Showing papers on "Optical Carrier transmission rates published in 1998"

Broad-band millimeter-wave (38 GHz) fiber-wireless transmission system using electrical and optical SSB modulation to overcome dispersion effects

Abstract: A spectrally efficient millimeter-wave (mm-wave) fiber-wireless transmission system is presented demonstrating downstream transportation of 155-Mb/s BPSK data at 38 GHz over 50 km of standard single-mode fiber and a 5-m wireless link. The effect of fiber chromatic dispersion on the transmission of the mm-wave optical carrier was overcome by using a single dual-electrode Mach-Zehnder modulator to generate optical single-sideband (SSB) modulation with carrier. We also demonstrate a simple technique for obtaining electrical SSB that will allow the effect of fiber dispersion across the bandwidth of the information to be overcome with simple electrical delay equalization. We predict that this fiber-wireless system could permit the transportation of mm-wave signals with large bit rates over long optical fiber distances.

Wavelength tracking in adjustable optical systems

Abstract: An optical system such as an add and/or drop WDM multiplexer allows the wavelength fluctuation of an optical carrier to be tracked so that a corresponding fiber Bragg grating (FBG) can be responsively tuned. The preferred embodiment of the wavelength tracking system in an optical system such as an add and/or drop module includes a three-port optical circulator, three optical fibers, a series of tunable FBGs, a source of a broadband optical noise signal, an optical spectrum analyzer (OSA), and an FBG tuner. In operation, an LED generates modulated probe lightwaves that are inserted into a drop module. The LED lightwaves and the optical carriers propagating through the drop module are monitored by an OSA. The monitoring procedure determines the conditions, in terms of target wavelengths of the FBGs, and the stability or instability of the optical carriers. The FBGs are then tuned in response to the FBG and optical carrier information. In another embodiment, the wavelength of an optical carrier is tracked using a modulated tracking grating and an FBG is adjusted in response to the tracking information.

System and method for free space optical communications

Abstract: A method and system of communicating in free space using an optical communication system, such as for intersatellite and satellite-to-ground communications, is disclosed. Digital communication signals are multiplexed with a plurality of other analog communication signals into a single broad band frequency division multiplexed signal. A laser generates an optical carrier and an electro-optic modulator modulates the optical carrier signal with the frequency division multiplexed signal to produce a phase modulated optical communications signal. A receiver is positioned, such as in a satellite, to receive the phase modulated optical communications signal. The receiver includes a demodulator for demodulating the phase modulated optical communication system back into the broad band frequency division multiplexed signal and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of communication signals. The portion of those signals that were previously digital data can be demodulated back into the digital communication signals.

Optical differential phase shift keying transmission system having multiplexing, routing and add/replace capabilities

Abstract: A Differential Phase Shift Keying (DPSK) optical transmission system provides time division multiplexing, channel routing and channel add/replace functions. The DPSK transmitter comprises a laser to generate an optical carrier signal; a delay encoder to provide a different delay for each of a plurality, M, of input signal channels; and a M channel phase modulator which phase modulates the optical carrier signal with each of the differently delayed M input signal channels to form a Time Division Multiplexed (TDM) phase modulated optical signal. A DPSK receiver demodulates a received TDM phase modulated optical signal. The system may also include apparatus to route, add, and replace TDM channels.

16-channel (1- to 16-GHz) microwave spectrum analyzer device based on a phased array of GaAs/AlGaAs electro-optic waveguide delay lines

Abstract: We demonstrate a sixteen channel, GaAs/AlGaAs staring spectrum analyzer device based on a phased-array of sixteen electro-optic waveguide delay lines. The device is effectively a high resolution version of the widely reported optical wavelength division multiplexer phased-array devices, using electro-optic waveguides to adjust the optical phases across the array. The device comprises: a 1- to-16 way multimode interference coupler; 16 electro-optic phase controllers; 16 folded waveguide delay lines, from 0 to 1 nanosecond in equal steps; and a waveguide phased array output. By making use of novel waveguide and corner designs we demonstrate the device as a spectrum analyzer, the RF signal to be analyzed was superimposed on an optical carrier using a GaAs/AlGaAs electro-optic waveguide push-pull Mach Zehnder interferometer, and the intensity modulated light was then passed through the phased-array chip. The spectrum of the RF input signal was displayed in the far field of the phased-array as diffraction lines on either side of the main diffraction lines. By biasing the modulator to extinction, the CW carrier could be removed from the far field diffraction pattern so that only the RF spectrum was displayed. In this presentation we describe the device design, fabrication and testing including measurements of the dynamic range and resolution.

Method and arrangment for stabilizing wavelength of multi-channel optical transmission systems

Abstract: The invention relates to a method and a device for wavelength stabilizing for multichannel optical transmission systems An optical multiplexer is used directly for the generation of the optical total signal This makes possible a simple electronic regulation of wavelengths of the optical carrier signals through analysis of the amplitude values of low-frequency signals, which modulate the optical carrier signals by means of amplitude modulation

Optoelectronic analog-to-digital converter using wavelength division multiplexing

Abstract: An optoelectronic system is provided for converting analog electrical sigs into digital electrical signals. An optical carrier produced by a laser source is separated into spectral components. An electro-optical modulator modulates the optical carrier with a radio frequency input signal so as to produce an amplitude modulated optical output signal. The optical output signal is then outputted to a wavelength division demultiplexer which separates the output signal into a plurality of separate channels, based on wavelength. Photodetectors connected to each of the channels convert the separated signals into analog electrical signals. These analog electrical signals are outputted to a plurality of standard analog to digital converters which convert the analog electrical signals into digital signals.

Optical transmitter system and method

Abstract: The present invention relates to an optical duobinary transmitter system and method using optical intensity modulation. The system comprises an input terminal (51) arranged to receive a first binary signal, a driving circuit (53) connected to the input terminal and arranged to convert the first binary signal into a second and a third binary signal, a double electrode optical modulator (55) connected to the driving circuit in such a way that its upper and lower electrode may be driven by said second and third binary signal, respectively, said modulator being further arranged to modulate the amplitude and phase of an optical carrier according to the binary driving signals so as to provide an optical duobinary signal corresponding to said first binary signal and with a predetermined negative modulation chirp parameter, and an output terminal (57) connected to the optical modulator and arranged to feed an optical transmission line with the modulated optical duobinary signal. The modulator may alternatively be arranged to be driven by quasi-ternary signals.

2.488 Gb/s silicon bipolar clock and data recovery IC for SONET (OC-48)

Abstract: A Si bipolar IC recovers the clock and retimes the data at 2.488 GHz, while meeting all specifications for SONET (Synchronous Optical Network) OC-48 (optical carrier at 48 times base frequency). This is the first single chip, low power, fully integrated solution in the market. Previous ICs have either required external components or have not been fully compliant with all the specifications. The IC incorporates a voltage controlled oscillator (VCO) with delay tuning that uses integrated spiral inductors. The lock range is broad enough to hold up against process, power supply and temperature variations.

Low-loss 1.3-/spl mu/m MQW electroabsorption modulators for high-linearity analog optical links

Abstract: Low-loss InAsP-GaInP multiquantum-well electroabsorption waveguide modulators have been developed for transmitting microwaves as subcarriers over optical fibers. The fiber-to-fiber insertion loss is only 5 dB at 1.32-/spl mu/m wavelength. The electrooptic slope efficiency of an 185-/spl mu/m-long 11-GHz bandwidth device is equivalent to a Mach-Zehnder modulator with a V/sub /spl pi// of 2.2 V. The linearity performance was characterized for a test link without any form of amplification. A RF-to-RF link efficiency of -25.5 dB, noise figure of 27 dB and suboctave spurious-free dynamic range of 114 dB.Hz/sup 4/5/ have been achieved with 16 mW input optical carrier power. The measured 3-dB electrical bandwidth exceeds 20 GHz for a 90-/spl mu/m-long device.

40 Gbit/s quaternary dispersion supported transmission field trial over 86 km standard singlemode fibre

Abstract: 40 Gbit/s transmission on a single optical carrier using electrical time division multiplexing is demonstrated for the first rime reusing already installed standard single mode fibres. Bit-error measurements as well as video transmission via STMI interfaces are reported.

4 x SONET OC-192 Field Installed Dispersion Managed Soliton System over 450km of Standard Fiber in the 1550nm Erbium Band

Abstract: Standard single mode fiber is by far the most widely deployed fiber to date. Spurred by advances in optical amplifier technology, significant research over the past 8 years has investigated transmission techniques to increase the capacity and/or the distance achievable over this fiber type in the 15μm window.

System and method for improved signal to noise ratio in optical communications networks

Abstract: A system and method are described for modulating phase and polarization aspects of an optical carrier signal with URZ and URZ d coded representations of source data, where the source data itself is transmitted via an optical transmission system using UNRZ coding. At a receiver, the URZ and URZ d signals are summed to provide a UNRZ equivalent encoding of the source data. That UNRZ-equivalent encoded signal is then combined with the received UNRZ signal to produce a composite UNRZ encoded representation of the transmitted source data. In carrying out the method of the invention, noise attributable to random fluctuations in phase and polarization of the optical carrier signal is reduced and the composite UNRZ coded signal obtained at the receiver provides a more reliable indicia of the encoded transmitted data.

Method and apparatus for generating a modulated optical return to zero signal

Abstract: The present invention generally relates to the field of signal generation and particularly to a method and an apparatus for generating a modulated RTZ signal from a RTZ signal by driving an modulator with a non-RTZ signal. For the transmission of optical high bit-rate signals over a fibre mainly intensity modulated optical signals are used. To intensity modulate an optical signal with data formed by a bit sequence the optical power of an optical carrier is switched on and off according to the bit sequence. There are non-RTZ signals having a constant high power level for consecutive bits of the bit sequence having a high level, and RTZ signals for which the power level is set back to zero within each bit interval. To correctly modulate the RTZ signal with the electrical non-RTZ signal a fixed phase relation between the two signals is necessary. The invention under consideration provides a method and an apparatus for automatically aligning the phases of the RTZ signal and the non-RTZ signal by phase modulation of one of the signals with an auxiliary signal and analysing the modulated RTZ signal generated from the signals. The analysis and the phase alignment are based on deviations in the mean signal power of the modulated RTZ signal.

Centralized wavelength distribution for wavelength division multiplexed systems

Abstract: A combination and method for centralized distribution of laser carrier beams (800) to collocated wavelength division multiplexing systems (200) divide and couple the optical carrier beam from high power laser sources (101) to each of more than one collocated system. The carrier beam (800) is then modulated by modulators (253, 454) in transponders (263) residing in each wavelength division multiplexing system (200). Each modulated signal is then combined by a wavelength division multiplexer (290) for transmittal onto an output fiber (292).

Field trial at 40 Gbit/s over 28.6 and 86 km of standard singlemode fibre using quaternary dispersion supported transmission

Abstract: 40 Gbit/s transmission using a single optical carrier and electrical time division multiplexing is demonstrated for the first time reusing standard singlemode fibres from the existing fibre infrastructure of Portugal Telecom. Bit error measurements as well as video transmission via STM1 interfaces demonstrate the robustness of dispersion supported transmission under real operating conditions.

The application of code division multiple access for transport overhead information in transparent optical networks

Abstract: Summary form only given. The operation, administration, and maintenance (OAM) of a transport network require the generation, transmission, and detection of OAM signals that are related to each network layer. In the modelled system Gold codes have been applied for transport of the OAM-signals at channels, which have been modulated externally (by Mach-Zehnder modulators) at different modulation levels in order to characterize the influence of the modulation depth. The simulation has shown the feasibility of CDMA for transport of OAM-signals with a bandwidth up to l0-kbit/s per optical carrier in transparent optical networks with minimised distortion of the high speed data stream.

Method and apparatus for decompressing pulses making up a binary optical signal

Abstract: In communications systems having optical networks, data rates in the electrical domain can be matched to data rates in the optical domain by means of time-division multiplexing, with the pulses forming the transmitted optical data being compressed. A method performs the necessary pulse decompression on reception in all-optical manner. The method includes forming q auxiliary signals respectively obtained by amplitude modulating each of q optical carrier waves having different wavelengths by the received signal, and superposing q delayed auxiliary signals obtained by applying delays to the auxiliary signals such that any two consecutive delayed auxiliary signals are offset in time by the duration of the pulses making up the received signal.

Suppression of polarization hole burning with an acousto-optic modulator

Abstract: An apparatus and method for reducing polarization hole burning in a rare-earth-doped fiber amplifier within an optical communication system by converting an optical carrier having a characteristic wavelength into a polarization-rotating optical carrier is disclosed. The apparatus includes a polarization-fixing device optically coupled in the optical transmission system to transform the optical carrier to a polarized optical carrier, and an acousto-optic modulator positioned to receive a first portion of the polarized optical carrier and to orthogonally convert the polarization of the polarized optical carrier and to shift the polarized optical carrier by a modulation frequency. The apparatus and method further includes a polarization beam combiner optically coupled to receive the orthogonally polarization converted and frequency shifted polarized signal and a portion of the original polarized optical carrier. The polarization beam combiner produces a polarization-rotating carrier signal that is transmitted downstream in the optical communication system to a rare-earth-doped fiber amplifier.

Broadband wireless infrared LAN architecture compatible with Ethernet protocol

Abstract: A wireless infrared (IR) LAN for the indoor environment is proposed which is compatible with the familiar CSMA/CD protocol used in Ethernet. Eye safe 140 Mbit/s transmission at only 5 mW transmitter power in a 20 m/sup 2/ cell is experimentally demonstrated.

Characteristics of photonic time shifters based on switched gratings

Abstract: A cascade of n independently controlled gratings can be used to route an optical carrier through one of 2 inch evenly spaced time delay paths. The resulting optical systems include digital time shifters for phased arrays with the potential for improving attainable performance in terms of insertion loss, crosstalk, and compactness. We describe results from an effort in which these characteristics of free-space optical time delay system based on switched- volume-diffraction gratings were modeled and investigated experimentally. In one experiment, a 1 by 4 router, which constitutes the front end of a 2-bit photonic time delay circuit, was used to validate the low insertion loss and miniaturization capabilities of this technology. We fabricated electrically switched gratings which demonstrated 20 dB contrast and a response time of 15 microseconds. Realistic loss and crosstalk parameters were used in detailed systems modeling to show that practical system can be built using this technology with very low insertion loss and crosstalk. Various configurations are described, including a multi-pass device that may replace many single channel time shifters with a single optical system.

Method and a circuit for concatenating binary information, and use in optical packet transmission

Abstract: In packet time-division multiplexing communications systems using optical networks, an optical method and circuits used in electrical-to-optical conversion interfaces assure that data rates of the electrical domain match the data rates of the optical domain. An optical method of concatenating binary information contained in successive time windows of an input signal includes forming g converted input signals obtained by amplitude modulating g optical carrier waves having different wavelengths, each converted input signal presenting, within the time windows, amplitude modulation as a function of the input signal. The method also includes forming a multiplex signal made up of a combination of g delayed signals obtained by applying delays to the converted input signals, the delays being such that any two consecutive delayed signals are offset in time by the duration w of the time windows.

Automatic compensation method and device for primary polarization mode dispersion

Abstract: PROBLEM TO BE SOLVED: To provide a device which can automatically fit a primary polarization mode dispersion(PMD) level by producing a control signal proportional to the total value of the differential optical time delay of the optical signal occurring at the output part of a variable birefringence element via an optical signal analyzer and controlling the differential time delay value, which is generated for the control of selecting a specific orthogonal polarization state by means of the control signal. SOLUTION: Automatic fitting is attained to a PMD level, via the differential time delay of a variable differential time delay line 50 and the supply of a feedback signal, that controls the polarization transformation of a polarization transformer 30. Some of signals which are outputted from a compensation device 25 are supplied to a path 87 which reaches a fast photodetection device 55 via an optical tap 85, and other signals are supplied to a path 86 reaching a receiver 90. The device 55 converts the fast digital information signal modulated on an optical carrier signal into an electric signal. The electric signal is amplified by an amplifier 60 and sent to an electrical distortion analyzer 70 which measures the distortion of the amplified optical current and coverts the amplified result into a voltage that is proportional to the measured distortion.

Use of bandwidth efficient modulation techniques in a wavelength division multiplexed optical link

Abstract: Systems and methods that improve data transmission over a wavelength division multiplexed optical link. First and second wavelength division multiplexed modulators modulate data for transmission onto a microwave carrier signal to produce first and second carrier signals having a first carrier frequency. A downconverter downconverts the first carrier signal to a lower carrier frequency. A combiner combines the downconverted and second carrier signals to provide a composite microwave signal. A wavelength division multiplexed transmitter transmits the composite microwave signal on a wavelength division multiplexed channel over an optical fiber. A wavelength division multiplexed receiver reproduces the composite microwave signal transmitted over the optical fiber. A splitter and filters separate out the downconverted and second carrier signals from the composite microwave signal. An upconverter upconverts the downconverted carrier signal from the lower carrier frequency to the first carrier frequency. Demodulators demodulates the upconverted and second carrier signals to generate the originally transmitted data. The systems and methods use higher order modulated microwave carriers (M-ary ASK, PSK, QAM, etc.) to intensity modulate the optical carrier. As a result, more than 1 bit/Hz of optical channel can be transmitted.

Multiplexed optical transmission systems

Abstract: In an optical transmission system two or more digital signals are multiplexed at a transmitter using one or more electrical sub-carriers before the multiplexed resultant is employed to modulate a single optical carrier for onward transmission to a receiver. The modulated optical carrier may be multiplexed with one or more similarly modulated other optical carriers, each of different wavelength.

Switching of 100 Mbit/s channels from 60 Gbit/s data-stream in new broadcast-and-select WDM/TDM local network

Abstract: A new broadcast-and-select WDM/TDM local network architecture is proposed for constructing a future low-cost broadband network. As a feasibility study, the switching of 100-Mbit/s channels from a 20-Gbit/s/spl times/3-WDM data-stream is demonstrated and bit-error rates are measured; the power penalties are less than 1.9 dB across the entire tuning range.

Method and device for concatenating binary informations and use thereof for optical transmission of packets

Abstract: The procedure involves forming a number (g) of converted input signals, obtained respectively by the amplitude modulation of g optical carrier waves of different wavelengths. Each input signal displaying inside successive time windows of a synchronous amplitude modulated input signal, the windows having a duration (w) and a period (T) at least double the duration. A multiplex signal is then formed, made up of a combination of g delayed signals (Er1-Er4) obtained by applying delays to the converted input signals from two consecutive delayed signals.

Electro-optical microwave signal processor for high-frequency wideband frequency channelization

Abstract: An electro-optic microwave signal processor for activity monitoring in an electronic warfare receiver, offering wideband operation, parallel output in real time and 100 percent probability of intercept is presented, along with results from a prototype system. Requirements on electronic warfare receiver system are demanding, because they have to defect and identify potential threats across a large frequency bandwidth and in the high pulse density expected of the battlefield environment. A technique of processing signals across a wide bandwidth is to use a channelizer in the receiver front-end, in order to produce a number of narrow band outputs that can be individually processed. In the presented signal processor, received microwave signals ar unconverted onto an optical carrier using an electro- optic modulator and then spatially separated into a series of spots. The position and intensity of the spots is determined by the received signal(s) frequency and strength. Finally a photodiode array can be used for fast parallel data readout. Thus the signal processor output is fully channelized according to frequency. A prototype signal processor has been constructed, which can process microwave frequencies from 500MHz to 8GHz. A standard telecommunications electro-optic intensity modulator with a 3dB bandwidth of approximately 2.5GHz provides frequency upconversion. Readout is achieved using either a near IR camera or a 16 element linear photodiode array.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Characterization of an optical wireless communication channel

Abstract: We describe four measurement techniques to characterize the performance of an optical wireless channel. The characteristics of each technique are illustrated through experimental measurements. These four techniques include: (1) bit-error rate measurements, (2) measurements of the mean and variance of the received optical power from which the bit- error rate can be estimated, (3) measurements of the fade rate and fade duration histograms of the optical carrier, (4) measurements of the intensity and phase distributions of atmospheric propagated laser beams using a Shack-Hartmann wavefront sensor.

Evaluation of optical channelizers in terms of rf performance

Abstract: The demonstration of RF photonic links with bandwidths of 100 GHz or more is expected in the near future, due to rapid and continuing progress in modulator and detector technology. Since it is very difficult to electronically process such a large bandwidth after photodetection, photonic approaches that reduce the burden on the electronics are increasingly relevant.One such approach is an optical channelizer, where an RF modulator optical carrier is optically dispersed onto a detector array. Each element of the array only sees a portion of the original wideband RF spectrum. We analyze the RF performance of optical channelizers in terms of crosstalk and uniformity of response. Both direct detection and heterodyne channelizers will be considered. Analysis of this kind is necessary for our application, since the usual parameters of a dispersive optical system, such as resolution, resolving power or filter linewidth do not provide enough information to determine the RF performance. The analysis has shown that a Fabry-Perot filter based channelizer cannot provide adequate RF performance, while a grating-based channelizer can. For channelizer to 1 GHz channels with a -70 dB crosstalk specification, a total grating length of roughly 80 cm is required, so a multiple bounce geometry is necessary to obtain a reasonably compact system.