Showing papers on "Optical Carrier transmission rates published in 2007"

Centralized Lightwave Radio-Over-Fiber System With Photonic Frequency Quadrupling for High-Frequency Millimeter-Wave Generation

Abstract: We have proposed a novel radio-over-fiber architecture to reduce the system cost at both central office (CO) and base station (BS). In this architecture, by incorporating the proper dc bias and optical filtering techniques in CO, the optical millimeter- wave (mm-wave) carriers are generated with four times frequency of the local oscillator signal. The BS is simplified by using the separated optical carrier along with downlink mm-wave signals to carry the upstream data. We have experimentally demonstrated optical mm-wave carrier generation up to 64-GHz, and both down- and upstream signal delivery over 20 km fiber with 1-dB power penalty.

A Novel Radio-Over-Fiber Configuration Using Optical Phase Modulator to Generate an Optical mm-Wave and Centralized Lightwave for Uplink Connection

Abstract: We have designed a novel radio-over-fiber configuration using an optical phase modulator along with optical filtering to generate an optical millimeter-wave for carrying downstream data and centralized lightwave for carrying upstream data. Since the remaining optical carrier with high power has been reused, the optical power is effectively utilized; therefore, the system cost can be reduced. We have calculated the power margin, and found that the margin is large even if no boosted erbium-doped fiber amplifier is used in the system. The eye diagrams and bit-error-rate performance at the receivers have been evaluated

Simultaneous Generation of Independent Wired and Wireless Services Using a Single Modulator in Millimeter-Wave-Band Radio-Over-Fiber Systems

Abstract: We experimentally demonstrated a novel radio-over-fiber scheme to simultaneously obtain independent wired and wireless signals by using only a single intensity modulator. The optical 40- or 60-GHz millimeter-wave (mm-wave) carriers are generated by means of subcarrier-multiplexing techniques to carry 2.5-Gb/s wireless signals while 10-Gb/s wired signals are imposed on the original optical carrier via regular intensity modulation. The signals with dual services are successfully transmitted over 20-km single-mode fiber (SMF-28) with less than 1.5-dB power penalty.

A Novel Radio-Over-Fiber System With Wavelength Reuse for Upstream Data Connection

Abstract: We have experimentally demonstrated a novel wavelength reuse scheme for up-link connection in a radio-over-fiber (ROF) system. The dual-mode lightwave generated by optical carrier suppression modulation is separated by an optical interleaver. One of the dual-mode lightwaves is modulated with a baseband data at 2.5 Gb/s. The other lightwave will be used for the optical carrier for the up-link data modulation. There is no additional laser source for the upstream data generation in the base station. By this method, we simplify the configuration of the ROF system and reduce the cost of the system

Terahertz transfer onto a telecom optical carrier

Abstract: In a GaAs crystal, owing to the anomalous dispersion introduced by optical phonon absorption, a phase-matched interaction is possible between a near-infrared beam and a terahertz (THz) wave. We exploit this nonlinear optical process to allow the merging of THz-quantum-cascade-laser and telecom technologies by injecting a telecom beam into a suitably designed THz quantum-cascade laser. Within the optical cavity, the phase and amplitude of the THz wave are recorded onto the near-infrared beam, which can be transported through an optical fibre. We show that the process is phase-matched and can be tuned over the entire telecom range by waveguide engineering. This nonlinear up-conversion technique opens up new possibilities in the optical treatment of THz, by taking advantage of the highly developed telecom technology.

Class-B Microwave-Photonic Link Using Optical Frequency Modulation and Linear Frequency Discriminators

Abstract: A class-B optical link is demonstrated as a means to provide high spur-free dynamic-range (110.4 dBmiddotHz2/3) with a minimum average received power associated with the optical carrier. The link uses optical frequency modulation, linear fiber-Bragg-grating frequency discriminators, and balanced detection to provide high linearity and maximum signal power. Shot and intensity noises are minimized by the low total average received photocurrent (0.88 mA) that results from class-B operation

Frequency upconversion of multiple RF signals using optical carrier suppression for radio over fiber downlinks.

Abstract: We propose and analyze a technique of an optical carrier transmitting two RF signals using optical carrier suppression. A single optical Mach-Zehnder modulator is used for both optical carrier suppression and signal modulation, and optical carrier suppression modulation is also used for frequency conversion of RF signals. This work shows that in contrary to the case of an optical carrier transmitting a single RF signal with optical carrier suppression where stronger optical carrier suppression improves the upconverted RF signal, weaker optical carrier suppression is preferred for an optical carrier transmitting two RF signals due to nonlinear distortion because the nonlinear distortion is reduced by using weaker optical carrier suppression. We find that the usable range of optical carrier suppression ratio is from 10 to 18 dB for RF signal upconverted to 20 GHz and beyond, and the best optical carrier suppression ratio is around 10 dB. We verify the concept and analysis with experiment. In experiment, we used two RFs at 6 and 18 GHz transmitting two 750 Mb/s signals. The experiment for the first time demonstrated that an optical carrier can transmit two RF signals using optical carrier suppression and showed that upconverted RF signals are degraded by nonlinear distortion, particularly for upconverted RF signal at 12 GHz, i.e. the RF signal at the lower frequency.

Bidirectional ROF Links Using Optically Up-Converted DPSK for Downstream and Remodulated OOK for Upstream

Abstract: We propose a novel radio-over-fiber system to provide full-duplex services by using optical differential phase-shift keying modulation format at the central station for downstream and on-off keying remodulation of the downlink carrier at the base station (BS) for upstream. The optical carrier suppression modulation scheme is employed to simultaneously generate and up-convert 40-GHz optical millimeter wave. As the same optical carrier is used for both uplink and downlink, no additional light source is required at the BS, which greatly reduces the cost and simplifies the overall system. Simulations and experimental results show that the bidirectional 2.5-Gb/s data is successfully transmitted over 40-km single-mode fiber (SMF-28) with less than 2-dB power penalty

Message Encryption by Phase Modulation of a Chaotic Optical Carrier

Abstract: We present a numerical and experimental evaluation of message encryption by phase modulation, using a chaotic optical carrier generated by a laser subject to delayed optical feedback. This method offers better security than the conventional amplitude masking, where the signal is simply added to the chaotic waveform

Tunable Photonic Microwave Bandpass Filter With Negative Coefficients Implemented Using an Optical Phase Modulator and Chirped Fiber Bragg Gratings

Abstract: A continuously tunable photonic microwave bandpass filter with positive and negative coefficients implemented using an optical phase modulator and chirped fiber Bragg gratings (FBGs) is proposed and experimentally demonstrated. The positive and negative coefficients are generated through optical phase-modulation to intensity-modulation conversion by reflecting the phase-modulated optical carrier from linearly chirped FBGs (LCFBGs) with positive and negative dispersions. The tunability of the filter is realized by changing the wavelength of the optical carrier such that it is reflected at different physical locations in the LCFBGs. A two-tap microwave bandpass filter with a free spectral range tunable from 1.14 to 4.55 GHz is experimentally demonstrated.

Microwave Optoelectronic Oscillator with Optical Gain

Abstract: Optoelectronic oscillators (OEO) are unique compared to radio-frequency (RF) oscillators in that they do not fundamentally require a RF gain element in order to satisfy the amplitude threshold condition for oscillation. All of the energy required for oscillation can be obtained from the optical carrier. This, however, was not initially possible, due to the inefficiency and power limitations on the optical components used in the OEO. Recent improvements driven by the need for optical-RF links have improved modulator and detector technology. Electro-optic modulators (EOM) with ultra-low half-wave voltage (Vpi), and high optical power capabilities, when coupled with high-power photodetectors, have achieved optical links with gain. With sufficient gain from the photonic components in the OEO, the RF loop amplifier becomes unnecessary. Eliminating this amplifier removes one of the major noise contributing elements of the oscillator. Here we present designs and phase noise results of several OEOs, operating at RF frequencies up to 10 GHz, constructed with only optical gain.

Communication Network with Skew Path Monitoring and Adjustment

Abstract: Embodiments of the present invention route a WDM signal across multiple communication paths using skew characteristics of at least some of the communication paths. The network is an optical transport network, using either circuit or packet based switching, and wavelength division multiplexed wavelengths and/or optical carrier groups (“OCGs”) over a fiber link to another node in the network. The plurality of communication paths involves different signal and path attributes such as a plurality of carrier wavelengths, optical carrier groups, physical communication paths (different nodes, different fibers along a same path, or any combination of the foregoing), or any other differentiating factors between two paths.

A True Time Delay Beamforming System Incorporating a Wavelength Tunable Optical Phase-Lock Loop

Abstract: A true time delay (TTD) beamforming system incorporating a wavelength tunable optical phase-lock loop (OPLL) module is proposed and experimentally demonstrated. In the proposed system, instead of using a high-frequency intensity modulator to modulate the optical carrier with an RF signal, we use two laser diodes (LDs) that are phase locked to generate an RF signal, which is then sent to a fiber Bragg grating (FBG) prism to produce different time delays. Since no optical intensity modulator is used, the system can operate at much higher frequencies with a reduced cost. In addition, the use of only two wavelengths eliminates the power-penalty problem caused by chromatic dispersion. In the proposed approach, the wavelengths from the two LDs are phase-locked using a frequency-discriminator-aided OPLL. A TTD beamforming system, using the OPLL in combination with an FBG prism to achieve tunable time delays, is investigated. Experimental time-delay results are provided.

Transmission of 10-Gb/s and 40-Gb/s Signals over 3.7 km of Multimode Fiber using Mode-Field Matched Center Launching Technique

Abstract: We experimentally demonstrate the transmission of 10-Gb/s and 40-Gb/s signals over 3.7 km of multimode fiber by using the mode-field matched center launching technique.

PMD Tolerant Direct-Detection Optical OFDM System

Abstract: We show that PMD degrades the transmission performance of an optical OFDM system which is based on direct-detection and single side-band transmission. Maximum PMD tolerance can be achieved applying polarization diversity together with polarization control. Introduction Optical transmission systems deploying orthogonal frequency division multiplexing (OFDM) have gained interest recently. Two principle architectures have been proposed in order to preserve linearity of distortions in the optical domain beyond optoelectrical conversion: A setup using coherent detection was shown to be robust against chromatic dispersion. Transmission over 3000 km SSMF is possible with less than 2 dB OSNR penalty at a bit error ratio of 10 [1]. Extending this approach to a polarization diversity receiver yields a PMD tolerant transmission system [2]. An alternative setup which is less demanding from optical component point of view is based on single side-band (SSB) transmission and direct detection (DD) [3], which also shows chromatic dispersion tolerance. This contribution examines the influence of PMD on the transmission performance of this architecture. It turns out that PMD causes fading which leads to performance degradation. We propose a PMD tolerant extension which uses a polarization diversity receiver. Investigated Setup The basic building blocks of the investigated setup are depicted in Figure 1 [3]. A certain number of subcarriers are modulated using a 4-QAM-constellation occupying the upper half of the upper side-band. Lower sub-carriers are not modulated; the spectral part of negative frequencies is fed by corresponding complex-conjugates. Hence, after inverse discrete Fourier transform, cyclic extension, and digital to analogue conversion we obtain an up-converted, real valued signal s(t). Alternatively, the signal can be generated by up-converting the original complex valued base-band signal in the electrical domain through RF mixing. The resulting signal is modulated onto an optical carrier by a Mach-Zehnder modulator; then the lower side-band of the optical signal is suppressed (see insets of Figure 1). The SSB signal propagates over the optical link and is received through direct detection. Even after squaring there are no beat-products within the used spectrum. In contrast to the architecture based on coherent detection laser phase noise is not an issue. The received signal r(t) is sampled; after cyclic prefix removal and DFT one retrieves distorted symbols Yk,l. Zero-forcing equalization uses estimates of the respective channel coefficients (which are supposed to be perfectly known to the receiver in our simulations)

Photonic Frequency Upconversion Based on Stimulated Brillouin Scattering

Abstract: We demonstrate a method of photonic frequency upconversion useful in radio-over-fiber systems, which is based on Brillouin selective amplification. One of the optical sidebands generated from the applied radio-frequency carrier at 10.831GHz is selected and amplified by Brillouin gain. By carrying the 1-GHz intermediate-frequency (IF) signal on the optical carrier and beating them with the amplified sideband, the IF signal of 1 GHz is upconverted to 11.831 GHz. This scheme can also be applied to the IF signal with bandwidth larger than the Brillouin gain bandwidth. The upconverted 11.831-GHz signal has the phase noise of -83.3dBc/Hz at 10-kHz offset. Also, the proposed upconversion scheme shows the spurious-free dynamic range of 89.5 dBmiddotHz2/3

Polarization tracking and signal equalization for optical receivers configured for on-off keying or pulse amplitude modulation signaling

Abstract: According to one embodiment, an optical receiver adapted to recover OOK or PAM data carried by a modulated optical carrier has an optical detector adapted to produce a sequence of vector pairs having first and second digital vectors indicative of complex values of first and second polarization components, respectively, of the modulated optical carrier at a corresponding sampling time. The optical receiver also has a digital processor that is connected to receive the sequence and is adapted to perform a rotation on each pair in a manner that tends to compensate for polarization rotation produced by transmitting the modulated optical carrier from an optical transmitter thereof to the optical receiver. The digital processor is further adapted to estimate values of the OOK or PAM data encoded onto each of the first and second polarization components based on the vectors produced by the rotation in a manner responsive to values of energy errors in the estimated values.

Efficient Transmission Scheme for AWG-Based DWDM Millimeter-Wave Fiber-Radio Systems

Abstract: We propose and demonstrate an upstream transmission scheme using a semiconductor optical amplifier (SOA) for arrayed waveguide grating (AWG)-based dense wavelength-division-multiplexed (DWDM) millimeter-wave fiber-radio systems and show improved link performance. In our scheme, unused optical carriers from the cyclic AWG in the downlink (DL) are tapped for uplink (UL) transmission. An SOA in conjunction with the AWG simultaneously amplifies the DL RF subcarriers and UL optical carrier, thus improving carrier-to-sideband ratio in the DL while also yielding an improved power budget for the UL. Our experimental results show that the proposed scheme can be a practical solution for future bidirectional wavelength interleaved DWDM transmission systems

High-Performance and Low-Cost 10-Gb/s Bidirectional Optical Subassembly Modules

Abstract: High-performance and low-cost 10-Gb/s bidirectional optical subassembly (BOSA) modules that are obtained by adopting low-cost transistor outline (TO)-Can materials and processes are proposed and demonstrated. The BOSA module consists of an uncooled 1.3-mum distributed-feedback laser diode and a 1.5-mum p-i-n/transimpedance amplifier receiver (Rx), which integrate a 45deg tilted thin-film wavelength-division multiplexing filter to transmit a 1.3-mum light into the fiber and reflect a 1.55-mum light into the Rx. The matching resistor and low parasitic inductance packages are applied with the TO-Can laser diode to enable 10-Gb/s operation. A modulation bandwidth of 11.86 GHz and an OC-192 eye diagram of a 19% mask margin are obtained from the transmitter side. After a 10-km single-mode fiber (SMF) transmission, the mask margin for the OC-192 eye diagram decreases to 11%. For the Rx, an OC-192 eye diagram of a 31% mask margin is obtained under back-to-back connections. The mask margin is maintained at 29% after a 10-km SMF transmission. The measured crosstalk penalty is 0.9 d 15 at the Rx side. These results indicate that the BOSA module is capable of a 10-Gb/s bidirectional transmission. This unique high-performance 10-Gb/s BOSA module not only demonstrates the feasibility of a 10-Gb/s bidirectional transmission on an SMF for fiber-to-the-home applications but also shows the low-cost possibility to ensure the success of next-generation 10-Gb/s access networks.

An LTCC-Based Wireless Transceiver for Radio-Over-Fiber Applications

Abstract: This paper describes the realization of a low-temperature co-fired ceramic (LTCC)-based wireless transceiver with optical interface for radio-over-fiber applications involving several standards. The RF front-end including an antenna is fabricated in LTCC technology, while the optical transceiver with a single-mode optical interface is built on a silicon motherboard. The front-end operates in the 5-6-GHz band, while the modulated optical carrier is transmitted at 1.55-mum wavelength. The front-end module is an attractive solution for wireless local area network applications such as IEEE 802.11a or HIPERLAN2 requiring a direct link to an optical backbone

Experimental Demonstration of 1.25-Gb/s Radio-Over-Fiber Downlink Using SBS-Based Photonic Upconversion

Abstract: We experimentally demonstrate a radio-over-fiber downlink system using a stimulated Brillouin scattering (SBS)-based photonic upconversion technique. The Brillouin selective amplification characteristic of SBS is incorporated to generate the 11-GHz band radio-frequency (RF) carrier. The dual-electrode Mach-Zehnder optical modulator, which is used to carry the broadband data in the optical carrier instead of the optical sideband, is adopted along with the SBS-based carrier generation setup. To vindicate the broadband capabilities of the proposed scheme, 1.25-Gb/s pseudorandom bit sequence data is carried in the optical carrier. Error-free operation of the 1.25-Gb/s downlink is achieved without critical power penalties after the 13-km fiber transmission.

LiNbO 3 optical modulator for MMW sensing and imaging

Abstract: We present several novel technologies for sensing millimeter-wave (mmW) radiation for imaging and spectroscopy based on photonic devices. Along these lines, in our high-sensitivity millimeter-wave (mmW) imaging system, which is based on optical upconversion, the power of mmW radiation is transferred to the sidebands on an optical carrier via an electro-optic (EO) modulator fed by a broadband horn antenna. 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 (e.g. 95GHz). Thus, modulators are required that exhibit an ultra-broad bandwidth and small drive voltage. In this paper, we present the design, fabrication, and characteristics of LiNbO 3 traveling-wave modulator for the mmW detection system. In a traveling-wave modulator, the bandwidth is limited by the mismatch between electrical and optical propagation constants. We have developed several techniques to finely tune the propagation constant of the mmWs in the modulator and have thereby eliminated this mismatch. Further bandwidth limitations for the modulator arise from losses in the electrode conductor, the substrate and buffer layer dielectrics, and coupling between the traveling-wave mode and the substrate modes. Modulator structures are described to reduce those losses without increasing the device driving voltage. The bandwidth and conversion limits of these structures are also discussed. The mmW detection pixels using the fabricated modulators were assembled, characterized, and analyzed. A high-sensitivity W-band detection system with a low noise-equivalent temperature difference (NETD) has been demonstrated. In addition, we present ongoing work to improve coupling millimeter-wave energy to the modulator at the W-band using techniques viable for packaged devices.

Method for emulating digital trunk TDM services over synchronous ethernet packets

Abstract: In a Metropolitan Ethernet Network (MEN) with upgraded transport capability encompassing Circuit Emulation Service (CES) at the Interworking Interfaces within backhaul nodes, a substantial improvement has been introduced which consists of fixing a constant cadence of the TDM payloads packets in the whole network. In this way the design of Jitter buffer at the MEN bound is made uniform everywhere. This also entails constant time duration of all TDM payloads packets and hence constant number of octets for a given type of TDM service. These features are more easily achieved by distributing a common synchronization signal SYNC with constant period in the whole network, planned preferably as 125, or 250, or 500 µs in order to accommodate the following most popular tributaries: • DS1 (T1) at 1.544 Mbit/s as defined in ANSI (T1.102) and (T1.107); • E1 at 2.048 Mbit/s as defined in ITU-T Recommendations (G.702) and (G.704); • N x 64kbit/s data (i.e. 64 kbit/s, 128 kbit/s, 192 kbit/s) such as defined in ITU-T Recommendation (1.231.1); • DS3 (T3) at 44.736 Mbit/s as defined in ANSI (T1.107); • E3 at 34.368 Mbit/s as defined in ITU-T Recommendation (G.751); Tributary frames are firstly synchronized to a local clock by means of conventional positive/negative justification technique based on elastic store and bit-stuffing, then the residual space to the end of the packet is filled up with optional Reed-Solomon error correcting code opportunely shortened. Different combinations of TDM payloads are possible ( fig.13a,b ).

Orthogonal Frequency Division Multiplexing (OFDM) and other Advanced Options to achieve 100Gb/s Ethernet Transmission

Abstract: Based on the demand for transmission technologies offering high ratio of bits per symbol, two promising candidates to achieve a data rate of 100 Gb/s per optical carrier are discussed, namely optical orthogonal frequency division multiplexing and 16-ary multilevel modulation.

Multiplexed Transmission of Uncompressed HDTV Signals Using 120-GHz-band Millimeter-wave Wireless Link

Abstract: This paper describes 10-Gbit/s wireless link system for use in the transmission of six-channel uncompressed high-definition television (HDTV) streams. The wireless link employs 120-GHz-band millimeter waves, and can transmit high-speed IP (Internet Protocol) data signals such as 10 GbE (10 Gigabit Ethernet) and OC-192. Enabling technologies, system configurations, and field trials in collaboration with TV broadcasting industries are presented.