Showing papers on "Optical Carrier transmission rates published in 1992"

Apparatus and method for linearizing an external optical modulator

Abstract: An external optical modulator is linearized to reduce second order distortion. An optical carrier is modulated in the modulator by a pilot signal. The modulated optical carrier is sampled and an error signal is generated indicative of a phase difference between a second harmonic of the pilot signal and second order harmonics thereof present in the sampled modulated optical carrier. The error signal is fed back to the modulator to adjust the bias thereof to minimize the phase difference and thereby minimize second order distortions produced by the modulator. Where a plurality of external modulators are operated in series, each is provided with a feedback loop to minimize the second order distortions produced therein.

Narrow band incoherent optical carrier generator

Abstract: A narrow bandwidth incoherent optical source is provided. A superluminescent source includes a gain medium having an input end and an output end. The input end of the gain medium is optically coupled to a reflector to cause spontaneous emissions within a predetermined band exiting the input of the gain medium to be reflected back into the medium. Spontaneous emissions outside of the predetermined band are lost. The gain medium can comprise a doped fiber, such as an Erbium doped fiber. An optical isolator prevents the superluminescent source from lasing. By providing a plurality of reflectors operating in different bands, the superluminescent source can generate a plurality of optical carriers.

An 8 Gb/s QPSK optical homodyne detection experiment using external-cavity laser diodes

Abstract: A quadrature-phase-shift-keying optical homodyne detection experiment was conducted at a bit rate of 8 Gb/s. External-cavity laser diodes and a single-body QPSK phase modulator were used. The optical carrier was recovered by a decision-directed phase-locked loop. The first reported measurement of bit-error-rate performance is given. A receiver sensitivity of -27.8 dBm was achieved. >

Optical source with frequency locked to an in-fiber grating resonantor

Abstract: A frequency stabilized optical signal source is provided. A laser produces an optical carrier at a wavelength λ. Feedback is provided to adjust the wavelength λ. In order to provide the feedback, a portion of the optical carrier is modulated by a periodic reference signal. An optical fiber with an in-fiber resonator is coupled to receive the modulated optical carrier. The resonator effects a phase and/or amplitude change between the modulated optical carrier and a sideband thereof at a resonant frequency of the resonator. The phase or amplitude change is detected and used to adjust the laser wavelength. In a preferred embodiment, a moire grating having a single resonant frequency is used as the in-fiber resonator. The feedback scheme can lock either to the carrier frequency itself, or to a selected sideband of the modulated optical carrier.

Subscriber distribution networks using compressed digital video

Abstract: Emerging standards for highly compressed digital video create interesting possibilities for providing broadcast and switched video services over fiber in the subscriber loop. Experiments are reported which simulate transmission of 200-400 compressed digital video signals using conventional Fabry-Perot lasers and p-i-n diode lightwave receivers. In addition to featuring a robust, low-cost transmission system, compressed digital video networks can offer significant additional advantages, including provisioning of broadcast and switched-video services on a single optical carrier, offering remote service provisioning, and use of video line concentration to significantly reduce the number of switched-video access lines required on each fiber-loop. >

Optical protocols for communication networks

Abstract: The invention is a fiber-optic communication network, including a fiber-optic coupler having multiple fiber-optic ports and multiple optical transceivers which are individually connected to one of the fiber-optic pods. Each optical transceivers includes apparatus for transmitting to and receiving from the fiber-optic coupler, optical pulse signals in accordance with a predetermined code sequence of the transceiver, and optical amplifiers for amplifying the optical pulse signals. Each optical transceivers also includes apparatus for spectrally phase encoding/decoding, in accordance with the predetermined code sequence, optical pulse signals being transmitted to and received from its associated fiber-optic port, and apparatus for reconfiguring the code sequence in accordance with a user select signal. Each optical transceivers further includes detection apparatus for detecting a received optical pulse signal transmitted from another of the optical transceivers. The detector apparatus includes apparatus for magnifying the amplitude of the received optical pulse signal. Additionally, each of the optical transceivers includes apparatus for selecting an optical carrier center frequency at which the optical transceiver receives and transmits optical pulse signals within a predetermined frequency band in accordance with a user center frequency select signal. The different carrier center frequencies are selectable from a set of non-overlapping carrier frequency bands. This allows communications on the network between different user pairs at different carrier center frequencies.

Ultrafast polarisation-independent optical demultiplexer using optical carrier frequency shift through crossphase modulation

Abstract: A novel polarisation-independent all-optical 1:N demultiplexer is proposed using optical carrier frequency shift induced by a strong pump pulse in Kerr media. A 1:4, 60Gbit/s polarisation-independent demultiplexing operation at 1.307μu is demonstrated using a 70 ps broad pump pulse from an Nd:YLF laser.

Method and apparatus for communicating amplitude modulated signals over an optical communication path

Abstract: A block of amplitude modulated television channel signals frequency modulates an optical communication path. In one embodiment, the AM modulated channel signals FM modulate an RF subcarrier which, in turn, is used to intensity modulate an optical carrier for transmission. Frequency modulation of the RF subcarrier by the amplitude modulated channel signals is advantageously performed at microwave frequencies. The FM modulated subcarrier signal is then converted down to a frequency range compatible with transmitter and receiver components used in the system. The frequency modulation and conversion can be performed by a pair of voltage controlled oscillators coupled in a push-pull mode of operation. The outputs of the oscillators are combined in a double balanced mixer to down convert the FM signal spectrum. In another embodiment, the optical frequency of an optical carrier is FM modulated by the block of AM signals. Receivers for the FM modulated band of AM channel signals are also disclosed.

Optical prefiltering in subcarrier systems

Abstract: A novel approach to demultiplexing in subcarrier optical systems is described The technique of optical prefiltering microwave subcarriers from an optical carrier, enabling direct detection of baseband signals, is proposed The technique is experimentally verified by demultiplexing two 10 Mbit/s channels

Method of transmitting digital HDTV signals

Abstract: For transmitting digital HDTV signals, the HDTV signal, which is either fed with a data rate of ≦20.48 Mbit/s or which is data-reduced to such a data rate of ≦20.48 Mbit/s by means of a method utilizing the psycho-optical phenomena of the human eye, is split at the transmitter side of a broadband transmission link operating on the DSR method into two data streams of ≦10.24 Mbit/s each, and is fed to the I/Q interface of the 4PSK modulator of the DSR transmission link. These two data streams whch are transmitted to the I/Q output of the 4PSK demodulator of the DSR transmission link are then further processed thereat.

Acousto-optic comparison switch for optical switching networks with analog addressing techniques

Abstract: Sorting networks based on perfect-shuffle or Banyan interconnection techniques are useful in parallel processing and telecommunications applications. An acousto-optic comparison switch that is useful in such networks is implemented, which ensures high-bandwidth optical data transmission by multiplexing the data and the address on orthogonal polarizations of light. Addresses are encoded either as the frequencies of amplitude modulation of the optical carrier or as discrete optical power levels, and are compared by using simple analog techniques. An analysis of both address techniques with respect to speed and noise is crucial to estimating the switch performance.

Longitudinal mode selection laser

Abstract: PURPOSE: To make it possible to supply a clean optical carrier wave by comprising a laser cavity including an active medium, a means which pumps up the active medium and a lattice resonator having a narrow area characteristic in a guided wave in the laser cavities and selecting a laser operation mode demanded by the lattice resonator. CONSTITUTION: A ring cavity laser comprises an erbium-doped optical fiber where the laser cavity is pumped up with a pump laser 10 and transmitted to an output fiber 28 by way of a coupler through an optical fiber 12. An optical isolator 16 is provided in the ring so as to depress the waves of the ring to one direction and the output is transmitted to a first mirror re Pelot by way of the optical fiber and then is connected to a second mirror 4 by way of an optical fiber 22. Wavelength selectivity is available in a pair of series unequal length Fabry-Perot interferometer. Owing to this construction. The energy produced from the laser provides a clean optical carrier wave for signal transmission.

Wavelength-multiplexed analog fiber optic link for wideband radio-frequency and local oscillator signal transmission

Abstract: A wavelength-multiplexed fiber optic link architecture has been designed for transmitting ri signals with wide instantaneous band width and LO signals at microwave frequencies over long distances. The architecture involves downconverting the input rf signal, directly amplitude modulating a laser diode, transmitting the resulting rf-modulated optical carrier through single-mode fiber, and subsequently up-converting the recovered rf signal to the original band. Wavelength division multiplexing and demultiplexing is used to transmit the local oscillator signal (required for down- and up-conversions) from the transmitter to the receiver through the same fiber. By using a frequency-divided LO signal in conjunction with frequency multipliers, the wideband rf signal can be down/up-conveiled anywhere in the rf spectrum up to 100 GHz. A demonstration link has been implemented using this architecture and operates from 6.3 to 16 GHz. This link uses a 1.3-μm, 10-GHz rf bandwidth laser diode for IF transmission and a 1.55-μm, 1.5-GHz rf bandwidth laser diode for LO transmission.

An OC-48 SONET optical transmission system for gigabit computer networks

Abstract: Results on the performance characteristics of four experimental prototype 2.5 Gb/s SONET optical transmission systems to be deployed in gigabit computer networks are presented. The long-term error performance of the systems has been evaluated with measured ultra low error rates of less than 10/sup -15/. This level of performance is an important feature in the design of high-speed computer communication networks. It also demonstrated that for a nonreturn-to-zero (NRZ) modulated 1310-nm transmitter, a negative dispersion penalty can be achieved for up to 200 km by using dispersion-shifted single mode fiber (DS-SMF). Therefore, DS-SMFs have a potential advantage over conventional SMFs for dual-window multi-Gb/s transmission systems, particularly for wavelength division multiplexed applications. >

High-speed pulse time modulation techniques

Abstract: A principal factor in realizing a high-performance bandwidth-efficient fiber communication system at an acceptable cost is the choice of modulation format on the optical carrier. In this context pulse time modulation (PTM) techniques represent an attractive alternative to purely digital or analogue methods. This paper reviews the PTM family and explores their potential for use in high-speed fiber systems intended for transmission of analogue data.

OC-12/STS-3c/ATM interface for gigabit network applications

Abstract: The implementation of an experimental OC-12/STS-3c/ATM transmission interface is described. This interface maps four streams of ATM cell data into the SONET STS-3c transmission format and multiplexes these channels onto a single OC-12 (622 Mbit/s) optical signal. The interface also performs the reverse demultiplexing functions. This application represents the first known demonstration of a 622 Mbit/s ATM workstation interface.

Method for transmission of digital HDTV signals

Abstract: In order to transmit digital HDTV signals, the HDTV signal (which is supplied at a data rate of

A heterodyne receiver for 40-GHz-modulated 1.3- mu m optical signals using a multi-tasked InP-based HEMT

Abstract: Heterodyne reception of a millimeter-wave modulated 1.3- mu m optical carrier signal is achieved with an InP-based HEMT (high-electron-mobility transistor) that performs four simultaneous functions all in one. The functions are carrier demodulation, generation of a local oscillation signal, frequency multiplication thereof, and transistor-internal downconversion of the modulation signal to a lower intermediate frequency band. The measured performance characteristics of the heterodyne receiver are reported together with results derived from a systematic study of optical detection and mixing properties of a HEMT by itself, observed as functions of modulation signal frequencies up through 40 GHz and bias conditions. >

Optically amplified TDMA distributive switch network with 2.488 Gbit/s capacity offering interconnection to over 1000 customers at 2 Mbit/s

Abstract: An optically amplified distributive switch network based on a simplex passive optical network is described. The capacity is 2.488 Gbit/s and the loss budget is 72 dB, sufficient for more than 1000 customers to be served with an individual capacity of 2 Mbit/s. Effectively only a single stage of amplification is used with no optical filtering.

Quadrature light phase modulator for light wave system

Abstract: PURPOSE: To send an optical signal with different carrier frequencies via a single fiber at a high spectral efficiency by the elimination of secondary inter- modulation product. CONSTITUTION: Modulation signals V1 (t) and V2 (t) of a multiplex subcarrier (V1 (t)=Σβi1 sin(Wi1 t+δi1 ) and V2 (t)=ΣWi2 cos(Wi2 t+δi2 )+Vpi/2 (where βi, Wi, δi are an amplitude, an angular frequency and a phase of a i-th subcarrier, and Vpi/2 is a voltage at which a phase shift of π/2 is generated in the optical carrier frequency) are fed respectively to electrodes 96, 100, and an optical carrier is phase-modulated at modulation sections 88, 90 via an optical splitter 86. Outputs of the respective modulation section are synthesized by a photocoupler 92 and an optical phase modulation signal with a very small secondary inter-modulation signal is obtained at an output section 94.

Few-moded solitary-fibre optical transversal filter

Abstract: A new type of transversal filter for RF and microwave signals on an optical carrier is described. It is based on the coupling and delay between different spatial modes of a solitary few-moded optical fibre. The principle is demonstrated experimentally by constructing four point rectangular and Hamming filters from standard telecommunication fibre using microbend couplers

High performance coding systems for digital transmission of TV and HDTV signals

Abstract: The studies performed in the framework of CMTT/2 for the transmission of 4:2:2 video signals through digital networks, have led to the definition of a bitrate reduction algorithm. In order to implement this videoalgorithm on a single board, a considerable effort has been made to develop an ASIC chipset, capable of processing 27 M samples per second (4:2:2 picture). For HDTV signals, the same technique can be used to provide a bitrate reduction from 1.152 Gbit/s to about 120 Mbit/s. This compression algorithm allows the transmission of one HDTV channel with audio and service channels on a 139.264 Mbit/s (or 2*34.368 Mbit/s) G703/G751 link or on an ATM network (155.5 Mbit/s). The authors describe the hardware implementation of the chipset in TV and HDTV codecs; emphasis is put to the features and performances of the equipment.

Wavelength-multiplexed analog fiber optic link for wideband rf and LO signal transmission

Abstract: A wavelength-multiplexed fiber optic link architecture has been designed for transmitting wideband IF and LO signals at microwave frequencies over long distances. The architecture involves downconverting the input RF signal, directly amplitude modulating a laser diode, transmitting the resulting RF-modulated optical carrier through single mode fiber and subsequently upconverting the recovered RF signal to the original band. Wavelength division multiplexing and demultiplexing is used to transmit the local oscillation signal (required for down- and up-conversions) from the transmitter to the receiver through the same fiber. By using a frequency-divided LO signal in conjunction with frequency multipliers, we can down/up convert the wideband RF signal anywhere in the RF spectrum up to 100 GHz. A demonstration link has been implemented using this architecture and operates from 6.3 to 16 GHz. This link uses a 1.3 micrometers , 10 GHz RF bandwidth laser diode for IF transmission and a 1.55 micrometers , 1.5 GHz RF bandwidth laser diode for LO transmission.

Radio communication system, particularly cell-shaped vehicle wireless system

Abstract: PURPOSE: To simplify an expensive transmission equipment in a system having many radio stations like a cell vehicle radio system. CONSTITUTION: A transmission equipment 10 is connected to a radio station 2 by a light transmitting body 4 and transmits an optical carrier having a first optical frequency ν1 modulated by an information signal and an optical carrier having a second non-modulated optical frequency ν0 to the radio station 2, and optical frequencies ν1 and ν0 of two optical carriers are different by a value of a radio carrier frequency f1 , and the radio station 2 is provided with a device 6 which mixes two carriers to generate a radio signal which includes an information signal and has the carrier frequency f1 as a difference signal between them.

Optoelectronic beam-forming network for a spaceborne phased-array antenna

Abstract: Optoelectronic techniques offer major benefits in the construction of space-borne phased arrays with stringent performance requirements, not only in signal distribution functions but also in the beam forming processing itself. In the course of a current project for European Space Agency we have designed the constructed proof of concept hardware to demonstrate the use of coherent optical techniques in the formation of antenna beams. The scenario at the basis of our study is for a telecommunication satellite with a 160-element phased array antenna, forming 15 beams, each of which can carry up to 20 QPSK modulated carriers, with up to 6 operating simultaneously. Operation is in the 12/14 GHz bands for downlink and uplink operation respectively. In our beamforming concept we have employed an optical heterodyne approach in which the phase shift and amplitude required for beamforming is imposed upon an optical carrier, the RF waveform required for transmission being derived subsequently by mixing with an optical local oscillator signal. Phase encoding for data modulation is also carried out in the optical domain.

Device for combining different electrical signals by means of an optical carrier modulation.

Abstract: of EP05044922.1 It is known to combine electrical signals of a device for modulation and conversion, which have two electro-optical transducers and a modulation device. 2.2 In an arrangement for combining various electrical signals, the economic and technical expenditure can be considerably reduced if an electro-optical modulator (41) is used as device for modulation and conversion (40). This not only reduces the expenditure but, when several cascaded electro-optical modulators are used, only one carrier frequency is needed so that there cannot be any mutual influencing of various carrier frequencies as in the known arrangement. 2.3 The arrangement is particularly applicable to tunnel radio. 3. The drawing shows an electro-optical modulator which is used as device for modulation and conversion.

Performance analysis of wavelength division- and subcarrier-multiplexing (WDM-SCM) transmission using fibre Brillouin amplification

Abstract: A subcarrier multiplexing based optical wavelength division multiplexing system with fibre Brillouin amplification (FBA) is analysed. In the optical domain, a pump laser is tuned to amplify the corresponding optical carrier by FBA for the desired group of SCM signals. In the electrical domain, a microwave tuner is used to select the desired channel in the selected SCM group. This system has the benefits of eliminating the need for polarisation control, the ability to cancel phase noise due to the ‘squaring’ photodetection process of the selected optical carrier together with its SCM channels, and enhancement of optical receiver sensitivity by amplification of the carrier. Comparisons with other systems are also presented.

Coherent analog FM-SCM video transmission using direct frequency modulation of semiconductor lasers

Abstract: The advantages of analog subcarrier-multiplexed (SCM) FM video transmission using frequency modulation of the optical carrier over other analog laser modulation schemes include the reduced impact of laser relative intensity noise and the phase noise suppression achievable in a receiver employing FM demodulation of both the subcarrier and optical carrier. Way et al.1 detected these FM-FM signals using an erbium-doped fiber amplifier and an optical frequency discriminator followed by a direct-detection receiver. We examine the performance of a coherent receiver for the same use.