Amplified Spontaneous Emission Noise Research Articles

Suppression of Gordon-haus effect and interaction of dark soliton by optical phase conjugation

The optical phase conjugation is put forward for the first time to suppress the Gordon-Haus effect caused by amplifier spontaneous emission noise, and soliton interaction in the dark soliton transmission system. The simulation results show : If the conjugator is sited at proper situation, it can suppress the Gordon-Haus effect or the dark soliton interaction effectively.

Noise of the stretched pulse fiber laser. I. Theory

A perturbation formalism is developed for the passively mode-locked stretched pulse fiber ring laser analogous to that of the fiber ring soliton laser. It is applied to determine the amplitude fluctuations, carrier frequency noise, and the pulse to pulse jitter due to the amplifier spontaneous emission noise.

BER performance of multiwavelength optical cross-connected networks with deflection routing

The transmission performance of regular two-connected multihop transparent optical networks in uniform traffic under hot-potato, single-buffer deflection routing schemes is presented. Manhattan Street Network (MS) and ShuffleNet (SN) are compared in terms of bit error rate (BER) and packet error rate (PER) both analytically and by simulation. The authors implement a novel strategy of analysis, in which the transmission performance evaluation is linked to the traffic randomness of the networks. Amplifier spontaneous emission (ASE) noise, and device-induced crosstalk severely limit the characteristics of the network, such as propagation distance, sustainable traffic and bit rate. The results indicate that under the same load the BER performance of single-buffer deflection routing is worse than hot-potato. However, at BER = 10-9 single-buffer has a higher throughput than hot-potato. It is shown that the feasibility of deflection routing in transparent networks with MS and SN topologies heavily depends on the power coupling coefficient of the routing space switch used in each node.

Performance analysis of an optical serial-to-parallel converter with erbium-doped fiber amplifier

In this paper, we develop a performance analysis of an surface-emitting second harmonic generation (SESHG) optical serial-to-parallel converter using an erbium-doped fiber amplifier (EDFA) as a preamplifier. The analysis is complicated by the fourth-order nonlinearity that acts on the signal plus amplified spontaneous emission (ASE) noise to create many beat noises at the binary decision device. However, we demonstrate that Gaussian approximation for the beat noise statistics is reasonable. We calculate the BER of the system as a function of the SHG nonlinear cross section (A/sup NL/), EDFA gain, the bandwidth of the optical filter that band-limits the ASE noise, and the timing pulse-to-data pulse power ratio. We find that for reasonable values of these and other parameters, the EDFA/SESHG serial-to-parallel converter combination should be able to operate at or below a BER of 10/sup -12/. We find that small increments (0-2 dB) in the signal power that is input to the EDFA are enough to compensate the effects of ASE noise for most of the parameter variations we consider. From this point of view, the ASE noise has little effect on system performance. However, when the input power is fixed, we show evidence in terms of BER that the ASE noise plays a significant role, particularly in the high A/sup NL/, high gain case. Also in this case, we show that the optimal timing pulse-to-data pulse power ratio is somewhat different from the value that is optimal for the system without an EDFA.

Elimination of all-optical cycles in wavelength-routed optical networks

A transparent (wide-area) wavelength-routed optical network may be constructed by using wavelength cross-connect switches connected together by fiber to form an arbitrary mesh structure. The network is accessed through electronic stations that are attached to some of these cross-connects. These wavelength cross-connect switches have the property that they may configure themselves into unspecified states. Each input port of a switch is always connected to some output port of the switch whether or not such a connection Is required for the purpose of information transfer. Due to the presence of these unspecified states, there exists the possibility of setting up unintended all-optical cycles in the network (viz., a loop with no terminating electronics in it). If such a cycle contains amplifiers [e.g., erbium-doped fiber amplifiers (EDFA's)], there exists the possibility that the net loop gain is greater than the net loop loss. The amplified spontaneous emission (ASE) noise from amplifiers can build up in such a feedback loop to saturate the amplifiers and result in oscillations of the ASE noise in the loop. Such all-optical cycles as defined above (and hereafter referred to as cycles) must be eliminated from an optical network in order for the network to perform any useful operation. Furthermore, for the realistic case in which the wavelength cross-connects result in signal crosstalk, there is a possibility of having closed cycles with oscillating crosstalk signals. We examine algorithms that set up new transparent optical connections upon request while avoiding the creation of such cycles in the network. These algorithms attempt to find a route for a connection and then (in a post-processing fashion) configure switches such that white cycles that might get created would automatically get eliminated. In addition, our call-set-up algorithms can avoid the possibility of crosstalk cycles.

Dynamic range and switching speed limitations of an N×N optical packet switch based on low-gain semiconductor optical amplifiers

Two important system performance limitations-dynamic range and switching speed-of an integrated packet switch fabric based on low-gain semiconductor optical amplifiers (SOA's) have been examined by using cascaded blocks of an SOA model, which includes transient effect, nonlinear pulse distortion effect, and amplified spontaneous emission (ASE) noise. Low-gain SOA's were used to minimize ASE noise considering that no optical filters can be integrated in an SOA-based switch fabric. The system performance with and without a narrowband optical filter at the receiver were both studied. By assuming fixed-wavelength transmitters and no optical filter can be used at the receiving end owing to the unpredictability of arriving packet wavelengths, our simulation results indicate that the dynamic ranges of 4/spl times/4 and 8/spl times/8 SOA-based packet switches at 2.5 Gb/s can only be about 3.2 and 0.8 dB, respectively. However, at 155 Mb/s, even without a receiving-end optical filter, the dynamic range of each switch size can be increased by more than 17 dB as compared to the cases of 2.5 Gb/s. Note that the dynamic ranges were estimated under the conditions of a bit error rate (BER) /spl les/10/sup -9/ and a pulse distortion ratio /spl les/30%. We have also shown that, when an optical filter with a 1 nm bandwidth was used at the receiving end to simulate (1) a circuit-switched condition where the center wavelength of the filter can be adjusted according to the established circuit, or (2) a packet-switched condition where each receiver has a wavelength demultiplexer and a detector array, the dynamic range of 4/spl times/4 and 8/spl times/8 switches can be increased to 16.3 and 14 dB, respectively, at 2.5 Gb/s.

Impact of Laser Linewidth on Performance of Pre-amplified Optical Direct Detection ASK and M-PPM Systems

A theoretical analysis of optical direct detection M-ary PPM and ASK is provided when an optical preamplifier is used to improve receiver sensitivity considering the effect of laser phase noise, amplifier's spontaneous emission noise and receiver noise. Computed results show that the performace of the system is highly degraded due to the effect of laser phase noise and ASE. The penalty suffered by the system is higher for higher amplifier gain and higher optical bandwidth. However, the effect can be reduced significantly by increasing the PPM order.

Complete statistical characterization of signal and noise in optically amplified fiber channels

A very simple model is found for phase insensitive laser amplification. Signal and noise along the active fiber are modeled as marked Poisson processes (corresponding to flows of photon bunches of random size) and are dealt with as independent processes. A probabilistic approach, founded on the theory of birth-and-death processes, enables us to give a simple characterization of the amplifier in terms of the statistics of the random gain, of the time intensity of the ASE (amplified spontaneous emission) noise bunches, and finally of the statistics of their sizes. The theory is limited to the linear amplification range, while is valid also for nonhomogeneous inversion along the active fiber. The model can be easily applied for the evaluation of the statistics of the global gain and of the accumulated ASE noise in optically amplified links.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Comparison of the performance of optical systems in fiber links 4000 km long

Abstract This article reports a numerical investigation of the performance of single-channel and WDM optical systems, assuming a fiber link 4000 km long in the presence of the Kerr effect, chromatic dispersion, and the amplifier spontaneous emission noise of the optical amplifiers. Both solitons and NRZ signals are considered, and IM-DD and coherent asynchronous ASK detections are used. Results on the technique of the midpoint spectral inversion are also reported.

Noise in optical amplifiers

Abstract This article presents an application of a recently published probablistic model for traveling wave optical amplification. Both optical signal and amplified spontaneous emission (ASE) noise are modeled as bunches of photons traveling along the amplifying region with size varying according to simple random rules. The results of the theory enable one to obtain a complete and accurate characterization of the signal and noise counting at the amplifier output. On the basis of the above statistics, we find a realistic evaluation of the limits imposed by both quantum and ASE noise on the performances of a receiver including an optical amplifier at a preamplifier stage.

Reduction of amplified spontaneous emission (ase) noise from transmitted soliton signals with a nonlinear amplifying optical loop mirror

AbstractSince the storage of the amplified spontaneous emission (ASE) noise of an amplifier is a cause for the degradation of the transmission characteristics in a long distance soliton transmission using an optical amplifier, the reduction of the ASE is a key issue to be solved for a soliton transmission. A new method to remove the ASE noise using the threshold characteristics (self switching) of a nonlinear amplification loop mirror (NALM) which utilizes the difference in intensity between the soliton signal and the ASE noise is presented in this paper and its application to a transmission experiment is discussed. First, the transmission characteristics of the NALM for a pulse signal are examined. It is demonstrated that the ASE noise can be successfully removed from the pulse signal of high level. The present method is applied to a soliton signal transmitted over 500 km at 10 Gbit/s. The ratio in intensity between the soliton signal and the ASE noise is improved when the NALM is used as compared to the case without it. Finally, it is shown that the switching of pulse close to the transform limit is possible when the phase difference of a pulse peak propagating in a nonlinear loop with a high gain optical amplifier is less than 0.3 π.

Performance of DPSK and CPFSK systems with significant post-detection filtering

A rigorous model for preamplifier implemented DPSK and CPFSK systems with delay-detection and postdetection filtering is presented. The system performance is impaired by amplifier spontaneous emission noise as well as laser phase noise. A best sensitivity for the system is 20 (DPSK) and 36 (CPFSK) received signal photons for a 10/sup -9/ bit error probability. It is found that, using the CPFSK system, significant amounts of phase noise can be tolerated provided that sufficient bandpass bandwidth is allocated and a large modulation index value is used. A linewidth as large as five times the bit rate causes only a 4.2-dB penalty for a receiver employing polarization control and a 5.3-dB penalty for a polarization diversity receiver. >

Fundamental limitations in EDFA-based subcarrier-multiplexed AM-VSB CATV systems

This paper presents and discusses fundamental limitations for EDFA-based subcarrier-multiplexed AM-VSB CATV distribution systems. The impairments we consider are fundamental, namely, shot noise, amplifier spontaneous emission noise, and laser, clipping-induced, nonlinear distortion. Treating the amplifier input signal power and pump power as resources, we obtain limits on the number of receivers to which we can deliver, say, 60 (or 80) channels at a carrier-to-noise ratio (CNR) of 55 dB (or 48 dB). Moreover, we present a simple approach that can be used to recalculate the results presented here for different system and amplifier fiber parameters.

The impact of optical amplifiers on long-distance lightwave telecommunications

The potential of erbium-doped fiber amplifiers (EDFA) and wavelength-division multiplexing (WDM) technology for expanding transmission capacity in long-distance telecommunications is examined. Properties of EDFA are nearly ideal for application in lightwave long-haul transmission. Nonlinear effects in the transmission fiber and amplifier spontaneous emission noise limit the performance and therefore dictate the design of long-distance amplified systems, especially those employing WDM. The next-generation transoceanic system will use EDFA as repeaters, yielding a capacity almost ten times larger than what is available today. Multichannel WDM soliton transmission promises further substantial enhancement. Terrestrial long-haul networks will also benefit greatly from amplified WDM systems designed to mine the large inherent bandwidth in the embedded fiber. The ten- to fifty-fold capacity increase over present systems not only will provide for ample growth, but also will enable network operators to enhance operational flexibility and network functionality, and to facilitate a fast-recovery self-healing capability through cost-effective redundant routing. >

Study of Heterodyne and Direct Detection Receivers with an Optical Preamplifier in Space Communications

In this paper, expressions for the noise figure (NF) of a free space optical balanced heterodyne receiver for FSK signalling scheme and direct detection receiver for OOK signalling scheme have been derived in presence of various sources of noise like receiver noise, background noise and optical amplifier spontaneous emission noise and their comparative study has been made

Heterodyne and optically implemented dual-filter FSK systems: comparison based on a rigorous theory

The performance of heterodyne and optically implemented dual-filter FSK systems are compared based on a new rigorous theory that accounts for noise correlation (due to nonorthogonal signaling), laser phase noise, receiver noise, and amplifier spontaneous emission noise. Ideally, the two implementations have the same sensitivity with and without polarization control. The results emphasize the practical tradeoff between the heterodyne implementation (where receiver noise means that a low modulation index gives the best sensitivity) and the optical one (where the difficulty in making high-quality narrowband optical filters means that a larger modulation index gives the best sensitivity).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Forward and backward Raman amplifications in coherent optical communication systems

Abstract This paper investigates the applications of the fiber Raman amplifier (FRA) in coherent optical communication systems. We present analytical expressions for the signal and amplified spontaneous emission (ASE) noise. The signal spectrum is found to be nearly unchanged by the Raman pumping while the ASE noise spectrum is much wider than the signal. The amplified signal and ASE noise powers are calculated and the achievable amplifier gain is presented. When the pumping source is identical, the forward and backward FRA's provide the same amplifier gain. However, the backward FRA exhibits better noise performance than the forward one.

Signal Enhancement by Optical Amplification in Autocorrelation Measurements

Abstract The effect of optical amplification on the signal-to-noise ratio of autocorrelation measurements has been investigated experimentally. A light signal containing correlation information was amplified by an inverted population (phase-insensitive) optical amplifier. The data clearly show that the amplification may either degrade or enhance a subsequent autocorrelation measurement, depending on the experimental conditions. In particular, enhancement is possible when the detector quantum efficiency is low, or its noise is high. However, when all the signal photons are already being detected with no extra noise, then any optical amplification will inevitably lead to degradation of the data quality, due to addition of amplified spontaneous emission noise (ASE) from the amplifier itself.

Modeling of gain in erbium-doped fiber amplifiers

An analytic method is described for fully characterizing the gain of an erbium-doped fiber amplifier (EDFA) that is based on easily measured monochromatic absorption data. The analytic expressions presented, which involve the solution of one transcendental equation, can predict signal gains and pump absorptions in an amplifier containing an arbitrary number of pumps and signals from arbitrary directions. The gain of an amplifier was measured over a range of more than 20 dB in both pump and signal powers. The measured theoretical results agreed to within 0.5 dB. Although the results described apply explicitly to EDFAs pumped in the 1480-nm region, they are also applicable to EDFAs pumped in the 980-nm region. The method is valid whenever the gain saturation by amplified spontaneous-emission noise can be neglected, which is typically the case for amplifiers with less than about 20 dB of gain.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Noise properties of a bidirectional optical fiber transmission system using Raman amplifers

Abstract Noise properties of a bidirectional optical fiber transmission system using Raman amplification are analyzed. Analytical expressions for both forward and backward amplified spontaneous emission (ASE) noise are established in terms of system parameters. The signal to ASE noise ratio (SNR) and the achievable repeater length are discussed. Based on the results, we find that there exist optimum pump and initial power levels for the maximum SNR and repeater spacing. The maximum system transmission length and accumulated ASE noise for a multiple‐amplifier system are calculated. A maximum system transmission length up to 5,000 km with 12 dB SNR is then predicted.