Semiconductor Optical Amplifier Fiber Ring Research Articles

All-optical reservoir computing system based on polarization dynamics

Reservoir computing (RC) is a simplified recurrent neural network and can be implemented by using a nonlinear system with delay feedback, thus it is called delay-based RC. Various nonlinear nodes and feedback loop structures have been proposed. Most of existing researches are based on the dynamical responses in intensity of the nonlinear systems. There are also a photoelectric RC system based on wavelength dynamics and an all-optical RC based on the phase dynamics of a semiconductor laser with optical feedback, as well as so-called polarization dynamics of a vertical cavity surface emitting laser (VCSEL). However, these VCSEL-RCs actually are based on the intensity dynamics of two mutually orthogonal polarization modes, or polarization-resolved intensity dynamics. The RC based on rich dynamical responses in polarization has not yet been found. A semiconductor optical amplifier (SOA) fiber ring laser can produce rich dynamical states in polarization, and is used in optical chaotic secure communication and distributed optical fiber sensing. To further expand the application of polarization dynamics of the SOA fiber ring laser and open up a new direction for the research of optical RC neural network, an all-optical RC system based on polarization dynamics of the ring laser is proposed. The ring laser is used as the reservoir, and the SOA as the nonlinear node. After the input signal is masked according to a synchronization scheme, it is injected into the reservoir by intensity modulation for a continuous wave generated by a superluminescent light emitting diode (SLED). The dynamical response in polarization of the ring laser is detected by a polarizer and a photodetector. The influences of the SOA operation current, output power of the SLED and attenuation of a variable optical attenuator (VOA) in the fiber loop on the polarization dynamic characteristic (mainly referring to the output degree of polarization) of the laser are analyzed experimentally. The fading memory and nonlinear response of the RC system based on the polarization dynamic response and intensity dynamic response are compared experimentally. The influences of output power of the SLED and attenuation of the VOA on fading memory, consistency and separation of the RC system based on the two kinds of dynamic responses are investigated experimentally. Thus the range of the VOA attenuation is determined. The network performance of the polarization dynamics RC system is evaluated by processing a Santa Fe time series prediction task and a multi-waveform recognition task. The normalized mean square error can be as low as 0.0058 for the time series prediction task, and the identification rate can be as high as 100% for the recognition task under the appropriate system parameters and only 30 virtual nodes. The experimental results show that the polarization dynamics RC system has good prediction performance and classification capability, which are comparable to the existing RC system based on intensity dynamics of the ring laser. The system can be expected to process two tasks in parallel when the polarization dynamics and intensity dynamics are used at the same time.

Beam Combining of SOA-Based Bidirectional Tunable Fiber Nested Ring Lasers With Continuous Tunability Over the C-band at Room Temperature

Nested ring cavities are used to develop a simple compact, low-cost semiconductor optical amplifier (SOA)-based bidirectional tunable fiber ring laser source. We propose a bidirectional tunable fiber ring laser structure based on ( N > 1) number of SOAs that has a great potential for achieving a high power laser source that uses low-power optical components by coherently coupling the nested ring cavities. A commercial tunable filter is used to deliver a wavelength tuning range of 30 nm. The lasing tunable range can be further changed by using SOAs with operating wavelengths in different regions of the optical spectrum. The output power of the bidirectional fiber ring resonator with three SOAs was around 3.5 times larger than the output of a single SOA fiber ring laser (i.e., 17.7 versus 5.14 mW) at 1550 nm wavelength. The optical signal-to-noise ratio was measured to be up to +49 dB, wavelength stability was ±0.015 nm, and optical power stability was better than ±0.2 dB.

Chirp Evolution Algorithm of a Dark-Optical-Comb Injection Mode-Locked SOA Fiber Laser Pulses During Soliton Compression

The chirp evolution of a dark-optical-comb injection harmonic mode-locked (HML) semiconductor optical amplifier fiber ring laser (SOAFL) with a nonlinearly driven electro-absorption modulator is demonstrated. The dispersion compensation of the 10-GHz HML-SOAFL pulse with a 100-m-long dispersion compensation fiber is performed to shorten the pulsewidth from 29 to 2.9 ps with a compression factor of 10, and a time bandwidth product (TBP) of 0.5. The soliton compression with a 10-m-long single-mode fiber is employed to deliver the amplified 10-GHz HML-SOAFL soliton pulse with a peak power of 38.2 W and a pulsewidth of 1.6 ps, while the spectrum is broadened from 1.4 to 2.3 nm with a TBP of 0.45. To monitor the dynamic chirp evolution, a second-harmonic generation frequency-resolved optical gating (SHG-FROG) is used to retrieve the amplitude and phase contour profile of the HML-SOAFL. The phase fitting result distinguishes the linear chirp from the nonlinear chirp associated with the HML-SOAFL pulse, which are 0.016 ps2 and 0.002 ps3. The Schrodinger equation assists to retrieve the phase evolution of the 10-GHz HML-SOAFL with negative group velocity dispersion. Disregarding the linear dispersion compensation and soliton compression, the original 10-GHz HML-SOAFL pulse with a negative GDD of -5 ps2 is quantified.

Optical self-injection mode-locking of semiconductor optical amplifier fiber ring with electro-absorption modulation—fundamentals and applications

The optical self-injection mode-locking of a semiconductor optical amplifier incorporated fiber ring laser (SOAFL) with spectrally sliced multi-channel carriers is demonstrated for applications. The synthesizer-free SOAFL pulse-train is delivered by optical injection mode-locking with a 10 GHz self-pulsed electro-absorption modulator (EAM). Such a coupled optical and electronic resonator architecture facilitates a self-feedback oscillation with a higher Q-factor and lower phase/intensity noises when compared with conventional approaches. The theoretical model of such an injection-mode-locking SOAFL is derived to improve the self-pulsating performance of the optical return-to-zero (RZ) carrier, thus providing optimized pulsewidth, pulse extinction ratio, effective Q-factor, frequency variation and timing jitter of 11.4 ps, 9.1 dB, 4 × 105, <50 kHz and 0.6 ps, respectively. Such a synthesizer-free pulsed carrier is also employed for the application in a 10 Gbit s−1 bi-directional WDM transmission network with down-stream RZ binary phase-shift keying (RZ-BPSK) and up-stream re-modulated RZ on–off-keying (RZ-OOK) formats. Under BPSK/OOK bi-directional data transmission, the self-pulsed harmonic mode-locking SOAFL simultaneously provides four to six WDM channels for down-stream RZ-BPSK and up-stream RZ-OOK formats with receiving sensitivities of −17 and −15.2 dBm at a bit error rate of 10−9, respectively.

SOA Fiber Ring Lasers: Single- Versus Multiple-Mode Oscillation

Earlier investigations have demonstrated that a narrow bandwidth intracavity filter in a semiconductor optical amplifier (SOA) fiber ring laser results in an output spectrum comprising multiple longitudinal modes, whereas a large bandwidth filter generally leads to quasi-single-mode oscillation. In this paper, we report on a numerical model simulating the SOA fiber ring laser dynamics and compare its predictions with experimental results obtained with two different SOAs. We demonstrate that the observed experimental behavior results from the interplay between the complex transfer function of the intracavity optical filter, fast gain saturation and four-wave mixing (FWM) due to the linewidth enhancement factor. The dispersion introduced by the complex transfer function of the filter can lead to modulation instability, which plays a key role in the laser dynamics that can evolve into a single-longitudinal mode (SLM) operation. We also simulate the behavior of the laser emission when the wavelength of the optical filter is finely tuned.

Electron–Hole Plasma-Induced Spectral Blueshift of Optical-Data Injection Mode-Locked Semiconductor Optical Amplifier Fiber Laser

Under an optical nonreturn-to-zero (NRZ) data injection at 10 Gbit/s, the 10-GHz mode-locking and pulsed return-to-zero (RZ) clock extraction from a semiconductor optical amplifier (SOA) based fiber ring is investigated in this paper. The diagnoses on gain and intracavity-power-controlled anomalous blueshifted spectrum and subpicosecond timing jitter are demonstrated. By increasing the injecting power of the optical NRZ data from -3 to 8 dBm into the SOA bias at different currents, the mode locking is completed with a dc level greatly decreasing from 480 to 50 ¿W (only 1.5% of the mode-locked pulse power at 3 mW), corresponding to a pulse/dc amplitude contrast ratio up to 18 dB. Increasing the SOA bias current up to 350 mA significantly suppresses the timing jitter from 1.8 ps to 345 fs, and the extracted RZ clock pulse is shortened from 55 to 27 ps. The pulsewidth of the amplified SOAFL is compressed from 11 ps to 836 fs after dispersion compensation. At constant data injection level, the increasing SOA bias or gain oppositely redshifts the mode-locked SOA fiber ring laser (SOAFL) spectrum by 5 nm. The amplifier spontaneous emission of SOA at short wavelength region ( ~ 1520 nm) is eliminated with increasing NRZ data power, whereas the mode-locking gain peak arises and blueshifts from 1558 to 1552 nm due to the band-filling effect. Such a blueshift in mode-locking spectrum becomes more significant in SOA at lower bias (or gain) condition. A theoretical model interprets the correlation between the nonlinear gain suppression-induced variation of electron-hole plasma in SOA and the blueshifted mode-locking SOAFL spectrum, which is occurred when the gain saturation condition for the SOA becomes more pronounced.

Photonic Generation of 60 GHz Millimeter-Wave by Frequency Quadrupling Based on a Mode-Locking SOA Fiber Ring Laser with a Low Modulation Depth MZM

Generation and processing of millimeter-wave (MMW) signal based on photonic technologies is a new trend. A simple and effective optical technique to generate 60 GHz millimeter-wave signal by frequency quadrupling is proposed and demonstrated. In this approach, the frequency quadrupling efficiency is greatly improved by a semiconductor optical amplifier (SOA) fiber ring laser with 2nd-order rational harmonic mode-locking and a Mach-Zehnder modulator (MZM) which is biased at odd-order optical modulation side-bands suppressing state. A center-wavelength tunable comb filter outside the ring laser is tuned to select the optical sidebands separated by 60 GHz. The result shows that the power ratio between quadruple-frequency signal and double-frequency signal is improved at least 30 dB with the mode-locking ring laser when the modulation depth is less than 0.4 and the phase noise of the 60 GHz signal generated is better than –75 dBc/Hz at 1-kHz offset. The key advantage of the technique is that a high-frequency MMW signal can be generated with high efficiency by a low power microwave signal.

82-channel multi-wavelength comb generation in a SOA fiber ring laser

We demonstrate a multi-wavelength semiconductor optical amplifier (SOA) fiber ring laser with a dual-pass Mach–Zehnder interferometer (MZI) filter. Two SOAs with different gain spectra provide sufficient gain and a wider gain spectrum to facilitate multi-wavelength lasing. The dual-pass MZI, configured by adding an optical isolator to the two outputs of the conventional MZI, serves as comb filter for multi-wavelength operation, and its extinction ratio can be enhanced to twofold as that of the conventional MZI in the same parameters. To investigate the influences of a dual-pass MZI filter and a conventional MZI filter on multi-wavelength operation, two different cavity configurations are presented and compared, including a single-SOA ring cavity and a double-SOA ring cavity. Stable simultaneous operation at 82 wavelengths, with a wavelength spacing of 40 GHz and a power deviation of 5 dB, and with a minimum optical signal-to-noise ratio (OSNR) of 28 dB, is observed from the double-SOA ring cavity using a dual-pass MZI filter.

All-optical clock recovery of 20 Gbit/s NRZ-DPSK signals using polarization-maintaining fiber loop mirror filter and semiconductor optical amplifier fiber ring laser

All-optical clock recovery (CR) from 20 Gbit/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signals are demonstrated experimentally by using a polarization-maintaining fiber loop mirror filter (PMF-LMF) and a semiconductor optical amplifier (SOA) fiber ring laser. Only by adjusting polarization controller (PC), NRZ-DPSK signals were conveniently and fast converted to pseudo return-to-zero (PRZ) signal via PMF-LMF. Then the PRZ signals are injected into the SOA fiber laser for CR. The recovered clock signals is with the extinction ratio (ER) of 10 dB and the root-mean-square (RMS) timing jitter of 750 fs in 2 31 − 1 long pseudorandom binary sequence (PRBS) NRZ-DPSK signals measurement. Moreover, the broad wavelength tunability of recovered clock stemmed from the use of SOAs as modulator and the gain medium are shown too.

基于半导体光放大器光纤环形腔的光数据包复制器的噪声特性研究

基于半导体光放大器光纤环形腔的光数据包复制器的噪声特性研究

SOA based fiber ring laser with Fiber Bragg Grating

AbstractA semiconductor optical amplifier fiber ring laser (SOAFRL) utilizing a Fiber Bragg Grating (FBG) is demonstrated. The laser operates at a wavelength of 1547.64 nm, equal to the Bragg wavelength. By removing FBG, the SOAFRL shows a multi‐modes output due to the resonant characteristics of the semiconductor optical amplifiers (SOA's) gain. The output power ripple is observed around 5 dB. The experimental results show that when the saturation level is reached, the SOAFRL with the FBG shows a higher saturation current and peak power compared to that of the SOAFRL without the FBG. Mode competition in the cavity for the free‐running ring SOAFRL results in a lower peak power as well as a broader bandwidth as the current is increased. By incorporating the FBG in the SOAFRL, a lasing wavelength is generated and as such the side mode suppression ratio (SMSR) of the laser is significantly improved, resulting in a higher peak power at higher bias currents. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3101–3103, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23895

Rational harmonic mode-locking pulse quality of the dark-optical-comb injected semiconductor optical amplifier fiber ring laser

We study the rational harmonic mode-locking (RHML) order dependent pulse shortening force and dynamic chirp characteristics of a gain-saturated semiconductor optical amplifier fiber laser (SOAFL) under dark-optical-comb injection, and discuss the competition between mode-locking mechanisms in the SOAFL at high-gain and strong optical injection condition at higher RHML orders. The evolutions of spectra, mode-locking and continuous lasing powers by measuring the ratio of DC/pulse amplitude and the pulse shortening force (I(pulse)/P(avg)(2) ) are performed to determine the RHML capability of SOAFL. As the rational harmonic order increases up to 20, the spectral linewidth shrinks from 12 to 3 nm, the ratio of DC/pulse amplitude enlarges from 0.025 to 2.4, and the pulse-shortening force reduces from 0.9 to 0.05. At fundamental and highest RHML condition, we characterize the frequency detuning range to realize the mode-locking quality, and measure the dynamic frequency chirp of the RHML-SOAFL to distinguish the linear and nonlinear chirp after dispersion compensation. With increasing RHML order, the pulsewidth is broadened from 4.2 to 26.4 ps with corresponding chirp reducing from 0.7 to 0.2 GHz and linear/nonlinear chirp ratio changes from 4.3 to 1.3, which interprets the high-order chirp becomes dominates at higher RHML orders.

A novel actively and passively mode-locked semiconductor optical amplifier fiber ring laser

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.

10 GHz regeneratively mode-locked semiconductor optical amplifier fiber ring laser and its linewidth characteristics

A 10 GHz regeneratively mode-locked semiconductor optical amplifier fiber ring laser with a picosecond pulse duration was newly constructed, and the linewidth change of a longitudinal mode was measured for various laser cavity lengths using a delayed self-heterodyne detection method. The detected line shape was approximately Gaussian for cavity lengths of 3.4-171 m. This result indicates that the laser linewidth depends strongly on thermal or acoustic cavity length fluctuations. The linewidth was proportional to the inverse square root of the cavity length, and a linewidth of 1.7 kHz was obtained for a cavity length of 171 m.

NUMERICAL STUDY OF A RATIONAL HARMONICAL MODE-LOCKED SEMICONDUCTOR OPTICAL AMPLIFIER FIBER RING LASER

Based on the self-reproduction theory, a rational harmonic mode-locked semiconductor optical amplifier fiber ring laser was numerically investigated. The system parameters effects on pulse-amplitude equalization of rational harmonic mode locking was analyzed and the numerical result shows that the 2∼5 order rational harmonic mode-locked pulse with the small amplitude ripple can be obtained only by adjusting the system parameters.

Switching-wavelength pulse source constructed from a dispersion-managed SOA fiber ring laser

A new approach to generate switching-wavelength picosecond pulses is developed based on a dispersion-managed semiconductor optical amplifier (SOA) fiber laser cavity. Gain modulation on a 1.55-/spl mu/m SOA is used together with subharmonic gating of pulses in the cavity. An 8-GHz, eight-wavelength output is obtained with a constant spacing of 0.91 nm between neighboring wavelengths. The wavelength channels have nearly identical peak powers. The total amplitude and time jitter of the output is measured to be smaller than 0.4 ps. The spacing and the number of output wavelengths can be easily tuned by changing the operating frequency and the subharmonic ratio without modifying the optical cavity.