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We report, for the first time to our knowledge, experimental results on pedestal waveguides produced with Yb 3+ /Er 3+ codoped Bi 2 O 3 –WO 3 –TeO 2 thin films deposited by RF Sputtering for photonic applications. Thin films were deposited using Ar/O 2 plasma at 5 mTorr pressure and RF power of 40 W on substrates of silicon wafers. The definition of the pedestal waveguide structure was made using conventional optical lithography followed by plasma etching. Propagation losses around 2.0 dB/cm and 2.5 dB/cm were obtained at 633 and 1050 nm, respectively, for waveguides in the 20–100 μm width range. Single-mode propagation was measured for waveguides width up to 10 μm and 12 μm, at 633 nm and 1050 nm, respectively; for larger waveguides widths multi-mode propagation was obtained. Internal gain of 5.6 dB at 1530 nm, under 980 nm excitation, was measured for 1.5 cm waveguide length (∼3.7 dB/cm). The present results show the possibility of using Yb 3+ /Er 3+ codoped Bi 2 O 3 –WO 3 –TeO 2 pedestal waveguide for optical amplifiers. [ABSTRACT FROM AUTHOR]

We demonstrate a channel-reuse bidirectional 10-Gb/s/λ long-reach DWDM-PON and an optical beat noise-based automatic wavelength control method for a tunable laser used in a colorless optical network unit. 100-GHz channel spacing 55- and 100-km full-duplex bidirectional 320 Gb/s (32 x 10 Gb/s) capacity transmissions are achieved without and with optical amplification. Transmission performance is also measured with different optical signal to Rayleigh backscattering noise ratios and different central wavelength shifts between upstream and downstream in the channel-reuse system. [ABSTRACT FROM AUTHOR]

We present analytical results on the bit-error probability (BEP) of arbitrary order pulse-position modulation (PPM) of optically pre-amplified receivers. We use the Laguerre photon counting distribution so as to model the statistic of the optical noise, in order to accurately model the effects of signal and spontaneous noise beating at the optical detector. The great advantage of our proposed results is that they are exact and only require a finite summation over the optical noise modes and the modulation order. In addition, this approach enables the efficient calculation of the BEP in optical wireless communication links, under the presence of atmospheric scintillations and pointing errors. [ABSTRACT FROM AUTHOR]

We present a time-polarization multiplexing setup that overcomes the maximum amplification limit of semiconductor optical amplifiers (SOAs) in the pulsed regime. A coherent optical pulse at the input is equally divided into two, which are independently amplified, and coherently recombined to compose an oversaturation amplified optical pulse at the output. This simple topology, containing an SOA and few extra devices, offers 1.96-dB oversaturation gain in comparison with a single SOA. Furthermore, little experimental complexity and, thus, cost, are required by the proposed topology. [ABSTRACT FROM AUTHOR]

Abstract: Circular polarization shift keying (CPolSK) modulation technique has many advantages such as excellent BER performance and freedom from the alignment of polarization coordinates of the transmitter and the receiver, etc., and it turns out to be a good choice to FSO system. In this paper, a FSO system using CPolSK modulation is studied by simulation; it is found that the communication performance of the system is excellent in most weather condition. Additionally, three ways of optical signal amplification are proposed, and contrastive analysis on performance of corresponding optical amplification systems is carried out by examining SNR、BER and transmission distance with different specific attenuation. The results show that the system with optical amplifier at the transmitter have the optimum performance, and then the system with optical amplifier at the both ends with the same total gain, it is worst for the system with optical amplifier at the receiver. In addition, the safety factor for high emission power induced by optical amplification is also considered in this paper for practical application. The study above may be utilized in the system design for enhancing performance. [Copyright &y& Elsevier]

We numerically and analytically calculate sensitivity and link power budget of an optically amplified electronically compensated dual polarization quadrature phase-shift keying (DP-QPSK) coherent homodyne optical system, taking into account the main parameters of both the optical amplifier and the coherent receiver. After deriving an expression for the signal-to-noise ratio (SNR) of the amplified coherent receiver, we calculate an analytical expression for the optimum local oscillator (LO) optical power which maximizes the SNR, and an approximated closed-form solution for the receiver sensitivity, valid in most of practical cases. This analytical calculation allows to derive, when the impairments of the fiber are compensated, the position of the amplifier into the link that maximizes the optical link power budget. The approximated closed-form solutions are compared with results obtained with a numerical approach. From our investigation it emerges that, in a single-channel fully compensated DP-QPSK coherent system, the performances of both booster and in-line configurations can be even better than that ones of the preamplifier, but they are strongly dependent on the unamplified receiver features, and can require a proper adjustment of the LO optical power, to make the sensitivity compliant with the requirements. Diversely, the performances of a preamplified coherent receiver can be worse, but the amplifier position makes the coherent receiver practically independent on its intrinsic noise sources. [ABSTRACT FROM PUBLISHER]

The relationship between gain and oscillation spectral profiles is studied and analysed from an educational perspective. A theoretical explanation based on simple models is presented. Expressions of spectral profiles and widths are deduced by means of this theory. Spectral profiles and widths are measured with a laboratory experiment based on low-cost lasers. Theoretical and experimental values are in agreement. [ABSTRACT FROM AUTHOR]

A photonic generation of tunable microwave phase shifter with capability of frequency doubling is proposed and experimentally demonstrated using optical spectral shaping technique. Our proposed configuration only consists of a phase modulator (PM), a programmable optical filter, and one photodetector (PD). The phase modulated optical signal is fed into the programmable optical filter, where two specific harmonic sidebands of the modulated signal are chosen in order to apply a tunable phase shift to one of the selected sidebands. After optical amplification and beating at the PD, a frequency doubling microwave signal with continuously tunable phase shifter from 0° to 360° is obtained with less than 2.5 dB power fluctuation over a frequency range from 20 GHz to 33 GHz. Moreover, simultaneous four-channel microwave signals with independent phase shift setting are achieved, due to that the proposed configuration is compatible with wavelength division multiplexing (WDM) operation. [ABSTRACT FROM PUBLISHER]

Abstract: Optical properties of PbS quantum dot (QD)-embedded silicate glasses prepared through post annealing were investigated. By modulating the heat treatment condition, tunable near-infrared (NIR) photoluminescence (PL) was obtained. Noticeable optical amplification was achieved at both 1330nm and 1550nm windows with similar amplification characteristics in single PbS QD-embedded glass, which indicated that broadband optical amplification is expected at the entire PL band of PbS QD-embedded glass. The PbS QD-embedded glass with multi-wavelength optical amplification is promising as the gain medium of broadband fiber amplifiers and tunable fiber lasers. [Copyright &y& Elsevier]

Light-analyte interaction systems are key elements of novel near-field optics based sensing techniques used for highly-sensitive detection of various kinds of targets. However, it is still a great challenge to achieve quantitative analysis of the targets using these sensing techniques, since critical difficulties exist on how to efficiently and precisely introduce the analytes into the desired location of the near-field light focusing, and quantitatively measure the enhanced optical signal reliably. In this work, we present for the first time a localized photonic nanojet (L -PNJ) based sensing platform which provides a strategy to achieve quantitative biosensing via utilizing a unique light-analyte interaction system. We demonstrate that individual fluorescent microsphere of different sizes can be readily introduced to the light-analyte interaction system with loading efficiency more than 70%, and generates reproducible enhanced fluorescence signals with standard deviation less than 7.5%. We employ this sensing platform for fluorescent-bead-based biotin concentration analysis, achieving the improvement on the detection sensitivity and limit of detection, opening the door for highly sensitive and quantitative biosensing. This L -PNJ based sensing platform is promising for development of next-generation on-chip signal amplification and quantitative detection systems. • A novel localized photonic nanojet based sensing platform for highly sensitive and quantitative biosensing was developed. • The light-analyte interaction system allows for introducing microscale analytes with high efficiency and spatial accuracy. • The signal amplification is negatively correlated with the size of the microscale analytes. • Improvements on the detection sensitivity and LoD for fluorescent-bead-based biotin concentration analysis was achieved. [ABSTRACT FROM AUTHOR]

We present new trends in the performance evaluation of submarine fiber cable system with different ultrahigh multiplexing and propagation techniques over a wide range of the affecting parameters. Our model takes into account the ultimate optical transmission of huge submarine cables with 14,400 channels under different depth conditions. We employ Raman and erbium-doped fiber amplifiers in our study. We investigate the double impact of both temperature and pressure through the defined depth penalty. We also study the soliton transmission technique using two multiplexing methods considered in the design of ultra-wide wavelength division multiplexing (UW-WDM) with 14,400 optical channels and ultra-wide space division multiplexing (UW-SDM) with 440 fiber links. Based on experimental data, both the deep ocean water temperature and pressure are obtained as functions of the water depth. [ABSTRACT FROM AUTHOR]

Abstract: Silicon-on-insulator (SOI) waveguide devices are emerging for the realization of optical signal processing systems for the last couple of years. The recent technological advancement in silicon photonics is the main driving force at the back of these devices. Using non-linear optical phenomenon in silicon wires and their compatibility with CMOS devices provide the stage for integrated photonic devices. All-optical signal processing devices are being investigated at present, but the chip-scale solution provided by the silicon photonics is the most promising. In this research we have investigated all-optical signal processing in a 10mm long SOI waveguide by exploiting well established coupled wave equations. We consider single pulsed pump to analyze frequency shifting by four-wave-mixing (FWM). For the wavelengths 20⿿30nm far from the pump, the gain overcomes nonlinear losses resulting in higher frequency conversion efficiency. [Copyright &y& Elsevier]

A double-cascade-type four-level system of semiconductor multiple quantum wells (MQWs) was constructed with biexcitons and excitons. The nonlinear optical properties for amplification, absorption, and dispersion of 2-weak fields in this scheme are investigated. It shows that the amplification, absorption, and dispersion responses of 2-weak fields can be achieved by appropriately adjusting the relative phase, the probe detuning, and the two control Rabi frequencies. The investigation is much more practical than its atomic counterpart because of its flexible design and the widely adjustable parameters. It may provide a new possibility in technological applications for the light amplifier and optical switch working on quantum coherence effects in MQW solid-state systems. [ABSTRACT FROM AUTHOR]

The wavelength filtering characteristics of active defective Photonic Band Gap (PBG) waveguides based on dilute nitrides are examined. The analyzed structure is made of GaInNAs-GaInAs MQW ridge waveguides in which a geometrical active defect in the periodic lattice induces selective transmission spectral regions centered at different wavelengths inside the PBG. The device show the advantage of simultaneous DWDM selective filtering and amplification of the filtered signal. The performances of the active PBG filters are investigated as a function of the geometrical and the electrical parameters. The analysis is performed by using proprietary codes, based on the Bidirectional Beam Propagation Method with the Method of Lines introducing the rate equations. Highly selective 9-channel active filter with minimum value of the bandwidth at half-height transmittance B3dB=0.12 nm has been calculated. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Broadband 1.20μm emission originating from the Thulium (Tm3+): 1G4 → 3H4 transition was observed in Tm3+-doped gallogermanate glasses under 476.5nm excitation. The stimulated emission cross-section is calculated to be 2.85×10–21 cm2 using the Füchtbauer–Ladenburg approach. Difficulty in the population inversion between the upper 1G4 and lower 3H4 levels resulting from the cross relaxation process Tm3+ [1G4, 3H6]→[3H4, 3H5] was overcome by the incorporation of Terbium (Tb3+) and Europium (Eu3+) ions. A Judd–Ofelt analysis was performed based on the absorption spectrum and the derived intensity parameters (Ω 2 =4.65×10–20, Ω 4 =1.51×10–20, and Ω 6 =1.42×10–20 cm2) reveal a strong asymmetry and covalent environment between Tm3+ ions and ligands in the host matrix. The results indicate that the Tm3+/Tb3+, Eu3+ codoping scheme is promising in the development of amplifiers and lasers operating at the relatively unexplored 1.2μm wavelength region. [Copyright &y& Elsevier]

Abstract: In order to develop efficient optical amplifiers with broad and flat gain profiles in the near-infrared range an active phosphate matrix codoped with Er3+ and Yb3+ rare earth optically active ions has been studied by carrying out steady-state and time-resolved luminescence spectroscopies. Taking advantage of the high absorption transition probability of the Yb3+ ions, these ions are excited with cw 980nm radiation from a commercial laser diode and subsequently de-excited by efficiently transferring energy to the Er3+ ions, producing an intense emission at around 1.5μm at which wavelength-division-multiplexing devices work. From the experimental data, the emission cross-section σem (λ) of the 4I13/2 → 4I15/2 transition at 1.5μm has been calculated using the Füchtbauer–Landerburg method. The result of this calculation, together with the absorption cross-section σabs (λ), allows the gain cross-section G to be estimated. Other important spectroscopic parameters associated with this transition, such as full width at half maximum FWHM, effective bandwidth Δeff and lifetime of the 4I13/2 level τexp , have been measured and analysed as a function of the Er3+ concentration. As figures of merit, FWHM×σem (λ), Δeff ×σem (λ) and σem (λ) × τexp calculations have been carried out. Comparing the obtained values to those reported in other Er3+-doped materials, the phosphate glasses doped with 1mol% of Yb2O3 ions and 1–2mol% of Er2O3 can be considered excellent candidates for developing broadband optical amplifiers, providing a large gain cross-section that covers the C (1530–1565nm) and the L (1565–1625nm) bands in the optical telecommunication window. [Copyright &y& Elsevier]

Abstract: Spatial multiplexing provides a solution for fiber capacity increase beyond the limits foreseen for enhanced bandwidth efficiency by higher order modulation and more channels by additional wavelength bands in long haul optical transmission. Its adoption also offers potential for a reduction of the cost and energy per transmitted bit. Two fiber types have been identified as candidates for transmission of multiple signals at the same wavelength inside a single cladding: fibers with multiple single mode cores and single core multi-mode fibers. Major challenges arise from the coupling of signals along the transmission path. Multiple input/multiple output signal processing may provide a solution for the separation of signals at the end of the link. Concepts such as tapers in case of multi-core fibers and field transformation in case of single core multi-mode fibers exist to provide the spatial multiplexing and demultiplexing functions. The potential of spatial multiplexing for cost and energy efficiency can only be realized, if optical amplifiers are found which are capable of processing all channels simultaneously. Concepts for such amplifiers were analyzed with promising results. Direct pumping of the cores leads to acceptable power requirements of lumped erbium-doped as well as distributed Raman amplifiers. [Copyright &y& Elsevier]

Abstract: Silicate glasses containing PbS quantum dots (QDs) with narrow size distribution were prepared through heat treatment. Transmission electron microscopy (TEM) results show that spherical PbS QDs are densely dispersed in the glassy matrix. Using ZnS–PbO to replace PbS as precursor of PbS QDs, the size distribution of PbS QDs in glasses becomes more uniform. Tunable infrared luminescence from 1100 to 2200nm has been obtained by controlling the glassy matrix and preparation parameters. Obvious optical amplification at communication windows of 1.55μm and 1.33μm is probed, and the PbS QDs doped glasses using ZnS–PbO as precursor exhibit larger optical amplification. The PbS QDs doped glasses with intense optical amplification are considered to be promising candidate as gain medium for broadband fiber amplifier and tunable fiber laser. [Copyright &y& Elsevier]

Abstract: Single-mode fiber optical system with saturable amplification, saturable losses and spectral filtering as proposed by Rozanov and Fedorov (1998) is studied. The system of ordinary differential equations (ODE’s) that can help investigation of the original physical system is proposed. It allows calculation of linear and nonlinear fixed points as well as the study of their stability, so it can be used for analysis of coherent structures and their classification. Derived system of ODE’s extends the earlier one proposed by van Saarloos and Hohenberg (1992) , for the analysis of coherent structures of the qubic–quintic Ginzburg–Landau equation, by including additionally the temporal dependences of the gain and losses. In order to verify it, it was applied to the earlier considered cases of fast and slow changes in the amplification and losses. Earlier obtained localized structures namely pulses, have been observed via numerical solution of the proposed system. In addition, new families of fronts have been identified. [Copyright &y& Elsevier]

Abstract: Evidence of a positive optical gain has been observed in an Er3+-doped LuVO4 crystal in a pump and probe experiment. The radiative transition from the 4S3/2(2H11/2) level to the 4I13/2 metastable level of the Er3+ ion gives rise to an intense emission centred at 850nm. The 4S3/2(2H11/2) level of Er3+ ions is populated with high power laser pulses at 532nm due to the 4I15/2 → 4S3/2(2H11/2) ground state absorption. The 4S3/2(2H11/2)→ 4I13/2 electronic transition is stimulated with a low signal cw beam at 850nm. Under these conditions, the high power pump pulses allowed to reach the population inversion necessary between the Er3+ levels of the transition 4S3/2(2H11/2)→ 4I13/2. An increase of the emission intensity of the sample is observed at the signal wavelength, due to the stimulated emission. Positive optical gain around 2cm−1 (8.6dB/cm) has been measured in Er3+-doped LuVO4 crystal. [Copyright &y& Elsevier]

Abstract: We report on a new hybrid approach to realize optical slab waveguides for optical amplification purposes. The structure consists of a dye-doped polymer core (PMMA) deposited over an oxidized porous silicon (PS) cladding layer formed on a silicon wafer. The very low refractive index (n =1.16) achievable in the cladding allows obtaining monomodal behavior with high confinement factors (Γ TE =96%) even for very thin cores (400nm). Optically excited guided luminescence shows stimulated emission, strong line narrowing and a clear threshold and superlinear behavior with pump energy. By means of the variable stripe length (VSL) technique, values of net optical gain up to 113dB/cm (constant over 3mm) and absolute amplification values up to 34dB have been measured at 694nm when pumping with 80mJ/cm2 energy pulses. These results validate the use of oxidized PS as a cladding layer in silicon photonics. [Copyright &y& Elsevier]

Abstract: This paper describes optical amplification properties in a polymeric waveguide doped with Tb–Al nanoclusters. The Tb–Al nanocluster is a promising fluorescent material for polymeric waveguides, which can be uniformly dispersed in polymer matrices while restraining the concentration quenching of Tb3+. Under the continuous optical pumping by 488nm laser light, optical amplification for the green emission of Tb3+ was achieved. The optical gain coefficients were estimated to be as high as 0.25 and 0.56mm−1 at the Tb–Al nanocluster concentrations of 4.5 and 5.0wt%, respectively. Taking into account our previous works for the polymeric waveguide doped with Eu–Al nanocluster, the rare-earth-metal nanocluster is believed to be a promising candidate for various photonic applications such as multicolor polymer lasers and waveguide-type optical amplifiers. [Copyright &y& Elsevier]

We present yet another quasi-analytic model for an optically amplified receiver, comprising an optical preamplifier, an optical prefilter, a photodetector, and an electrical postfilter. Due to the square-law nonlinearity and its interaction with the linear pre- and postfilters, the understanding of this seemingly simple structure has been elusive, gradually evolving over a succession of studies, culminating in the models by Lee and Shim and Forestieri. Here we adopt a new approach to this old problem, applying Volterra nonlinear theory to obtain fresh insight deriving a simplified model streamlining the pseudoanalytic simulations. Volterra series is a powerful mathematical tool for simulating nonlinear systems, applied here to quadratic optical detection in an unconventional way, by deriving a mixed frequency-time representation, leading to a simple and compact quadratic form in the combined signal-plus-noise signal spectra, albeit not computationally efficient. Next, Forestieri's results, which used distinct bases for the signal and noise, are rederived using the insightful Volterra formalism. Finally, we reformulate the model using an expansion of both signal and noise in a common harmonic basis over a sliding window of duration equal to the ISI system memory. This final version of the optically amplified receiver model is most computationally efficient, provides the most compact description, and lends itself to intuitive interpretation. Applications of the new method include accurate determination of the bit error ratio of amplitude-shift keying, frequency-shift keying, and differential phase-shift keying transmission systems in the linear optical link propagation regime, including the effects of dispersion and fully accounting for intersymbol interference. The theory developed here is naturally extensible to advanced optical equalization techniques, involving Volterra nonlinear optoelectronic equalizers. [ABSTRACT FROM PUBLISHER]

We analyze numerically an erbium-doped segmented-cladding fiber (SCF) for optical amplification. The fiber has a uniform high-index core and a leaky cladding consisting of alternating high and low refractive-index angular segments of equal size, where erbium is doped in the core and the high-index cladding segments. By choosing the fiber parameters properly, the fiber can offer effective single-mode operation at both the signal (1530 nm) and pump (980 nm) wavelengths with an ultralarge core. We calculate the mode-field distributions in the fiber at these two wavelengths with a full-vector finite-element method. We obtain the gain characteristics and the pump threshold of the fiber by solving the propagation rate equations. With a typical erbium-ion concentration of 0.7 times 1025 ions/m3 , an input pump power of 280 mW, and an input signal power of 0.1 muW, the maximum gain achievable varies from ~ 14 dB to ~ 37 dB with an optimal fiber length of several meters, when the core diameter varies from 40 mum to 28 mum. The threshold pump power required is of the order of 100 mW at 0.1-muW input signal power, and the saturation output signal power is of the order of 100 mW at 280-mW input pump power. The noise figure is ~ 4 dB. Our analysis suggests that, by using a high enough pump power, a few meters of erbium-doped ultralarge-core SCF can provide a small-signal gain comparable with that of a conventional erbium-doped fiber. [ABSTRACT FROM PUBLISHER]

In this paper, Brillouin gain performances of tellurite fiber are investigated for photonics applications. We demonstrate stimulated Brillouin amplification and lasing and the simulated performance of slow light generation in a single-mode tellurite fiber. A Brillouin gain of 29 dB is achieved in a 100-m tellurite fiber with a pump power of 10 mW at 1550 nm. A peak value of Brillouin gain coefficients of 1.6989 X 10-10 m/W is measured on the base of gain characteristics. An all-fiber Brillouin laser with the maximum unsaturated power of 54.6 mW at 1550 nm and a slope efficiency of 38.2% is achieved from a 200-m tellurite fiber by employing a ring cavity. Furthermore, widely tunable (~27 nm) Brillouin comb laser with 26 lines spaced at 7.97 GHz is obtained from the ring laser cavity including an erbium-doped fiber amplifier (EDFA). A simple theoretical model based on laser threshold theory successfully explains the properties of Brillouin comb lasers. Stimulated Brillouin scattering (SBS)-induced time delay per unit power and per unit length is also calculated using the measured data of Brillouin gain coefficients. A peak value of 0.09246 ns/mW/m and a time delay slope efficiency of 1.75 ns/dB are obtained for this tellurite fiber. Potential performance of a tellurite fiber for slow light generation is clarified on the base of Brillouin gain characteristic. Our results show that tellurite fiber is a promising gain medium for Brillouin fiber amplifiers, lasers, and slow light generation due to its low background loss and large Brillouin gain coefficient. [ABSTRACT FROM PUBLISHER]

Abstract: We have developed transparent 3.5mol% Ho3+ and Tm3+ single-doped oxyfluoride glass–ceramics, where a large fraction of dopant ions is segregated into PbF2-based nano-crystals. The absorption and emission cross-sections corresponding to the 5I7 ↔ 5I8 transitions of the Ho3+ (at 2.0μm), and to the 3H6 ↔ 3F4 transitions of the Tm3+ (at 1.8μm), have been obtained and respective gain cross-section spectra have been computed as a function of population inversion. For Ho3+-doped samples, the maximum gain cross-section increased by 20% on ceramming of the precursor glass and reached, for the ensuing glass–ceramics, a value 1.5 times higher than that reported for fluoride glasses. The maximum gain cross-section for Tm3+-doped samples increased 2.5 times on ceramming of the precursor glasses and reached for the ensuing glass–ceramics a value 2–3 times higher than for other fluoride hosts, such as ZBLAN glass, and 1.5 times higher than for silicate and germanate glass hosts. Hence, these Ho3+- and Tm3+-doped glass–ceramics have an advantage for application in planar and fibre lasers/amplifiers at about 2.0, and 1.8μm, respectively. [Copyright &y& Elsevier]

In this paper, we analyze the performance of a nonlinear two-photon-absorption (TPA) receiver and compare its performance with that of a single-photon-absorption (SPA) receiver in the context of spectral-phase-encoded optical code-division multiple access (CDMA) technique. The performances for the above systems are evaluated for two different transmission scenarios, namely, asynchronous and slot-level synchronous transmitters. Performance evaluation includes different sources of degradation such as multiple-access interference, noise due to optical amplification, shot noise, and thermal noise. In obtaining the performance, the mean and variance of the received signal in each of the above techniques are derived, and bit error rate is obtained using Gaussian approximation. In general, it is shown that TPA receivers are superior in performance with respect to SPA receivers when the receiver employs a much slower photodetector in comparison with the laser's transmitted pulse duration. This, indeed, is the reason behind the choice of nonlinear receivers, such as TPA, in most spectral-phase-encoded optical CDMA systems. [ABSTRACT FROM PUBLISHER]

Abstract: Optical planar waveguides have been fabricated by the titanium in-diffusion process in lithium niobate crystals activated with erbium ions. The waveguides were studied by m-line technique in order to recover the index profile. The effect of the Ti in-diffusion on the structural and spectroscopic properties of the lithium niobate crystals was investigated by Raman and photoluminescence spectroscopies. The presence of titanium has only minor effects on the vibrational properties of the crystal, and no change in the emission properties of the erbium ions is observed. [Copyright &y& Elsevier]

Abstract: Fiber-optic extrinsic Fabry–Perot (EFPI) sensors have been successfully used for a wide range of applications. The recent progress in EFPI sensors is reviewed in this paper. First, the optical amplification technology is adopted into the EFPI sensor system to enhance the interferometric signal considerably. Second, both spatial-frequency multiplexing and coarse-wavelength-division multiplexing technologies are demonstrated for multiplexing of a modified EFPI sensor called the Fizeau sensor. Finally, the EFPI sensor is integrated with other fiber-optic sensing elements to realize the measurement of multiple parameters, for example, the EFPI is integrated with the in-fiber Bragg-grating (FBG) or the long-period-fiber-grating (LPFG) to achieve simultaneous strain and temperature measurement. Furthermore, simultaneous measurement of displacement, transverse load, static strain, temperature, and vibration can be achieved by using the combination of EFPI/FBG/LPFG. [Copyright &y& Elsevier]

We present the tradeoffs of employing highly compressed erbium-doped fiber amplifiers (EDFAs) in analog microwave photonic links. We employ the newly developed concept of noise penalty and introduce the concept of generalized relative intensity noise to facilitate system design. Theoretical and experimental results demonstrate that a highly compressed EDFA: 1) can achieve near shot-noise-limited performance, even with large optical noise figure and 2) can simultaneously increase the spurious-free dynamic range, increase the compression dynamic range, increase the analog gain, and decrease the analog noise figure, as compared to an unamplified link with identical components. [ABSTRACT FROM AUTHOR]

Advances in optical technology now allow practical reconfigurable wavelength networks to be constructed. These networks use wavelength-switching components to dynamically route wavelengths, and provide a level of flexibility and scalability previously not possible. Other components such as low-noise optical amplifiers, electronic dispersion compensators, and advanced modulation techniques simplify system operation, increase capacity, and extend reach. From an application perspective, the architecture of optical transport networks is evolving based on the requirement to support a higher bandwidth access infrastructure. The network architecture also needs to provide the flexibility to incrementally expand on the basis of customer demand and to provide key features such as optical broadcast to lower the cost of video services. The development of new architectures for optical transport networks and how these networks are influenced by critical system parameters and emerging component technologies is reviewed [ABSTRACT FROM PUBLISHER]

Achieving light amplification and lasing in silicon is one of most challenging goals in silicon-based optoelectronics. As a nonlinear optical effect, stimulated Raman scattering (SRS) provides a means to generate optical gain in silicon. Recent results of a nonlinear optics approach to optical amplification and lasing in silicon at the Photonics Technology Laboratory of Intel Corporation are reviewed. This paper starts with the description of the underlying physics related to the Raman scattering in silicon and experimental results of SRS in silicon waveguides. Then, it is shown that nonlinear optical absorption associated with the two-photon absorption (TPA)-induced free carrier absorption (FCA) is a dominant loss mechanism limiting optical gain in a silicon waveguide in addition to the linear optical scattering loss due to the waveguide sidewall roughness. The design and fabrication of a low-loss silicon waveguide containing a p-i-n diode to reduce the nonlinear optical loss are described. It is demonstrated that the free carrier density inside the waveguide can be reduced significantly with a reverse bias of the p-i-n diode. As a result, net optical gain in a silicon waveguide is achieved. The design, fabrication, and characterization of a Raman silicon laser are also described. Both pulsed and continuous-wave (CW) lasing in silicon are achieved using SRS [ABSTRACT FROM PUBLISHER]

In this paper, the authors study the performance of a two-photon absorption (TPA) receiver in a typical communication system employing an optical amplifier. For the study, the authors develop a comprehensive performance analysis, taking into account noises due to an optical amplifier, shot noise, and thermal noise, using Gaussian approximation technique. In evaluating the performance of the system using this technique, the mean and the variance of the received signal will be derived. Comparing the results of receivers using the TPA process with that of a typical single-photon absorption (SPA) structure leads the authors to conclude that TPA receivers can be used when the speed of the electronic parts of the receiver structures is not too high, as expected [ABSTRACT FROM PUBLISHER]

In this paper, we present a comprehensive comparison of the performance of an 80-km-per-span erbium-doped fiber amplifier (EDFA) system and a hut-skipped (160-km-per-span) all-Raman system over standard single-mode fiber (SSMF) for the first time, using semianalytic models. The numerical results reveal that a hut-skipped all-Raman system (using one-order Raman pumping) can achieve comparable performance as the conventional 80-km-per-span EDFA system for a common 50-GHz-spaced 80 times 10 Gb/s nonreturn-to-zero (NRZ) wavelength division multiplexing (WDM) system at typical fiber loss of 0.22 dB/km. For 100-GHz-spaced 40 times 40 Gb/s carrier-suppressed return-to-zero (CS-RZ) WDM transmission, it was found that a hut-skipped all-Raman system can achieve even better performance than the current 80-km-per-span EDFA system. It was also found that the impact of pattern-dependent Raman crosstalk is more severe than interchannel cross-phase modulation (XPM) in a hut-skipped all-Raman system with 80 times 10 Gb/s capacity [ABSTRACT FROM PUBLISHER]

Self-assembled cylindrical tubules of chiral phospholipids are interesting supramolecular structures. Understanding the molecular- tilt order is a key step in controlling the size and shape of the tubules and designing new functional materials. The current theories based on the chiral interactions, coupled with molecular tilt, have predicted that the tubules could have both uniform and modulated tilt states. Here, we image the molecular-tilt order in the self-assembled tubules of a chiral phospholipid by using liquid crystals as an optical amplification probe. We demonstrate that the organization of the molecular-tilt azimuth in the lipid tubules can induce an azimuthal orientation in the liquid crystals. Both uniform and modulated tilt states of the lipid tubules are observed after liquid-crystal optical amplification. [ABSTRACT FROM AUTHOR]

Abstract: We have developed novel inert and stable erbium (Er)(III)-cored complexes based on metalloporphyrins for optical amplification. The functionalized metalloporphyrin ligands have been designed and synthesized to provide enough coordination sites for the formation of inert and stable 9-coordinated Er(III)-cored complexes. Er3+ ions were encapsulated by the metalloporphyrin ligands, such as Zn(II)- and Pt(II)-porphyrins. The near-infrared (IR) emission intensity of Er3+ ion is much stronger in the Er(III)-cored complex based on Pt(II)-porphyrin than Er(III)-cored complex based on Zn(II)-porphyrin. Furthermore, we have incorporated a G2-aryl-ether functionalized dendron into the Er(III)-cored complex, yielding an Er(III)-cored dendrimer complex bearing the Pt(II)-porphyrin. The Er(III)-cored dendrimer complex shows the stronger near-IR emission intensity than the corresponding complex based on Pt(II)-porphyrin by seven times in solid state. The lifetimes of the emission band of Pt(II)-porphyrin ligands in the visible region were found to be 30 and 40μs for the Er(III)-cored complex and the Er(III)-cored dendrimer complex based on Pt(II)-porphyrin in deoxygenated THF solution samples, respectively. Also, in both cases, the sensitized luminescence intensity is increased in deoxygenated solution. Therefore, it indicates that the energy transfer from the metalloporphyrins to Er3+ ions takes places through the triplet state. In this paper, the synthesis and photophysical properties of novel Er(III)-cored complexes based on metalloporphyrins and Er(III)-cored dendrimer complex based on metalloporphyrin will be discussed. [Copyright &y& Elsevier]

Abstract: We present a study of the basic optical properties of colloidal CdSe/ZnS core/shell quantum dots entrained in a microstructured optical fiber. Quantum dots suspended in heptane were pulled into the holes surrounding the solid core of a microstructured optical fiber of the holey fiber class via capillary action and are found to remain in the fiber. In this experiment, a laser coupled into the fiber photoexcited quantum dots along the length of the fiber. Quantum dot emission was observed to couple into the fiber core and propagate along the fiber. To investigate the use of such a system in fiber-based light generation or amplification, a second laser overlapping the low-energy portion of the quantum dot emission was simultaneously coupled into the fiber. We observed apparent amplification of this light when photoexciting the quantum dots well above their bandedge. [Copyright &y& Elsevier]