Showing papers on "Optical Carrier transmission rates published in 2000"

A 3 GHz, 32 dB CMOS limiting amplifier for SONET OC-48 receivers

Abstract: An optical receiver front-end for SONET OC-48 (2.5 Gb/s) is shown. The limiting amplifier (LA) receives a small-non-return to zero (NRZ) voltage signal (e.g., 8 mV/sub pp/) from the transimpedance amplifier (TIA) and amplifies it to a level (e.g. 250 mV/sub pp/) sufficient for the reliable operation of the clock and data recovery circuit. The noise contribution of the LA must be small compared to that of the TIA so that the overall bit error rate and sensitivity are not affected adversely. Currently, commercial 2.5 Gb/s SONET systems are composed of several discrete chips implemented in GaAs and more recently silicon bipolar technology. The future trend, however, is to integrate most of the front-end together with the digital framer on a single CMOS chip. Furthermore, the integration of multiple 2.5 Gb/s channels on a single CMOS chip is desirable for wavelength division multiplexing (WDM) application. CMOS amplifiers for optical receivers and related applications with bandwidths up to 2.1 GHz are recently reported. This CMOS limiting amplifier with improved bandwidth (3 GHz) and noise figure (16 dB) is suitable for 2.5 Gb/s SONET receivers. Power dissipation is 53 mW and the chip is fabricated in a standard 2.5 V, 0.25 /spl mu/m CMOS technology. This result is achieved with: (i) Inverse scaling to increase gain-bandwidth and reduce power dissipation while keeping noise and offset voltage low and (ii) active inductors to increase gain-bandwidth and improve gain stability. The active area of the amplifier is 0.03 mm/sup 2/, less than 10% that of a comparable design with spiral inductors.

High-performance microwave transversal filter using fiber Bragg grating arrays

Abstract: Measured results from a microwave photonic traversal filter exploiting fiber Bragg grating (FBG) arrays and achieving a high-performance tunable bandpass microwave response are presented. Tuning is affected by changing the optical carrier wavelength to select the operating gratings, and the high-quality frequency response is obtained by weighting the reflections of the gratings. This experiment demonstrates that sophisticated passive signal processing functionality can be achieved practically using FBGs.

Nonlinear crosstalk and two countermeasures in SCM-WDM optical communication systems

Abstract: We investigate, theoretically and experimentally, crosstalk between wavelengths in subcarrier-multiplexed (SCM) wavelength-division multiplexed (WDM) optical communication systems. Crosstalk arises mainly from interactions between subcarriers on one wavelength and the optical carrier of another wavelength. In a dispersive fiber, crosstalk can be attributed to stimulated Raman scattering (SRS) and cross-phase modulation (XPM) combined with group velocity dispersion (GVD). We investigate the phase relationship between SRS-induced and XPM-induced crosstalks. Crosstalks induced by SRS and XPM add in the electrical domain and can interfere constructively or destructively. Experimental results show that the combined crosstalk level can be as high as 40 dBc after 25 km of SMF with two wavelengths and 18 dBm per wavelength of transmitted power. We propose two crosstalk countermeasures. The first countermeasure uses parallel fiber transmission. We show theoretically that both SRS-induced and XPM-induced crosstalks can be cancelled to the first order. We present an experimental demonstration of concept which has achieved 15 dB of crosstalk cancellation over 200 MHz. The second countermeasure uses optical carrier suppression. We show, theoretically and experimentally, that by suppressing the optical carrier, we can significantly reduce crosstalk while maintaining the same link budget and carrier-to-noise ratio (CNR) at the receiver, 20 dB of crosstalk reduction over 2 GHz has been demonstrated experimentally.

Optical upconverter apparatuses, methods and systems

Abstract: Apparatuses, methods, and systems are disclosed that provide for simultaneously upconverting electrical signals carrying information at electric frequencies onto optical subcarrier lightwave frequencies that are greater and less than the carrier frequency of the lightwave onto which the electrical frequencies were upconverted. The upconversion of the electrical signals can be performed with or without suppression of the optical carrier frequency.

Optical SCM data extraction using a fiber-loop mirror for WDM network systems

Abstract: We demonstrate the use of a polarization-independent dual-port filter to extract subcarrier multiplexed (SCM) data from a baseband/SCM channel while the baseband is passed through with minimal distortion. This architecture solves the fiber dispersion-induced fading problem for SCM channels and eliminates the complexity of single-sideband modulation techniques by suppressing the optical carrier at the tap port prior to photodetection. Bit-error-rate (BER) measurements were performed on the baseband channel showing that the SCM removal prior to photodetection reduces crosstalk with the subcarrier channel. The BER on the SCM data shows no effect of dispersion-induced fading. The periodic optical frequency characteristic of the filter can be matched to the ITU grid, making this tap applicable to multichannel WDM networks.

Optical carrier Brillouin processing of microwave photonic signals.

Abstract: We introduce a novel concept in Brillouin signal processing based on modification of the optical carrier’s magnitude and phase by stimulated Brillouin scattering–induced depletion. The technique offers wideband processing and low noise and requires only low optical power. Application to the enhancement of a 25-km high-frequency analog link is experimentally demonstrated and yields a 6.5-GHz bandwidth extension and a 13-dB reduction in the link insertion loss without intermodulation distortion.

Tandem single sideband modulation scheme for doubling spectral efficiency of analogue fibre links

Abstract: Using a dual-electrode Mach-Zehnder modulator, a 'tandem' single sideband modulator has been constructed that doubles the spectral efficiency of a system by enabling the transmission of different data streams in the upper and lower sidebands of the same optical carrier.

Development of an ultrastable fiber optic frequency distribution system using an optical delay control module [for frequency standard and VLBI]

Abstract: An ultrastable fiber optic frequency distribution system is described. The ultrastable phase stability is achieved by configuring a closed phase-locked loop with a single-mode optical fiber transmission line in which two optical carrier signals with different wavelengths are transmitted as a forward and a backward signal, and installing an optical delay control module which has no differential dispersion effect between the two optical carrier waves and induces no electrical noise. A phase stabilized optical fiber (PSOF) is used for the signal transmission line. The stabilities of this system are 7.5/spl times/10/sup -17/ and 1.1/spl times/10/sup -17/ in Allan standard deviation at 1000 and 10000 s averaging time, respectively, while the environmental temperature of the PSOF cable varies as much as the range of 10/spl deg/C and the rate of 10/spl deg/C/12 h.

Method and apparatus of utilizing RF/microwave and optical mixing techniques to select a given band of an optical transmission

Abstract: A method and apparatus (10) are provided for transmitting (12, 14) and receiving (24, 26) multiple RF/microwave subcarriers on a single optical wavelength over an optical link. The method includes the steps of modulating a plurality of RF/microwave subcarrier frequencies with a respective communication signal and modulating an optical carrier wave with the plurality of modulated RF/microwave subcarrier frequencies. The method further includes the steps of detecting the plurality of RF/microwave subcarriers of the optical carrier wave and mixing (102) those subcarriers with a first local oscillator (LO) frequency to create a new heterodyne IF frequency above the highest frequency component of the modulated signal spectrum of the detected subcarriers, filtering an RF/microwave subcarrier frequency of the plurality of detected RF/microwave subcarriers utilizing a bandpass filter (106) at an IF center frequency of the new IF frequency and mixing the filtered RF/microwave subcarrier with a second local oscillator (LO) (108) frequency to derive a difference frequency at a desired center frequency for propagation over the subsequent network element.

Method and apparatus for wavelength conversion and switching

Abstract: A two-dimensional second order nonlinear lattice formed in a lattice body is utilized for performing a one-step optical carrier wavelength interchange between pairs of input optical signals. The lattice body includes sensitized regions arranged in a two-dimensional array in a matrix material with the sensitized regions differing from the matrix material in the sign of the second order susceptibility. When an optical pump signal is coupled to the lattice body at a frequency corresponding to the sum of the frequencies of the two input signals, nonlinear interactions in the lattice body produce wavelength interchange between the input signals, resulting in angularly deflected optical signals exiting the lattice body in which the signal information on the input signals is interchanged between the carrier frequencies of the two input signals. The apparatus can be utilized to provide switching of optical signals and wavelength interchange for applications such as in wavelength division multiplexed communication systems.

Radio-Optical System Design and Transmission Experiments for a Mobile Broadband Communications System at 60 GHz

Abstract: The paper presents the system design concept for a mobile broadband communications system at 60 GHz. A dense WDM system is used for the optical backbone employing novel add/drop multiplexers. For simplicity, there is no signal processing and frequency generation at the base station and a master oscillator signal are used for millimetric carrier generation. The master oscillator signal is modulated onto the optical carriers by a novel concept of simultaneous external modulation, simplifying system design significantly. Transmission experiments over a complete downlink path using uncoded 2-FSK have been carried out and a BER of 10-9 at 50 MBit/s has been obtained. Furthermore, 512-carrier DQPSK-OFDM transmission at 45.8 MBit/s using 35 MHz bandwidth at 60 GHz has been demonstrated.

Optical transmission apparatus

Abstract: In an optical transmission apparatus including an external optical modulator for modulating an optical carrier from a light source with an electrical signal, bias voltage applied to the external optical modulator is accurately adapted to fluctuations in optimal bias voltage due to DC drift. A bias voltage control circuit 150 controls bias voltage applied by a bias voltage applier 105 to an external optical modulator 110 so as to minimize an amount of second order distortion included in an optical signal from the external optical modulator 110 and caused by non-linearity thereof.

Signal transmission system

Abstract: A signal transmission system has a number of wave division multiplex optical carriers linking a number of switching units arranged in a closed ring network The carriers are amplified to compensate for loss and attenuation, but the ring gain of each carrier must be less than unity to prevent unwanted signal oscillation An automatic gain control arrangement is operative for each optical carrier which is detected as being present at a switching unit, and the gain control is disabled for each carrier which is detected as being absent

Photonic conversion of OC-192 OTDM-to-4 × OC-48 WDM by supercontinuum generation

Abstract: The authors propose a novel method for converting optical time division multiplexed (OTDM) signals to wavelength division multiplexed signals (WDM) by using supercontinuum (SC), followed by spectrum slicing and time-gating OC-192 (9953 Gbit/s) OTDM signals to 4/spl times/OC-48 (2488 Gbit/s) WDM signals conversion with a BER of under 10/sup -9/ is experimentally demonstrated

Signal transmission system

Abstract: PROBLEM TO BE SOLVED: To determine the reference of the error rate of traffic without directly monitoring traffic data by providing a means for specifying an error existent in optical modulation and a means for utilizing the error as the reference of possibility of error in the traffic data or the like. SOLUTION: A data traffic 4 is received in an SDH format as a complicated and multiplexed wide band electric signal and modulated on the optical carrier of a narrow band generated by a laser 6 by a modulator 5. The modulated optical carrier is transmitted over an optical guide 3, received by a remote receiver 2 and dispatched to a section overhead-(SOH) extraction unit 21 after first removing an SOH signal in a demodulator 20. Then, the performance error is monitored in an error check unit 32 while using a bit interleave parity on SOH and the reference of the error rate of traffic is determined.

Beam steering device used in 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 pulse generator

Abstract: PROBLEM TO BE SOLVED: To provide an optical pulse generator in which a driving is made with an arbitrary modulation frequency within a modulation band, the chirping characteristic of an optical pulse is controlled, the pulse width is made independent against an operating wavelength and carrier suppressed optical pulses are generated. SOLUTION: The generator is provided with a light source 1, which outputs optical carrier, an optical intensity modulator 2, in which a transmissive characteristic has a periodic response of an even function centered around an operating bias point against driving signals and the optical carrier is intensity modulated by the driving signals, a driving means 3 which outputs electric signals having an amplitude 2Vπ corresponding to two periods of the transmissive characteristic of the modulator 2 and a frequency f, and a bias controlling means 4 which controls the operating bias point of the driving signals of the modulator 2. Thus, the modulator 2 outputs optical pulses each having a repetitive frequency 2f.

System and method for free space optical communications using time division multiplexing of digital communication signals

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.

A system for native Ethernet optical transport at 10 Gb/s

Abstract: The first system to transport native Ethernet data at a serial rate of 1O Gb/s is reported. Up to 8 asynchronous gigabit Ethernet signals are multiplexed to 10 Gb/s and directly modulate a Fabry-Perot laser at 1310 nm for 2-8 km transport over standard single-mode fiber.

Optical communication system

Abstract: PROBLEM TO BE SOLVED: To enable optical transmission over a wide band and at very high speed. SOLUTION: For an optical transmitter 100, multipliers 11-14 have mutually different frequencies according to plural data signals, modulate corresponding subcarrier signals by multiplying them and output modulated signals and laser diodes 31-34 respectively generate optical carrier signals having mutually different wavelengths, modulate corresponding optical carrier signals according to plural modulated signals and radiate the modulated optical transmission signals from an optical radiator 4. In an optical spatial receiver 200, a photodiode 42 receives plural radiated optical transmission signals and photoelectrically converts them to electric signals, band pass filters 51-54 perform band-pass filtering to the photoelectrically converted electrical signals, so as to pass the modulated signals of corresponding subcarrier signals, and afterwards, detection reproducers 61-64 output corresponding data signals by detecting and reproducing the modulated signals of plural subscarrier signals.

Method and device for optically transmitting data via optical waveguides

Abstract: The invention relates to a method for optically transmitting data via optical waveguides during which the electric signal (Sel) or optical information signal (Sopt) to be transmitted is split into a plurality of partial signals (Sel1 to Seln) each having a lower bandwidth. In addition, each partial signal (Sel1 to Seln) is converted into an optical partial signal (Sopt1 to Soptn) each having different medium wave lengths ( lambda 1 to lambda n) or having an optical carrier frequency and/or having a different orthogonal polarization. Optical partial signals (Sopt1 to Soptn) are transmitted on an optical waveguide which forms the transmission path (7). The optical partial signals (Sopt1 to Soptn) are each separately detected again at the end of the transmission path (7) and are composed into the information signal (Sel) to be transmitted. The invention also relates to a transmitting unit, a receiving unit, and to a complete system for carrying out the inventive method.

Optical central office

Abstract: A method and a system for distributing optical carrier signals involve generating (130) multiple optical carrier signals at unique carrier wavelengths, splitting (132) the carrier signals a first time, amplifying (134) the split carrier signals, splitting (136) the carrier signals a second time, modulating (138) data onto the twice-split carrier signals, and then multiplexing (140) modulated carrier signals of different wavelengths together for transmission over common optical paths. In one embodiment, the multiple optical carrier signals are split and amplified separately by unique carrier wavelength before being multiplexed. In other embodiments, the multiple optical carrier signals are multiplexed together for the first signal splitting and for the carrier signal amplification. The multiplexed signals are then demultiplexed so that the optical carrier signals can be individually modulated. The modulated optical carrier signals are then multiplexed with carrier signals of different carrier wavelengths for transmission throughout a subscriber area. By amplifying optical carrier signals during signal distribution, a low number of optical sources are required to distributed multiple optical carrier signals over a wide subscriber area.

Active matching photonics assembly body

Abstract: PROBLEM TO BE SOLVED: To provide an active matching photonics assembly body actively connecting optical energy between optical devices. SOLUTION: In an optical matching photonics assembly body, an adjustable fiber 54 or another optical carrier transmits an optical signal 52, which is received by a detector 60, and the detector measures a power level of the optical signal. Based on the measurement of the power level, matching of the fiber or another optical devices contained in the assembly body is achieved by an optical feedback loop 66 controlling the position of the fiber or the another optical device with respect to the detector by using micro-actuators 74, 76, 78.

Wideband signal processing applications for coherent optical channelizers

Abstract: As the frequencies and bandwidths in military RF systems escalate, we enter a realm where photonic technologies can play an important role in signal transmission and processing Since it is very difficult to process large data bandwidths, either tunable or instantaneous, using conventional electronics, conventional receiver electronics becomes a bandwidth bottleneck, thus development is timely for optical processing of wideband signals A review of critical mission requirements and photonics capabilities reveals a variety of military missions that can benefit immediately or in the near future from the advantages offered by photonics In this paper we will discuss the implementation of an Integrated Sensor System (ISS) that is greatly simplified through the use of a coherent optical channelizer In this system the received RF signal, which has been modulated onto an optical carrier, is routed via an all-optical switch to the coherent optical channelizer A signal channelizer has the capability to process signals at frequencies of up to 100 Ghz and translate all the frequency channels to a convenient IF That is compatible with advanced digital receivers currently under development The channelizer is also used on the transmit side of the system where a signal waveform is electronically synthesized at a convenient IF then photonically translated to a desired frequency band and transmitted to the aperture over fiber

High-performance transimpedance amplifier for OC-48 optical transceiver application

Abstract: A high performance low noise common gate CMOS cascoded transimpedance amplifier designed and simulated in a 0.35 micrometers CMOS technology is presented in this paper. This novel transimpedance amplifier design provides a transimpedance gain of 1k(Omega) with a -3db bandwidth of 2.49GHz, with the input and output noise current spectral density of 7.08pA/(root)Hz and 7.09nV/(root)Hz respectively. With the rapidly emerging optical data-communication technology, this amplifier design is thus well-suited for optical transceiver applications such as the OC-48 standard.

SBS in fiber for modulation depth enhancement of optically carried microwave signals

Abstract: Summary form only given. For future radar systems based on photonic technologies, the implementation of highly linear optoelectronic links is necessary. Regarding characteristics of classical optoelectronic components used in optical links, the optical carrier is very weakly-modulated at RF frequencies. It then consist in low modulated part and a large DC component. This last one is mainly responsible for the possible saturation of components like photodetectors or optical amplifiers. Thus, there is a need to enhance the modulation depth of such signals. Stimulated Brillouin scattering (SBS) is a nice way for depleting the strong carrier (which carries no information) and leaving the weak modulation sidebands (which carry information) unchanged. SBS is then used intentionally as a carrier filter, with an ultimate bandwidth as low as 15 MHz (in silica fibers).

Optical signal transmission system

Abstract: A signal transmission system uses an optical signal for carrying traffic information, and is also brightness modulated by a relatively low frequency signal. It is impractical to monitor directly the traffic information on the optical carrier for the presence of errors, and the error rate in the low frequency modulation is monitored, as its error rate is found to be indicative of traffic error. The system uses a number of traffic-carrying optical carriers, and also a supervisory or overhead optical carrier, all of which are provided with low frequency modulations whose error rates can be monitored to provide an indication of system performance.

Method and device for assembling optical module

Abstract: PROBLEM TO BE SOLVED: To provide a method and a device for assembling an optical module, capable of assembling the optical module having an optical element such as a laser diode in an optical carrier equipped with an optical system by carrying out highly accurately and quickly the optical axis alignment between the optical system and the optical element SOLUTION: This method comprises the steps of positioning an optical system carrier equipped with an optical system such as a lens optical system in a preset first position based on the observation of interference fringes by an interference microscope (S11), positioning an optical element such as an LD loaded on the optical system carrier in a preset second position based on the observation of interference fringes by the interference microscope (S13), and loading the optical element on the optical system carrier while a relative positional relation between the first and second positions is maintained (S12, S14, S15 and S16) The interference microscope is constructed as a one-eye and two visual field interference microscope, and by observing interference fringes observed in one visual field, the optical system and the optical element are positioned on an optical axis, and the inclination of the optical axis is positioned

Recording and reproducing device for optical carrier

Abstract: PROBLEM TO BE SOLVED: To reduce the generation of error at the time of recording a recordable optical carrier. SOLUTION: In the recording/reproducing device 15 for the recordable optical carrier 1, when an ADIP(address in pregroove) code is unable to decode by an ADIP decoder 8 pulling out the clock from the ADIP code preliminarily recorded on the optical carrier 1, the recording operation to the optical carrier 1 is temporarily stopped by an error signal outputted from the ADIP decoder 8, and an information signal inputted in this stopping period is stored in a storage means 4, and after the error signal is released, the recording to the malfunctioned part is prevented by providing a changeover means 9 for recording the information signal stored in the storage means 4 to the optical carrier 1.

Optical a/d converter and method

Abstract: PROBLEM TO BE SOLVED: To optically perform an A/D conversion by using a downward-folding successive approximation approach. SOLUTION: In a modulator 30, an optical carrier signal from a laser 28 is frequency modulated by an analog signal 24 to be divided into two signals in the splitter of a stage 12. In filters 16, 18, a signal is outputted from either of them is accordance with frequencies of signals from the splitter. When frequencies of the signal enter into the passband of a filter 16, the signals are outputted to an adder 22 as they are and when the frequencies of the signal enter into the epasband of a filter 18, the signals are down-shifted in a frequency-down shifter 20 to be inputted to an addrer 22 and generates the first bit signal MSB1 of a digital signal is generated. Frequencies are successively lowered in subsequent states 46, 48, 50 and bit signals MSB2, MSB3, MSBn are generated in accordance with in which ranges frequencies of an input 36 enter and, finally, this converter outputs a digital signal whose bits are composed of these bit signals MSB1, MSB2, MSB3, MSBn.