Showing papers on "Optical communication published in 2011"
TL;DR: Graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.
Abstract: Graphene, the single-atom-thick form of carbon, holds promise for many applications, notably in electronics where it can complement or be integrated with silicon-based devices. Intense efforts have been devoted to develop a key enabling device, a broadband, fast optical modulator with a small device footprint. Now Liu et al. demonstrate an exciting new possibility for graphene in the area of on-chip optical communication: a graphene-based optical modulator integrated with a silicon chip. This new device relies on the electrical tuning of the Fermi level of the graphene sheet, and achieves modulation of guided light at frequencies over 1 gigahertz, together with a broad operating spectrum. At just 25 square micrometres in area, it is one of the smallest of its type. Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects1,2. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties3. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms4,5,6. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances7. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1 GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6 µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25 µm2, which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.
3,105 citations
TL;DR: A metallic-silicon waveguide system in which the optical potential is modulated along the length of the waveguide such that nonreciprocal light propagation is obtained on a silicon photonic chip is designed and fabricated.
Abstract: Optical communications and computing require on-chip nonreciprocal light propagation to isolate and stabilize different chip-scale optical components. We have designed and fabricated a metallic-silicon waveguide system in which the optical potential is modulated along the length of the waveguide such that nonreciprocal light propagation is obtained on a silicon photonic chip. Nonreciprocal light transport and one-way photonic mode conversion are demonstrated at the wavelength of 1.55 micrometers in both simulations and experiments. Our system is compatible with conventional complementary metal-oxide-semiconductor processing, providing a way to chip-scale optical isolators for optical communications and computing.
615 citations
TL;DR: Various defenses against the security threats in an optical network are discussed, including optical encryption, optical code-division multiple access (CDMA) confidentiality, self-healing survivable optical rings, anti-jamming, and optical steganography.
Abstract: The physical layer of an optical network is vulnerable to a variety of attacks, including jamming, physical infrastructure attacks, eavesdropping, and interception. As the demand for network capacity grows dramatically, the issue of securing the physical layer of optical network cannot be overlooked. In this survey paper, we discuss the security threats in an optical network as well as present several existing optical techniques to improve the security. In the first part of this paper, we discuss various types of security threats that could appear in the optical layer of an optical network, including jamming, physical infrastructure attacks, eavesdropping, and interception. Intensive research has focused on improving optical network security, in the above specific areas. Real-time processing of the optical signal is essential in order to integrate security functionality at the physical layer while not undermining the true value of optical communications, which is its speed. Optical layer security benefits from the unique properties of optical processing-instantaneous response, broadband operation, electromagnetic immunity, compactness, and low latency. In the second part of this paper, various defenses against the security threats outlined in this paper are discussed, including optical encryption, optical code-division multiple access (CDMA) confidentiality, self-healing survivable optical rings, anti-jamming, and optical steganography.
291 citations
TL;DR: In this article, the spin information associated with electrons injected from Co2FeSi and Fe layers into the quantum wells of spin light emitting diodes (spin-LEDs) can be transported optically in the form of circularly polarized light and deciphered electrically via the magnetic field dependence of the photocurrent in a distant detector spin-LED.
Abstract: For the full implementation of spintronic circuits, it is necessary to transmit spin information from one device to another. Electrons in semiconductors often suffer from high spin relaxation rates, making electrical transport of spin information highly inefficient. Here, we propose optical transport of spin information as an alternative. We demonstrate that the spin information associated with electrons injected from Co2FeSi and Fe layers into the quantum wells of spin light emitting diodes (spin-LEDs) can be transported optically in the form of circularly polarized light and deciphered electrically via the magnetic field dependence of the photocurrent in a distant detector spin-LED.
270 citations
TL;DR: Sorgeret et al. as mentioned in this paper reported the first experimental demonstration of truly nanoscale guided waves in a metal- insulator-semiconductor device featuring low-loss and broadband operation.
Abstract: Emerging communication applications call for a road map towards nanoscale photonic components and systems. Although metal-based nanostructures theoretically offer a solution to enable nanoscale photonics, the key demonstration of optical modes with deep sub-diffraction-limited confinement and significant propagation distances has not been experimentally achieved because of the trade-off between optical confinement and metallic losses. Here we report the first experimental demonstration of truly nanoscale guided waves in a metal– insulator–semiconductor device featuring low-loss and broadband operation. Near-field scanning optical microscopy reveals mode sizes down to 50×60 nm2 at visible and near-infrared wavelengths propagating more than 20 times the vacuum wavelength. Interference spectroscopy confirms that the optical mode hybridization between a surface plasmon and a dielectric mode concentrates the hybridized mode inside a nanometre thin gap. This nanoscale waveguide holds promise for next generation on-chip optical communication systems that integrate light sources, modulators or switches, nonlinear and quantum optics. Metal-based nanostructures offer a solution to scale down photonics to the nanoscale. Sorgeret al. directly demonstrate waveguiding of ultra-small propagating waves at visible and near-infrared frequencies using NSOM imaging, with the potential for nanoscale photonic applications such as bio-sensing.
250 citations
Posted Content•
TL;DR: In this article, the performance and full potential of ACO-OFDM has been investigated in the literature, and a new detection scheme was proposed to reduce the noise at the Flip-OFD receiver by almost 3dB.
Abstract: Unipolar communications systems can transmit information using only real and positive signals. This includes a variety of physical channels ranging from optical (fiber or free-space), to RF wireless using amplitude modulation with non-coherent reception, to baseband single wire communications. Unipolar OFDM techniques enable to efficiently compensate frequency selective distortion in the unipolar communication systems. One of the leading examples of unipolar OFDM is asymmetric clipped optical OFDM (ACO-OFDM) originally proposed for optical communications. Flip-OFDM is an alternative approach that was proposed in a patent, but its performance and full potentials have never been investigated in the literature. In this paper, we first compare Flip-OFDM and ACO-OFDM, and show that both techniques have the same performance but different complexities (Flip-OFDM offers 50% saving). We then propose a new detection scheme, which enables to reduce the noise at the Flip-OFDM receiver by almost 3dB. The analytical performance of the noise filtering schemes is supported by the simulation results.
192 citations
TL;DR: In this article, the amplitude and phase of ultrafast optical pulses with the aid of a synchronized incoherently related clock pulse were measured using a novel variation of spectral phase interferometry for direct electric field reconstruction (SPIDER) that exploits degenerate four-wave mixing.
Abstract: he recent introduction of coherent optical communications has created a compelling need for ultrafast phase-sensitive measurement techniques operating at milliwatt peak power levels and in timescales ranging from sub-picoseconds to nanoseconds. Previous reports of ultrafast optical signal measurements in integrated platforms include time-lens temporal imaging on a silicon chip and waveguide-based frequency-resolved optical gating (FROG). Time-lens imaging is phase-insensitive, and waveguide-based FROG methods require the integration of long tunable delay lines, which is still an unsolved challenge. Here, we report a device capable of characterizing both the amplitude and phase of ultrafast optical pulses with the aid of a synchronized incoherently related clock pulse. It is based on a novel variation of spectral phase interferometry for direct electric-field reconstruction (SPIDER) that exploits degenerate four-wave mixing in a CMOS-compatible chip. We measure pulses with a peak power of 1 THz, and up to 100 ps pulsewidths, yielding a timeg-bandwidth product of >100.
184 citations
TL;DR: A field trial of 100-Gbit/s Ethernet over an optical transport network (OTN) is conducted using a real-time digital coherent signal processor and the recovery time of 12 msec is observed in an optical route switching experiment, which is achieved through fast chromatic dispersion estimation functionality.
Abstract: A field trial of 100-Gbit/s Ethernet over an optical transport network (OTN) is conducted using a real-time digital coherent signal processor. Error free operation with the Q-margin of 3.2 dB is confirmed at a 100 Gbit/s Ethernet analyzer by concatenating a low-density parity-check code with a OTN framer forward error correction, after 80-ch WDM transmission through 6 spans x 70 km of dispersion shifted fiber without inline-dispersion compensation. Also, the recovery time of 12 msec is observed in an optical route switching experiment, which is achieved through fast chromatic dispersion estimation functionality.
158 citations
TL;DR: In this article, the authors provide a review of optical OFDM slanted towards emerging optical fiber networks, from its basic mathematical formation to its salient disadvantages and advantages, and reveal the unique characteristics of the fiber optical channel and identify the challenges and opportunities in the application of OFDM.
Abstract: Fast advancing silicon technology underpinned by Moore's law is creating a major transformation in optical fiber communications. The recent upsurge of interests in optical orthogonal frequency-division multiplexing (OFDM) as an efficient modulation and multiplexing scheme is merely a manifestation of this unmistakable trend. Since the formulation of the fundamental concept of OFDM by Chang in 1966 and many landmark works by others thereafter, OFDM has been triumphant in almost all the major RF communication standards. Nevertheless, its application to optical communications is rather nascent and its potential success in the optical domain remains an open question. This tutorial provides a review of optical OFDM slanted towards emerging optical fiber networks. The objective of the tutorial is two-fold: (i) to review OFDM fundamentals from its basic mathematical formation to its salient disadvantages and advantages, and (ii) to reveal the unique characteristics of the fiber optical channel and identify the challenges and opportunities in the application of optical OFDM.
152 citations
01 Dec 2011
TL;DR: This work uses the Monte Carlo approach to simulate the trajectories of emitted photons propagating in water towards the receiver and shows that in most practical cases, the time dispersion is negligible and does not induce any inter-symbol interference on the received symbols.
Abstract: We consider in this paper channel modeling for underwater optical channels. In particular, we focus on the channel impulse response and quantify the channel time dispersion under different conditions of water type, link distance, and transmitter/receiver parameters. We use the Monte Carlo approach to simulate the trajectories of emitted photons propagating in water towards the receiver. We show that in most practical cases, the time dispersion is negligible and does not induce any inter-symbol interference on the received symbols. Our results can be used to appropriately set different system design parameters.
141 citations
TL;DR: In the encoding process, conventional algorithm employed for the generation of collinearly superimposed OVs is combined with a genetic algorithm to achieve high-volume OV multiplexing to increase the number of signal channels in free-space optical communication.
Abstract: We report an approach to the increase of signal channels in free-space optical communication based on composed optical vortices (OVs). In the encoding process, conventional algorithm employed for the generation of collinearly superimposed OVs is combined with a genetic algorithm to achieve high-volume OV multiplexing. At the receiver end, a novel Dammann vortex grating is used to analyze the multihelix beams with a large number of OVs. We experimentally demonstrate a digitized system which is capable of transmitting and receiving 16 OV channels simultaneously. This system is expected to be compatible with a high-speed OV multiplexing technique, with potentials to extremely high-volume information density in OV communication.
TL;DR: The results indicate that the performance of the relay-assisted system is much better than that of the MT system in different cases considered and shows that there is an optimum place for the relay from the BEP point of view.
Abstract: Fading and path loss are the major challenges in practical deployment of free space optical communication systems. In this paper, a cooperative free space communication via an optical amplify-and-forward relay is considered to deal with these challenges. We use photon counting approach to investigate the system bit error probability (BEP) performance and study the effects of atmospheric turbulence, background light, amplified spontaneous emission, and receiver thermal noise on the system performance. We compare the results with those of the multiple-transmitter (MT) system. The results indicate that the performance of the relay-assisted system is much better than that of the MT system in different cases considered. We show that there is an optimum place for the relay from the BEP point of view.
01 Dec 2011
TL;DR: The performance analysis of Flip-OFDM is conducted and additional modification to the original scheme is proposed in order to compare the performance of both techniques, showing that both techniques have the same performance but different hardware complexities.
Abstract: We consider two uniploar OFDM techniques for optical wireless communications: asymmetric clipped optical OFDM (ACO-OFDM) and Flip-OFDM. Both techniques can be used to compensate multipath distortion effects in optical wireless channels. However, ACO-OFDM has been widely studied in the literature, while the performance of Flip-OFDM has never been investigated. In this paper, we conduct the performance analysis of Flip-OFDM and propose additional modification to the original scheme in order to compare the performance of both techniques. Finally, it is shown by simulation that both techniques have the same performance but different hardware complexities. In particular, for slow fading channels, Flip-OFDM offers 50% saving in hardware complexity over ACO-OFDM at the receiver.
TL;DR: It was shown that practical communication is only feasible when the line rate of the dimming modulation is at least twice the frequency assigned to the largest multitone subcarrier frequency, and under this constraint and when using a suitably modified demodulation scheme, dimming does not influence the data transmission.
Abstract: In the field of indoor wireless networks, visible-light communications is garnering increasing attention. One of the type of emitters used in this technology is white light-emitting diodes, which can synergistically provide both illumination and data transmission. Discrete multitone modulation is attractive for visible-light communications. One of the issues to be addressed in these synergetic use cases is how to incorporate light dimming while not corrupting the communication link. In this paper, the performance of a visible-light communication system combining pulse-width modulation for dimming and discrete multitone for data transmission was investigated. Performance indicators were addressed, i.e., the signal-to-interference ratio due to dimming and the achievable bit-error ratio in the absence of additional noise. By aid of simulations it was shown that practical communication is only feasible when the line rate of the dimming modulation is at least twice the frequency assigned to the largest multitone subcarrier frequency. The results demonstrate that under this constraint and when using a suitably modified demodulation scheme, dimming does not influence the data transmission.
Patent•
20 Nov 2011
TL;DR: In this paper, a standardized electrical connector of a conventional light bulb or tube with one or more light emitting diodes (LEDs) electrically coupled to at least one electrical connector compatible with the conventional light connector, wherein the LEDs include a multiband-type ultra-wideband (UWB) transceiver, a controller coupled to the LEDs, the controller adjusting LED light output and communicating with the optical network using the optical transmitter and receiver.
Abstract: Systems and methods are disclosed for use in conjunction with a standardized electrical connector of a conventional light bulb or tube with one or more light emitting diodes (LEDs) electrically coupled to at least one electrical connector compatible with a conventional light connector, wherein the LEDs include at least one multiband-type ultra-wideband (UWB) transceiver having one or more optical channels defined using one or more OFDM bands; and a controller coupled to the LEDs, the controller adjusting LED light output and communicating with the optical network using the optical transmitter and receiver. In other embodiments, the LEDs include at least one optical transmitter and receiver optically coupled to an optical network using at least one LED with a first mode to generate light and a second mode to receive optical transmissions using ambient light.
TL;DR: In this article, a simple on-off keying (OOK) predistortion scheme together with a simple first-order resistance-capacitance equalisation circuit was proposed to increase the modulation speed of a white-light high-brightness LED (HB-LED).
Abstract: In addition to the illumination purpose, using a light-emitting diode (LED) for indoor optical wireless communication has attracted much attention recently. Proposed and demonstrated is the use of a simple on-off keying (OOK) predistortion scheme together with a simple first-order resistance-capacitance equalisation circuit to increase the modulation speed of a white-light high-brightness LED (HB-LED). Optical filtering and complicated modulation formats are not required. Since only OOK modulation is used, the signal modulation and detection are very simple. Also are compared the different combinations of the system designs. By using first-order equalisation together with a predistortion, a bit-error rate of -10 -10 at 10 Mbit/s can be easily achieved when using the 1 MHz bandwidth phosphor-based white HB-LED.
18 Sep 2011
TL;DR: A routing and spectrum assignment algorithm for elastic optical networks that achieves high utilization of spectrum resources by considering the consecutiveness of common available spectrum slots among relevant fibers is proposed.
Abstract: This paper proposes a routing and spectrum assignment algorithm for elastic optical networks. The algorithm achieves high utilization of spectrum resources by considering the consecutiveness of common available spectrum slots among relevant fibers.
TL;DR: This letter reports an experimental demonstration of an indoor optical wireless multiple-input-multiple-output (MIMO) system with an imaging receiver, with results and discussion of how the system might be improved.
Abstract: This letter reports an experimental demonstration of an indoor optical wireless multiple-input-multiple-output (MIMO) system with an imaging receiver. The system setup consists of a 2 × 2 array of white light-emitting diodes (LEDs) and a 3 × 3 photodetector array, separated by a range of 2 m. The system operates at a bit rate of 2 Mb/s/channel, with error-free operation at certain positions within the system coverage area. An overview of the design specifications, optical design, and experimental setup are reported in this letter, together with results and discussion of how the system might be improved.
TL;DR: This paper reviews the history of coherent optical communications, the principle of coherent detection, and the concept of the digital coherent receiver, and discusses digital signal processing (DSP) for mitigating transmission impairments, coherent transmission characteristics of multi-level optical signals, and future prospects of coherent Optical communications.
Abstract: The recently-developed digital coherent receiver enables us to employ a variety of spectrally-efficient modulation formats such as M-ary phase-shift keying (PSK) and quadrature-amplitude modulation (QAM). Moreover, in the digital domain, we can equalize linear transmission impairments, which may stem from group-velocity dispersion (GVD) and polarization-mode dispersion (PMD) of fibers for transmission, because the phase information is preserved after coherent detection.This paper reviews the history of coherent optical communications, the principle of coherent detection, and the concept of the digital coherent receiver. After that, we discuss digital signal processing (DSP) for mitigating transmission impairments, coherent transmission characteristics of multi-level optical signals, and future prospects of coherent optical communications.
22 Dec 2011
TL;DR: Visible Light Communications uses modern solid-state lighting sources for free-space communication, and can also provide other functions such as illumination and information display.
Abstract: Visible Light Communications uses modern solid-state lighting sources for free-space communication, and can also provide other functions such as illumination and information display. This paper outlines some the challenges, and potential of this technique.
TL;DR: The findings of the paper suggest that the maximum capacity of nonlinear dispersive optical links can only be achieved by using multiple subcarriers carrying a few Gbaud each, and not by high symbol rate systems.
Abstract: In this paper, we use numerical simulations to show that the symbol rate has a significant effect on the nonlinearity-limited performance of coherent optical communication systems. We consider the case where orthogonal subcarriers are used to maximize the spectral efficiency. Symbol rates from 0.78125 Gbaud to 100 Gbaud and links of up to 3200 km, without inline dispersion compensation, were simulated. The results show that the optimal symbol rates for the 800-km link and 3200-km link were 6.25-Gbaud and 3.125-Gbaud respectively. The optimal baud rate decreases as the length of the link is increased. After 3200 km, the performance of the 100-Gbaud system was worst in the nonlinearity-limited regime producing a received Q 2.4-dB lower than the 3.125-Gband system. The variation in the nonlinearity-limited performance is explained by using Cross-Phase-Modulation (XPM) theory and by considering the RF spectra of the intensity fluctuations of the signal along the link. The findings of the paper suggest that the maximum capacity of nonlinear dispersive optical links can only be achieved by using multiple subcarriers carrying a few Gbaud each, and not by high symbol rate systems.
TL;DR: In this paper, the authors demonstrate that the number of kernels of a Volterra model based equalizer can be significantly reduced using the modified Gram-Schmidt method with reorthogonalization techniques.
Abstract: A main drawback of Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) system is its sensitivity to fiber nonlinearity. Nonlinear electrical equalizer based on Volterra model has been demonstrated capable of compensating fiber nonlinear distortion in an OOK or PSK optical communication system. However, the implementation complexity of a Volterra model based electrical equalizer prohibits its deployment in a real-life CO-OFDM system. In this paper, we demonstrate that the number of kernels of a Volterra model based equalizer can be significantly reduced using the modified Gram-Schmidt method with reorthogonalization techniques. The resulting “sparse” Volterra model based electrical equalizer and the electrical equalizer based on the “full” Volterra model have comparable performance and can compensate intra-channel nonlinearity of a 16-QAM 100 Gbit/s CO-OFDM System.
TL;DR: An optical transmitter based on dynamic optical arbitrary waveform generation (OAWG) which is capable of creating high-bandwidth (THz) data waveforms in any modulation format using the parallel synthesis of multiple coherent spectral slices is demonstrated.
Abstract: We demonstrate an optical transmitter based on dynamic optical arbitrary waveform generation (OAWG) which is capable of creating high-bandwidth (THz) data waveforms in any modulation format using the parallel synthesis of multiple coherent spectral slices. As an initial demonstration, the transmitter uses only 5.5 GHz of electrical bandwidth and two 10-GHz-wide spectral slices to create 100-ns duration, 20-GHz optical waveforms in various modulation formats including differential phase-shift keying (DPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK) with only changes in software. The experimentally generated waveforms showed clear eye openings and separated constellation points when measured using a real-time digital coherent receiver. Bit-error-rate (BER) performance analysis resulted in a BER < 9.8 × 10(-6) for DPSK and QPSK waveforms. Additionally, we experimentally demonstrate three-slice, 4-ns long waveforms that highlight the bandwidth scalable nature of the optical transmitter. The various generated waveforms show that the key transmitter properties (i.e., packet length, modulation format, data rate, and modulation filter shape) are software definable, and that the optical transmitter is capable of acting as a flexible bandwidth transmitter.
Patent•
31 Mar 2011
TL;DR: In this article, a first optical coupler consisting of a first arm, a second arm and a third arm was used to increase the repetition rate of a light source. But the second arm of the first coupler was either delayed by an amount (τ) or substantially undelayed.
Abstract: In one embodiment, the invention relates to an apparatus for increasing the repetition rate in a light source. The apparatus includes a first optical coupler comprising a first arm, a second arm and a third arm; a first mirror in optical communication with the second arm of the first optical coupler; and a first optical delay line having a first end in optical communication with the third arm of the first optical coupler and a second end in optical communication with a second mirror, wherein light entering the first arm of the first optical coupler leaves the first arm of the first optical coupler either delayed by an amount (τ) or substantially undelayed.
TL;DR: This work combines the attractive properties of slow light propagation in a nanostructured periodic waveguide together with a high speed semiconductor pn diode, and demonstrates a highly efficient and mass manufacturable 500 µm-long silicon electro-optical device, exhibiting error free modulation up to 20 Gbit/s.
Abstract: While current optical communication networks efficiently carry and process huge amounts of digital information over large and medium distances, silicon photonics technology has the capacity to meet the ceaselessly increasing demand for bandwidth via energy efficient, inexpensive and mass producible short range optical interconnects. In this context, handling electrical-to-optical data conversion through compact and high speed electro-optical modulators is of paramount importance. To tackle these challenges, we combine the attractive properties of slow light propagation in a nanostructured periodic waveguide together with a high speed semiconductor pn diode, and demonstrate a highly efficient and mass manufacturable 500 µm-long silicon electro-optical device, exhibiting error free modulation up to 20 Gbit/s. These results, supported by modulation rate capabilities reaching 40 Gbit/s, pave a foreseeable way towards dense, low power and ultra fast integrated networks-on-chip for future chip-scale high performance computing systems.
04 Jul 2011
TL;DR: It is found that the implementation of a light emitting diode based visible light communication system, for intelligent transportation in road safety applications, is well suited for traffic broadcast at low data rate and medium range.
Abstract: This paper discusses the implementation of a light emitting diode based visible light communication system, for intelligent transportation in road safety applications. The signal processing of both, transmitter and receiver are realized in a field programmable gate array using two Spartan-3E development kits. The implemented modulation scheme is based on direct sequence spread spectrum techniques. The performance of the overall system is evaluated and results are presented. It is found that the system is well suited for traffic broadcast at low data rate and medium range. The simulation results also show that spread spectrum modulation techniques mitigate the effect of noise produced by ambient artificial light sources.
14 Mar 2011
TL;DR: In this article, the suitability for optical communication towards 100 Gbit Ethernet as well as properties using optical feedback are investigated using quantum dot monolithic mode-locked lasers at 40 GHz.
Abstract: Quantum-dot monolithic mode-locked lasers at 40 GHz show sub-ps pulses using dispersion compensation techniques. Their suitability for optical communication towards 100 Gbit Ethernet as well as properties using optical feedback are investigated.
TL;DR: In this article, the performance analysis of a photonic microwave mixer used as a signal down-and up-converter based on cross-gain modulation in a semiconductor optical amplifier (SOA) is presented.
Abstract: The key goal of this paper consists of a theoretical and an experimental performances analysis of a photonic microwave mixer used as a signal down- and up-converter based on cross-gain modulation in a semiconductor optical amplifier (SOA). We give, by a small-signal analysis approach, the analytical equations of the output optical power carrying the down- and up-converted signal. Simplified formulas are developed, relating the mixing conversion gain to the modeling parameters of the SOA. The efficiency of the photonic microwave mixer based on an SOA has been evaluated in terms of mixing conversion gain, third-order input intercept point, and electrical phase noise. In addition, a subcarrier modulated by a QPSK, a 16 quadratic-amplitude modulation (QAM) and a 64 QAM at a data rate of 270 ksymb/s has been down converted from 1 GHz to 100 MHz with a low error vector magnitude of about 3.5%.
11 May 2011
TL;DR: In this paper, the authors presented a design for a photon counting optical receiver based on superconducting NbN nanowire detector arrays that will be employed in the ground terminal for the NASA Lunar Laser Communications Demonstration.
Abstract: In this paper we present a design for a photoncounting optical receiver—based on superconducting NbN nanowire detector arrays—that will be employed in the ground terminal for the NASA Lunar Laser Communications Demonstration. The ground receiver is designed with four, 40 cm apertures, each coupled to a novel multi-mode polarization-maintaining fiber. The receiver is designed to receive a variable-rate pulse-position-modulated signal with a maximum data rate of 622 Mb/s.
01 Jan 2011
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