Amplified Spontaneous Emission Spectrum Research Articles

16.8 Tb/s True Random Number Generator Based on Amplified Spontaneous Emission

We report a 16.8 Tb/s true random number generator (TRNG) based on amplified spontaneous emission (ASE) of Erbium-doped fiber amplifier (EDFA), which is sliced into 42 parallel channels by an arrayed waveguide grating (AWG). The true randomness of ASE is enhanced and guaranteed by a novel extraction approach utilizing two orthogonal polarized components of ASE. Consequently, the random number generation rate (RNGR) can be significantly increased via higher sampling rate. The experimental results show that, the single-channel RNGR of 400 Gb/s is achieved, while the overall RNGR is 16.8 Tb/s for the full ASE spectrum. The proposed TRNG is of great significance in the field of secret key distribution and confidential communication.

A fluorescein sodium wide-area pH optical sensor based on amplification characteristics

We studied the characteristics of fluorescein sodium (FS) to cause changes in the amplified spontaneous emission (ASE) spectrums under different acid and alkaline environments. According to the characteristics of light amplification, the spectrum width became narrower and the highest peak wavelength of the ASE spectrum became stabilized, establishing a connection between the light wavelength and the solution pH. Compared with the amplifier’s performances, the host and guest materials of different ratios were tested with FS as the host material, and the best ratios were determined to be 1.5 and 0.1 mg/mL for FS and 4-methylumbelliferone, respectively. The gains for signals with wavelengths of 535–555 nm were all greater than 7 dB, and the amplified signal-to-noise ratios (SNRs) were greater than 7 dB. Moreover, the gains of the wavebands (543–550 nm) in the pH test were all greater than 10 dB. The best operating wavelength of the amplifier was 542 nm, and the best gain and SNR were 14.3 and 12.3 dB, respectively. Following this, we measured the output signal wavelengths of the pH standard solutions corresponding pH values of 3–10, and measured the pH values of tap water and three dyeing pigments that could not be measured with pH test paper owing to dyeing. We compared the measured values of the pen-shaped pH meter with the measured pH values of the wavelengths to test the effectiveness of this detection method, which the deviation was all less than 1 pH.

Narrowband Spontaneous Emission Amplification from a Conjugated Oligomer Thin Film.

In this paper, we studied the laser and optical properties of conjugated oligomer (CO) 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF) thin films, which were cast onto a quartz substrate using a spin coating technique. BECV-DHF was dissolved in chloroform at different concentrations to produce thin films with various thicknesses. The obtained results from the absorption spectrum revealed one sharp peak at 403 nm and two broads at 375 and 428 nm. The photoluminescence (PL) spectra were recorded for different thin films made from different concentrations of the oligomer solution. The threshold, laser-induced fluorescence (LIF), and amplified spontaneous emission (ASE) properties of the CO BECV-DHF thin films were studied in detail. The ASE spectrum was achieved at approximately 482.5 nm at a suitable concentration and sufficient pump energy. The time-resolved spectroscopy of the BECV-DHF films was demonstrated at different pump energies.

Mid-Infrared Amplified Spontaneous Emission from the f′ 0g+ (1D2) Ion-Pair State and Spectroscopic Characterization of the Shallow 0g+ (ab) Valence State of I2

In this paper, we describe amplified spontaneous emission (ASE) from the f' 0g+ (1D2) ion-pair state of I2 populated through a two-step laser excitation technique via the B 3Π(0u+) valence state. The intense infrared emission propagating in the direction of the incident laser beam is assigned to the ASE transition from the f' 0g+ (1D2) state to the F' 0u+ (1D2) ion-pair state. The subsequent ultraviolet fluorescence transition from the F' 0u+ (1D2) state to the 0g+ (bb) state as well as the 0g+ (ab) state is also reported. By Franck-Condon simulation of the cascading F' 0u+ (1D2) → 0g+ (bb) band, we determine the population distributions in the F' 0u+ (1D2) state generated by ASE, which are consistent with the intensity profile of the mid-infrared ASE spectrum. Finally, employing these vibrational distributions for the F' 0u+ (1D2) state, spectral parameters for the shallow 0g+ (ab) state are derived.

Tm3+/Ho3+ co-doped germanate glass and double-clad optical fiber for broadband emission and lasing above 2 µm

In this paper, a 2 µm broadband emission under 796 nm laser diode excitation in low phonon energy GeO2-Ga2O3-BaO glass system is co-doped with 0.7Tm2O3/(0.07-0.7)Ho2O3 (mol%). The widest emission band (where the Tm3+ → Ho3+ energy transfer efficiency is 63%) was obtained for 0.7Tm2O3/0.15Ho2O3 co-doped glass from which a double-clad optical fiber was realized and investigated. Optimization of Tm3+/Ho3+ concentration enabled the acquisition of broadband amplified spontaneous emission (ASE) in double-clad optical fiber with a full width at half maximum (FWHM): 377 nm and 662 nm for 3 dB and 10 dB bandwidth, respectively. ASE spectrum is a result of the superposition of (Tm3+: 3H4 →Η3F4) 1.45 µm, (Tm3+: 3F4 → 3H6) 1.8 µm and (Ho3+:5I7 → 5I8) 2 µm emission bands. Hence, highly rare-earth co-doped germanate glass is characterized by a remarkably broader ASE spectrum than silica and tellurite fibers showed promising lasing properties for their further application in tunable and dual wavelength lasers.

A Temperature-Insensitive Amplified Spontaneous Emission Broadband Source Based on Er-Doped Fiber**Supported by the National Natural Science Foundation of China under Grant No 11504320.

To obtain a stable amplified spontaneous emission (ASE) source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperatures. We optimize the structure of the ASE source to flatten the ASE spectrum, and study the output characteristics in terms of output power and optical spectrum under different pump powers. Then the performance of the ASE source is investigated in the temperature range from −18.9°C to 50°C. A stable-power and flat-spectrum ASE source can be obtained by structural optimization and pump control.

Compensating power depletion due to stimulated Raman scattering in high-power delivery fiber via spectral inversion revisited in a view of experimental implementation

Broadband spectral inversion was proved theoretically to be an effective method to compensate power depletion due to stimulated Raman scattering in high-power delivery fiber. A critical difficulty in implementing the method in experiment is to realize broadband spectral inversion of incoherent light as Raman Stokes waves are incoherent due to their origin from spontaneous emission noise. Broadband spectral inversion of incoherent light is investigated experimentally in this article. A beam from an amplified spontaneous emission (ASE) light source is used as an approximated Raman Stokes waves in the experiment. ASE Spectrum of width of 10.5nm is inverted via four-wave mixing in a highly nonlinear dispersion-shifted fiber in efficiency of -10dB without significant spectrum deformation. A theoretical model for four-wave mixing of ASE incoherent light is established, and based on which the limitation in more broadband spectral inversion of ASE incoherent light is analyzed.

Quantum dot semiconductor optical amplifier: investigation of amplified spontaneous emission and noise figure in the presence of second excited state

In this paper, amplified spontaneous emission (ASE) in quantum dot semiconductor optical amplifier (QDSOA) is investigated and analyzed theoretically. The presented model is based on a set of rate equations that consider all possible carriers transitions including the second excited state (ES2). This assumption is possible, if the QDSOA’s active region is grown in such a way that the presence of ES2 becomes distinguishable from upper states and wetting layer. Optical gain of QDSOA is calculated using density matrix approach. The coupled rate equations are solved numerically along with propagation equations. It is shown that in the presence of ES2, QDSOA performance can be improved and an ultra-high bit-rate signal amplification without wave distortion is possible. Furthermore, it is illustrated that the obtained ASE spectrum has three peeks which are related to ground, first excited and second excited states. Moreover, noise figure (NF) is calculated numerically using ASE power. It is shown that considering the effect of ES2 in the band diagram of quantum dots (QDs) decreases the NF of amplifier. The effect of increased input power on the reduction of NF is illustrated, too. It is shown that ASE and NF of amplifier can be ignored in the modeling QDSOA at high input powers.

Nematicon-driven injection of amplified spontaneous emission into an optical fiber

We investigate experimentally the interaction between amplified spontaneous emission (ASE) and a soliton, which are both generated in a dye-doped nematic liquid crystal (LC) cell. A light beam is injected through an optical fiber slid into the cell to form a soliton beam. ASE is then automatically collected by this self-induced waveguide and efficiently coupled into the same optical fiber, in the backward direction. We demonstrate that the presence of the soliton improves the ASE collection by one order of magnitude. We also show that the ASE is highly polarized in the plane of the LC cell and that the ASE spectrum depends on the pump stripe orientation with respect to the LC director. The origin of the spectral anisotropy of the gain curves is determined with the help of femtosecond pump-probe spectroscopy.

A highly sensitive chemosensor for solution based on organic semiconductor laser gain media

Laser has been widely applied in the scientific and engineering areas including communications, medical treatment, industry, and military due to its extremely strict monochromaticity, high coherence and high energy density. Organic laser based on solution processable polymer gain media has attracted considerable attention in various applications due to its easy fabrication, compact system and flexibility. At present, the chemosensors based on organic semiconductor laser have been widely developed. It has been reported to achieve solution monitoring by organic DFB (distributed feedback) laser. Although the method has its own advantages, there are still many operability and craftsmanship problems to be resolved. In this paper we introduce a new type of the real-time monitoring for various solution. The monitor is realized by using amplified spontaneous emission (ASE) from optically pumped organic semiconductor gain media. The gain media comprising blends of poly(9, 9-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly(3-hexylthiophene) (P3HT) at a ratio of 15:85 wt.% is dissolved into toluene (25 mg/mL). Thin films (90 nm thickness) of P3HT/F8BT are obtained by spin coating (2000 rpm) from solution onto pre-cleaned quartz substrates. The P3HT/F8BT film demonstrates the absorption peak at 471 nm, the PL peak at 622 nm, and the ASE peak at 661 nm with FWHM (full-width-at-half-maximum) linewidth of ～ 10 nm under the stripe laser pumping. The thin films are, then, covered by droplet of solution to form planar waveguide structure with variable effective refractive index. Upon analyte binding, a change in refractive index at the P3HT/F8BT film surface results in a change in the effective refractive index of the planar waveguide and in turn induces shift of the ASE mode wavelength and variation of ASE threshold of the organic gain media. The changes in ASE wavelength and threshold can be monitored for sensing. The red shift of 4.5 nm in the ASE spectrum is from 661 to 665.5 nm and the threshold increases from 0.579 J/pulse to 1.447 J/pulse which can be detected with the concentration of sodium chloride increasing from 0 to 25 wt.% in pure water. Our experimental results show that this method is easy to detect the concentration grads of 1 wt.% sodium chloride solution. The measurement sensitivity of solution reaches 97.8 nm/RIU (refractive index unit), and accuracy reaches 141.9 nm/RIU. Furthermore, we demonstrate that the chemosensor could be used for detecting different kinds of solution in the same concentration. The ASE peak position and threshold display clearly different when the droplet 10 wt.% sodium, chloride solution and hydromel solution onto P3HT/F8BT film. Our study suggests that the organic gain media films have potentiality to be developed as a high sensitivity and high accuracy chemosensor to detect solution due to the high sensitivity of the ASE peak position and threshold to the refractive index of the solution.

Self-Seeded RSOA-Fiber Cavity Lasers vs. ASE Spectrum-Sliced or Externally Seeded Transmitters—A Comparative Study

Reflective semiconductor optical amplifier fiber cavity lasers (RSOA-FCLs) are appealing, colorless, self-seeded, self-tuning and cost-efficient upstream transmitters. They are of interest for wavelength division multiplexed passive optical networks (WDM-PONs) based links. In this paper, we compare RSOA-FCLs with alternative colorless sources, namely the amplified spontaneous emission (ASE) spectrum-sliced and the externally seeded RSOAs. We compare the differences in output power, signal-to-noise ratio (SNR), relative intensity noise (RIN), frequency response and transmission characteristics of these three sources. It is shown that an RSOA-FCL offers a higher output power over an ASE spectrum-sliced source with SNR, RIN and frequency response characteristics halfway between an ASE spectrum-sliced and a more expensive externally seeded RSOA. The results show that the RSOA-FCL is a cost-efficient WDM-PON upstream source, borrowing simplicity and cost-efficiency from ASE spectrum slicing with characteristics that are, in many instances, good enough to perform short-haul transmission. To substantiate our statement and to quantitatively compare the potential of the three schemes, we perform data transmission experiments at 5 and 10 Gbit/s.

Design and experimental realization of a highly efficient superfluorescent fiber source with flat C-band spectrum

Design and experimental realization of C-band superfluorescent fiber sources using a well-designed high reflector/filter of fiber Bragg grating (FBG) in three configurations, namely double-pass forward (DPF), double-pass backward (DPB), and DPF+DPB , is realized. Using a numerical method, the optimum length and peak absorption coefficient of erbium-doped fiber as well as the optimum specifications of FBG, i.e., its 3-dB bandwidth and central wavelength, are calculated. Our numerical calculations illustrate that an appropriate design may result in a flattened amplified spontaneous emission (ASE) output spectrum with a 3-dB bandwidth of about 22 nm and a central wavelength of 1550 nm. Furthermore, the peak power of the flattened ASE spectrum is 16 dBm larger than the power at a wavelength of 1530 nm that is beneficial for increasing the 3-dB bandwidth. The experimental results show that using an optimum design, there are negligible differences between ASE output spectra acquired by different double-pass configurations. However, the DPB configuration has a higher efficiency as compared with other configurations and can provide a C-band superfluorescent fiber source with a simultaneously good spectral flatness, , high output power of 12 dBm, and maximum 3-dB bandwidth of about 22 nm.

WDM optical steganography based on amplified spontaneous emission noise.

We propose and experimentally demonstrate a wavelength-division multiplexed (WDM) optical stealth transmission system carried by amplified spontaneous emission (ASE) noise. The stealth signal is hidden in both time and frequency domains by using ASE noise as the signal carrier. Each WDM channel uses part of the ASE spectrum, which provides more flexibility to apply stealth transmission in a public network and adds another layer of security to the stealth channel. Multi-channel transmission also increases the overall channel capacity, which is the major limitation of the single stealth channel transmission based on ASE noise. The relations between spectral bandwidth and coherence length of ASE carrier have been theoretically analyzed and experimentally investigated.

Temperature-Insensitive Bend Sensor Using Entirely Centered Erbium Doping in the Fiber Core

A fiber based bend sensor using a uniquely designed Bend-Sensitive Erbium Doped Fiber (BSEDF) is proposed and demonstrated. The BSEDF has two core regions, namely an undoped outer region with a diameter of about 9.38 μm encompassing a doped, inner core region with a diameter of 4.00 μm. The doped core region has about 400 ppm of an Er2O3 dopant. Pumping the BSEDF with a conventional 980 nm laser diode gives an Amplified Spontaneous Emission (ASE) spectrum spanning from 1,510 nm to over 1,560 nm at the output power level of about −58 dBm. The ASE spectrum has a peak power of −52 dBm at a central wavelength of 1,533 nm when not spooled. Spooling the BSEDF with diameters of 10 cm to 2 cm yields decreasing peak powers from −57.0 dBm to −61.8 dBm, while the central wavelength remains unchanged. The output is highly stable over time, with a low temperature sensitivity of around ∼0.005 dBm/°C, thus allowing for the development of a highly stable sensor system based in the change of the peak power alone.

Amplified spontaneous emission spectrum and gain characteristic of a two-electrode semiconductor optical amplifier

A two-electrode multi-quantum-well semiconductor optical amplifier is designed and fabricated. The amplified spontaneous emission (ASE) spectrum and gain were measured and analyzed. It is shown that the ASE spectrum and gain characteristic are greatly influencedby the distribution of the injection current density. By changing the injection current density of two electrodes, the full width at half maximum, peak wavelength, peak power of the ASE spectrum and the gain characteristic can be easily controlled.

High power narrow-band fiber-based ASE source

In this paper we describe a high power narrow-band amplified spontaneous emission (ASE) light source at 1030 nm center wavelength generated in an Yb-doped fiber-based experimental setup. By cutting a small region out of a broadband ASE spectrum using two fiber Bragg gratings a strongly constrained bandwidth of 12±2 pm (3.5±0.6 GHz) is formed. A two-stage high power fiber amplifier system is used to boost the output power up to 697 W with a measured beam quality of M2≤1.34. In an additional experiment we demonstrate a stimulated Brillouin scattering (SBS) suppression of at least 17 dB (theoretically predicted ~20 dB), which is only limited by the dynamic range of the measurement and not by the onset of SBS when using the described light source. The presented narrow-band ASE source could be of great interest for brightness scaling applications by beam combination, where SBS is known as a limiting factor.

Measurement of the carrier recovery time in SOA based on four-wave mixing on narrow-band ASE spectrum

Carrier recovery time is a key parameter that determines the performance of a semiconductor optical amplifier (SOA). A measurement method of carrier recovery time in SOA based on a nearly degenerate four-wave mixing of narrowband amplified spontaneous emission (ASE) spectra is presented. The results show the carrier times are 50.2, 44.6, and 23.6 ps when the injected currents are 120, 180, and 240 mA, respectively, which are in agreement with the nominal values of the sample.

Effects of Pumping Scheme and Double-Propagation on the Performance of ASE Source using Dual-Stage Bismuth-Based Erbium-Doped Fiber

In this paper, a new configuration of the wide-band amplified spontaneous emission (ASE) source is proposed using dual-stage scheme with a broadband fiber Bragg grating. The ASE source utilizes a Bismuth-based erbium-doped fiber (Bi-EDF) as a gain medium with either forward or backward pumping scheme. A wide-band and flat ASE output is achieved using a forward pumping scheme with the power ripples of less than 4.9 dB and 3 dB bandwidth of 90.5 nm. The ASE spectrum obtained covers the whole C-, L- and extended L-band regions from 1520 to 1620 nm. However, the backward pumping scheme provides a better pumping efficiency as compared to the forward pumping. The total ASE power reaches up to 26.6 mW at maximum pump power of 320 mW with a pumping efficiency of 8%.

Equivalent circuit model for erbium-doped fibre amplifiers including amplified spontaneous emission

An equivalent circuit model of erbium-doped fibre amplifiers (EDFAs), including amplified spontaneous emission (ASE), is proposed. Using the circuit model, static and dynamic characteristics of EDFAs with the help of a SPICE simulator can be analysed conveniently. DC gain, ASE spectrum, frequency response and transient analysis of EDFAs can be simulated. A good agreement is obtained between the result of circuit-model simulation and that of numerical computation.

A standard fiber-based loop mirror as a gain-flattening filter for erbium-doped fiber amplifiers

We report flattening of the amplified spontaneous emission (ASE) spectrum from an erbium-doped fiber (EDF) using a standard fiber-based loop mirror (FLM), realized with an "over-coupled" fiber coupler. Through simulation, a bend-induced birefringent FLM as a gain-flattening filter is designed. Subsequently, an over-coupled coupler with a free spectral range of 140 nm is fabricated to realize the FLM, which is integrated to an EDF that is pumped by a 980-nm laser diode. By introducing an appropriate amount of bend-induced birefringence in the loop, the ASE spectrum of the EDF could be flattened within /spl plusmn/0.5 dB over a wavelength range of 32 nm in the C-band.