Showing papers on "Optical Carrier transmission rates published in 2009"

Ultrafast all-optical modulation in GaAs photonic crystal cavities

Abstract: We demonstrate all-optical modulation based on ultrafast optical carrier injection in a GaAs photonic crystal cavity using a degenerate pump-probe technique. The observations agree well with a coupled-mode model incorporating all relevant nonlinearities. The low switching energy (∼120 fJ), small energy absorption (∼10 fJ), fast on-off response (∼15 ps), limited only by carrier lifetime, and a minimum 10 dB modulation depth suggest practical all-optical switching applications at high repetition rates.

10-Gbit/s Wireless Link Using InP HEMT MMICs for Generating 120-GHz-Band Millimeter-Wave Signal

Abstract: We have developed a 120-GHz-band wireless link whose maximum transmission data rate is 11.1 Gbit/s. The wireless link uses millimeter-wave monolithic integrated circuits (MMICs) for the generation of a 120-GHz-band millimeter-wave wireless signal. The MMICs were fabricated using 0.1-mum-gate InP-HEMTs and coplanar waveguides. The wireless link can handle four kinds of data rate for OC-192 and 10-Gbit Ethernet standards with and without forward error correction (FEC). We succeeded in the error-free transmission of a 10-Gbit/s signal over a distance of 800 m. The introduction of FEC into the 120-GHz-band wireless link decreased the minimum received power for error-free transmission, and improved the reliability of the link.

Microwave Frequency Measurement Based on Optical Power Monitoring Using a Complementary Optical Filter Pair

Abstract: An approach to the measurement of a microwave frequency based on optical power monitoring using a complementary optical filter pair is proposed and investigated. In the proposed system, a microwave signal is applied to a Mach-Zehnder modulator, which is biased at the minimum transmission point to suppress the optical carrier. The carrier-suppressed optical signal is then sent to the complementary optical filter pair, with the powers from the complementary filters measured by two optical power meters. A mathematical expression that relates the microwave frequency and the optical powers is developed. Experiments are performed to verify the effectiveness of the proposed approach. The performance of the proposed system in terms of the frequency measurement range, operation stability, and robustness to noise is also investigated.

Modulation and multiplexing in optical communication systems

Abstract: Digital electronics and optical transport The rapid transition from analog to digital systems over the past ~50 years has enabled universal processing of all kinds of information, fundamentally without loss of quality [1]. Breakthroughs in digital semiconductor technologies and their enormous ability to scale [2] have enabled cost-effective mass-production of richly functional yet highly reliable and power-efficient microchips that are found in virtually any electronic device today, from high-end internet routers to low-end consumer electronics. Closely coupled to the generation, processing, and storage of digital information is the need for data transport, ranging from short on-chip [3] and board-level [4,5] data buses all the way to long-haul transport networks spanning the globe [6,7] and to deep-space probes collecting scientific data [8], cf. Fig. 1 [5,10]. Each of these very different applications brings its own set of technical challenges, which can be addressed using electronic, radio-frequency (RF), or optical communication systems. Among the different communication technologies, optical communications generally has the edge over baseband electronic or RF transmission systems whenever high aggregate bit rates and/or long transmission distances are involved. Both advantages are deeply rooted in physics: First, the high optical carrier frequencies allow for high-capacity systems at small relative bandwidths. For example, a mere 2.5% bandwidth at a carrier frequency of 193 THz (1.55 μm wavelength) opens up a 5-THz chunk of continuous communication bandwidth. Such “narrow-band” systems are much easier to design than systems with a large relative bandwidth. Second, transmission losses at optical frequencies are usually very small compared to baseband electronic or RF technologies. Today’s optical telecommunication fibers exhibit losses of less than 0.2 dB/km; the loss of typical coaxial cables supporting ~1 GHz of bandwidth is 2 to 3 orders of magnitude higher. In free-space systems optical beams have much smaller divergence angles than in the microwave regime, at the expense of significantly exacerbated antenna pointing requirements, though. The narrow beam width favorably translates into the system’s link budget, in particular in space-based systems where atmospheric absorption is less of a problem. Apart from the above two major advantages, other considerations sometimes come into play, such as the unregulated spectrum in the optical regime or the absence of electromagnetic interference.

Microwave Photonic Delay Line With Separate Tuning of the Optical Carrier

Abstract: Significant performance improvement for photonic delay lines in microwave-photonics based on a new concept of separately tuning the optical carrier is proposed and analyzed. Optical microresonator delay lines using a balanced SCISSOR design with additional resonators to separately tune the carrier phase delay to provide a true-time-delay for the broadband microwave signal are presented. Significant improvements in broadband tunable delay and devices losses are predicted.

Stable transmission of radio frequency signals on fiber links using interferometric delay sensing.

Abstract: We demonstrate distribution of a 2850 MHz rf signal over stabilized optical fiber links. For a 2.2 km link we measure an rms drift of 19.4 fs over 60 h, and for a 200 m link an rms drift of 8.4 fs over 20 h. The rf signals are transmitted as amplitude modulation on a continuous optical carrier. Variations in the delay length are sensed using heterodyne interferometry and used to correct the rf phase. The system uses standard fiber telecommunications components.

Instantaneous Microwave Frequency Measurement Using Photonic Technique

Abstract: We propose a novel photonic technique for measuring microwave frequency instantaneously over a wide bandwidth. In our approach, an optical carrier is divided into two parts. Both parts are modulated by an unknown microwave signal; one part is phase modulated while the other one is intensity modulated. The two differently modulated optical signals are then launched into single-mode fibers with the same lengths to introduce microwave signal power fading. After photodetection, the radio-frequency powers of the two parts are used to generate an amplitude comparison function which provides a frequency-to-power mapping. The proposed scheme is simple and is experimentally verified over a frequency range of 13.5 GHz with a measurement error less than plusmn0.3 GHz.

A Novel Bidirectional 60-GHz Radio-Over-Fiber Scheme With Multiband Signal Generation Using a Single Intensity Modulator

Abstract: We experimentally demonstrated a novel radio-over-fiber system to simultaneously generate dispersion-tolerant multiband downstream signals, including millimeter-wave, microwave, and baseband signals, based on multicarrier modulation in an intensity modulator and a subsequent optical filter. The uplink connection is realized by remodulation of downlink optical carrier and by baseband detection in the central office. The high-dispersion tolerance comes from the subcarrier cross-selection with only one data-bearing tone before signal beating in the receiver. The power penalty of 1.4 dB for 60-GHz carrier and negligible degradation for baseband and upstream are achieved for 2.5-Gb/s signal after 50-km single-mode fiber (SMF-28) and 4-m air link transmission. The theoretical analysis is also provided to obtain the optimal operation point.

Photonic measurement of microwave frequency based on phase modulation

Abstract: A photonic approach for microwave frequency measurement is proposed. In this approach, an optical carrier is modulated by an unknown microwave signal through a phase modulator. The modulated optical signal is then split into two parts; one part passes through a spool of polarization maintaining fiber (PMF) and the other one, through a dispersion compensation fiber (DCF), to introduce different microwave power penalties. After the microwave powers of the two parts are measured by two photodetectors, a fixed frequency-to-power mapping is established by obtaining an amplitude comparison function (ACF). A proof-of-concept experiment demonstrates frequency measurement over a range of 10.5 GHz, with measurement error less than ±0.07 GHz.

Sampled Analog Optical Links

Abstract: We present a new intensity-modulated analog optical link architecture in which a pulsed optical carrier replaces the standard low-noise continuous-wave laser. Through a time-domain analysis of the sampled link architecture, we show that the link performance metrics reduce to those of a conventional analog optical link in the absence of photodiode nonlinearity. Experimental measurements of the link gain and third-order nonlinearity are presented, emphasizing the link performance as a function of received photocurrent. The work presented here demonstrates that the performance of sampled analog optical links rivals that of the conventional architecture, even in the presence of significant photodiode nonlinearity.

Internal Bandwidth Equalization in a CMOS-Compatible Si-Ring Modulator

Abstract: Bandwidth equalization using a simple complementary metal-oxide-semiconductor-compatible tunable silicon-ring modulator is shown. We demonstrate >35-GHz small signal bandwidth and use the resonator to mitigate bandwidth limitations from other measurement system components. Configuring the optical carrier to be off resonance within the ring free-spectral range allows high-frequency enhancement and low-frequency suppression of the S21 parameter to achieve system response equalization. Our results suggest that the carrier and modulation sidebands can have very different transient characteristics within the ring modulator.

Optical Counter-Phase System And Method Of RF Interference Cancellation

Abstract: A system and method for cancellation of RF interference in the optical domain. The system and method utilize two Mach-Zehnder electrooptic modulators biased for parallel counter-phase modulation. The method of signal subtraction is referred to as incoherent optical subtraction, since two independent laser sources serve as the optical carrier waves. The system has produced the broadband cancellation result while simultaneously recovering a 50 dBm signal which was initially “buried” under the broadband interference. The cancellation depths achieved by the system are due to the accurate channel tracking and precise time delays attainable with modern optical devices—unattainable with state-of-the-art electronic devices at the time of this writing.

Highly Linear Integrated Optical Transmitter for Subcarrier Multiplexed Systems

Abstract: A highly linear optical transmitter for radio-over-fiber subcarrier-multiplexed systems is presented. An integrated dual Mach-Zehnder modulator (MZM) is utilized to combine an optical carrier suppressed signal with an optical carrier. The proposed transmitter enables more than 10-dB improvement in the carrier-to-interference ratio compared to a quadrature biased MZM, and similar results to low biased MZM considering similar insertion loss. Negligible radio-frequency power dependence with temperature-induced bias drift is reported, while the low biased MZM is penalized by more than 12 dB for a 15% bias drift. The proposed transmitter reduces the minimum error vector magnitude from 4.2% to 3.5%, when compared to quadrature biased MZM, for a 54-Mb/s orthogonal frequency-division-multiplexed signal.

Single wavelength source-free OFDMA-PON communication systems and methods

Abstract: Methods and systems for processing communication signals in an Orthogonal Frequency Division Multiple Access (OFDMA)-Passive Optical Network (PON) are disclosed. An optical carrier at a wavelength generated at an optical line terminal (OLT) may be reused by optical network units (ONUs) in the network for upstream transmission of data signals to the OLT. In addition, each ONU may perform carrier suppression to avoid broadband beating noise resulting from the simultaneous transmission of upstream data signals on the same wavelength. Further, the optical source at the OLT used to generate the optical carrier may be reused as a local oscillator for coherent detection of received upstream signals to minimize any frequency offsets.

Optical I-Q-modulator

Abstract: The invention describes a modulator for the quadrature modulation of an optical carrier signal with an I- and a Q-portion, where a first optical multimode interferometer (MMI) splits the optical carrier signal into four branches and that in pairs of branches the I-portion and the Q-portion respectively is modulated with a Mach-Zehnder-Structure and a second optical multimode interferometer (MMI) combines the modulated I-portion and Q-portion again to one quadrature modulated optical output signal (OS).

Photonic scanning receiver using an electrically tuned fiber Bragg grating

Abstract: A 5-cm-long electrically tuned fiber Bragg grating is used to filter a microwave signal on an optical carrier at 1.55 mum. A chirped distributed-feedback structure is employed, with a transmission bandwidth of 54 MHz and relative optical carrier rejection of >30 dB for rf frequencies >2 GHz. The rapid monotonic sweep of the Bragg wavelength is translated into a fast-frequency sweep for rf analysis.

Optical Millimeter-Wave Up-Conversion Employing Frequency Quadrupling Without Optical Filtering

Abstract: This study presents two optical frequency quadrupling techniques for generating high-purity millimeter-wave signals with optical carrier suppression. To our best knowledge, this investigation demonstrates for the first time that a frequency quadrupling system requires only a single integrated Mach-Zehnder modulator without an optical narrowband filter to remove undesired optical sidebands. Since no optical filter is needed, fast frequency tuning is straightforward and this approach is particularly attractive for the optical up-conversion in the wavelength-division-multiplexing radio-over-fiber systems. This study provides both theoretical analysis and experimental demonstration. The generated optical millimeter-wave signals are of very high quality with optical carrier and undesired harmonic distortion suppression ratio of more than 36 dB.

Wideband Time-Domain Transfer Matrix Model Equivalent Circuit for Short Pulse Propagation in Semiconductor Optical Amplifiers

Abstract: A general time-domain transfer matrix model is presented which is able to handle waves perturbed by a locally uniform medium and which is particularly well adapted to equivalent circuit implementations. We use this model for the simulation of a picosecond pulse propagating through a semiconductor optical amplifier (SOA). The signal propagation through the SOA is described by an envelope propagation equation, taking into account the optical carrier's wavelength evolution (modulated wavelenght division multiplexing spectrum consideration). We present the SOA equivalent circuit and its implementation under a commercially available software. The SOA is described through the wideband definition of all parameters which makes it comparable to a real component. Simulations have been validated with experimental results over at least 60 nm. We simulate both amplitude and phase evolutions of a picosecond pulse and a continuous-wave probe at various pulse's optical carrier wavelengths. We show a strong influence of the imaginary part of the complex time delay on the phase variations, and as a consequence on the additional spectral red or blue shift.

Development of Electro-Optic Phase Modulator for 94 GHz Imaging System

Abstract: This paper presents the latest improvements in design and fabrication of ridged LiNbO3 optical phase modulators operating in the W-band for millimeter-wave imaging applications at 94 GHz. It describes the design conditions for effective index matching between optical carrier at 1550 nm and millimeter-wave signal, as well as impedance matching and propagation losses reduction. The impacts of different geometric parameters on the device performance are discussed. In addition, the paper reports the diverse material processing techniques for device fabrication. Characterization of the fabricated devices shows conversion efficiency as high as 1.045 W- 1 at 94 GHz with a 7 V dc half-wave voltage and a 3.7 dB optical insertion loss.

Optical mm-Wave Signal Generation by Frequency Quadrupling Using an Optical Modulator and a Silicon Microresonator Filter

Abstract: By adjusting the direct current (DC) bias on an electrooptic modulator to suppress the first-order sideband and subsequently using a double-waveguide micro-ring resonator to filter out the optical carrier, millimeter (mm)-wave signal was generated at a frequency of four times the 10-GHz local oscillator. A monolithic integrated silicon-based optical mm-wave signal generator by frequency quadrupling is proposed. A silicon integrated microresonator filter was fabricated and its design parameters are given. High extinction ratio optical mm-wave signal was obtained. The single sideband noise spectrum of the generated 40-GHz optical signal was measured, showing similar performance when compared with that generated by a radio-frequency synthesizer.

A Single-40 Gb/s Dual-20 Gb/s Serializer IC With SFI-5.2 Interface in 65 nm CMOS

Abstract: Demands for reducing power, size, and cost of optical transponder module have been increasing. Recent development of 40Gb/s optical signal transmission technology like DQPSK modulation [1] and sub-100nm CMOS IC technology with f T of more than 100GHz opened up new CMOS IC solution [2,3]. This paper describes the prototype serializer (SER) IC for a 40Gb/s optical transponder module featuring SFI5.2 input interface and two output modes, dual 20Gb/s and single 40Gb/s, to support SONET OC-768, SDH STM 256 and ITU G.709. The data rate covers from 21.5 to 22.3Gb/s for the dual-20Gb/s mode, and from 39.8 to 44.6Gb/s for the single-40Gb/s mode.

$W$ -band Transmitter and Receiver for 10-Gb/s Impulse Radio With an Optical-Fiber Interface

Abstract: A W-band millimeter-wave transmitter and receiver that are based on impulse radio (IR) architecture were developed. The IR-based apparatuses have an optical-fiber input/output interface board that supports multi protocol signals (OC-192 and 10 GbE) and that implements a forward error correction (FEC), enabling 10-Gb/s data transmission both in space and fiber seamlessly. Analyzing an IR-based receiver model with simple on/off demodulation architecture, required signal-to-noise ratios were calculated for IR-based systems affected by various inter-symbol interference (ISI) levels. A millimeter-wave module used in the transmitter, consisting of a 6.5-ps pulse modulator with InP-based HEMTs and a band-pass filter formed on an alumina substrate, emitted wavelets, or RF pulses, with an average power of -26 dBm, occupying frequencies between 78-93 GHz. A front-end module used in the receiver, consisting of two cascaded low-noise amplifiers, an envelope detector, and a limiting amplifier, had a sensitivity of -36 dBm. In a back-to-back test where the transmitter and receiver were connected by a waveguide, disabling the FEC, error-free operation was achieved with a test pattern of PRBS 231-1 at the OC-192 compliant data rate of 9.95328 Gb/s. Furthermore, using a horn antenna and enabling the FEC, radio transmission and reception in a distance of 20 cm were confirmed with a bit error rate of less than 10-12. These results confirmed the basic technologies for simple and compact IR-based systems, which could be used as an alternative to fiber optic cables.

Ultrafast all-optical modulation in GaAs photonic crystal cavities

Abstract: We demonstrate all-optical modulation via ultrafast optical carrier injection in a GaAs photonic crystal cavity using a degenerate pump-probe technique. The low switching(absorption) energy∼120fJ(10fJ), and fast response(∼15ps), limited only by carrier lifetime, suggest practical all-optical switching applications.

Time stretch enhanced recording scope

Abstract: A time-stretched enhanced recording scope (TiSER) is described using time stretch analog-to-digital conversion in a real-time burst mode. A chirped optical signal is modulated in response to receiving segments of an input signal. The optical signal with its modulated input signal, is stretched through an optical medium and digitized to represent the waveform segment. TiSER provides ultra-fast real-time sampling within short segment bursts of the original input signal while providing an ability to detect non-repetitive events. Methods and apparatus are also described for providing real-time information about inter-symbol information (ISI), rapidly determining bit-error rates (BER), performing time-domain reflectometry (TDR), generating eye diagrams for serial data, facilitating digital correction of data, clock recovery, optical carrier phase recovery, and otherwise increasing the speed and/or accuracy of a diverse range of high-speed signal measurement and processing activities.

Measurement of Microwave Frequency Using a Monolithically Integrated Scannable Echelle

Abstract: A novel approach to the measurement of microwave signal frequency is studied and demonstrated. The approach is based on a monolithically integrated echelle diffractive grating (EDG). The microwave signal is converted to an optical signal of two sidebands using an optical carrier and a Mach-Zehnder modulator. One of the sidebands is then filtered out by a fiber Bragg grating, while the other sideband is characterized by an EDG-based interrogator. Due to the better than 1-pm interro- gation resolution of this interrogator, the center wavelength of the sideband tested is capable of being accurately measured. Combining this data with the wavelength of the optical carrier used, the frequency of the microwave signal can be calculated. The results obtained are found to be in good agreement with those of the microwave signals.

Uplink downlink construction for radio frequency optical fiber transmission system and method for providing light carrier to uplink

Abstract: The invention relates to an uplink, downlink construction of radio-frequency optical fiber transmission system, and a method for providing an optical carrier to the uplink. An uplink downlink construction of radio-frequency optical fiber transmission system is proposed, and an optical carrier filter is provided in the downlink construction. A double band signal having an optical carrier is generated by a Mach-Zhender modulator, wherein the optical carrier is suppressed using the optical carrier filter, so as to improve modulation degree of the signal. And an optical signal generated by the SBS having frequency lower than the optical carrier frequency 11GHz is provided as optical carrier. The invention is simple in construction, easy to implement, stable in performance, low in cost, easy to apply and propagate.

Generation of optical millimeter-wave signals and vector formats using an integrated optical I/Q modulator [Invited]

Abstract: This study discusses two key technologies used in radio-over-fiber (RoF) systems, namely, the generation and transmission of millimeter-wave signals and optical modulation schemes capable of carrying vector signal formats and utilizing the continuous performance improvements offered by digital signal processing. A cost-effective frequency-quadrupling technique capable of generating millimeter-wave signals up to 72 GHz is proposed. The generated optical millimeter-wave signals have very high quality, with an optical carrier and harmonic distortion suppression ratio exceeding 36 dB. An optical modulation scheme that can support a 64-QAM, 16 Gbits/s orthogonal frequency-division multiplexing RoF system is also demonstrated. Results of this study demonstrate that both methods offer realistic solutions to support future wireless systems.

Design and performance of a distributed aperture millimeter-wave imaging system using optical upconversion

Abstract: Passive imaging using millimeter waves (mmWs) has many advantages and applications in the defense and security markets. All terrestrial bodies emit mmW radiation and these wavelengths are able to penetrate smoke, blowing dust or sand, fog/clouds/marine layers, and even clothing. One primary obstacle to imaging in this spectrum is that longer wavelengths require larger apertures to achieve the resolutions typically desired in surveillance applications. As a result, lens-based focal plane systems tend to require large aperture optics, which severely limit the minimum achievable volume and weight of such systems. To overcome this limitation, a distributed aperture detection scheme is used in which the effective aperture size can be increased without the associated volumetric increase in imager size. However, such systems typically require high frequency (~ 30 - 300 GHz) signal routing and down conversion as well as large correlator banks. Herein, we describe an alternate approach to distributed aperture mmW imaging using optical upconversion of the mmW signal onto an optical carrier. This conversion serves, in essence, to scale the mmW sparse aperture array signals onto a complementary optical array. The optical side bands are subsequently stripped from the optical carrier and optically recombined to provide a real-time snapshot of the mmW signal. In this paper, the design tradeoffs of resolution, bandwidth, number of elements, and field of view inherent in this type of system will be discussed. We also will present the performance of a 30 element distributed aperture proof of concept imaging system operating at 35 GHz.

A 40 Gb/s Multi-Data-Rate CMOS Transmitter and Receiver Chipset With SFI-5 Interface for Optical Transmission Systems

Abstract: A fully integrated 40 Gb/s transmitter and receiver chipset with SFI-5 interface is implemented in a 65 nm CMOS technology and mounted in a plastic BGA package. The transmitter chip provides good jitter performance with a 40 GHz full-rate clock architecture that alleviates pattern-dependent jitter and eliminates duty cycle dependence. The measured RMS jitter on the output is 570 fs to 900 fs over the range of 39.8 Gb/s to 44.6 Gb/s with a 231-1 PRBS pattern. The receiver chip operates over the range of 37 Gb/s to 41 Gb/s. The measured RMS jitter on the recovered clock is 359 fs to 450 fs. By taking advantage of CMOS technology, each chip achieves low power consumption of 2.8 W and full integration of SFI-5 functions, PRBS generators/error checkers, a DPSK precoder/decoder, and control interfaces in a 4.9 × 5.2 mm2 die.