers are attained through the use of a reduced-stimulated Brillouin scattering single-clad erbium doped fiber. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 202–204, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23040