Showing papers on "Optical communication published in 1994"

Polarization independent wavelength conversion using fiber four-wave mixing with two orthogonal pump lights of different frequencies

Abstract: This paper describes polarization independent wavelength conversion, utilizing fiber four-wave mixing. By using two orthogonal pump lights having different frequencies, the baseband signal of the wavelength converted light is insensitive to the polarization state of the original signal light. Experiments that include bit error measurements confirm the polarization independent operation. >

Fibre-supported optical generation and delivery of 60 GHz signals

Abstract: A novel ‘frequency quadrupling’ technique for the optical generation and delivery via fibre of modulated 60 GHz band millimetre-wave signals is described. The technique requires only microwave frequency capability for the optical modulator and drive electronics, and these are readily available commercially. The frequency quadrupling technique is demonstrated experimentally with a high spectral purity 60 GHz signal obtained using a 15 GHz source and optical modulator.

Electro-Optics Handbook

Abstract: All-inclusive opto electronics guideA valuable "must-have" tool for electronic and optical engineers, this Handbook is the only single-volume, tell-it-all guide to the use of optical devices and light in electronics systems. Developed by a towering figure in the field, this manual familiarizes you with UV, VUV and X-Ray lasers; visible, solid-state, semiconductor and infrared gas lasers; FEL and ultrashort laser pulses; visible and infrared optical materials; infrared and imaging detectors; optical fibers and fiber optic sensors; holography; laser spectroscopy and photochemistry; high resolution lithography for optoelectronics; and much more. In this up-to-the-minute edition you'll find new chapters on optical communications, electro-optic devices, and high intensity optical fields, in addition to extensively updated material throughout, and abundant charts, diagrams and data tables.

Indoor propagation measurements at infrared frequencies for wireless local area networks applications

Abstract: In a combination tutorial and research paper, propagation aspects of transmission at infrared (IR) frequencies for wireless in-building communications are explored. The tutorial section of the paper presents basic principles of propagation at IR, a comparison with indoor radio propagation, and the derivation of the channel's baseband model. The research aspect of the paper reports on the results of recent frequency response measurements at eight different sites in a university building. A major result shows that the indoor wireless optical channel is very dynamic, with great variations in the channel's characteristics for data collected in different rooms, in different locations within the same room, and for different orientations of the optical receiver at the same location of the same room. Numerical values of the channel's relative path loss and 3 dB bandwidth, along with frequency response plots covering a wide range of conditions, are presented and discussed. Finally, on the basis of the results of measurements, schemes for improving the performance of future wireless in-building optical transceivers are proposed. >

Digitally tunable channel dropping filter/equalizer based on waveguide grating router and optical amplifier integration

Abstract: We demonstrate a novel and powerful device that permits individual and simultaneous control of all the wavelength channels in a WDM system. The device is based on the monolithic integration of two identical waveguide grating routers with semiconductor optical amplifiers. By biasing appropriately the individual amplifier, each WDM channel can be amplified, detected or modulated. The device exhibits a channel bandwidth of 60 GHz, a channel spacing of 195 GHz and a crosstalk of /spl minus/19 dB. >

Pulse compression, fiber communications, and diffraction : a unified approach

Abstract: A unified approach is developed to three important areas of signal and image processing: pulse compression and real-time spectrum analysis, fiber-cable communications and dispersion, and Fresnel diffraction and optical filtering. The results are based on the properties of quadratic phase filters and Fresnel transforms, and they lead to a variety of analogies among the time responses of fiber cables, the spatial variations of diffracted fields, and the role of frequency modulation in narrow-band systems. The analysis includes deterministic and stochastic excitations.

Optical transmission of narrow-band millimeter-wave signals by resonant modulation of monolithic semiconductor lasers

Abstract: We demonstrate the use of monolithic semiconductor lasers as efficient narrow-band (20-300 MHz) millimeter-wave optical transmitters at a cavity round-trip resonant frequency of 45 GHz. The modulation efficiency within the passband is >10 dB above that of a conventional laser diode at frequencies below relaxation oscillation. At an input RF drive power of 10 dBm, a carrier-to-noise ratio of 90 dB (1 Hz) is achieved. We also present a system demonstration of this technique in which 50 Mb/s digital data is transmitted at a 45 GHz subcarrier over optical fiber. This is the highest subcarrier frequency transmission reported to date. >

Wireless optical communication system with adaptive data rates and/or adaptive levels of optical power

Abstract: The wireless optical (in particular infrared) communication system with at least one transmitter (75) and one receiver (76) comprises control means (77, 78), which dynamically adapt the data rate and/or the optical power of the transmitter in dependence of signal-to-noise ratio of the receiver. Due to this adjustment, optimized system performance is maintained even under the influence of ambient light which statistically changes the signal-to-noise ratio of the receiver. The best compromise between data rate, bit error rate and transmission range is dynamically determined. The control function is distributed between transmitting and receiving system unit. The control information is communicated via wireless optical communication.

Enhanced recovery rates in semiconductor laser amplifiers using optical pumping

Abstract: The authors show that gain recovery times of approximately 10 ps are achievable in semiconductor laser amplifiers using an optical beam to speed the gain recovery rate This technique should permit high data rate (up to 100 Gbit/s) all optical signal processing applications (eg demultiplexing, clock recovery) >

Quantum cryptography using optical fibers

Abstract: Quantum cryptography permits the transmission of secret information whose security is guaranteed by the uncertainty principle. An experimental system for quantum crytography is implemented based on the linear polarization of single photons transmitted by an optical fiber. Polarization-preserving optical fiber and a feedback loop are employed to maintain the state of polarization. Error rates of less than 0.5% are obtained.

On the number of wavelengths and switches in all-optical networks

Abstract: The authors consider optical networks using wavelength division multiplexing, where the path a signal takes is determined by the network switches, the wavelength of the signal, and the location the signal originated. Therefore, a signal is routed through a combination of circuit switching and wavelength routing (assigning it a wavelength). They present a bound on the minimum number of wavelengths needed based on the connectivity requirements of the users and the number of switching states. In addition, they present a lower bound on the number of switching states in a network using a combination of circuit switching, wavelength routing, and frequency changing. The bounds hold for all networks with switches, wavelength routing, and wavelength changing devices. Several examples are presented including a network with near optimal wavelength re-use. >

Prescaled 6.3 GHz clock recovery from 50 Gbit/s TDM optical signal with 50 GHz PLL using four-wave mixing in a travelling-wave laser diode optical amplifier

Abstract: Successful 50 GHz operation of a phaselocked loop is demonstrated using four-wave mixing in a travelling-wave laser diode optical amplifier. A prescaled 6.3 GHz clock is recovered from a 50 Gbit/s TDM optical signal using the 50 GHz phase comparison output obtained as the crosscorrelation between a 50 Gbit/s optical signal and a short ( >

Error-free demultiplexing of 160 Gbit/s pulse signal using optical loop mirror including semiconductor laser amplifier

Abstract: The authors demonstrate the bit error rate (BER) measurement of an optically multiplexed single polarised 160 Gbit/s pulse signal with a gate-width tunable demultiplexer based on an optical loop mirror that includes a semiconductor laser amplifier (SLA). It is found that the excess signal power in the optical loop mirror induces BER degradation. A BER of less than 10-10 at 160 Gbit/s is successfully achieved for the first time.

Distribution of 60 GHz signals to more than 1000 base stations

Abstract: The applicability of a novel optical method for generation and transport of millimetre-wave signals in the upper frequency bands has been successfully demonstrated. The authors report for the first time to their knowledge, the generation of high purity 60GHz signals and their fibre-optic distribution to more than 1000 microwave base stations. >

Optical transmission and receiving module and optical communication system using the same

Abstract: A bidirectional optical transmission and receiving module of a simplified structure and an optical communication system using the same. The optical transmission and receiving module includes a light emitting device and a light receiving device disposed with in a same package having an opening covered with a cover glass sheet, and a holographic diffraction grating provided on a top or lower surface of the glass sheet. In transmitting operation, a light beam emitted from the light emitting device passes through the diffraction grating to be concentrated onto an end face of an optical fiber by a lens. In receiving operation, a received light beam emanated from the end face of the optical fiber reaches the diffraction grating via the lens to be thereby diffracted. A plus-sign primary diffracted light beam resulting from the diffraction is concentrated onto a light detecting surface of the light receiving device. Signal as transmitted through the optical fiber in the form of signal light can thus be received.

Device for extraction and re-insertion of an optical carrier in optical communications networks

Abstract: The device includes a first optical circulator connected in series with the line (1e, 1u) in order to receive a signal stream including a carrier to be extracted, modulated by an information signal, and to transmit a signal stream including the same carrier, re-inserted into the stream after having being modulated with another information signal, and a second optical circulator connected to local information processing means, to which it supplies the extracted carrier and from which it receives the carrier to be re-inserted. Between the two circulators there is an optical-fibre bandpass filter that can be tuned to the carrier wavelength.

High performance, 12 frequency optical multichannel controller

Abstract: An optical multichannel controller that gives full access to 12 individual wavelength channels is reported. The device consists of two waveguide grating routers integrated with semiconductor optical amplifiers. It exhibits a channel spacing of exactly 3.2 nm (400 GHz) and an off-peak signal rejection of more than 40 dB. The amplifiers compensate for the multiplexer insertion losses. >

Oscillation polarization mode selective semiconductor laser, light source apparatus and optical communication system using the laser

Abstract: A distributed feedback semiconductor laser selectively performs one of two oscillations in different polarization modes having different polarization planes. The laser includes a substrate, a light waveguide formed on the substrate, which at least partially includes an active layer, a diffraction grating formed around the waveguide, and an injecting unit for injecting a modulation current into a portion of the waveguide. The waveguide and the grating are constructed such that oscillation wavelengths of the polarization modes are different from each other and minimum values of threshold gain in the polarization modes near the Bragg wavelength are approximately equal to each other. The semiconductor laser can be driven by a minute modulation current and prevents degradation of response characteristics due to dynamic wavelength fluctuation in a high-frequency range when used in optical communication systems in which the switching of polarization mode is performed.

Optical communication using dispersion-induced FM to AM conversion with nonlinearity-induced stabilization

Abstract: An optical communication system and method are provided which utilize dispersion-induced FM to AM conversion with nonlinearity-induced AM stabilization. The system and method utilize a frequency modulated optical signal transmitter, a fiber span, an optical receiver which receives the transmitted optical signal and detects an AM signal resulting from dispersion-induced energy overlaps and voids in the optical signal, and one or more in-line amplifiers spaced within the optical fiber span. By adjusting the number, position and/or output power levels of the in-line amplifiers, stabilization of the energy voids and overlaps and resulting AM signal can be achieved, yielding a substantial increase in achievable transmission distance at a given bit rate.

Inter-channel crosstalk phenomena in optical time division multiplexed switching networks

Abstract: The nature of inter-channel crosstalk arising in OTDM switching networks formed from imperfectly isolated 2/spl times/2 crosspoints and optical delay lines is investigated and a novel classification is identified. It is shown that the mixing of crosstalk and signal waveforms which are either, a) mutually coherent or, b) incoherent and (optical) frequency matched to within the receiver bandwidth, may result in intensity noise and far greater performance degradation than for c) incoherent signals whose optical beat frequency exceeds the receiver bandwidth. Initial experimental studies indicate that crosspoint isolation >

Ultra-high capacity non-soliton optical transmission using optical phase conjugation

Abstract: The present invention provides an apparatus and method for achieving bit rate distance products on the order of 200 Tbits/s-km in non-soliton optical communication using optical phase conjugation. The apparatus and method utilize phase conjugation and adjustments of in-line amplifier number, spacing, and/or output power in order to compensate for the interaction between first order dispersion and fiber nonlinearity dispersion effects in an optical fiber span. The present invention provides additional techniques for adjusting system parameters, such as dispersion-length products of first and second portions of the fiber span, in order to compensate for changes in first order dispersion resulting from non-zero second order dispersion. The method and apparatus also provide an improved multi-channel optical phase conjugation system design.

Performance analysis of an optical correlator receiver for SIK DS-CDMA communication systems

Abstract: An all-optical parallel delay line unipolar-bipolar correlator receiver is proposed for SIK DS-CDMA optical fibre communication systems such as LANs and the local loop. The receiver BER performance is assessed as a function of the incident optical power for noncoherent transmission with the number of simultaneous users as a parameter.

Fibre transmission of 10 Gbit/s signals following wavelength conversion using a travelling-wave semiconductor optical amplifier

Abstract: The wavelength of an intensity-modulated signal at 10 Gbit/s was translated from 1546 to 1531 nm using cross gain-compression in a semiconductor optical amplifier. The shifted signal was transmitted with less than 1 dB penalty over a 121 km span of dispersion-shifted fibre with two in-line amplifiers. A dispersion penalty of nearly 2 dB is measured for transmission of 6 Gbit/s data over 20 km conventional fibre.

5 Gbit/s optical transmission terminal equipment using forward error correcting code and optical amplifier

Abstract: Using forward error correction (FEC) technology and erbium-doped fibre amplifiers (EDFAs), 5 Gbit/s optical transmission terminal equipment provides better than −40dBm receiver sensitivity at a BER of 10-11. The experiments focused on the FEC feature of the removal of the BER floor together with long-distance repeaterless transmission.

Design and performance of a novel automatic fiber line testing system with OTDR for optical subscriber loops

Abstract: This paper proposes architecture for a novel automatic fiber line testing system with an optical time-domain reflectometer (OTDR) and describes the system requirements, the design method, and the system evaluation. The results of a trial on a manufactured system and an evaluation of its characteristics are presented with evidence that an in-service optical fiber can be tested with no degradation in communication quality and the desired measurement accuracy and system component characteristics can be realized. In addition, it is confirmed that a failure between an optical fiber cable and a digital service unit (DSU) can be identified with 100% accuracy. >

Tunable optical filter

Abstract: An tunable optical filter of the kind used, for example, in wavelength-division multiplexing (WDM) optical communication systems and tunable source applications, has an interference filter element which is pivotable to adjust the operating wavelength of the filter. In order to reduce polarization dependency as the angle of the interference filter element changes, the light beam to be filtered is passed through the filter element twice, the second time with its polarization state shifted, specifically orthogonal, relative to the polarization state during the first pass. As a result, polarization dependent effects are equalized. The optical filter comprises a pivotally mounted filter element, an input optical fiber for directing a light beam to be filtered through the filter element in a first direction with a first polarization state, optical elements for rotating the polarization state of the filtered light beam and returning the light beam through the filter element (10) a second time, and an output optical fiber for receiving the light beam following passage of the light beam though the filter element the second time. The optical elements may comprise a reflector for reflecting a light beam emerging from the optical filter element to return through the optical filter element in the opposite direction, and a polarization rotator, such as a quarter-wave plate or a Faraday rotator, for rotating the polarization state of the light beam through 90 degrees before passage in the opposite direction.

Overview of the Optical Communications Demonstrator

Abstract: The Optical Communications Demonstrator is a laboratory-based lasercom demonstration instrument designed to validate effective beacon acquisition, high bandwidth tracking, precision beam pointing, and point ahead compensation functions. The instrument is designed using an array detector for both spatial acquisition and high bandwidth tracking, and a fiber coupled laser transmitter. The array detector tracking concept provides wide field of view acquisition as well as high update rate using a single output channel device. At the same time, it permits effective platform jitter compensation and point ahead control using only one steering mirror. The use of fiber coupled transmitter further modularizes transmitter design and decouples the thermal management problem. The reduction in design complexity can lead to a reduced system cost and an improved system reliability. Furthermore, it can permit the implementation of a new generation of lasercom instruments capable of realizing the inherent advantages of optical frequency communication systems.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Prechirp technique as a linear dispersion compensation for ultrahigh-speed long-span intensity modulation directed detection optical communication systems

Abstract: Prechirp technique, as a linear dispersion compensation for intensity modulation direct detection (IM-DD) optical transmission systems, has been investigated theoretically and experimentally. This technique is based on a predistortion technique in an optical transmitter. Implementation to the ordinary IM-DD optical transmitter, which uses an external intensity modulator, is easily realized merely by adding a small injection current modulation to a semiconductor laser diode, allowable optical transmission fiber dispersion will be more than doubled with this technique, modified prechirp technique, which utilizes a time division superimposing prechirped bit streams, has also been investigated to achieve greater dispersion compensation capability. >

100 Gbit/s to 6.3 Gbit/s demultiplexing experiment using polarisation-independent nonlinear optical loop mirror

Abstract: Polarisation-independent 100 Gbit/s demultiplexing is demonstrated for the first time with a nonlinear optical loop mirror using a polarisation diversity scheme. Error free operation is confirmed with a 0.6 dB variation in received optical power as the input signal polarisation direction is varied by 90°.

Compensation for pulse waveform distortion in ultra-long distance optical communication systems by using midway optical phase conjugator

Abstract: In long-distance optical communication systems using in-line optical amplifiers, the waveform distortion is induced by both the Kerr effect and the group-velocity dispersion of optical fibers. In this letter, we show that the optical phase conjugator placed at the midway of the transmission line can compensate for the Kerr effect as well as the group-velocity dispersion, preventing the waveform distortion. >