bluuebunny/crossref_metadata_2025 huggingface dataset:
1.7 Gb/s - 419km Transmission Experiment Using a Shelf-Mounted FSK Coherent System and Packaged Fiber Amplifier Modules
Authors: Park Y. K. , Delavaux J-M. P. , Tench R. E. , Cline T. W.
Published: February 2023

The use of Erbium Doped Fiber Amplifiers (EDFAs) as in-line optical repeaters allows significantly increased fiber transmission distance. Coherent detection schemes can further enhance this fiber amplifier capability because coherent detection offers high receiver sensitivity and narrow IF (Intermediate Frequency) filtering function. Recent experimental results have clearly demonstrated the advantages of combining fiber amplifier technology and coherent systems in long distance transmission applications.1,2,3 However, in order to determine commercial viability, the experiments using robustly packaged modules are essential.
Long-span IM/DD Transmission System Experiment using High-efficiency EDF Amplifiers
Authors: Aida Kazuo , Masuda Hiroji , Takada Atushi
Published: February 2023

The combination of an EDF booster amplifier and pre-amplifier allows 1.8Gb/s 308km non-repeatered transmission with a repeater gain of 55dB, by using non-dispersion shifted fibers.
Observation of Cross Phase Modulation in a Semiconductor Laser Amplifier near 1.3 um
Authors: Dijaili S.P. , Wiesenfeld J.M. , Raybon G. , Burrus C.A. , Smith J.S. , Dienes A. , Whinnery J.R.
Published: February 2023

Self phase modulation in optical amplifiers has been theoretically and experimentally studied [1]. The self phase modulation is due to the dynamic change in the carrier density resulting from gain saturation that occurs in the amplifier. It is possible to obtain phase modulation of another beam (signal beam) that differs in frequency or in polarization with respect to the beam that experiences gain saturation (pump beam). This situation is referred to as cross phase modulation in an amplifying medium; that is to say, the intensity of a strong pulse affects the phase of a weaker pulse. Cross phase modulation due to the Kerr effect in nonlinear media such as glass and liquids has been reported [2] and was referred to as induced phase modulation. In this paper we report the observation of cross phase modulation in a semiconductor laser amplifier. It was the intent of the authors to begin research on a potentially integrable tunable chirping element on a tens of picosecond time scale. Other attempts at making a tunable chirping element could be realized using electrooptic phase modulators.
A High-Power Pumping Laser Module for Er-doped Fiber Amplifier
Authors: Fujita Masayuki , Iseki Yuji , Takahashi Keiichi , Mito Ikuo
Published: February 2023

It is very important to get a high power pumping laser module to realize an effective Er-doped fiber amplifier[1]. In this paper, we describe a newly developed high-power pumping laser module with over 100mW output power at 1.48μm using a long cavity DC-PBH MQW-LD and a low aberration coupling lens. And a polarization maintaining fiber pigtail for duplication or redundancy is also described.
Simultaneous Distribution of AM/FM FDM TV Signals to 65,536 Subscribers Using 4 Stage Cascade EDFAs
Authors: Kikushima K. , Yoneda E. , Suto K. , Yoshinaga H.
Published: February 2023

The advantages of erbium-doped fiber amplifiers (EDFAs) have been well reported [1]-[4]. One existing application is in a cascade configuration for TV signal distribution [4]. This paper is an extension of our previous paper and reports the first distribution of multiplexed AM/FM TV signals. The new technique is ideal to support and extend traditional CATV services and area while ensuring support for future CATV services such as FM-NTSC-TV and HDTV signals as shown in Fig. 1.
Field Test of Multichannel AM-VSB Transmission Using an Erbium Doped Optical Fiber Amplifier at 1.55µm Wavelength Range in the CATV Network.
Authors: Shigematsu Masayuki , Nakazato Kouji , Okita Toshio , Tagami Yasushi , Nawata Kiyoshi
Published: February 2023

The amplitude-modulated vestigial-sideband (AM-VSB) optical signal transmission is very attractive for Cable Television (CATV) systems because of its compatibility to current coaxial CATV systems. However, unlike frequency-modulated or digital signals, an AM-VSB signal requires a much higher received power for satisfying a required carrier to noise ratio (CNR) and a low distortion. Consequently, a loss margin of this transmission system results in about 7dB, which limits a transmission distance around 10km at 1.3µm and cannnot do a multi-drop at the optical stage.
Simultaneous Transmission and Amplification of 622 Mb/s, 10 FM NTSC Video Channels and 3 FM HDTV Components Using a High Gain Erbium Doped Fiber Amplifier
Authors: Tohme H. E. , Lo C. N. , Saifi M. A.
Published: February 2023

The evolution of the SONET as a transport for future switched digital Broadband-ISDN services coupled with the advances in using subcarrier multiplexing (SCM) as an economical alternative to distribute NTSC and future HDTV video channels, has fueled research in systems capable of transporting both services. The simultaneous transmission of baseband digital signals and SCM, FM video channels on one wavelength has been proposed as a bandwidth efficient and cost effective way to distribute high speed digital signals and a large menu of video channels to subscribers [1], [2], [3], but previous experiments required high bandwidth optoelectronics and had limited power budgets. Erbium doped fiber amplifiers (EDFAs) with their high gain, insensitivity to modulation formats and ease of integration with lightwave systems offer an elegant way to overcome splitting losses in distribution systems. We report an experiment where a single laser was modulated with a signal with RF bandwith of 2 GHz containing 622 Mb/s (SONET STS-12 rate) at baseband, 10 SCM FM NTSC video channels and 3 SCM FM HDTV components. The signals were further transmitted over 15 km of fiber and distributed to 8192 terminals. A system power budget of 49.5 dB was made possible by an in-line EDFA pumped at 532 nm with a gain of 31.5 dB.
FDMA-FSK 1 Gb/s Star Network Using LD-Pumped Erbium-Doped Fiber Preamplifiers with Optimal Noise Filtering
Authors: Willner A. E. , Desurvire E. , Presby H. M. , Edwards C. A.
Published: February 2023

A key advantage of a frequency-division-multiple-access (FDMA) optical star network is high-speed simultaneous distribution of information to many users. An attractive implementation [1,2] is to frequency-shift-key (FSK) modulate N laser transmitters (Tx) and use direct-detection receivers (Rx), each consisting of a fiber Fabry-Perot [3] demodulator/demultiplexer. One disadvantage of this simple scheme is the limitation placed on the number of network users due to the inherent (1/N) power splitting losses of the N×N star coupler. These splitting losses as well as substantial component insertion losses can be compensated for by including an Erbium-doped fiber amplifier (EDFA) [4-6] in each receiver [1]. Such amplifiers have the advantages of being compatible with a fiber-based system, providing high gain and output saturation power, and being insensitive to polarization and crosstalk effects.
High Sensitivity, Preamplified Direct-Detection-FSK Distribution System
Authors: Chow T. , Miniscalco W. J. , Thompson B. A. , Childs R. B. , Yu A. W. , Fye D. M.
Published: February 2023

Direct detection of FSK signals (DDFSK), using a baseband optical receiver and a tunable Fabry-Perot interferometer (FPI) for channel selection and optical frequency discrimination, has been proposed as a practical alternative to coherent techniques for polarization-insensitive FSK demodulation [1]. DDFSK also lends itself naturally to the use of optical preamplifiers since the FPI also serves as a narrow band optical filter to suppress spontaneous emission. We report the first use of an optical amplifier in a DDFSK system and show that a high-gain erbium-doped fiber amplifier can simultaneously improve the sensitivities of more than 10 receivers by 20 dB, to better than -40 dBm. We also assess the implications for multi-optical-channel systems as well as the trade-offs between receiver sensitivity and distribution capacity. A receiver sensitivity with the ASK equivalent of 171 photons/bit was achieved, the best reported to date for an erbium fiber preamplifier.
Twin-Guide Laser Amplifier Switch With Spatially Separated Output
Authors: Mace D A H , Adams M J , Singh J , Fisher M A , Henning ID
Published: February 2023

Optical switches incorporating laser amplifiers are very attractive because the amplifier gain can be used to compensate for the switch insertion loss[1]. Using a twin-guide amplifier (TGA) with two closely spaced parallel semiconductor laser amplifiers, we reported the first demonstration of optical crosspoint switching with gain[2]. We report here measurements on a TGA which also has curved active guides, enabling the device to be connected to three optical fibres simultaneously and used as 1×2 optical switch.
Wide Band Phase Modulation of a Semiconductor Optical Amplifier
Authors: Joyce G. R. , Olshansky R. , Hill P.
Published: February 2023

Previous studies have reported using semiconductor optical amplifiers as phase modulators 3 dB bandwidths of up to 500 MHz1, including baseband DPSK transmission of 140 Mb/s2 and 565 Mb/s3. In this paper we show that, when operated at high bias, an optical amplifier has a modulation bandwidth of over 3 GHz, with a phase response of 0.02 rad/mA, equivalent to a V
π
of 8 V. Use of the amplifier as a high frequency modulator is demonstrated by transmitting a 100 Mb/s DPSK signal on a 3.6 GHz subcarrier.
Application of Diode Laser Amplifier to Ultrafast, Desk-Top Electrooptic Sampling System
Authors: Takahashi Ryo , Liu Hai-Feng , Kamiya Takeshi
Published: February 2023

Optical amplifiers have been attracting keen attention among fiber-optic communication researchers and engineers because of the capacity to remarkably increase the transmission span for any multiplexing schemes. Although it is almost certain that optical amplifiers will be useful as well in other optical systems to improve the signal quality, extensive studies on the potential and the limitation of them in optical sensing application are still insufficient.
Development of compact Er3+-doped fiber amplifiers for practical applications
Authors: Yoshida M. , Ohizumi H. , Koyama T. , Gozen T. , Tanaka H. , Yotsuya M.
Published: February 2023

Recently, Er3+-doped fiber amplifiers have emerged as an attractive source for 1.55-μ m optical communications1). This paper reports the development of three types of Er3+-doped fiber amplifiers having novel fiber devices.
Temperature Variation of Gain in a 1480nm-Pumped Erbium-Doped Fibre Amplifier
Authors: Suyama M. , Laming R.I. , Payne D.N.
Published: February 2023

The excellent performance of erbium-doped fibre amplifiers1 (EDFA) has been confirmed by many recent experiments2 and there is little doubt that EDFAs will soon be used in practical applications. Although an understanding of the amplifier temperature characteristics is indispensable in any application, surprisingly only one measurement has been reported to date. This measurement3 used the 0.6μm pump band and reported no significant temperature dependence of either the gain or the amplified spontaneous emission (ASE) spectrum. However, when resonantly pumped at the more practical wavelength of 1.48μm, the situation is different. In this case, temperature-dependent gain characteristics are expected owing to a combination of the proximity of the pump and signal energies and the temperature-dependent distribution of ions within the metastable and the ground levels.
A Comparison of Direct and Coherent Detection Systems with Optical Amplifiers
Authors: Granlund S. W. , Park Y. K.
Published: February 2023

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 direct detection systems [1,2]; but some experiments, including a record transmission distance experiment, have used coherent detection systems [3,4]; 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&T’s commercial, 1.7 Gb/s system and a shelf-mounted, coherent detection regenerator from a recent AT&T field trial [5]. We will also emphasize a direct comparison by using transmitters of the same wavelength and identical optical paths including erbium-doped fiber amplifiers.
High Receiver Sensitivity at 2.5 Gb/s obtained with a Highly Efficient Low Noise Diode Pumped Erbium Doped Fiber Amplifier
Authors: Mikkelsen B. , Joergensen C.G. , van den Berk J.A. , Pedersen C.F. , Larsen C.C. , Durhuus T. , Stubkjaer K.E.
Published: February 2023

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 [1], 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.
Signal Statistical Effects from Stimulated Brillouin Scattering in CPFSK Repeaterless Transmission System With Optical Booster Amplifier
Authors: Sugie Toshihiko
Published: February 2023

For a 2.5 Gb/s CPFSK repeaterless transmission system with EDF-booster amplifier, the bit error rate performance and the penalty improvement by signal randomization are clarified in the presence of stimulated Brillouin scattering along a 280-km dispersion shifted fiber.
Combined Effect of Self-Phase Modulation and Dispersion in SLA Post-Amplified Transmission Systems
Authors: Medeiros C. R. , O’Reilly J. J.
Published: February 2023

In this paper we consider the performance implications of using semiconductor laser amplifiers (SLAs) as post-transmitter power amplifiers in long-haul directly modulated optical systems operating in the 1.55μm region. The combined effect of the dispersion, nonlinear self phase modulation, attenuation and the inherent SLA nonlinearity is numerically investigated.
Simultaneous Distribution of Analogue AM-TV and Multigigabit HDTV with Optical Amplifier
Authors: Heidemann R. , Junginger B. , Krimmel H. , Otterbach J. , Schlump D. , Wedding B.
Published: February 2023

Analogue FDM transmission of AM-VSB TV-channels over optical fibres is used today to upgrade existing copper-based CATV networks. With the aid of optical amplifiers (EDFA) cost competitive FTTC systems will be realized /1,2/. The strategy for the distribution of HDTV-channels is not so clear today, but in any case, digital transmission will yield the highest quality /3/. In this paper we demonstrate the feasibility of flexible TV/HDTV-distribu- tion using simultaneous analogue AM and digital PCM transmission over optical amplifiers without any mutual quality degradation.
A 40 Channel AM-VSB Distribution System with a 21 dB Link Budget
Authors: Joyce G. R. , Olshansky R. , Childs R. , Wei T.
Published: February 2023

An AM-VSB fiber video distribution system combines an erbium-doped fiber power amplifier with a low-noise receiver to attain a 21 dB link budget for 40 channels.
Optical Amplifiers Used as Functional Components
Authors: Thylén Lars , Gustavsson Mats , Gillner Lars
Published: February 2023

The optical amplifier is having a large impact on current research on optical networks, where the Er doped fiber amplifier (EDF) is the prime candidate for creating a transparent optical, analog network. The EDF will most likely be used for preamplification, power boosting, linear repeating because of its advantages of polarization insensitivity, extremely low ”facet” reflectivity, good noise and saturation output power properties. However, the EDF amplifier is limited in versatility: In the semiconductor laser amplifier (SCLA), light amplification is effected by the coupling between the photon field and inverted electron population system, implying that the quasifermi level separation provides an electronic means of monitoring the optical field. Further, since the spontaneous recombination time is of the order of ns, the optical field can be detected (simultaneously with amplification), frequency converted and gated up to bandwidths of ≈ 1 GHz. In the EDF, there is no analog to the electrooptic interface (although the monitoring might be possible to perform optically) and the spontaneous recombination time is on the order of ms. Hence, the SCLA offer unique possibilities, and all of the above functions can be implemented by one single generic structure which is integrable, in contrast to the EDF. But it should also be noted that the ns time scale introduces severe crosstalk problems in multichannel systems.
The Effect of Pump Induced Temperature Variation on Erbium-Doped Fiber Amplifiers
Authors: Nishi S. , Masuda H. , Nakajima J. , Aida K.
Published: February 2023

The temperature increase of an erbium-doped fiber by 1.48 µm pumping was measured. The mechanism of heat generation and its influence on amplification characteristics are discussed.
Optical Amplifiers Operating in a Random Access Fiber Loop Optical Memory
Authors: Großkopf G. , Küller L. , Ludwig R. , Pieper W. , Schnabel R. , Weber H.G.
Published: February 2023

In a fiber loop optical memory the applications of semiconductor laser amplifiers as switching elements and of Erbium doped fiber amplifiers as gain controlling elements are investigated.
Evaluation of Theoretical Limits of Cascaded EDFA Transmission Systems
Authors: Audouin O. , Prigent L. , Blondel J.P , Hamaide J.P , Gabriagues J.M
Published: February 2023

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 theoritical 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.
Spectral Gain Cross Saturation and Hole-Burning In Wideband Erbium-Doped Fibre Amplifiers
Authors: Tachibana M. , Laming R.I. , Morkel P.R. , Payne D.N.
Published: February 2023

Cross saturation characteristics are investigated in broadband 1.48 µm 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.
Femtosecond Soliton Collapse by Frequency Modulation Instability in Erbium-Doped Fiber Amplifiers
Authors: Gabitov I.R. , Romagnoli M. , Wabnitz S.
Published: February 2023

Recent experiments [1-3] 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.
Characterization of high bit rate phase modulators based on semiconductor optical amplifiers
Authors: Nielsen T.N. , Gliese U. , Mikkelsen B. , Stubkjaer K.E. , Fernier B. , Doussiere P. , Lafragette J-L.
Published: February 2023

Optical phase modulation with a semiconductor optical amplifier is investigated. By equalizing the phase response, the 3 dB bandwidth is extended from 600 MHz to 2.5 GHz.
Fibre Bragg filters for pump rejection and recycling in erbium doped fibre amplifiers
Authors: Farries M.C. , Ragdale C.M. , Reid D.C. J.
Published: February 2023

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.
73.6km Attenuation Free Concatenated Fibers Doped with Distributed Erbium
Authors: Tanaka D. , Wada A. , Sakai T. , Nozawa T. , Yamauchi R.
Published: February 2023

Recently, distributed Er-doped fiber amplifiers have become of great interest.1)-5) Intrinsic fiber loss can be compensated by the distributed gain. As a result, a fiber which is free from the attenuation can be realized.2) 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.5)
Conversion Efficiency and Noise in Erbium-Doped Fiber Power Amplifiers
Authors: Pedersen B. , Dakss M.L. , Miniscalco W.J.
Published: February 2023

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.
Towards Network Transparency with Photonic Amplifiers
Authors: Cochrane Peter , Todd Christopher J
Published: February 2023

Over the past 15 years optical fibre transmission systems have largely replaced their copper forebears on a point to point basis. The approach has been, quite simply, to overlay one-on-one the copper and radio systems by an optical fibre network with improved repeater spacing, smaller physical size, increased capacity and lower cost being the key benefits gained so far. With the advent of the optical amplifier and the possibility of access to the total fibre bandwidth, insensitivity to 'lossy' components and the eradication of much of the electronics necessary in transmission, there now exists an opportunity for radically new forms of network. The key feature that an optical amplifier has to offer is transparency. The ability to convey a number of wavelengths that can act as independently-modulated orthogonal carriers for a diverse mix of traffic in both digital and analogue forms offers a revolutionary step in the evolution of telecommunication networks.
Prospects for Fiber Amplifiers at 1.3μm
Authors: Brierley Mike
Published: February 2023

The erbium doped silica fiber amplifier for the 1.55μm telecommunications has now become a well established research laboratory tool. It offers high gain, high efficiency, low noise, low cross-talk, and high saturation power. It has been used in both land and under-sea systems demonstrations, and is commercially available from a number of manufacturers. In distribution experiments splits of up to 39 million ways have been demonstrated for only two stages of amplification [1]. In short it has revolutionised thinking on future optical fibre networks. Unfortunately the vast majority of current operational systems are deployed in the 1.3μm window, and some fiber designs may prohibit upgrading to 1.55μm. A similar amplifier for 1.3μm has been much more elusive. Examination of the observed energy levels of the trivalent rare-earth ions reveals three principal candidates; neodymium with a known laser transition around 1.32μm, praseodymium with known laser transitions but not until very recently at 1.3μm, and promethium with known laser transitions at 0.933μm and 1.098μm, but not around 1.3μm. Promethium is radioactive and has not been studied in fibers, leaving two practical possibilities for fiber amplifiers for 1.3μm.
1.48μm and 0.98μm High-Power Laser Diodes for Erbium-Doped Fiber Amplifiers
Authors: Mito Ikuo , Endo Kenji
Published: February 2023

The development of erbium-doped fiber amplifiers has recently progressed rapidly. Highly efficient power conversion for 1.48μm wavelength pumping enables a post-amplifier to achieve output power greater than 100mW1). When pumped in 0.98μm wavelength, the erbium-doped fiber amplifiers showed very low noise property2), which permits high receiver sensitivity as a pre-amplifier.
0.98-μm Strained Single Quantum Well Lasers Launching High Optical Power in a Single-Mode Fiber
Authors: Wada Masato , Yoshino Kaoru , Okayasu Masanobu , Temmyo Jiro
Published: February 2023

Erbium-doped optical fiber amplifiers (EDFA) pumped by 0.98-μm laser diodes exhibit a small noise figure (1) and small temperature-induced variation in amplification compared with pumping by 1.47-μm laser diodes (2). Recently, considerable research interest has focused on 0.98-μm laser diodes (3)-(8).
Materials for Erbium-Doped Fiber Amplifiers
Authors: Miniscalco William J.
Published: February 2023

Fiber offers an extremely favorable geometry for optical devices, and fiber lasers [1] and amplifiers [2] 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].
Strained Layer Quantum Well Semiconductor Optical Amplifiers: Polarization Insensitive Amplification
Authors: Joma M. , Horikawa H. , Nakajima M. , Kawahara M. , Kamijoh T.
Published: February 2023

Polarization insensitive optical amplification was demonstrated in newly developed semiconductor optical amplifiers which have strained GaInAsP quantum well structures. We tailored the active region of the quaternary strained layer quantum well structure with small biaxially tensile strain of 0.2% in the well layers for polarization insensitive operation.
Compressive Coatings on Optical Components for Improving Mechanical Durability and Increasing Strength
Authors: Marion J. E.
Published: February 2023

Techniques for realizing high strength and good mechanical durability in optical components is the focus of the present work. Currently, we are investigating methods applicable to slab geometry solid state lasers for high average power output.1 However, many of our analyses and methods are applicable to glass and single crystal components in other applications.
Damage Threshold and Environmental Durability Of Oxide Coatings Deposited Using Ion Assisted Deposition
Authors: McNally James J. , McNeil J. R.
Published: February 2023

The optical, physical and chemical properties of materials in thin film form can vary significantly from bulk properties. These differences in properties are directly related to film microstructure which is predominantly columnar, containing voids and material inhomogeneities. A number of novel deposition techniques have been developed in attempts to improve the properties of thin films. In these techniques, energetic processes are employed to increase adatom mobility and eliminate the formation of columnar microstructure. One of these techniques is ion assisted deposition (IAD).
Ion Assisted Deposition of Optical Coatings at Low Temperature
Authors: Williams Forrest L. , Reicher D. W. , McNally J. J. , Al-Jumaily G. A. , McNeil J. R.
Published: February 2023

The heavy metal fluoride (HMF) glasses are a new class of optically useful but environmentally unstable materials. These materials possess desirable optical properties, including a broad transmittance range from the mid-IR (~7 μm) to the near-UV (~0.3 μm), low absorption and scatter losses, low dispersion, low index of refraction and low thermal distortion.1 However, despite their promising optical characteristics, many HMF compositions are hygroscopic and relatively soft. Thus, hermetic coatings are required that will protect HMF glasses without degrading their optical properties. The problem is compounded by the fact that HMF materials have low softening temperatures, typically ~200 °C. This precludes standard thin film deposition techniques that require a substrate temperature of ~300°C. It is important to note that optical coatings conventionally deposited at low temperature usually exhibit reduced refractive index, increased optical absorption, poor environmental stability and less resistance to abrasion.
Holography in Adverse Environment
Authors: Surget J.
Published: February 2023

The important sizes of easily available holoplates compared with the diameter of a classical microscope lens makes it possible to obtain a given value of angle u with a much greater distance of view D using holography rather than using any conventional optical system.
Line shape of intracavity absorption
Authors: Schröder H. , Schultz K. , Toschek P. E.
Published: February 2023

Intracavity absorption (ICA) combines extreme sensitivity with ease of operation. Realistic theoretical models have predicted simple linear spectra.1 In fact, clear-cut ICA spectra have been observed, e.g., in time-resolved studies of the rotational kinetics of molecules in the afterglow of a discharge.2 The occasional observation of complicated nonsymmetric line shapes have, however, raised some questions about the practical applicability of ICA. Moreover, frequency locking of narrowband oscillators, related to ICA, has not been given a satisfactory quantitative explanation. We propose an analytical two-parameter model which takes into account the interplay of resonator loss and line dispersion. It gives rise either to absorption or dispersion profiles or to complex multipeaked line shapes. In corresponding experiments, Cs vapor has been used as line absorber (6s2S1/2 - 6p2P01/2 inside the cavity of a

LiF

2
+

color center laser. On variation of the resonator parameters and the vapor density, a broad variety of line shapes has been generated which are satisfactorily matched by predicted profiles. These observations confirm the applicability of the model. As a consequence, the line shapes unwanted in practical applications are avoided when selecting the resonator geometry close to the condition of minimum loss. For efficient locking, the opposite condition is favorable.
Comparison of the Fourier transform and flip-flop thin-film synthesis methods
Authors: Dobrowolski J. A.
Published: February 2023

The synthesis of thin-film systems with prescribed spectral characteristics has been the subject of many papers in the past three decades. A particularly powerful method, first described by Sossi, uses Fourier transforms to solve the inverse scattering problem for an inhomogeneous layer.1 This layer can then be transformed into a multilayer consisting of homogeneous films of many refractive indices. Through the use of the Herpin equivalent index concept, this multilayer can be transformed into a system consisting of two materials only. More recently Southwell described a simple numerical method which directly yields solutions based on the use of two materials.2 He applied it to the design of antireflection coatings. In this paper the two methods are applied to several different spectral filtering problems. The properties of the resulting numerical solutions are compared and contrasted.
Reflection vs transmission holograms in energy-related applications
Authors: Jannson J. , Jannson T. , Winston R.
Published: February 2023

The energy-related holographic applications such as spectrum-splitting holoconcentrators,1 solar-control Lippmann holowindows,2 heliostat dichroic/polychroic non-Snellian mirrors,3 etc. have unique potential of realizing wavelength/angular selective spatial processing operations. Therefore, the systems with properties such as spectrum-selective Snellian/non-Snellian reflection, deflection concentration, and collimation can be produced by using large-size (1-m2 area), flat or curved thin holographic coatings. In this paper it was shown that only superhigh-efficiency (SHE) holographic technology, based on Bragg reflection Lippmann holograms,3 can satisfy all necessary conditions to be competitive with conventional techniques. These conditions are high diffraction efficiency values close to the theoretical limit, rectangular shape of diffraction efficiency spectral characteristics, low absorption/scattering losses (below1%), low coupling losses (below 5%), and optical efficiency of the compound holographic system close to its average diffraction efficiency within all spectra of interest. In the case of solar applications (inc1uding PV and TPV holoconcentrator systems), the last condition is especially difficult to satisfy because of the relatively wide range of the solar spectrum. To prove the advantages of reflection holograms (compared with transmission holograms) in broadband energy-related applications (solar, chemical, etc.), the wave-tracing kinematic model was applied to 1-D-limited 3-D holographic Bragg structures with a well-defined grating vector. The model was based on the generalized solid-state physics Wulf-Bragg formalism.4
Relating low-vision CSFs to functional classifications of vision loss
Authors: Rubin Gary S.
Published: February 2023

The contrast sensitivity function (CSF) is becoming increasingly popular as a clinical test for detecting and diagnosing eye disease. But the value of this test in predicting visual performance has received little attention. We have reported1 that functional classifications of vision loss in terms of clarity of the ocular media and integrity of the central visual fields are predictive of reading performance. If the CSF is to be useful in predicting reading performance, we would expect these functional classifications to be reflected in properties of the CSF. We measured CSFs for thirty low-vision subjects using a forced-choice procedure. Spatial frequencies in the range 0.1-6 cycles/deg were tested. Observers with cloudy media and intact central fields show an increasing loss of contrast sensitivity with spatial frequency, compared to normal CSFs. Observers with clear media and central field loss show substantial loss of contrast sensitivity at all spatial frequencies, but the loss is greatest at high and low frequencies. Observers with peripheral field loss and clear or cloudy media show results that are intermediate between those of the two previous groups—sensitivity loss at both high and low spatial frequencies, with the high-frequency loss being greater. The differences between groups can be explained in terms of optical factors such as blur and nonoptical factors such as spatial summation.
Low spatial frequencies are necessary and sufficient for generalization of form
Authors: Ginsburg Arthur P.
Published: February 2023

If a requirement is to have a minimum range of spatial frequencies that also provide the most general shape sufficient for classification that is independent of the particular elements that make that object, low spatial frequencies of objects are both necessary and sufficient. That finding has been recently questioned by several researchers. They agree that low spatial frequencies of objects can provide sufficient information for general shape but argue that they are not necessary by noting that forms are still classified from high-pass filtered images of objects too. However, that criticism only applies to objects described in the luminance domain. Early nonlinearities in the visual system severely limit the use of high-pass images to question the generalizability of low spatial frequencies being necessary and sufficient for the classification of general shape information. Demonstrations of such early nonlinearities are shown to clearly support that assertion. Finally, in addition to using low spatial frequencies to describe general shape information in objects, Ginsburg has used the concept of low-pass filtering in a more general sense to describe the filtering properties of visual mechanisms at whatever stage of the visual system they occur.
Effects of quantum noise on modulation spectroscopy
Authors: Holm David A. , Sargent Murray
Published: February 2023

AM and FM modulation spectroscopies1,2 have been used to study the properties of matter as well as for applications such as reading out optical memories.3 Advances in the accuracy of these methods have turned what used to be an academic subject, quantum noise, into a practical consideration. For example, memory readout fields must be very weak to keep the medium from heating up too much and quantum noise puts a lower limit on the readout field strength. Similarly if weak modulation sidebands are used to study coherent dips via AM spectroscopy, quantum noise becomes relevant. We use our quantum theory of multiwave mixing4 to predict the effects of quantum noise on these problems. We find that, for modulation frequencies about equal to the Rabi frequency for the strong wave, spontaneous emission contributes a pronounced AM component that might be confused with the appearance of a hole in reading out optical memories. In AM spectroscopy we find that the coherent dips are partly filled in by spontaneous emission.
Line broadening characteristics of hollow cathode atomic hydrogen
Authors: Li Ayers E. , Benesch W.
Published: February 2023

Recently, we reported on the properties of atomic hydrogen lines as produced in an electric hollow cathode discharge.1 The principal finding there was the manifestation of highly articulated threefold line shapes with an extraordinary wing development not observed in the positive column of the same discharge. In the far wings of Hα, for example, the observed Doppler shifts indicated translational energies well in excess of 100 eV. Also noted for lines of the Balmer series was a difference in line shape for the case of observations made parallel to the cathode surface as opposed to those made perpendicular to that surface. In particular, while the parallel observations gave symmetric, unshifted lines, the perpendicular observations gave asymmetric blue-shifted lines. At present, we are examining the detailed structure of the blue-shifted lines as well as changes which are produced in the lines by alterations of cathode surface conditions. A comparison of results will be made with some very recent work of Cappelli et al.2 who have noted Doppler-broadened line shapes of atomic hydrogen in a parallel-plate radio-frequency discharge by means of a hole drilled in one of the discharge electrodes.
Readout optimization of volume holograms in bismuth silicon oxide
Authors: Marrakchi A. , Tanguay A. R. , Johnson R. V.
Published: February 2023

Dynamic holograms in bismuth silicon oxide (Bi12SiO20 or BSO) crystals exhibit pronounced optical polarization effects due to concomitant natural optical activity and electric-field-induced linear birefringence. Detailed computer studies of this polarization behavior have clarified the optimum configurations for maximizing the light diffraction efficiency and signal-to-noise ratio of recorded holograms. Experimental parameters that are most readily manipulated include the polarization state of the input readout light beam, the magnitude of the applied bias electric field after the grating has been written, and the angular alignment of the readout beam with respect to the grating. Bismuth silicon oxide exhibits very interesting polarization and diffraction efficiency characteristics for off- Bragg angles.1,2 For sufficiently thick crystals, the angular alignment sensitivity curve consists of multiple peaks. For thinner crystals, these multiple peaks are unresolved, but their impact on optimum diffraction configuration is nevertheless quite striking. For the {KG⊥ [001]) BSO crystal orientation, an increase in diffraction efficiency of up to a factor of 2 can be realized by using circularly polarized light rather than linearly polarized light and by realigning the BSO crystal for maximum diffraction. These results hold even in the case of thin crystals for which the multiple diffraction peak structure is inadequately resolved.
Digital spectrometry
Authors: Collett Edward
Published: February 2023

The most widely used method for determining the refractive index of optical materials is the minimum deviation method; it is the basis of the divided circle prism spectrometer.1 Another method is the Brewster angle reflection method. Both methods require the use of a rotating mechanical mount. Thus, these methods can be considered to be optomechanical. To overcome this mechanical and other limitations we have reconsidered the measurement of the refractive index in which there are no moving parts. We show that this is possible for an optical beam which is incident at 45° with respect to the normal.2 The optical surface is represented by its Mueller matrix from which a simple expression for the refractive index is found. We then present an experimental configuration for determining the refractive index. Because the measurement is done with a digital voltmeter we call this method digital spectrometry and it can be considered to be an optoelectronic measurement. Finally, we discuss the accuracy and the extension to measuring the extinction coefficient.
Optics in terms of observables
Authors: Collett Edward
Published: February 2023

Thirty years have now elapsed since the appearance of Wolf’s classic paper1; he introduced the concept of the mutual coherence function and showed that the components obeyed rigorous propagation laws. Wolf also noted their relation to the Stokes parameters. The Stokes parameters were originally introduced to describe the interference laws of Fresnel and Arago and, in particular, to provide a mathematical description of unpolarized light. In this paper we show that the Stokes parameters arise naturally in classical optics when the transformation from the nonobserved amplitude formulation to the observed intensity formulation is made. As a result this formulation shows that it is unnecessary to introduce quantum mechanical concepts or even operational definitions to describe them. After this we represent the Stokes parameters in the form of column matrices and then apply this formalism to the description of radiating systems such as the classical Zeeman effect, synchrotron radiation, and quantum dipole radiation.2 By introducing the principle of incoherent spectral decomposition we show that the Stokes vectors correspond exactly to the observed spectral lines and they contain all the information available in classical optics which is frequency, intensity, and polarization.
Focal and angular shifts of Gaussian beams reflected near the critical angle
Authors: Chan C. Chiu , Tamir T.
Published: February 2023

The lateral, focal, and angular shifts associated with fields incident on dielectric interfaces can be significant in applications involving guided waves and beams. For incidence angles θ that are close to the critical angle of total reflection θc, the conventional expressions for those shifts fail because their values become infinitely large as θ→θc, which is inconsistent with experimental evidence. For the lateral shift, Horowitz and Tamir have derived1 a formula that remains finite around θc and approaches asymptotically the conventional result for θ away from θc. We have obtained expressions that are valid around θc also for the focal and angular shifts. These results have been derived for Gaussian beams with normal or parallel polarization, and they hold also for incident beams that are either convergent or divergent. The new results approach asymptotically the conventional expressions for θ far from θc but they predict finite values for both the focal and angular shifts for θ around θc. As expected, we have ascertained that these shifts are most pronounced near θc, in which case their magnitudes are strongly dependent on the beamwidth/wavelength ratio, which is assumed large.
Rigorous diffraction analysis of metallic binary gratings
Authors: Moharam M. G. , Gaylord T. K.
Published: February 2023

Recently, surface relief dielectric and metallic gratings have generated great interest for diffractive optics applications. High quality gratings with deep grooves and small grating periods have been recently fabricated using electron-beam technology and using holographic techniques. These gratings exhibit high diffraction efficiencies as predicted by theoretical calculations.1 In this work the rigorous coupled-wave analysis is applied to metallic binary gratings with groove depths and grating periods comparable to the wavelength of light. Two practical binary gratings are considered (a) bulk finite conductivity gratings and (b) dielectric gratings with finite conductivity metallic coatings. Diffraction characteristics, including the angular and wavelength selectivities and their dependence on groove depth, aspect ratio, and polarization are presented and compared to the diffraction characteristics of infinite conductivity gratings. The approximation of infinite conductivity is shown to give very inaccurate results.