Method to improve the noise figure and saturation power in multicontact semiconductor optical amplifiers. The noise power from a simple load is equal to ktb, where k is boltzmanns constant, t is. Semiconductor optical amplifiers soas fiber raman and brillouin amplifiers rare earth doped fiber amplifiers erbium edfa 1500 nm, praseodymium pdfa 0 nm the most practical optical amplifiers to date include the soa and edfa types. Alan kost associate research professor of optical sciences, university of arizona. Yuksek, qi song and ozdal boyraz eecs department, university of california, irvine, 92697, email. Optical amplifiers are used to create laser guide stars which provide feedback to the adaptive optics control systems which dynamically adjust the shape of the mirrors in the largest astronomical telescopes. N0 looking at this equation, we need to minimize n0, which takes into account the. Optical amplifiers in order to transmit signals over long distances 100 km it is necessary to compensate for attenuation losses within the fiber.
Evaluation of edfa characteristics as key devices in longdistance, largecapacity transfers described in iec61290 and jisc6122 specifies the importance of gain and noise figure nf measurement items. Pdf noise figure improvement in semiconductor optical. Optical receiver tias must achieve a wide bandwidth, a low inputreferred noise current, and a reasonable gain to minimize the noise contribution of the subsequent stages. Friis introduced in 1944 the noise figure nf concept which characterized the degradation in signal. Theory and measurement techniques for the noise figure of optical. Definitions of noise figure are discussed along with applications of noise figure to circuits incorporating cascades of amplifiers and other optical and optoelectronic devices. His areas of research include optical data storage, optical communications, integrated optics, nanooptics. High noise figure and crosstalk levels due to nonlinear phenomenon such as 4 wave mixing. In part 2, it was mentioned already that most fiber amplifiers, e. Soas include highcoupling loss, polarization dependence, and a higher noise figure. Thus, gain and noise figure performance of an edfa given with its physical parameters can be graphically obtained or the required physical parameters of an edfa with desired operating performance can easily be optimised.
Two noise figure definitions for optical amplifiers are described that mesh with the ieee definition in the classical nonoptical regime. Noise analysis in operational amplifier circuits rev. The analysis technique for the nf characteristics of an soa is introduced in the literature 4. Request pdf theory and measurement techniques for the noise figure of optical amplifiers the theoretical basis for the noise figure of. Noise figure of highrepetitionrate optical parametric amplifiers in silicon xinzhu sang, enkuang tien, feng qian, nuh s. Raman amplifiers optimizing the noise figure becomes a challenge specially when change of the fiber length, attenuation, cladding and core index values are changed. Photonics and optical communication, spring 2005 dr. Noise figure and logarithmic amplifiers analog devices. The noise figure can be increased by excess losses at the amplifier. Apr 21, 2012 noise figure of cascade of two stages. An optical fiber amplifier is a fiber optic device used to amplify optical signals directly without conversion into electrical signals.
In steady state, dn2 dt 0, the ratio of level 1 and level 2 population to the total population can be written as. Optical amplifiers are used extensively in fiber optic data links. Consider a system with cascade of two gain stages having gains of, and with noise figure of and respectively. Noise figure nf measures of degradation of the signaltonoise ratio snr, caused by components, such as amplifiers, in an rf signal chain. The noise behavior of semiconductor laser or fiber amplifiers results from fig. Request pdf noise figure of optical amplifiers the implications of the heisenberg uncertainty principle for the optical amplifier noise figure are reexamined. Analysis techniques for soa characteristics analysis techniques for the nf and output power characteristics of an soa will be described in this section. Figure 1 semiconductor optical amplifier modern optical networks utilize soas in the follow ways. He came with ample prior experienceboth for this work and for his age. Noise figure of verticalcavity semiconductor optical. It can be shown, that the noise factor f remains unchanged, if the signaltonoise ratio are related to the electric power after the optoelectric conversion. Multiple communication devices, like optical transmitters and receivers, are used in optical fiber. An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. Fiber amplifiers as well as both traveling wave tw and fabryperot.
The noise performance of an optical amplifier is characterized by its noise figure nf, which is defined as the ratio of the signaltonoise ratio snr at the amplifier. By introducing an amplified spontaneous emission source as additional noise, two sets of experimental schemes are designed to measure noise figure characteristics of erbiumdoped fiber amplifier employed in an analog optical system. We measure the frequencyresolved noise figure of fiber optical parametric amplifiers both in phaseinsensitive and phasesensitive modes in the frequency range from 0. Two noise figure definitions for optical amplifiers are described that mesh with the ieee definition in the classical non optical regime. Electrical noise figure measurements are often thought of as. S represents the linear optical signal power and n is the linear optical noise power optical signal to noise ratio osnr db is the measure of the ratio of signal power to noise power in an optical channel. A numerical investigation on noise figure nf inside the silicon waveguides pumped. There, we have some signal reabsorption, which clearly increases the excess noise. Figure 1 shows three ways in which optical amplifiers can be used to enhance the performance of optical data links. Low price with high volume production disadvantages 1.
Flicker noise flicker noise is also called 1f noise. The purpose of the present paper is to present a consistent approach to modeling the noise figure of optical amplifiers and other optical components and to. The currently used noise figure definition for optical amplifiers is critiqued. Noise figure of verticalcavity semiconductor optical amplifiers. Optical fiber transmission has revolutionized networking and communication systems. This concept of a noise figure can also be applied to optical amplifiers 1 5, but it should be noted that not all definitions in the literature are the same. In addition to thermal noise, amplifiers or other devices with semiconductors also contribute to the total system noise. Eisenstein, noise sp ectra of semiconductor optical amplifiers. Noise figure is a number by which the noise performance of an amplifier or a radio receiver can be specified. It may be a preamplifier, mixer, or a complete receiver. Desurvire, on the physical origin of the 3db noise figure limit in laser and parametric optical amplifiers, opt.
Calculating noise figure in op amps introduction noise figure is commonly used in communications systems because it provides a simple method to determine the impact of system noise on sensitivity. Gain and noise figure performance of erbium doped fiber amplifiers edfa a. On the other hand, in a longdistance optical transmission system employing multiple inline optical. Invited paper theory and measurement techniques for the. Following the discussion on thermal noise and its modeling and noise figure computation for a simple resistor network, in this article let us discuss the noise figure of cascaded stages definition of noise figure. The noise figure number, displayed in decibels db, represents the performance by which an amplifier or rf receiver can. Invited paper theory and measurement techniques for the noise. Hausthe proper definition of noise figure of optical amplifiers conference on optical fiber communicationofc99, optical society of america, washington feb. Eindhoven university of technology master an optical amplifier. Mean value gaussian probability density function rms value noise signal 99. The noise figure of optical amplifiers has been extensively studied 815. Index terms amplifier noise, cascade systems, laser ampli fiers, measurement noise measurement, optical amplifiers, spon taneous emission. The noise figure number, displayed in decibels db, represents the performance by which an amplifier or rf receiver can be measured.
It can be shown, that the noise factor f remains unchanged, if the signaltonoise ratio are related to. Theory and measurement techniques for the noise figure of. Although simple, the topology of figure 3a faces several challenges. Noise figure improvement in semiconductor optical amplifiers. Erbiumdoped fiber amplifiers is exarnined, and furthermore an account of the measurements of absorption and fluorescence spectra, amplification and noise figures is given. Boosting of an optical signal without any conversion of. Noise figure nf measures of degradation of the signalto noise ratio snr, caused by components, such as amplifiers, in an rf signal chain.
Alan kost is an associate research professor of optical sciences in the university of arizona. Essentially the noise figure defines the amount of noise an element adds to the overall system. On the other hand, in a longdistance optical transmission system employing multiple inline optical amplifiers, the level of optical. Osa the proper definition of noise figure of optical amplifiers.
Noise figure of optical amplifiers request pdf researchgate. High noise figure and crosstalk levels due to nonlinear phenomenon such as 4wave mixing. Friis introduced in 1944 the noise figure nf concept which characterized the degradation in signal to noise ratio snr by the receiver. Haus, the noise figure of optical amplifiers, ieee photonics technology letters, vol. Another important purpose of the noise figure is to characterize the amount of ase produced by the amplifier, because the ase tends to accumulate in the communcation system. An important result of quantum optics 1 is that a phaseinsensitive highgain optical amplifier has a noise figure of at least 3 db. Boosting of an optical signal without any conversion of the. It is the ratio of the signaltonoise ratio at the input of the amplifier to the signaltonoise ratio at the output of the amplifier. Noise figure improvement in semiconductor optical amplifiers by holding beam at transparency scheme. Frequencyresolved noise figure measurements of phase in. Rp photonics encyclopedia noise figure, quantum noise. The amplified spontaneous emission ase, is regarded as noise in the optical amplifiers and considered as an average in both polarizations. The impacts of the signal power and the signal to noise ratio on the noise figure are systematically measured.
In the systems discussed earlier, optical noise is not accompanied with the optical signal that reaches the optical receiver, and therefore, ber can be reduced by increasing the level of signal optical power. Optical amplifiers, edfa, erbium doped fiber, gain, noise figure 1. Figure 1 illustrates the basics of a semiconductor optical amplifier. Noise figure nf and noise factor f are measures of degradation of the signalto noise ratio snr, caused by components in a signal chain. Rongqing hui, in introduction to fiberoptic communications, 2020. Leif was about thirty, well before the turn of the century, he joined analog devices as an ic designer. Gain, noise figure and forward ase spectrum of a forwardpumped erbiumdoped fiber amplifier. The noise performance of an optical amplifier is characterized by its noise figure nf, which is defined as the ratio of the signaltonoise ratio snr at the amplifier output. This makes the noise figure one of the most important properties of optical amplifiers for their applications in optical communication systems. Thorlabs praseodymiumdoped fiber amplifier pdfa offers high gain 20 db small signal gain, high output power 16 dbm, and a low noise figure s contribution to the overall noise in the system. The noise power at the output of the first stage is the sum of. Types of noise noise analysis in operational amplifier circuits 3 the terms 4ktr and 4ktr are voltage and current power densities having units of v2hz and a2hz. Request pdf noise figure of optical amplifiers the implications of the heisenberg uncertainty principle for the optical amplifier noise figure are re examined.
We also measure the variation in noise figure due to the degradation in pump optical signal to noise ratio and also as a function of the input signal powers. From the last lecture, remember the general expression for the optical amplifier noise figure, fn. This limit can be reached for a fourlevel laser amplifier, a nondegenerate optical parametric amplifier, or a raman amplifier, whereas quasithreelevel amplifiers have higher noise figures. It is a number by which the performance of an amplifier or a radio receiver can be specified, with lower values indicating better performance. The gain for an optical amplifier is defined by the equation. Semiconductor optical amplifiers with low noise figure.
Rp photonics encyclopedia tutorial fiber amplifiers, part. As an example, we consider an erbiumdoped fiber amplifier, as it could be used in optical fiber communications, e. Noise figure and logarithmic amplifiers the wit and wisdom of dr. The noise figure is the difference in decibels db between the noise output of the actual receiver to the noise output of an ideal receiver with the same overall gain and bandwidth when the receivers are connected to matched sources at the standard noise temperature t 0 usually 290 k. Soa noise figure the noise figure expression for an soa is pretty simple. Today, the performance of wideband op amps is making them viable alternatives to more traditional openloop amplifiers like monolithic microwave. A booster amplifier is used to increase the optical output of an optical transmitter just before the. Rp photonics encyclopedia tutorial fiber amplifiers. Noise figure to characterize the receiver alone, harald t. Method to improve the noise figure and saturation power in. The noise figure of optical amplifiers ieee xplore. In principle, the noise figure of an optical amplifier can be measured electrically or optically.
The proper definition of noise figure of optical amplifiers. Figure 1 shows graphically how the probability of the amplitude relates to the rms value. New pumping methods and materials are also improving the performance of raman amplifiers. Analysis and characterization of semiconductor optical amplifiers. We examine the concept of optical noise figure in to twoport devices.
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