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Fiber-based optical amplifiers such as the erbium-doped fiber amplifier(EDFA) and Raman fiber amplifier (RFA) offer the attraction of high gain, low coupling loss and polarization insensitivity. Hence their use in combination to form a nonregenerative repeater(NRR) deserves consideration. This paper provides a theoretical analysis and gain optimization for this form of NRR. This arrangement is found to provide higher gain than either an EDFA or a RFA repeater alone and offer the potential of extending the NRR span to over 300 km., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p284 thru p287.

Er-doped fiber amplifiers(EDFAs) are very attractive for applications to the near-future optical communication systems. High output power of +20 dBm was already reported by using 1.48 um pump LD modules2. Increasing the signal output power from EDFA will be one of the important issues for such uses as the booster amplifiers in long-haul transmission systems and in optical distribution network systems. In this paper, we report on development of an EDFA with signal output power more than +22 dBm by using high power 1.48 um pump LDs and integrating passive optical components. In addition, the components of the EDFA including an Er-doped fiber bobbin are installed in a small package to put it into practical use.

Er-doped fiber amplifiers (EDFA's) may find many potential application in optical networks due to their high gain, polarization insensitivity, low noise and immunity to cross-talk. They are especially useful in overcoming splitting losses in multiple access networks. Due to the very long 4I13/2 lifetime of Er3+, fast gain switching, which would be needed for packet switching for instance, is not possible with EDFA's. To direct traffic flow, however, slow gain switching schemes for EDFA's may still be very useful. The purpose of this letter is to demonstrate an optical feedback scheme, which allows remote switching of the gain, all-optically over the transmission fiber without the need for any electrical or mechanical control device., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p284 thru p287.

EDFA gain control is achieved by detecting the spontaneous emission power radiated along the EDF and modulating the pump LDs with optoelectronic feedback., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p276 thru p279.

Residual pump light emitted from an optical fibre amplifier can be a problem in a telecommunication system. The performance of a receiver can be adversely affected by the residual pump power emitted from a pre-amplifier, which is usually larger than the signal power, because it can cause excess noise and receiver saturation. A pre-amplifier which is designed for optimum gain and minimum noise figure will therefore have a large emission of unabsorbed pump light. If the unabsorbed pump light can be reflected back into the amplifier then the amplifier performance will be increased and the receiver will be free from pump light. We show for the first time how this can be achieved with an efficient wavelength dependent fibre reflection filter., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p144 thru p147.

Improved performance of EDFAs is achieved using wavelength-selective reflective filters to double-pass the pump beam. In low-gain amplifiers these filters can increase the saturation output power by 2 dB or reduce the pump power requirements.

Recently, distributed Er-doped fiber amplifiers have become of great interest. Intrinsic fiber loss can be compensated by the distributed gain. As a result, a fiber which is free from the attenuation can be realized. Due to its small gain, the distributed EDFA also has the advantage of low amplified spontaneous emission(ASE). Moreover, no isolator to prevent lasing is necessary, so bi-directional transmission is possible. This kind of fiber is also applicable to soliton transmission. In this paper, we describe a design of lengthwise-distribution of Er-concentration for long length attenuation-free fibers. An attenuation-free length of 73.6km has been realized at the signal level of -10dBm.

In a ultra-long system with cascaded erbium-doped fiber amplifiers(1) (EDFAs), in order to keep a signal-to-noise ratio (SNR) as high as possible, EDFA(2) having high output power and low noise is highly required as a post-amplifier or as an in-line-amplifier. Such an EDFA is also important for optical pre-amplifiers with large dynamic ranges. Although Way et al. reported a low noise figure (NF) in a saturation region under the condition of sufficiently high pump power(3), the relationship between lowering the NF and optimizing the gain of EDFA was not clear. In this paper, we report that an EDFA having both a high output power (+15dBm) and a low NF (6dB) can actually be realized using 1.48um pump LDs when the EDFA length is optimized to give a maximum gain for large signal power. In addition, we also show that there is a remarkable difference between forward and backward pump in terms of NF characteristics of EDFA in a deep saturation., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13, AD-A252 974, p174 thru 177.

Fiber offers an extremely favorable geometry for optical devices, and fiber lasers (1) and amplifiers 21 were reported only shortly after the first bulk glass laser 3. The choice of host composition has always been an important consideration. Silicates are the oldest and best understood glasses, and the first glass lasers used silicate compositions selected for high rare earth solubility and long lifetimes for the metastable state. The use of phosphate glass significantly improved the performance of early bulk Er3+ lasers (4) and it has become the most common host for bulk glass lasers doped with Er3+ and Nd3+. Although outstanding performance has been achieved using single-mode silica fiber, silica is a poor host for most activator ions, particularly rare earths. The influence of glass composition on the properties of Er3+ fiber amplifiers will be considered with particular emphasis placed upon silica; a more detailed discussion can be found in Ref. 5., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p-44 thru p-47.

Rapid progress in strained quantum well InGaAs/AlGaAs laser diodes has led to the wide acceptance of 980 nm diodes as potential pump sources for Er3+-doped fiber amplifiers (EDFA). In particular, ridge waveguides have proven to be ideal structures for such devices (1,21) promising ease of manufacture, and potentially high reliability. In this paper, we report high coupled power from ridge waveguide lasers into large NA single-mode fiber designed for use in EDFA systems, using an industry-standard 14-pin DIL package outline. We also report systems performance obtained using these lasers as the pump source in a broad-band EDFA power amplifier. The epitaxial structure is a graded-index separate confinement heterostructure, grown in a low pressure MOCVD reactor. A single quantum well was employed, using a strained InGaAs layer whose composition and thickness were engineered to provide lasing at a wavelength of 980 nm. The threshold current density, measured on a 50 Jim oxide stripe structure with 500 um cavity length, was 272Acm-2.

High-power semiconductor lasers emitting at 1.48um wavelength have been increasingly important as pumping light sources for Er3+-doped fiber amplifiers 1, 2. In this paper we report high power operation of 1.48 um GaInAsP/GaInAsP multiple quantum well (MQW) lasers which utilize strained-layer MQW structures as active layers.

In this paper, we present an analysis of unsaturated erbium-doped fiber amplifiers (EDFA) with fiber back-ground loss and bidirectional pumping. This analysis provides an exact, closed-form expression for the amplifier gain as a function of input pump power. This model is useful to study distributed EDFA's 1,2 and to determine the optimal Er3+ concentration and pumping configuration that minimizes the required pump power, as shown in this paper. In the case of forward pumping, it is also shown that a simple relation exists between the input pump power required for EDFA transparency and pump threshold, which can be usefully applied to EDFA characterization., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p152 thru p155.

The development of erbium-doped fiber amplifiers has recently progressed rapidly. Highly efficient power conversion for 1.48um wavelength pumping enables a post-amplifier to achieve output power greater than lOOmW1). When pumped in 0.98um wavelength, the erbium-doped fiber amplifiers showed very low noise property'), which permits high receiver sensitivity as a preamplifier. High power laser diodes (LDs), operating at 1.48um and 0.98um wavelength, are essential as pumping light sources. Recently, multi-quantum well (MQW) structures have been employed as active layers for 1.48um wavelength LDs3). We have obtained the highest cw output power reported so far, 25OmW4). Lasing at 0.98um wavelength was achieved with InGaAs strained quantum well structures grown on GaAs substrates5). Low internal absorption loss helped these devices to emit 24OmW cw power6). This paper reports recent progress in the development of 1.48um and 0.98um wavelength high power LDs for erbium-doped fiber amplifiers., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p22 thru 25.

Erbium-doped fiber amplifiers(EDFAs) are very attractive devices for single-mode fiber communication systems operating In the 1.55 p m wavelength band. (1) The main advantages of EDFAs are polarization-Insensitive high gain, high amplification efficiency, low Insertion loss, low noise and wide bandwidth. (2) There are two Important parameters to evaluate EDFA's performance; an energy conversion efficiency and a gain coefficient. In this paper, we report an extremely high efficiency EDFA with a slope efficiency of 86% and a gain coefficient of 6.3dB/mW at 1.48 p m by increasing the numerical aperture(NA) of the erbium-doped fiber and concentrating the dope Er3+ Ions near the center of the core. (3) (4) Both are the highest values reported to-date for EDFAs pumped at 1.48 um., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p166 thru p169.

There has been a growing awareness of the importance of Er3+-doped fibers as power amplifiers in many applications including wavelength- and frequency-multiplexed systems as well as distribution systems with large fanouts 1. This is a consequence of their excellent behavior under highly saturated conditions: immunity to crosstalk and high signal output powers. The characteristics of fiber power amplifiers, however, have not been extensively investigated. Relevant parameters include the operational configuration (forward, backward or bidirectional pumping), the signal and pump wavelength, fiber composition, fiber index and Er3+-doping profile. Due to the high cost of pump lasers and their limited power, the paramount consideration for a power amplifier is efficiency. The signal-to-noise ratio is also of importance, particularly in analog applications such as the AM-VSB systems now favored for video distribution 2. We have investigated both these properties using an accurate numerical model and measured input parameters. The optimum waveguides have been determined for both 980 nm and 1480 nm pumping, and the effects of confined Er3+-doping have also been elucidated., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p170 thru 173.

Though erbium-doped fiber amplifiers (EDFA) are very attractive candidates for optical transmissions, one of their important characteristics is the noise properties. These amplifiers generate low noise levels and corresponding noise figures are close to the quantum limit1,2. However, a number of applications, such as CATV and transoceanic links, will be highly sensitive to excess noise above this limit. Up to now, noise figures have been experimentally 1,3,4 and theoretically studied in several conditions, such as small-signal or highly-pumped amplifiers2,5. But when looking at the behavior of the noise figure in various signal regimes as a function of the amplifier working point, important variations appear 6. This indicates a highly complex reciprocal influence of the different propagating beams through the amplifying medium. In this paper, we study the noise properties of the EDFA, especially in the transition from small-signal regimes to saturated gain ones. Theoretical results are shown to explain experimental observations., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p162 thru p165.

Erbium doped fiber amplifiers(EDFAs) with high output power and no distortion degradation are very useful for the amplitude-modulated vestigial-sideband(AM-VSB) transmission systems which require a relatively high received power for a preferred carrier to noise ratio(CNR) and a low distortion (1) (2). A field trial was conducted and feasibility of multi-distribution for trunk lines was confirmed(3). We have developed an erbium doped fiber with a high conversion efficiency of 86 % and a small wavelength dependence. In this paper, by using this fiber as a post amplifier, we present a high power and low noise transmitter with monitoring functions for practical use. We also show the effectiveness of long-wavelength-pass filters which have a low insertion loss and no need for wavelength tuning unlike band-pass filters., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p214 thru p217.

Recently, Nd3+-doped fluoride fiber has attracted much interest, because it has the potential for optical amplification around the 1.3 um communication band. In terms of the effect of ESA(excited state absorption) and the probability of radiative transition, fluoride fiber is preferable to silica fiber as a host glass. However, some problems must be solved for the development of a practical amplifier. First, gain has not been sufficiently large for a practical pump power to be obtained from diode lasers. Second, gain has been obtained in wavelengths longer than 1.31 um. In this report, we focus on the first problem. This work reports that a gain of 10 dB was obtained by using bidirectional 25 mW pumpings and by applying a 1.05 um rejection filter in doped fiber., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p16 thru 19.

Erbium-doped optical fiber amplifiers (EDFA) pumped by 0.98-um laser diodes exhibit a small noise figure (1) and small temperature-induced variation in amplification compared with pumping by 1.47-um laser diodes (2). Recently, considerable research interest has focused on 0.98-um laser diodes (3)-(8). For practical application of EDFAs, however, optical power coupled to a single-mode fiber (SMF) is the key issue, a subject that few studies have addressed. In order to obtain high optical power in a SMF, we have improved the mode field emitted from lasers. Employing narrow-ridge waveguide lasers, we have sought to realize transverse lateral mode stabilization. We have also investigated epitaxial layer structures to enlarge optical spots for stabilizing the mode field and also for decreasing the vertical beam divergence. Aging test results are also described., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p-26 thru p-29.

Erbium-doped fiber amplifiers (EDFAs) are attractive for various optical fiber transmission systems and networks owing to their several advantages such as high gain and low noise. A EDFA with its high output saturation power and wide gain profile is specially suitable for wavelength-division multiplexing (WDM) applications such as multichannel CATV distribution systems 1. In these applications, the EDFA is normally used as a post (or a booster) amplifier and operates at a saturated region. Although it has been demonstrated that the EDFA is immune to patterning effects and interchannel interference, and has low gain saturation induced crosstalk 2, 3, there is little information about effects of wavelength spacing and fiber length in a saturated EDFA for multichannel applications. In this paper, we report the experimental results on wavelength and fiber length dependence of gain for saturated EDFAs in a two-channel amplification system. The experimental results show that when an EDFA operates at the saturated region in a multichannel system, a shorter fiber length than that in single-channel should be selected to get a flat gain profile, and that the Ge/Al/Er-doped silica fiber is desirable for multichannel amplification use since a gain hole-burning is observed for the Ge/Er-doped silica fiber., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p108 thru p111

Recent experiments have reported the amplification of femtosecond solitons in erbium doped optical fibers. Whenever the spectral width of the soliton is as wide as the linewidth of the amplifier, the gain that is seen by the pulse is reduced with respect to that of a weak continuous wave signal. However, it has been observed that the pulse width remains virtually unchanged, at least over some initial stage of the amplification process. Physically, this is due to the fact that the pulse shape is determined by two competing effects. From one side, the amplified pulse tends to remain a soliton and therefore to compress its time width. On the other hand, the finite spectral width of the gain leads to preferential amplification of the central part of the pulse spectrum and this would lead to pulse broadening. If these two effects balance each other, the output pulse width may remain almost undistorted. This compensation is however an unstable phenomenon., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p121 thru p123.

Cross saturation characteristics are investigated in broadband 1.48 micron pumped and 980nm pumped, gain-shaped EDFAs. Gain-shaping is shown to give a more uniform spectral gain compression on saturation. In addition room temperature spectral gain hole-burning is observed for the first time., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p104-107.

We report the measurement of non-linear excited state absorption (ESA) in Er 3+ doped fibres pumped at 980nm. The implications for high-power high-gain amplifiers are discussed.

The recent rapid development of Erbium doped fibre amplifiers with high gains, high saturation powers and low noise figures 1,2 has deflected the attention of system engineers from the older semiconductor technology 3 and it is thus now hard to find new published papers which use semiconductor amplifiers in a system context. Device development has not ceased however 4 and the performance of semiconductor amplifiers has improved considerably. In addition there are important applications for which doped fibre amplifiers are not suitable at present e.g. at 1.3 um, and others for which they will never be suitable, e.g. as fast optical switches. This presentation attempts to review these possibilities for future practical application of semiconductor optical amplifiers in the light of the recent developments of the technology., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p-66 thru p-67.

The performance of fiber amplifiers is extremely sensitive to the material-dependent properties of the pump band. High-power, reliable, low-cost diode lasers are currently only available at 800 nm, a poor pump band for Er3+ due to the low strength of the ground state absorption (GSA) transition and an intense, overlapping excited state absorption (ESA) band. High gains have been achieved with silica fibers by pumping the long-wavelength wing of the GSA band at =820 nm 1,2, thereby avoiding the ESA at shorter wavelengths but introducing another problem by reducing the already low GSA cross section at the pump wavelength. Alternatively, the use of other glass host compositions with reduced ESA has been proposed 3. We have examined both approaches using experimentally determined parameters in a highly quantitative numerical model to compare the performance of Al/P-silica, Ge/P-silica, and fluorophosphate fiber amplifiers. The analysis was performed for co- and bi-directional pumping and included treatments of waveguide design, Er3+ confinement, pump-wavelength dependence of gain and noise figure, and quantum conversion efficiency for power amplifiers., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p-56 thru p-59.

Recently, we reported the results of a 2.4 Gb/s and 5 Gb/s feasibility demonstration of long distance erbium-doped fiber amplifier (EDFA) transmission systems using a circulating loop.1 The significance of this experiment was threefold. First, it demonstrated that high bit rate all-optical EDFA transmission systems are capable of achieving transoceanic distances. Second, it demonstrated a new measurement technique in which bit-error-rate (BER) is measured in a circulating loop. And, third, it achieved a new record in bit rate distance products. In this paper, we expand on the previously reported results by giving details of the experiment along with new transmission results. At 2.4 Gb/s and 9000 km, we have found that the transmitter's wavelength could be tuned over a 2 nm region while maintaining low BER. In addition, at 2.4 Gb/s we have measured a BER of 10-9 at 16,000 km, using a transmitter with direct laser modulation., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p94-97.

Some experiments have already been presented for long haul transmission using in-line Erbium-Doped Fiber, Amplifiers (EDFA) 1,2. However, the question is to determine the actual system limitations for transoceanic links (up to 10,000 km), such as EDFA maximum output power, amplifier spacing, optical filter design. Some theoretical 3 and experimental 41 works have been published mainly with a recirculating loop. A specific problem is to predict the evolution of signal and Amplified Spontaneous Emission (ASE) powers along the link. To our knowledge, the calculations published so far have assumed that an optical filter was set after each amplifier. In this case, the cascaded EDFA behavior can be described by scalar values without spectral dependence, and an analytical calculation is possible. In order to predict the cascaded EDFA behavior in a more general case, spectral characteristics have to be considered, especially if there is no optical filter after each amplifier. The subject of this paper is to examine these specific aspects without taking into account the dispersive and non linear effects. Calculations for very long links are presented along with an experimental validation of the modeling.

In the future optical transmission systems, it is likely that Erbium doped fiber optical amplifiers will replace present electrical regenerators. Both experimental studies (1, 2) and computer simulations (3-5) have investigated the feasability of non-regenerated optical long haul systems. A considerable number of parameters are determining the overall performances of the transmission link. In this paper, we report on theoretical studies carried out using numerical simulations in order to investigate the limits of such systems. We have considered both cases of 5 Gbit/s and 10 Gbit/s transmission. The theoretical limit value of the amplifier spacing, as imposed by group velocity dispersion (GVD), self phase modulation (SPM) and accumulated amplified spontaneous emission (ASE) has been evaluated.

Laser diode pumped Erbium doped fiber amplifiers (EDFA) with low noise figures and high saturation powers are attractive because the ratio between the saturation power and the noise figure can be considered as a figure of merit for several applications. These include multichannel receivers where high sensitivity and high saturation power increases the number of channels to be received and in-line applications where the dynamic range is proportional to the above mentioned figure of merit. For 980 nm pumping the noise figure can reach the quantum limit of 3 dB 2, whereas the minimum noise figure obtainable with 1480 nm pumping is approximately 5 dB 3. However, pumping at 1480 nm has the advantage of a better pump-to-signal conversion efficiency at high signal power levels leading to a higher saturation power compared to that achieved with 980 nm pumping 4. Here we demonstrate that the advantages of the two pump wavelengths can be combined by pumping co-directionally at 980 nm and counter-directionally at 1480 nm. With this configuration the input end of the EDFA can be considered as a low noise preamplifier which determines the overall noise figure while the rear end serves as an efficient power amplifier.

Long distance transmission using a chain of optical amplifiers is potentially much cheaper and faster than with conventional electronic regenerators. Erbium doped fiber amplifiers, with their low pump-power requirements, lack of pulse chirping, independence of gain on polarization, built in automatic gain control, and perfect compatibility with transmission fibers, have done much to make this all-optical approach truly practical. It can be shown, however, that the full capacity of such a system can be realized only by using solitons. Solitons can be transmitted perfectly well through a chain of low gain amplifiers and dispersion shifted fiber segments, as long as the characteristic dispersion distance, (2/Pi) zo, is great enough with respect to the amplifier spacing 1. For such transmission, it is necessary only to make the path-average power over each amplification period equal to the usual soliton power in lossless fiber. We have verified this point experimentally 2,3 over paths as great as 12,000 km and at pulse rates to 2.5 Gbits/s by using the recirculating loop shown in Fig. 1. In all cases, broadening of the -50 ps pulse train can be explained almost entirely by a modest jitter in pulse arrival times from the GordonHaus effect 4; furthermore, at about 5000 or 6000 km, the pulse shapes look more nearly text book perfect than they do at the beginning., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p98 thru p101.

One of the key parameters for optimizing erbium-doped fiber amplifiers (EDFAs) is the Er3 -concentration profile. Below the concentration for onset of component clustering, up-conversion may play a significant role 1. Recent experiments have shown that up-conversion is a considerable deteriorating mechanism even below an erbium concentration of 1000 ppm by weight 2,3. In this paper, we have made an extensive study of eight different fibers in order to examine the up-conversion as a function of erbium concentration below 1000 ppm by weight. From these experiments and a computer model of up-conversion, we have been able to estimate the up-conversion coefficient used in our rate-equation model. These results are necessary for accurately modelling EDFAs with erbium concentrations down to approximately 100 ppm by weight and for erbium profile optimizations., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p-52 thru p-55.

The use of fiber amplifiers in future lightwave systems now appears certain. Many experiments have been published demonstrating both the long-distance and multi-channel capability of fiber amplifier-based systems. Most experiments have used conventional on direct detection systems but some experiments, including a record transmission distance experiment, have used coherent detection systems and models of both systems have been developed. This paper will compare the two systems under the same conditions using both experiments and models. We will emphasize a practical comparison by using a direct detection regenerator from AT and T's commercial, 1.7 Gb/s system and a shelf-mounted, coherent detection regenerator from a recent AT and T field trial. We will also emphasize a direct comparison by using transmitters of the same wavelength and identical optical paths including erbium-doped fiber amplifiers., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p187 thru p191.

The capability of a very long-distance transmission using erbium-doped fiber amplifiers (EDFAs) has been demonstrated by using a circulating loop.1,2 In a single-carrier long-distance fiber transmission system, the signal wavelength will usually be tuned to the zero dispersion wavelength of the fiber to avoid the pulse waveform distortion due to chromatic dispersion. It has also been reported that when the signal wavelength is located exactly at the zero dispersion wavelength, the mixing of the signal with the spontaneous emission from the optical amplifiers will produce fourwave mixing sidebands.3 However, in the practical systems, the fiber chromatic dispersion varies along the long transmission path and may alleviate the effect of the four-wave mixing.3 We have investigated the effect of the dispersion variations on long-distance optical amplifiers transmission by numerical simulations. The results show that variation of the fiber dispersion well maintain the signal quality. In addition, this consequence was confirmed by a circulating loop experiment including the fibers with +/- 1ps/km/nm dispersion., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p90 thru p93.

The performance, of an amplifier cascade system is taken to be the product of transmission bit rate, B, and transmission distance, L. In amplifier cascade systems using the IM/DD scheme, signal spontaneous beat noise, spontaneous-spontaneous beat noise and shot noise are present in addition to receiver thermal noise, while local oscillator shot noise and local oscillator-spontaneous beat noise are additional factors in coherent systems. Signal-spontaneous and spontaneous-spontaneous beat noises generally predominate in IM/DD systems if many cascaded amplifiers are used. Conversely, in coherent systems, local oscillator-spontaneous beat noise predominates. In such cases, system performance is approximated by B X L = fmod(SNR, /) X (PS/NF), where fmod(SNR, /) is a function of required SNR and amplifier spacing, /, depending on the mod/demod scheme, Ps is the amplifier output power, and NF is the amplifier noise figure. Therefore, the system performance depends on amplifier spacing and amplifier performance given as PS/NF. As the spacing decreases and/or amplifier performance increases, system performance increases. However, it is limited by four conditions: (1) Fiber dispersion, (2) Amplifier performance, (3) Noise accumulation, and (4) No cascaded amplifier., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p-78 thru p-81.

Recent progress on erbium-doped fiber amplifiers (EDFAs) and their application to optical communications has been very rapid since the EDFA has many advantages such as polarisation-insensitive high gain, a low noise-figure, and low insertion loss.1 It is well known that in order to obtain a broader and relatively flatter gain profile, Aluminum (AI203) is co-doped into the core of the fibers.2,3 To make a wavelength independent flat gain profile is very important from the viewpoint of ultrashort pulse amplification and wavelength division multiplexing technique. Payne and Laming investigated a Borolanthanate co-doped EDFA.4 Although LaF3 or La2O3 were used as hosts for Nd ions5-7, detailed gain characteristics of a Lanthanum co-doped Er/SiO2 fiber amplifier have not yet been clarified. In this paper, we describe for the first time the detailed gain characteristics of a Lanthanum (La) co-doped EDFA and compare then with those of Al codoped and non co-doped EDFAs., This article is from 'OSA Proceedings of the Topical Meeting on Optical Amplifiers and their Applications Held in Snowmass Village, Colorado on 24-26 July 1991. Volume 13,' AD-A252 974, p-60 thru p-63.

This report updates Naval Ocean Systems Center TR 1185, 104-km Unrepeatered Bidirectional Fiber-Optic Demonstration Link, May 1987. Provided are discussions on improvements made to the original demonstration system. These include enhanced receiver sensitivities, increased laser-transmitter optical power outputs, refined operation of the PFM and Manchester encoding subsystems, and reduced splice losses. Also discussed is the emerging technology of fiber amplifiers that promise to significantly extend the repeaterless distance beyond the present range., Update to Rept. no. NOSC/TR-1185, AD-A190 282.

This work shows the generation of an array of chirped compressed periodic waves with distributed gain in a nonlinear fibre. In particular, with suitable tailoring of the gain to vary along the longitudinal distance while the dispersion and nonlinearity parameters are kept constant. Exact analytical equations using the self-similar analysis technique were obtained to describe this process. In addition, the stability of these generated periodic waves is studied under finite perturbations.

Thesis (Ph. D.)--University of Rochester. The Institute of Optics, 2019., This thesis explores enhancements of nonlinear effects in optical fibers through gain, dual pumping, and decreasing dispersion. The emphasis is in supercontinuum and frequency comb generation applications. The study is based on numerical simulations of the nonlinear light propagation equation. It is shown that a soliton propagating in an active fiber leads to the emergence of a cascade of solitons at the fiber output. Dual-pumping together with decreasing dispersion is shown to be a feasible platform for frequency comb and supercontinuum generation as well as for creating trains of ultrashort pulses with repetition rates in the THz regime. Temporal reflections are recognized as a spectral broadening mechanism in dual-pumped supercontinuum generation, and dispersive wave emission is shown to be a special case of the more general phenomenon of temporal reflections. The effects of various key parameters, such as third-order dispersion, on the resulting spectra and time domain dynamics are detailed.

This work shows the generation of an array of chirped compressed periodic waves with distributed gain in a nonlinear fibre. In particular, with suitable tailoring of the gain to vary along the longitudinal distance while the dispersion and nonlinearity parameters are kept constant. Exact analytical equations using the self-similar analysis technique were obtained to describe this process. In addition, the stability of these generated periodic waves is studied under finite perturbations.