Amplified Spontaneous Emission Noise Research Articles

Compact quantum random number generator based on superluminescent light-emitting diodes.

By measuring the amplified spontaneous emission (ASE) noise of the superluminescent light emitting diodes, we propose and realize a quantum random number generator (QRNG) featured with practicability. In the QRNG, after the detection and amplification of the ASE noise, the data acquisition and randomness extraction which is integrated in a field programmable gate array (FPGA) are both implemented in real-time, and the final random bit sequences are delivered to a host computer with a real-time generation rate of 1.2 Gbps. Further, to achieve compactness, all the components of the QRNG are integrated on three independent printed circuit boards with a compact design, and the QRNG is packed in a small enclosure sized 140 mm × 120 mm × 25 mm. The final random bit sequences can pass all the NIST-STS and DIEHARD tests.

The Impact of Transceiver Noise on Digital Nonlinearity Compensation

The efficiency of digital nonlinearity compensation (NLC) is analyzed in the presence of noise arising from amplified spontaneous emission noise (ASE) as well as from a non-ideal transceiver subsystem. Its impact on signal-to-noise ratio (SNR) and reach increase is studied with particular emphasis on split NLC, where the digital back-propagation algorithm is divided between transmitter and receiver. An analytical model is presented to compute the SNR's for non-ideal transmission systems with arbitrary split NLC configurations. When signal-signal nonlinearities are compensated, the performance limitation arises from residual signal-noise interactions. These interactions consist of nonlinear beating between the signal and co-propagating ASE and transceiver noise. While transceiver noise-signal beating is usually dominant for short transmission distances, ASE noise-signal beating is dominant for larger transmission distances. It is shown that both regimes behave differently with respect to the optimal NLC split ratio and their respective reach gains. Additionally, simple formulas for the prediction of the optimal NLC split ratio and the reach increase in those two regimes are reported. It is found that split NLC offers negligible gain with respect to conventional digital back-propagation (DBP) for distances less than 1000 km using standard single-mode fibers and a transceiver (back-to-back) SNR of 26 dB, when transmitter and receiver inject the same amount of noise. However, when transmitter and receiver inject an unequal amount of noise, reach gains of 56% on top of DBP are achievable by properly tailoring the split NLC algorithm. The theoretical findings are confirmed by numerical simulations.

Performance improvement of 64-QAM coherent optical communication system by optimizing symbol decision boundary based on support vector machine

High-order modulation signals are suited for high-capacity communication systems because of their high spectral efficiency, but they are more vulnerable to various impairments. For the signals that experience degradation, when symbol points overlap on the constellation diagram, the original linear decision boundary cannot be used to distinguish the classification of symbol. Therefore, it is advantageous to create an optimum symbol decision boundary for the degraded signals. In this work, we experimentally demonstrated the 64-quadrature-amplitude modulation (64-QAM) coherent optical communication system using support-vector machine (SVM) decision boundary algorithm to create the optimum symbol decision boundary for improving the system performance. We investigated the influence of various impairments on the 64-QAM coherent optical communication systems, such as the impairments caused by modulator nonlinearity, phase skew between in-phase (I) arm and quadrature-phase (Q) arm of the modulator, fiber Kerr nonlinearity and amplified spontaneous emission (ASE) noise. We measured the bit-error-ratio (BER) performance of 75-Gb/s 64-QAM signals in the back-to-back and 50-km transmission. By using SVM to optimize symbol decision boundary, the impairments caused by I/Q phase skew of the modulator, fiber Kerr nonlinearity and ASE noise are greatly mitigated.

Experimental Demonstration of ASE Noise Suppression by Soliton Self-Frequency Shift

Amplified spontaneous emission (ASE) noise self-suppression effect on soliton self-frequency shift (SSFS) has been already reported, but its experimental verification has not been demonstrated. In this letter, we experimentally demonstrate ASE noise suppression effect on SSFS using a metric of power penalty on bit error rate (BER) for on–off keying signals before and after ASE noise suppression. We added an additional 1% of ASE noise to the signal generated from an erbium-doped fiber amplifier. In addition, we examined the degradation of power penalties on BER for different percentages of the noise in the signal in simulation to assess the effective range of ASE noise suppression on SSFS.

BER Performance of an Optically Pre-amplified FSO System Under Turbulence and Pointing Errors With ASE Noise

The performance of a free space optical (FSO) communication system is significantly affected by various atmospheric turbulence conditions and pointing errors (PEs) apart from the additive noise, which is assumed to be Gaussian. Optical pre-amplifiers are an essential component of FSO systems for improving the receiver sensitivity. However, optical pre-amplification results in amplified spontaneous emission (ASE), which dominates the receiver thermal and shot noises. The square law photodetection process at the receiver in a FSO system necessitates the consideration of chi-square statistics for the decision variable contrary to the Gaussian approximation that is widely used in the literature. In this paper, we evaluate the bit error rate (BER) performance of a FSO system assuming non-return-to-zero on–off keying modulation in the presence of ASE noise under weak, moderate to strong, and very strong atmospheric turbulence regimes and PEs. We also derive asymptotic BER expressions for the considered FSO system for large values of the signal-to-noise ratio in terms of simple elementary functions. Further insight into the system is provided by performing a diversity analysis.

Rapid, k-space linear wavelength scanning laser source based on recirculating frequency shifter.

We propose and successfully demonstrate a k-space linear and self-clocked wavelength scanning fiber laser source based on recirculating frequency shifting (RFS). The RFS is realized with a high speed electro-optic dual parallel Mach-Zehnder modulator operating at the state of carrier suppressed single sideband modulation. A gated short pulse is injected into an amplified RFS loop to generate the wavelength scanning pulse train. We find that the accumulation of in-band amplified spontaneous emission (ASE) noise over multiple scanning periods will saturate the erbium-doped fiber amplifier and impede the amplification to the pulse signal in the RFS loop. To overcome the degradation of temporal signal due to the accumulation of ASE noise over multiple scanning periods, we insert a modulated optical switch into the RFS loop to completely attenuate the in-band ASE noise at the end of each scanning period. The signal to noise ratio of the temporal pulsed signal is greatly enhanced. K-space linear and self-clocked wavelength scanning fiber laser sources in 6.1 nm/7.2 nm scanning range with 20 GHz/30 GHz frequency shifting are successfully demonstrated.

The effect of ASE reinjection configuration through FBGs on the gain and noise figure performance of L-Band EDFA

In this study, we present the gain and noise figure performance improvement in L-band erbium-doped fiber amplifier (L-EDFA) provided by amplified spontaneous emission (ASE) reinjection through different configurations of 1533nm band FBGs. The experimental results are compared with a single-stage bidirectionally pumped conventional L-EDFA design. It is shown that when the forward and/or the backward ASE noise is partly reinjected to L-EDFA using a double/single 1533nm fiber Bragg gratings (FBG), the gain and noise figure performance of L-EDFA increases depending on the FBG configuration. The best gain and NF performance in our L-EDFA was achieved by reinjection of forward and backward ASE through FBG1 and FBG2 leading to an 4.5dB increase in gain and 1dB decrease in NF at 1585nm and −30dBm input signal power. The results show that both FBGs must be used at the same time to improve gain and NF performance in L-band EDFAs.

Cost efficient amplifier placement and gain adjustment in all-Optical networks: A noise-minimizing approach

Erbium doped fiber amplifiers (EDFA) are known to be well suited for transparent optical networks due to their proper relative properties. Link amplifiers are responsible for adequately compensating fiber loss in optical links. However, amplified spontaneous emission (ASE) noise would degrade the optical signal to noise ratio (OSNR) which leads to degradation in quality of service (QoS). This paper aims at optimally determining the location and relative gain settings of the employed line amplifiers in order to minimize the total ASE noise power on each link. A non-linear optimization approach is developed. Then, two amplifier placement and gain adjustment algorithms called optimal EDFA placement (OEP) and Incremented-OEP are proposed. Numerical results in addition to simulations indicate the fact that the proposed schemes outperform the existing conventional EDFA placement (CEP) solution in terms of average ASE noise power and blocking rate.

Effects of Upstream Incoherent Crosstalk Caused by ASE Noise from Tx-Disabled ONUs in XG-PONs and TWDM-PONs

A large incoherent crosstalk (IC) caused by amplified spontaneous emission (ASE) noise power from Tx-disabled optical network units and a differential path loss has been shown to degrade upstream transmission performance in time-division multiplexing passive optical networks. This paper considers the IC-induced power penalty of an upstream signal both in an XG-PON and in a TWDM-PON. We investigate the degradation of the extinction ratio and relative intensity noise through a simulation and experiments. For the XG-PON case, we observe a 9.6 dB difference in the level of ASE noise power from Tx-disabled ONUs (hereafter known simply as ASE noise) between our result and the ITU-T XG-PON PMD recommendation. We propose an optical filtering method to mitigate an IC-induced power penalty. In the TWDM-PON case, the IC-induced power penalty is naturally negligible because the ASE noise is filtered by a wavelength multiplexer at the optical line terminal. The results provide design guidelines for the level of ASE noise in both XG-PONs and TWDM-PONs.

Demand Routing with ASE Impairment Consideration in Long Distance Optical Networks

AbstractIn this paper, a heuristic algorithm that considers ASE (Amplified Spontaneous Emission) noise impairment is developed for demand routing in long distance optical networks. Amplifier span constraints, determined by ASE noise impairment, are presented to constrain the maximal transparent reach of a lightpath. Problem formulation and heuristic algorithms are given. Simulation demonstrates that each demand stream is guaranteed to be successfully routed, and network resources (wavelength channels and transceivers) are effectively utilized.

Investigations of influences of spontaneous emission properties on surface plasmon polariton amplifications with the rate-equation theory

The influences of the position-related spontaneous emission properties of gain media on gain and amplified spontaneous emission (ASE) noise characteristics of surface plasmon polariton (SPP) amplification are investigated with rate-equation theory in this paper. It is found that both the spontaneous emission rate and the probability of spontaneous emission into the SPP mode of the gain media in an SPP waveguide are position related. Based on this, a rate-equation model considering those spontaneous emission properties is presented. With this model, the influences of the position-related spontaneous emission properties on the gain and ASE noise characteristics of a single-mode dielectric-loaded SPP amplifier are discussed. The results show that the spontaneous emission rate of gain media is enhanced near the metal interface and the probability of spontaneous emission into the SPP mode decreases near both the metal and air interfaces of the amplifier. This gives rise to reduced gain and low ASE output power. Moreover, the noise property of the amplifier may be improved because of the great decrease in the output ASE power.

Influence of ASE Noise on the Performance of DWDM Networks Using Low-Power Pumped Raman Amplifiers

ABSTRACTWe present the results of investigation of influence of amplified spontaneous emission (ASE) noise, noise figure (NF) and dispersion chromatic on the performance of middle-distance dense-wavelength-division-multiplexing (DWDM) networks using low-power pumped distributed Raman amplifiers (DRAs) in two different pump configurations, i.e., forward and backward pumping. We found that the pumping configurations, ASE noise, and dispersion play an important role for improving the network performance by reduction of NF and bit error rate (BER) of the system. Simulation results show that the lowest BER and low NF were obtained, when using the forward pumping configuration. Moreover, we have also compared ASE noise powers of the simulation with this experiment. These results conclude that DRA with low pump power (<1 W) is the promising key technology for short- and/or middle-distance DWDM transmission networks.

Influence of ASE Noise on Performance of DWDM Networks Using Low-power Pumped Raman Amplifiers

We present the results of investigation for influence of amplified spontaneous emission (ASE) noise, noise figure (NF) and chromatic dispersion on the performance of middle-distance Dense-wavelength-division-multiplexing (DWDM) networks using low-power pumped distributed Raman amplifiers (DRAs) in two different pump configurations, i.e., forward and backward pumping. We found that the pumping configurations, ASE noise, and dispersion play an important role for improving network performance by decrease of noise figure and bit error rate (BER) of the system. Simulation results show that the lowest bit error rate and low noise figure were obtained, when using forward pumping configuration. Moreover, we have also compared ASE noise powers of the simulation with these of the experiment. These results conclude that DRA with low pump power ($&lt;1$~W) is the promising key technology for short-- and/or middle-distance DWDM transmission networks.

Noise Suppression Phenomenon in Fiber Raman Amplifier

Abstract The problem of small bit error rate is actual in fiber Raman amplifiers. Our experimental data on the amplified spontaneous emission (ASE) with backward pumping as a base of optical noise evaluation are presented in this paper. Raman gain spectrum for useful Stokes low-powered signal is calculated and compared with obtained spectrum of non-coherent ASE noise. It is shown that output optical signal has better gain than the amplified spontaneous emission that leads to appreciable growth of output optical signal-to-noise ratio.

Modeling FWM and impairments aware amplifiers placement technique for an optical MAN/WAN: Inline amplifiers case

A new four wave mixing (FWM) model for an optical network with amplifiers and a comparative analysis among three proposed amplifiers placement techniques have been presented in this paper. The FWM model is validated with the experimental measured data. The novelty of this model is its uniqueness that on direct substitutions of network parameters like length, it works even for unequal inter amplifier separations. The novelty of the analysis done among three schemes is that it presents fair choice of amplifiers placement methods for varied total system length. The appropriateness of these three schemes has been analyzed on the basis of critical system length, critical number of amplifiers and critical bit error rate (10−9) in presence of four wave mixing (FWM) and amplified spontaneous emission noise (ASE). The implementation of analysis done has been given with the help of an example of a regenerative metropolitan area network (MAN). The results suggest that the decreasing fiber section scheme should be avoided for placements of amplifiers and schemes IUFS and EFS shows their importance interchangeably for different set of parameters.

Performance comparison of analogue inter‐satellite microwave photonics link using intensity modulation with direct detection and phase modulation with interferometric detection

The performance of optical inter-satellite communications using microwave photonics technologies employing intensity modulation with direct detection (IMDD) and phase modulation (PM) with interferometric detection are investigated and demonstrated with a numerical example. The theoretical model considering the saturated gain and amplifier spontaneous emission noise of optical booster amplifier and optical preamplifier is constructed for both architectures. Furthermore, the authors compare the performance of PM with interferometric detection to optimum biased IMDD in terms of radio frequency (RF) gain, RF noise figure and compression dynamic range (CDR). The numerical results show that the PM with interferometric detection can achieve better RF gain, RF noise figure and CDR than the optimum biased IMDD link as the laser output power is lower than 14.34, 12.45 and 4.2 dBm, respectively.

Complementary coding optical stealth transmission based on amplified spontaneous emission light source.

Complementary encoder of stealth signal is proposed and demonstrated for coding, modulating and enhancing the privacy of optical stealth transmission. With complementary encoding, the stealth signal carried by amplified spontaneous emission (ASE) light keeps the same characteristic to ASE noise and can be concealed well under public channel. The experiment results demonstrate the feasibility of the scheme and show the stealth signal has the same impact on public channel in transmission performance, compared to the ASE noise.

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.

ASE noise independent small signal modal gain measurements and mode imaging in double clad Nd³⁺- doped fiber around 900 nm.

The spatially and spectrally resolved mode imaging method (S²) and lock-in detection technique are combined to allow for low signal gain measurements in double clad, Nd³⁺- doped fiber in the spectral region of 900 nm. The combination of these methods gives us the opportunity to measure the low signal gain, without disruption of the result by the amplified spontaneous emission (ASE). Results of the modal gain measurements are compared to numerical calculations.

Performance Evaluation of Optically Preamplified PPM Systems With Dual-Polarized ASE Noise and Finite Extinction Ratios

Pulse position modulation (PPM) presents several advantages in free-space optical systems, unrepeatered fiber trans- mission, and passive optical networks. In this paper, we study the error performance in direct-detection optically preamplified M -ary PPM optical communication systems. We consider the impact of the amplifier spontaneous emission noise, as well of the finite extinction ratio of the transmitter, on the probability of bit error at the receiver. We derive expressions for the proba- bility of bit error under both assumptions of noise polarization, namely, single- and dual-polarized amplifier noise, and compute it numerically for different symbol sizes M and extinction ratios. In addition, we present the power penalty due to the transmitter finite extinction ratio for systems with and without forward error correction. Our findings show that, in the cases of practically achievable finite extinction ratios, systems with smaller M may perform equally well when compared to those using higher values of M. We also show that there is little benefit, if any, associated with using a polarization filter in the receiver since the additional size, weight, and power consumption requirements outweigh the error performance improvement.