Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier

We propose and demonstrate a novel single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier. The SOA biased in its low-gain regime greatly reduces the gain competition of the two wavelengths. The stable SLM operation is guaranteed by a passive triple-ring cavity and a fiber Fabry-Perot filter. The dual-wavelength output with a 40 GHz wavelength spacing is switchable in the range of 1533-1565.4 nm.     

Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier

A multiwavelength fiber ring laser obtained by use of a semiconductor optical amplifier (SOA) with a simple laser cavity configuration is reported. A Fabry-Perot filter was used in the fiber laser ring cavity to achieve more than 50 simultaneous wavelength lasing oscillations with a frequency separation of 50 GHz. The resulting stable broadband multiwavelength lasing operation was attributed to broadband and flat gain of the SOA, which has a gain flatness of 0.8 dB for more than 20 nm. The laser has a total output power of -3 dBm and a signal-to-spontaneous-noise ratio of 30 dB.     

Multiwavelength fiber laser using S-band erbium-doped fiber amplifier and semiconductor optical amplifier

A multiwavelength fiber ring laser that is based on an S-band erbium-doped fiber amplifier (EDFA) and a semiconductor optical amplifier (SOA) is developed. An optical switch is used to switch the multiwavelength fiber laser between S-band and L-band. This fiber laser can stably lase seven wavelengths in the S-band or 28 wavelengths in the L-band. Additionally, the lasing wavelengths with a signal-to-noise ratio of over 33 dB and a wavelength spacing of 100 GHz are demonstrated experimentally. The average powers of the lasing wavelength in the S-band and the L-band are −7.53 and −12.15 dBm, respectively.     

Hybrid flat gain C-band optical amplifier with Zr-based erbium-doped fiber and semiconductor optical amplifier

An efficient gain-flattened C-band optical amplifier is demonstrated using a hybrid configuration with a Zirconia-based Erbium-doped fibre (Zr-EDF) and a semiconductor optical amplifier (SOA). The amplifier utilizes a two-stage structure with a midway isolator to improve flat gain characteristic and reduce noise figure. At input signal power of −30 dBm, a flat gain of 28 dB is obtained from wavelength region of 1530 to 1560 nm with gain variation of less than 4 dB. The noise figure is maintained below 11 dB at the flat-gain region. This amplifier has the potential to be used in the high channel count dense wavelength division multiplexing system due to its simplicity and compact design.     

Multiwavelength fiber ring laser using a gain clamped semiconductor optical amplifier

We demonstrate a novel multi-wavelength fiber ring laser based on a gain clamped semiconductor optical amplifier. The number of lasing lines can be tuned by adjusting the loss inside the cavity. The wavelength interval between the wavelengths is 100 GHz. The proposed laser shows a stable operation with total intensity fluctuation for a single laser line within ±0.02 dB at room temperature for a period of 30-minutes.     

Numerical study of a harmonic mode-locked semiconductor optical amplifier fiber ring laser

An improved harmonic mode-locked Semiconductor optical amplifier (SOA) fiber ring lasers has been presented and numerically investigated based on the self-reproduction theory. The numerical result shows that a narrower optical pulse train with a more symmetrical-temporal shape can be obtained, when the modulation SOA is DC biased on high current, whereas the gain SOA is DC biased on the low current functions as a gain compensator in the experimental setup. Also, the system parameters effects on the characteristic of the harmonic mode-locked pulse have been investigated.     

Wavelength-tunable optical pulse generation from a fiber ring laser with a reflective semiconductor optical amplifier

This work describes, for the first time, wavelength-tunable optical pulse generation from a fiber ring laser with a reflective semiconductor optical amplifier. The optical signal to noise ratio of this fiber laser is higher than 49 dB over the wavelength-tunable range of 16 nm. Performance of this fiber ring laser operated at different wavelengths is also discussed.     

Low noise gain-clamped L-band erbium-doped fiber amplifier by utilizing fiber Bragg grating

A novel gain-clamped long wavelength band (L-band) erbium-doped fiber amplifier (EDFA) is proposedand experimented by using a fiber Bragg grating (FBG) at the input end of the amplifier. This designprovides a good gain clamping and decreases noise effectively. It uses two sections of erbium-doped fiber(EDF) pumped by a 1480-nm laser diode (LD) for higher efficiency and lower noise figure (NF). The gainis clamped at 23 dB with a variation of 0.5 dB from input signal power of -30 to -8 dBm for 1589 nm andNF below 5 dB is obtained. At the longer wavelength in L-band higher gain is also obtained and the gainis clamped at 16 dB for 1614 nm effectively. Because the FBG injects a portion of backward amplifiedspontaneous emission (ASE) back into the system, the gain enhances 5 dB with inputting small signal.     

Multi-wavelength fiber ring laser based on a chirped moire fiber grating and a semiconductor optical amplifier

A simple and cost-effective multi-wavelength fiber ring laser based on a chirped Moire fiber grating （CMFG） and a semiconductor optical amplifier （SOA） is proposed. Stable triple-wavelength lasing oscillations at room temperature are experimentally demonstrated. The measured optical signal-to-noise ratio （SNR） reaches the highest value of 50 dB and the power fluctuation of each wavelength is less than 0.2 dB within a 1-h period. To serve as a wavelength selective element, the CMFG possesses excellent comb-like filtering characteristics including stable wavelength interval and ultra-narrow passband, and its fabrication method is easy and flexible. The lasing oscillation shows a narrower bandwidth than SOA-based multi-wavelength fiber lasers utilizing some other kinds of wavelength selective components. Methods to optimize the laser performance are also discussed.     

Low noise double pass L-band erbium-doped fiber amplifier

A new double pass long wavelength band erbium-doped fiber amplifier with enhanced noise figure characteristics is demonstrated. The noise figure is improved by about 2.6 dB with the incorporation of broadband conventional-band fiber Bragg grating (FBG) in between the two segments of erbium-doped fiber. By incorporating both the pre-amplifier and the FBG, the noise figure is further improved, which varies from 4.0 to 5.0 dB in the flat gain region from 1570 to 1600 nm. The gain varies from 32.0 to 33.4 dB within this region. The new amplifier with high gain and low noise figure can be useful as an inline amplifier in a wavelength division multiplexing transmission system.     

Multiwavelength erbium-doped fiber ring lasers with overlap-written fiber Bragg gratings

Eight-wavelength Er-doped fiber lasers with lasing wavelength separations of ~1.6 and ~0.8 nm , respectively, have been achieved by use of overlap-written fiber Bragg gratings (OWFBG's) in the fiber lasers and by cooling of the Er-doped fiber with liquid N(2) . Our experiment shows that by utilizing the OWFBG's to select the lasing wavelengths one can achieve fiber lasers with lasing wavelengths and lasing wavelength separations that match the International Telecommunication Union channel-allocation grid well.     

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.     

Frequency noise reduction in erbium-doped fiber distributed-feedback lasers by electronic feedback

A novel technique for suppressing frequency noise in an erbium-doped fiber distributed-feedback laser incorporated into a master-oscillator-power-amplifier configuration by an electronic feedback technique is presented. The frequency noise is suppressed by locking of the laser emission to a fiber interferometer. The frequency noise spectral density of the laser is reduced by as much as 20 dB over the frequency range 1 Hz-10 kHz to 1.5 Hz/Hz(1/2) +/-25% at 1 kHz with a relative intensity noise spectral density below -120 dB/Hz over the frequency range 10 Hz-1 kHz. These lasers will have applications as sources for fiber-optic interferometry, high-resolution spectroscopy, and high-bandwidth communications.     

A quantum-chaotic encoding system using an erbium-doped fiber amplifier in a fiber ring resonator

This paper firstly presents a new concept of quantum-chaotic encoding of light traveling in a fiber optic ring resonator. The pumping input power can be controlled to generate the chaotic behavior of the circulated light within the fiber ring resonator. The Kerr nonlinear type of light circulating in a fiber optic ring resonator is induced and the superposition i.e. four-wave mixing of the propagating waves at resonance occurred. The output signals can be used to generate two different codes, of which one is the quantum bits i.e. code, the other is the chaotic signal i.e. code. The proposed system has shown the potential of using for communication security, where the double security via quantum-chaotic can be performed.     

Stable multiwavelength fiber ring laser with equalized power spectrum based on a semiconductor optical amplifier

We experimentally demonstrated a new structure of a multiwavelength semiconductor optical amplifier (SOA) ring laser based on a fiber Sagnac loop filter that can generate up to 25 stable output lasing wavelengths at room temperature. By varying the length of a polarization-maintaining (PM) fiber within the Sagnac loop filter, the wavelength spacing between the output lasing wavelengths can be changed to a desired value. By tuning a polarization controller (PC) within the Sagnac loop filter, stable multiwavelength 1550-nm operation with up to 17 lasing lines within 3 dB power level variation and with a wavelength spacing of ∼0.8 nm was achieved. The optical signal-to-noise ratios (OSNRs) of all the lasing wavelengths are greater than 40 dB.     

Optical pattern recognition by use of a segmented semiconductor optical amplifier

A technique for high-speed, all-optical pattern recognition based on cross correlation in a segmented semiconductor optical amplifier (SSOA) is presented. A counterpropagating pump-probe setup is used to perform cross correlation of the spatial gain-loss pattern in the SSOA with the optical data pattern (pump), and the result is read out with a counterpropagating probe. Cross correlation of 4-bit patterns at 85 Gbits/s is experimentally demonstrated. Simulations show reasonable agreement with experimental measurements and are used to address scalability to higher bit rates and longer data patterns.     

Suppression of mode competition in fiber lasers by using a saturable absorber and a fiber ring

An erbium-doped fiber (EDF) laser was configured with a fiber grating, a fiber ring resonator, and a saturable absorber by using un-pumped EDF as mode selection element. The laser showed single mode operation with a narrow linewidth of 5 kHz. The mode selection mechanisms of the un-pumped EDF and the ring resonator are theoretically and experimentally analyzed.     

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.     

Using C-band erbium-doped fiber amplifier with two-ring scheme for broadly wavelength-tuning fiber ring laser

In this demonstration, we propose and experimentally investigate a broad and stable wavelength-tuning fiber laser employing a C-band erbium-doped fiber amplifier (EDFA) and coupled-ring cavity scheme. Based on the proposed laser scheme, the wavelength-tuning range can be tuned in S- to C-bands (from 1510.0 to 1562.0 nm) due to the properly control of cavity loss. In addition, the performances of side-mode suppression ratio (SMSR), optical signal to noise ratio (OSNR), and output power and wavelength are also discussed and analyzed over the wavelength-tuning range.     

Performance of optical amplifier employing silica host magnesium-aluminum-germanium co-doped erbium-doped fiber

Two silica host magnesium(Mg)-aluminum(Al)-germanium(Ge) co-doped erbium-doped fibers (EDFs) have been fabricated, which have different Mg concentrations. The concentration of all the compositions in the preform is measured through electronics probe micro analysis (EPMA). The maximum Mg concentrations of fibers A and B are 3.98 and 1.28 mol%, respectively. The performance characteristics including absorption spectrum and gain are measured and analyzed. The absorption coefficients of fibers A and B are 13.3 and 14.3 dB/m respectively at wavelength of 1532 nm. The max gains of these two erbium-doped fiber amplifiers (EDFAs) are 30.1 and 35.9 dB with input signal power of -30 dBm and pump power of 100 mW at 980 nm. Fiber B with maximum Mg concentration 1.28 mol% has better performance than fiber A. Fiber B has high absorption coefficient and high gain characteristics. The optimum fiber B length of C-band EDFA is 7 m and that of L-Band EDFA is about 30 m, which is much shorter than standard commercial EDFAs.