Showing papers on "Optical Carrier transmission rates published in 2006"

Hybrid DWDM-TDM long-reach PON for next-generation optical access

Abstract: A novel long-reach passive optical network (PON) architecture based on hybrid dense wavelength-division multiplexing (DWDM) and time-division multiplexing (TDM) is presented as a possible candidate for the next generation of optical access networks. The approach combines access and backhaul functions in a single optical network infrastructure that links end customers directly to core networks without the need for intermediate electronic conversions. A centralized optical carrier distribution and wavelength-independent remote modulation scheme is employed to avoid the potential inventory and deployment costs associated with the use of wavelength-specific lasers in the customer transmitter (TX). The customer TX is based on an electroabsorption modulator (EAM) monolithically integrated with two semiconductor optical amplifiers (SOAs), providing sufficient net gain and bandwidth to support large splitting factors and upstream bit rates up to 10 Gb/s. The experimental results reported show that the network, with a total reach of 100 km and an upstream bit rate of 10 Gb/s, can potentially support 17 TDM PONs operating at different wavelengths each with up to 256 customers, giving an aggregate number of 4352 customers in total.

A full-duplex radio-over-fiber system based on optical carrier suppression and reuse

Abstract: We have experimentally demonstrated a full-duplex radio-over-fiber system using a single light source at central station (CS). Optical carrier suppression modulation scheme was employed to generate 40-GHz optical millimeter wave and up-convert the baseband signal simultaneously at CS for downlink transmission while the same optical carrier was reused at base station for uplink connection. The bidirectional full-duplex 2.5-Gb/s data was successfully transmitted over 40-km standard single-mode fiber (SMF-28) for both upstream and downstream channels with less than 2-dB power penalty. This system shows simple cost-efficient configuration and good performance over long-distance delivery

Ultrawideband Impulse Radio Signal Generation Using a High-Speed Electrooptic Phase Modulator and a Fiber-Bragg-Grating-Based Frequency Discriminator

Abstract: We propose a novel approach to generating ultrawideband impulse radio signals in the optical domain. The proposed system consists of a laser source, an electrooptic phase modulator (EOPM), a fiber Bragg grating (FBG), and a photodetector (PD). The light source is phase modulated by an electrical Gaussian pulse train via the EOPM. The optical phase modulation to intensity modulation conversion is achieved by reflecting the phase modulated light at the slopes of the FBG that serves as a frequency discriminator. Electrical monocycle or doublet pulses are obtained at the output of the PD by locating the wavelength of the optical carrier at the linear or the quadrature slopes of the FBG reflection spectrum. The use of the proposed configuration to implement pulse polarity and pulse shape modulation in the optical domain is discussed. Experimental measurements in both temporal and frequency domains are presented

Analysis of optical carrier-to-sideband ratio for improving transmission performance in fiber-radio links

Abstract: In this paper, we investigate the optimum carrier-to-sideband ratio (CSR) for maximizing the transmission performance of an optically modulated millimeter-wave signal in a fiber-wireless system via experiment, theory, and simulation. We present a simple analytical model to assess the performance enhancement resulting from optical CSR variations. The model is capable of analyzing systems incorporating binary phase-shift keyed and quaternary phase-shift keyed modulation formats. We quantify the optical CSR of a point-to-point fiber-radio link and establish that the performance of the fiber-wireless links can be significantly improved when the optical signal is transmitted at the optimum CSR of 0 dB. The analysis further shows that the optimum optical CSR is independent of transmission bit rates.

High resolution frequency standard dissemination via optical fiber metropolitan network

Abstract: We present in this article results on a new dissemination system of an ultrastable reference signal at 100 MHz on a standard fiber network. The 100 MHz signal is simply transferred by amplitude modulation of an optical carrier. Two different approaches for compensating the noise introduced by the link have been implemented. The limits of the two systems are analyzed and several solutions are suggested in order to improve the frequency stability and to further extend the distribution distance. Nevertheless, our system is a good tool for the best cold atom fountains comparison between laboratories, up to 100 km, with a relative frequency resolution of 10 −14 at 1 s integration time and 10 −17 for 1 day of measurement. The distribution system may be upgraded to fulfill the stringent distribution requirements for the future optical clocks.

A Radio-Over-Fiber System With a Novel Scheme for Millimeter-Wave Generation and Wavelength Reuse for Up-Link Connection

Abstract: We proposed and experimentally demonstrated a novel scheme to generate an optical millimeter-wave and realized wavelength reuse for uplink connection in a radio-over-fiber system. We employed an optical interleaver to separate the spectrum of the double-sideband signals generated by a single-arm intensity external modulator. The separated first-order sideband modes were used to generate optical millimeter-wave with double RF frequency, while the separated optical carrier was reused for uplink connection

Ultrahigh-Speed OTDM-Transmission Technology

Abstract: This paper reviews ultrahigh-speed data transmission in optical fibers based on optical time division multiplexing (OTDM) transmission technology. Optical signal processing in the transmitter and receiver as well as the requirements on ultrahigh-speed data transmission over a fiber link are discussed. Finally, results of several OTDM-transmission experiments, including 160-Gb/s transmission over 4320 km, 1.28-Tb/s transmission over 240 km, and 2.56-Tb/s transmission over 160-km fiber link, are described

Methods and apparatus for optical transmission of digital signals

Abstract: A system (100) for transmitting digital information includes a transmitting apparatus (102) for generating an optical signal bearing digital information, a dispersive optical channel (104), and a receiving apparatus (110) for receiving the optical signal. The dispersive optical channel (104) is disposed to convey the optical signal from the transmitting apparatus (102) to the receiving apparatus (110). The transmitting apparatus includes an encoder (114) for encoding digital information into a series of blocks, each including a plurality of data symbols corresponding with one or more bits of digital information. A signal generator (118) generates a time-varying signal corresponding with each of said blocks. An optical transmitter (136) is arranged to apply the time-varying signal to an optical source (138) to produce an optical signal which includes an optical carrier and substantially only a single information bearing optical sideband in an optical frequency domain, the sideband corresponding with the time-varying signal. The receiving apparatus (110) includes an optical detector (146) for detecting the optical signal to produce a corresponding received time-varying electrical signal. The receiver further includes means (166) for generating a series of received data blocks from the time-varying electrical signal. An equaliser (168) performs an equalisation of received data symbols included in each data block to mitigate the effect of dispersion of the optical channel, thereby enabling the transmitted data symbols to be recovered.

Progress in optical modulation formats for high-bit rate WDM transmissions

Abstract: With the progress of optical communication systems, and especially the constraints brought by wavelength division multiplexing (WDM) transmissions and increased bit rates, new ways to convert the binary data signal on the optical carrier have been proposed. It appears clearly now that several of the methods proposed by research laboratories will be applied into commercial products soon due to the large improvements generated. This paper intends to summarize some of the most interesting proposed modulation formats for high bit rate (especially 40 Gb/s) WDM transmissions

Remote downconversion with wavelength reuse for the radio/fiber uplink connection

Abstract: The authors present a novel technology for uplink transmission in radio-over-fiber distribution systems. The technique employs remote downconversion of the uplink data to intermediate frequency (IF) in the base station (BS). The local oscillator signal for the downconversion is optically generated in the central station (CS) and sent to the BS via optical fiber. The IF uplink data is then modulated onto an optical carrier, retrieved from the downlink signal, and sent to the CS, where the baseband conversion takes place. By employing this method of uplink connection, simplicity and cost efficiency of the BS is achieved

Phase-Noise Analysis of Optically Generated Millimeter-Wave Signals With External Optical Modulation Techniques

Abstract: In this paper, the phase-noise performance of optically generated electrical signals based on external optical modulation techniques is investigated theoretically and experimentally. Mathematical models are developed to represent perturbations on the transmitted optical signal caused by the phase fluctuations of the electrical drive signal applied to the external modulator and the optical carrier that feeds the external modulator. Closed-form expressions of the power spectral density (PSD) for the electrical signals, generated both locally and remotely, are derived. The calculated PSD of the locally generated electrical signal indicates that its phase noise is determined only by the phase noise of the electrical drive signal. The PSD of the remotely generated signal shows that its spectral quality is also affected by the chromatic dispersion of the fiber and the optical carrier linewidth. An experimental setup that can generate a millimeter-wave (mm-wave) signal, continuously tunable from 32 to 60 GHz using an electrical drive signal tunable from 8 to 15 GHz, is built. The spectra of the generated millimeter-wave signal are measured for both locally and remotely generated electrical signals, with optical carriers of different linewidths. The theoretical results agree with the experimental measurements

Extending optical transmission distance in fiber wireless links using passive filtering in conjunction with optimized modulation

Abstract: The authors demonstrate a simple passive technique for increasing the transmission distance in fiber wireless links through the application of a narrowband fiber Bragg grating (FBG) with high reflectivity (90-99%). They are applied in a conventional downstream link and also for the upstream in a wavelength-reused scheme. In the conventional nonwavelength-reused system, the grating is used to optimize the optical modulation depth and, hence, the receiver sensitivity in the downstream transmitted signal by reducing the power of the optical carrier before fiber transmission. In the wavelength-reused systems, the highly reflective FBGs can be effectively used at the base stations to recover a major portion of the optical carrier (as high as 99% of the downlink carrier) for uplink transmission from a weakly modulated downstream signal. In the latter case, the penalty in the downstream signal due to the large extraction of carrier power is partially offset by the sensitivity enhancement obtained in the filtering process. The authors present experimental results for the increased transmission performance for both the nonwavelength-reused and wavelength-reused scenarios. The increase in the sensitivity (at biterrorrate=10/sup -9/) in the nonwavelength-reused scheme for a given launch channel power that facilitates the increased transmission distance can be as large as 7 dB. The relative increase in the power margin for the upstream signal can be up to 4 dB in the wavelength-reused scheme. This would more than double the currently demonstrated transmission distances in such wavelength-reused systems without any optical amplification. The scheme is applicable to a wide range of radio frequencies and modulation depths.

An MLSE Receiver for Electronic Dispersion Compensation of OC-192 Fiber Links

Abstract: A maximum-likelihood sequence estimation (MLSE) receiver is fabricated to combat dispersion/intersymbol interference (chromatic and polarization mode), noise (optical and electrical), and nonlinearities (e.g., fiber, receiver photodiode, or laser) in OC-192 metro and long-haul links. The MLSE receiver includes a variable gain amplifier with 40-dB gain range and 7.5-GHz 3-dB bandwidth, a 12.5-Gb/s 4-bit analog-to-digital converter, a dispersion-tolerant phase-locked loop, a 1:8 demultiplexer, and a digital equalizer implementing the MLSE algorithm. The MLSE receiver achieves more than 50% reach extension at signal-to-noise levels of interest as compared to conventional clock data recovery systems

A novel millimeter-wave-band radio-over-fiber system with dense wavelength-division multiplexing bus architecture

Abstract: In this paper, we propose a novel millimeter-wave-band radio-over-fiber (RoF) system with a dense wavelength-division multiplexing (DWDM) bus architecture. Two lasers with a small wavelength difference, phase locked and polarization aligned, are allocated at a central station (CS) for connecting the CS and each base station (BS), one laser for transmitting and the other for detection (the remote local oscillator). For the conceptual illustration, we consider a DWDM RoF system with a channel spacing of 12.5 GHz and RF of /spl sim/30-GHz millimeter-wave band. In the downlink system, a single-sideband (SSB) subcarrier is used with low RF imposed on an optical carrier at the CS, and an millimeter-wave-band RF signal is obtained at each BS using direct photodetection by the SSB subcarrier beat with the remote oscillator. In the uplink system, the received millimeter-wave-band RF signal at each BS is imposed on the two optical carriers simultaneously, one optical carrier with the closest SSB subcarrier is optically filtered out and fed into in the uplink transmission fiber without frequency interleaving; the electrical signal with a low IF can be photodetected directly at the CS. Such an RoF system has simple, cost-effective, and maintenance-reduced BSs, and is immune to laser phase noise in principle.

Coherent phase-shift-keying

Abstract: A receiver for coherent detection of a PSK modulated optical carrier includes an optical detector, digital-to-analog converters, and a digital module. The optical detector is configured to mix the modulated optical carrier with two phase components of a reference optical carrier and to produce analog output signals representative of optical signals produced by said mixing. The digital-to-analog converters are connected to receive the analog output signals and to produce digital signals from the received analog output signals. The digital module is connected to receive the digital signals and to perform one of compensating the received digital signals for a conjugate phase misalignment between the mixed components, extracting phase of the received digital signals, and estimating a frequency offset between the two carriers from the received digital signals.

Frequency estimation in an intradyne optical receiver

Abstract: A method for determining symbols PSK modulated on an optical carrier includes interfering a first polarization component of the modulated optical carrier and a reference optical carrier in a first optical mixer and interfering the first polarization component of the modulated optical carrier and the reference with a different relative phase in a second optical mixer. The method also includes sampling the interfered carriers from the first optical mixer to produce first digital sampled values and sampling the interfered carriers from the second optical mixer to produce second digital sampled values. The first and second digital sampled values of a sampling period form a first complex sampling value thereof. The method also includes offsetting a phase of a complex signal value corresponding to each first complex sampling value to correct for a phase error caused by a frequency offset between the modulated and reference optical carriers.

An MLSE receiver for electronic-dispersion compensation of OC-192 fiber links

Abstract: A 9.953 to 12.5Gb/s MLSE receiver consisting of an AFE IC in a 0.18mum 3.3V ft=75GHz, and a digital IC in a 0.13pm 1.2V CMOS is presented. The AFE IC features a 7.5GHz 40dB VGA, a 4b 12.5GS/S ADC, a dispersion-tolerant clock-recovery unit, and a 1:8 DEMUX. The digital IC implements an 8-parallel, delayed recursion MLSE architecture and a nonlinear channel estimator. The 4.5W receiver meets the SONET jitter specifications with 2200ps/nm of dispersion at BER=104

A 10-Gb/s CMOS CDR and DEMUX IC With a Quarter-Rate Linear Phase Detector

Abstract: This paper presents a 10-Gb/s clock and data recovery (CDR) and demultiplexer IC in a 0.13-mum CMOS process. The CDR uses a new quarter-rate linear phase detector, a new data recovery circuit, and a four-phase 2.5-GHz LC quadrature voltage-controlled oscillator for both wide phase error pulses and low power consumption. The chip consumes 100 mA from a 1.2-V core supply and 205 mA from a 2.5-V I/O supply including 18 preamplifiers and low voltage differential signal (LVDS) drivers. When 9.95328-Gb/s 231-1 pseudorandom binary sequence is used, the measured bit-error rate is better than 10-15 and the jitter tolerance is 0.5UIpp, which exceeds the SONET OC-192 standard. The jitter of the recovered clock is 2.1 psrms at a 155.52MHz monitoring clock pin. Multiple bit rates are supported from 9.4 Gb/s to 11.3 Gb/s

High Resolution Frequency Standard Dissemination via Optical Fibre Metropolitan Network

Abstract: We present in this paper results on a new dissemination system of ultra-stable reference signal at 100 MHz on a standard fibre network. The 100 MHz signal is simply transferred by amplitude modulation of an optical carrier. Two different approaches for compensating the noise introduced by the link have been implemented. The limits of the two systems are analyzed and several solution suggested in order to improve the frequency stability and to further extend the distribution distance. Nevertheless, our system is a good tool for the best cold atom fountains comparison between laboratories, up to 100 km, with a relative frequency resolution of 10-14 at one second integration time and 10-17 for one day of measurement. The distribution system may be upgraded to fulfill the stringent distribution requirements for the future optical clocks.

Feasibility analysis of a HAP-LEO optical link for data relay purposes

Abstract: The aim of the paper is to prove the technical feasibility and the advantages of a joint RF and optical communication system. The reference scenario foresees the use of a HAP (high altitude platform) or multiple HAPs for data relay purposes. HAPs are based on airships or balloons placed at about 20 km height and they combine both the advantages of terrestrial networks (the highest mast in the town) and of satellites (a LEO in very low orbit). As earth observation (EO) satellites need the download of huge amount of data, HAPs could establish an optical link with a LEO EO satellite in order to exploit the high data rate. Optical space communications offer a wide bandwidth and low interference channel. By the use of this system, it is possible to increase the amount of information downloaded by a high altitude platform from a LEO satellite, reaching data rate up to 10 Gbit/s. There are some critical points to face in order to dimension this link. First of all, a fast pointing acquisition and tracking procedure must be implemented. Another point is related to the high relative speed between LEO satellite and HAP that leads to an important contribution of Doppler shift in the received signal spectrum, this phenomenon is not stochastic and it can be managed by a tunable filter. The third point to focus on, strictly related to the transmitter design, is the optical carrier choice. It is important to take into account the atmospheric layer from 20 to 100 km, in terms of absorption and scattering spectra, temperature and refractive index variations in altitude and time varying phenomena. The transmitter is designed choosing the best performing technology in different optical window frequencies in which the channel presents low absorption and scattering, this choice involves the modulation format, as well. Three optical windows are available: 850nm, 1064nm and 1550nm. The first one is the most affected by Doppler effect but offers high gain telescope and low cost components; devices that work in the second window can transmit high amount of power but the modulation constraints of laser source can make the design more complicated; the third window is the most used in terrestrial communication systems and many devices are available, the Doppler effect is lower than at other frequencies and for this carrier it is possible to carry out DPSK (differential phase shift keying) modulation schemes other than classical OOK (on off keying) techniques. Moreover, HAPs could use terrestrial electronics equipments in order to store the data received by the optical link (e.g. hard disks). The link between HAP and ground can be exploited by the use of high data rate RF links in Ka-band or X-band (mainly used in EO satellites), V-band (allocated for HAPs) or W-Band (the new frontier). Despite the impact by weather and atmospherics, it was demonstrated that the availability of W-band satellite links is at least 95% (Fragale, 2004). This scenario overcomes the limits imposed by the short time window for EO satellites data download, using an advanced "store and forward-data relay" concept.

Method and apparatus for detecting optical spectral properties using optical probe beams with multiple sidebands

Abstract: Techniques for detecting optical spectral properties of a target are described. The technique includes providing an optical carrier which has an optical frequency bandwidth which is narrow compared to the width of the narrowest spectral feature of the target to be determined. This optical carrier is then electro-optically modulated with an RF frequency chirp, creating an optical chirp probe beam with a frequency chirped optical spectrum having upper and lower frequency chirped sidebands that have amplitudes sufficient to be detected at a detector. The sidebands are frequency bands arranged symmetrically around the optical carrier frequency. The attributes of a sideband include a start frequency, bandwidth and chirp rate. A probe beam is generated with the sidebands and directed onto a target having a physical property with optical frequency dependence. An optical response signal resulting from an interaction between the probe beam and the target is detected. The optical frequency dependence of the physical property of the target is determined based on the optical response signal and the attributes of the sidebands.

Carrier-to-noise ratio optimization by modulator bias control in radio-over-fiber links

Abstract: We propose a method to optimize the carrier-to-noise ratio (CNR) in optically amplified narrowband radio-over-fiber links which employ a Mach-Zehnder modulator. This is achieved by control of the modulator bias in order to suppress the optical carrier. In this letter, we experimentally prove that this carrier suppression technique can simultaneously improve the link detected RF power and suppress the stimulated Brillouin scattering, which is shown to be an important source of noise. Thus, we observe an improvement of about 20 dB in CNR of our link with respect to the unsuppressed carrier case

10 Gb/s bidirectional transmission in a 116 km reach hybrid DWDM-TDM PON

Abstract: We report bidirectional transmission at 10 Gb/s over a 116 km-reach DWDM amplified PON using remote reflective modulation of an optical carrier. The full network supports up to 1088 customers with mean data rates of 155 Mb/s.

Broadband class-AB microwave-photonic link using polarization modulation

Abstract: A novel broadband class-AB (CAB) microwave-photonic link is demonstrated using an AlGaAs-GaAs electrooptic mode-converter-based polarization modulator (PolM). The polarization-modulated signal is split into two paths, each independently optically biased to provide two electrooptic transfer functions operating close to, but on opposing sides of, their nulls. Experimental results at 2 and 4 GHz confirm that detection of the transfer functions in a differential detector provides excellent cancellation of second-order distortion and recreates the same third-order distortion as a quadrature-biased Mach-Zehnder modulator. Biasing the operating points near the null reduces optical carrier power, and hence, carrier-related noise, thereby increasing achievable spur-free dynamic range. The use of the PolM allows the CAB link to be implemented with a single modulator, reducing the matching requirements of dual modulator schemes and allowing third-order distortion-limited broadband operation.

Timing distribution in accelerators via stabilized optical fiber links

Abstract: We present progress on fiber-optic based systems for highly stable distribution of timing signals for accelerators. This system has application for linac-based sources of ultrafast radiation which require sub-100 fsec synchronization or for very large accelerators such as the linear collider. The system is based on interferometrically stabilized optical fiber links with RF and timing signals distributed as modulations on the optical carrier. We present measurements of the stability of this link over distances of several hundred. This work was supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Adaptive optoelectronic filter for improved optical single sideband generation

Abstract: An optoelectronic filter to generate optical single sideband (OSSB) signals from carrier-unsuppressed modulations is experimentally shown. Sideband suppression is achieved by applying a phase modulation to the optical input signal, resulting in null intensity distortion on the filtered signal and suppression of one of the sidebands. Additionally, the proposed filter ability to generate OSSB signals is wavelength independent. These properties are experimentally shown at 10 Gb/s. Sideband suppression above 18 dB is obtained at 5 GHz apart the optical carrier, with variations not exceeding 2 dB along a wavelength band of more than 25 nm. An eye opening penalty of 4 dB is obtained after transmission along 160 km of standard single-mode fiber.

Development of photonic devices for MMW sensing and imaging

Abstract: In this paper we present several novel photonic technologies for sensing millimeter-wave (MMW) radiation for the imaging and spectroscopy applications. Based on the optical up-conversion approach, our high-sensitivity MMW imaging system transfers the power of MMW radiation received from a broadband horn antenna to the sidebands on an optical carrier via an electrooptic (EO) modulator. The detection is realized by measuring the transferred optical power of the sidebands. The sensitivity of this detection system is primarily controlled by the conversion efficiency of the EO modulator at the desired MMW frequency. In this paper, we present the design, fabrication, and characteristics of the ultra-broadband LiNbO3 traveling-wave modulator for the MMW detection system working at a frequency of 95 GHz. A numerical model based on the finite element analysis technique has developed to optimize the device geometric parameters and the fabrication processes. A modulation efficiency of ~0.9 W-1 at 95 GHz has been achieved for the optimized modulator, which corresponds to the half-wave voltages of 9 V and 18 V, at DC and 95 GHz, respectively. The detection pixel based on those modulators has shown a high sensibility with a noise equivalent temperature difference of ~17K at a refreshing rate of 30 Hz.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Two-wave mixing in an erbium-doped fiber amplifier for modulation depth enhancement of optically carried microwave signals.

Abstract: We experimentally and theoretically analyze an original method based on two-wave mixing in an erbium-doped fiber amplifier for optical carrier reduction of microwave signals. 75% optical carrier attenuation has been observed, and a 10 dB modulation depth increase of the microwave signal is experimentally demonstrated. Moreover, calculated results are in good agreement with measurements and predict that up to 80% carrier attenuation is easily possible.

Design of all-optical switches based on carrier injection in Si/SiO/sub 2/ split-ridge waveguides (SRWs)

Abstract: All-optical switches based on optical carrier injection in high-index-contrast Si/SiO2 split-ridge-waveguide (SRW) couplers are analyzed The waveguide devices are suitable for the construction of low-loss optical switch matrices as well as fast optical switching These devices exhibit robustness against fabrication tolerances, improved heat sinking, good carrier confinement, and high uniformity in transmission over the entire C-band of optical communications, in contrast to comparable devices based on buried or ridge waveguides Reasonably low electrical switching power of 1-10 mW is predicted for switching frequencies of 1 MHz to 1 GHz Carrier recombination measurements in thin Si layers passivated with different oxide layers confirm the feasibility of the designed switches and modulators

Demonstration of a class-B microwave-photonic link using optical frequency modulation and complementary fiber-Bragg-grating discriminators

Abstract: A high-dynamic-range (1104 dB · Hz2/3) class-B optical link is demonstrated using optical frequency modulation, linear Bragg-grating frequency discriminators, and balanced detection to eliminate the optical carrier A total average received photocurrent of only 088 mA minimizes shot noise and intensity noise