Showing papers on "Optical Carrier transmission rates published in 2002"

OC-192 transmitter and receiver in standard 0.18-/spl mu/m CMOS

Abstract: This paper presents the first fully integrated SONET OC-192 transmitter and receiver fabricated in a standard 0.18-/spl mu/m CMOS process. The transmitter consists of an input data register, 16-b-wide first-in-first-out (FIFO) circuit, clock multiplier unit (CMU), and 16:1 multiplexer to give a 10-Gb/s serial output. The receiver integrates an input amplifier for 10-Gb/s data, clock and data recovery circuit (CDR), 1:16 demultiplexer, and drivers for low-voltage differential signal (LVDS) outputs. An on-chip LC-type voltage-controlled oscillator (VCO) is employed by both the transmitter and receiver. The chipset operates at multiple data rates (9.95-10.71 Gb/s) with functionality compatible with the multisource agreement (MSA) for 10-Gb transponders. Both chips demonstrate SONET-compliant jitter characteristics. The transmitter 10.66-GHz output clock jitter is 0.065 UI/sub pp/ (unit interval, peak-to-peak) over a 50-kHz-80-MHz bandwidth. The receiver jitter tolerance is more than 0.4 UI/sub pp/ at high frequencies (4-80 MHz). A high level of integration and low-power consumption is achieved by using a standard CMOS process. The transmitter and receiver dissipate a total power of 1.32 W at 1.8 V and are packaged in a plastic ball grid array with a footprint of 11/spl times/11 mm/sup 2/.

Optical communications systems, devices, and methods

Abstract: A method of transmitting an optical communications signal, comprising receiving a first signal, encoding the signal with a differential or duobinary encoding scheme (52), encoding the signal with an oscillating signal component (52), and sub-carrier modulating the signal onto a sub-carrier of an optical carrier signal (56, 58). The invention also relates to corresponding systems and apparatuses.

A fully integrated CMOS receiver front-end for optic Gigabit Ethernet

Abstract: A fully integrated fiber-optic receiver chip in a CMOS technology is presented. The design was done in a low-cost mixed-signal analog pure CMOS technology with 0.35-/spl mu/m gate length. It incorporates every building block needed for standard fiber-optic receiver application, e.g., transimpedance amplifier, postamplifier, signal detect, and several control circuits. The chip works without any external components, such as capacitors usually needed to ensure the broadband operation down to several tens of kilohertz. Three designs were processed for typical data applications between 155 Mb/s and 1.25 Gb/s. The difference in the designs can be created by changing only one metal mask and programming some bandwidth and noise-relevant components on the chip. The results in sensitivity, dynamic range, and other behaviors are fully compliant with the relevant standards, such as SONET or IEEE 802.3 (Gigabit Ethernet) and future IEEE 1394 plastic optical fiber (POF) communication.

An optical FSK-based label coding technique for the realization of the all-optical label swapping

Abstract: A new approach on optical label encoding for the realization of the all-optical label swapping in transparent optical packet switched networks is proposed and tested via simulation. The proposed method is based on the combination of the optical frequency shift keying (OFSK) modulated label with the on-off keying (OOK) modulated payload on the same optical carrier. The combination has been achieved by feeding the two independent optical signals, carrying the OFSK modulated label, and the OOK modulated payload, at the input of a semiconductor optical amplifier (SOA). The obtained four wave mixing at the output of the SOA combines label and payload on one carrier. The simulations have been carried out for 625-Mb/s labels and 10-Gb/s payload and for three 80-km span hops. At each hop the label was removed and a new locally generated label was loaded on the payload. The bit error rate calculations were made for both label and payload at each node, which proved the feasibility of the proposed method.

12.5 GHz spaced 1.28 Tb/s (512-channel x 2.5 Gb/s) super-dense WDM transmission over 320 km SMF using multiwavelength generation technique

Abstract: We achieve a 512-channel super-dense wavelength-division-multiplexing (WDM) transmission with a 12.5 GHz channel spacing over 320 km (80 km/spl times/4) of standard single-mode fiber in the C+L-bands. Optical carrier supply modules, which are based on a flattened sideband generation scheme, are applied to generate the 512 wavelengths from only 64 distributed-feedback laser diodes with a frequency spacing of 100 GHz. Arrayed-waveguide gratings with a 12.5 GHz spacing are used in this super-dense WDM experiment.

Remotely locatable RF power amplification system

Abstract: A RF amplification system which includes a RF modulation unit fed by an optical carrier and an RF input signal, the modulation unit modulating the RF input signal onto the optical carrier to produce a modulated RF optical signal; an array of optical amplifiers coupled to the modulation unit for receiving and amplifying the modulated RF optical signals; and a detecting unit having at least one photodetector coupled to the array of optical amplifiers for receiving and detecting the modulated RF optical signals, the at least one photodetector producing an amplified RF output in response thereto.

Multiple optical carrier generation from a supercontinuum source

Abstract: The article reviews the generation of multiple optical carriers from a supercontinuum multicarrier source (SC-MCS). Advantages of SC-MCS include fixed channel spacing with microwave-oscillator (Hz) accuracy and the capability to generate a stream of more than 100 channels. In the future, SC-MCS will play a key role in applications such as WDM systems and optical frequency standards.

Lightwave single sideband wavelength self-tunable filter using an InP:Fe crystal for fiber-wireless systems

Abstract: A new optical single sideband filter is presented to compensate for chromatic dispersion effects in fiber-wireless systems. The device is based on three dynamic Bragg gratings, which are generated in a photorefractive iron-doped indium phosphide (InP:Fe) crystal. This filter is controlled by the input optical double sideband signal itself, which makes it independent of the modulated optical carrier wavelength. In this paper, the principle of the device is presented and demonstrated. Experiments include a 14-km fiber transmission followed by a 3-m radio link carrying a 140-Mb/s binary phase-shift keyed data stream at 16 GHz.

Figures of merit and performance analysis of photonic microwave links

Abstract: Introduction Microwave links serve important communication, signal processing and radar functions in many commerical and military applications. However, the attenuation of microwave RF signals in cables and waveguides increases rapidly as the frequency of the signal increases, and it is specially high in the millimeter wave range. Optical fibers offer the potential for avoiding these limitations for the transmission of RF signals. Photonic microwave links employ optical carriers that are intensity modulated by the microwave signals and transmitted or distributed to optical receivers via optical fibers. Since the optical loss for fibers is very low, the distance for photonic transmission and distribution of microwaves can be very long. When the modulation of an optical carrier is detected at a receiver, the RF signal is regenerated. Figure 1.1 illustrates the basic components of a simple photonic microwave link. Since the objective of a photonic microwave link is to reproduce the RF signal at the receiver, the link can convey a wide variety of signal formats. In some applications the RF signal is an unmodulated carrier – as for example in the distribution of local oscillator signals in a radar or communication system. In other applications the RF signal consists of a carrier modulated with an analog or digital signal.

Agile spread waveform generator

Abstract: An agile spread spectrum waveform generator comprises a photonic oscillator and an optical heterodyne synthesizer. The photonic oscillator comprises a multi-tone optical comb generator for generating a series of RF comb lines on an optical carrier. The optical heterodyne synthesizer includes first and second phase-locked lasers; the first laser feeding the multi-tone optical comb generator and the second laser comprising a rapidly wavelength-tunable single tone laser whose output light provides a frequency translation reference. A photodetector is provided for heterodyning the frequency translation reference with the optical output of the photonic oscillator to generate an agile spread spectrum waveform.

Multilevel light-intensity modulating circuit

Abstract: A multilevel light-intensity modulating circuit for suppressing the amplitude distortion regarding intermediate levels, caused by the conversion from a multilevel electric signal to a multilevel modulated optical signal. The circuit comprises a section for distributing an input optical carrier into n-channel optical carriers; n light-intensity modulators for modulating intensities of the optical carriers by using input two-level electric signals; a control section for producing a phase difference between the n-channel two-level modulated optical signals; a control section for assigning a different light intensity to each of the n-channel two-level modulated optical signals; and a section for combining the n-channel two-level modulated optical signals obtained via the control sections, and outputting a 2n-level modulated optical signal. The phase difference and the different light intensity are defined in advance so as to produce the 2n-level modulated optical signal.

Correcting misalignment between data and a carrier signal in transmitters

Abstract: A device and technique for aligning an optical carrier signal (e.g., a soliton pulse train) with a data signal in a transmitter. According to the invention, the device is configured to analyze the radio frequency (RF) spectrum of the transmitter's output. In one implementation, the device evaluates the amount of energy in a certain frequency band located near a selected null of the RF spectrum. In another implementation, the device examines the shape of the RF spectrum within that frequency band. In either case, based on the analysis, the device adjusts the phase of the clock signal driving an electro-optic (E/O) modulator in the transmitter. Such adjustment reduces misalignment between the optical carrier signal and data resulting, e.g., from thermal effects in the E/O modulator. The device may be used, e.g., in long-haul optical transmission systems operating at 10 GBit/s.

Mb/s data transmission over a RF fiber-optic link using a LiNbO3 microdisk modulator

Abstract: For the first time, we demonstrate data transmission over a radio frequency (RF) fiber-optic link using a LiNbO 3 microdisk configured to modulate an optical carrier. Initial experimental results demonstrate high-quality data transmission up to 100 Mb/s on a 8.7 GHz RF carrier.

Method of coupling a laser signal to an optical carrier

Abstract: A method and apparatus for coupling a laser signal to an optical carrier. The method and associated apparatus control a power of the laser signal to a power density level below a damage threshold of the optical carrier, couple the laser signal to the optical carrier, and measure an output power of the laser signal at an exit of the optical carrier. By translating a focusing lens or an entrance of the optical carrier along an optical axis between the focusing lens and the entrance to the optical carrier, a range in measured power output is determined in which the laser signal is incident within the entrance of the optical carrier. The method and associated apparatus set a distance between the focusing lens and the entrance to the optical carrier such that the entrance to the optical carrier is at a position beyond a focal point of the focusing lens where the laser signal is divergent-coupled to the optical carrier.

Optical phase modulation

Abstract: An optical modulator provides for precoding of a high data rate phase modulated optical signal. According to one embodiment, the modulator includes a first phase modulator and a second phase modulator. The first phase modulator modulates an optical carrier signal according to a first data signal to generate a modulated optical signal. The second phase modulator modulates the modulated optical signal according to a time delayed version of its optical output signal. According to another embodiment, the modulator electrically precodes multiple data streams and modulates the precoded data streams using a series of phase modulators to generate a precoded optical data signal.

Method and apparatus for measuring a frequency of an optical signal

Abstract: A method and apparatus are provided for detecting a frequency of an optical signal (26) within a communications channel having a plurality of optical carriers (12, 14, 16) separated by a predetermined frequency spacing. The method includes the steps of locking an optical carrier frequency to an axial mode of an optical resonator of known free spectral range; providing an additional optical resonator as a reference having a known free spectral range that differs from that of the first optical resonator; locking an optical reference signal to a closest axial mode of a reference optical resonator producing an optical reference signal that is spectrally offset from said optical carrier frequency by a spectral quantity less than the known free spectral range; mixing the optical carrier frequency with the reference optical signal frequency (22, 28) thus generating a difference signal as a beat frequency; and measuring a frequency of a difference signal (30, 31, 32).

RF Photonic Technology in Optical Fiber Links: Multiple quantum well electroabsorption modulators for RF photonic links

Abstract: Introduction Performance of multiple quantum well (MQW) electroabsorption (EA) modulators can best be evaluated in terms of a basic RF photonic link. A basic RF photonic link consists of a laser transmitter with its optical intensity modulated by an RF signal, an optical fiber transmission line and a receiver. In the externally modulated link shown in Fig. 6.1, the RF source supplies the signal to the EA modulator. The CW laser radiation is coupled directly or through a pigtailed fiber to the modulator input. The fiber transmission line couples the modulated output to the receiver. The receiver detects the optical radiation and converts the intensity modulation back into RF power. Because of the low transmission loss of fibers, a major advantage of an RF photonic link is its low RF transmission loss, especially for long distances and at high RF frequencies. Many RF channels at widely different frequencies can also share the same optical carrier. More sophisticated links may employ optical or electronic amplification, distribute the modulated optical carrier in a fiber network, down or up convert the RF frequencies using opto-electronic components. However, the fundamental effect of a component such as a modulator can most clearly be understood through the basic link. In Fig. 6.1, the optical carrier is obtained from CW laser and modulated by an external modulator, based on semiconductors or ferroelectrics such as LiNbO 3 or polymers.

Apparatus, system and method for optical packet switching using frequency header

Abstract: In the present invention, a single-frequency tone is used as addressing header for each optical packet (26). The frequency of the single-frequency tone is situated within the baseband of the digital payload signal and is preferably a radio-frequency tone. The single-frequency tone is multiplexed with teh digital payload and modulated into an envelope of an optical carrier. The frequency is indicative of an address or out-port (34, 36) for the optical packet (26), which means that different destinations in the network correspond to different frequencies. When switching such an optical packet, the power of the frequency tone (fj, fk) is measured. If a tone is present, the optical path corresponding to the allocation is opened by an electronic switch control (46), and when the tone disappears, the path is closed. Due to the narrow bandwith of the frequency tone, any disturbance of the digital payload is essentially negligible.

Agile spread waveform generator and photonic oscillator

Abstract: An agile spread spectrum waveform generator comprises a photonic oscillator and an optical heterodyne synthesizer. The photonic oscillator comprises a multi-tone optical comb generator for generating a series of RF comb lines on an optical carrier. The optical heterodyne synthesizer includes first and second phase-locked lasers; the first laser feeding the multi-tone optical comb generator and the second laser comprising a rapidly wavelength-tunable single tone laser whose output light provides a frequency translation reference. A photodetector is provided for heterodyning the frequency translation reference with the optical output of the photonic oscillator to generate an agile spread spectrum waveform.

Basics of digital optical communications

Abstract: Publisher Summary The main objective of this chapter is to present a comprehensive approach to the basic concepts of digital optical communications. Optical fiber communication systems use carrier frequencies in the near-infrared region of the electromagnetic spectrum. The typical value of the optical carrier frequency v is 193 THz for a wavelength in the 1550-nm range Binary information sequence and the asymmetric binary optical channel are introduced. It also discusses the properties and the performances of the various modulation formats of optical signals. The general discussion of spectral occupancy of baseband and optically modulated signals is applied to the nonreturn to zero and return to zero modulation formats whose bandwidth and properties are highlighted. This chapter also provides a system-oriented approach to noise generation and noise demonstration at the receiver level. The role of a digital communication optical receiver is to convert the incoming optical signal into an electrical signal and to make a decision for each received symbol. In addition, various noise sources are discussed and their individual contributions to the photocurrent fluctuation variance are expressed.

Optical signal transmission

Abstract: An optical signal transmission apparatus for transmitting a plurality of data signals (data-1 to data-n) comprises: a plurality of input means (1) for receiving a respective one of the data signals (data-1) and delivering the respective data signal with a controlled phase and at a controlled data rate; optical carrier generation means (4) for generating a plurality of optical carrier signals having different wavelengths (λ1 to λ2); a plurality of first modulation means (3) each being for modulating a respective one of the optical carriers with a respective data signal to provide a first-modulated optical carrier signal; and an optical signal-routing device (15) having a plurality of input ports (15a to 15n), each port being for receiving a respective one of the first-modulated optical carrier signals and delivering it to the output port of the device. The apparatus further comprises further modulation means (13, 14) for further modulating each of the first-modulated optical carrier signals in dependence upon a clock (9) to provide a plurality of further-modulated optical carrier signals; and a feedback arrangement (17, 16, 15, 8), including the optical signal-routing device (15), for feeding back a proportion of each of the further-modulated optical carrier signals to a respective input means (1b) for controlling the phase and rates at which the input means delivers the data signal to the first modulation means in dependence upon the further modulation to thereby synchronize each input data signal to the clock. The optical signal-routing device delivers each of the further-modulated signals applied to its output to a respective input along a path which is dependent upon the wavelength of the signal.

Non-linear optical carrier frequency converter

Abstract: A carrier frequency converter for converting a first information carrier frequency of a first carrier to a second information carrier frequency of a second carrier. The converter includes an input control optics assembly for receiving a first carrier and adjusting the first carrier in accordance with first desired frequency, polarization and beam propagation parameters. A non-linear optical medium provides optical rectification of an output of the input control optics assembly. An output control optics assembly receives an output of the non-linear optical medium and adjusts the output in accordance with second desired frequency, polarization and beam propagation parameters. The output of the output control optics is a second carrier having an information bandwidth equivalent to the information bandwidth of the first carrier.

Frequency agile spread waveform generator and method and pre-processor apparatus and method

Abstract: A frequency agile spread spectrum waveform generator comprises a photonic oscillator andan optical heterodyne synthesizer. The photonic oscillator comprises a multi-tone opticalcomb generator for generating a series of RF comb lines on an optical carrier. The optical heterodyne synthesizer includes first and second phase-locked lasers; the first laser feedingthe multi-tone optical comb generator and the second laser comprising a wavelength-tunablesingle-tone or multi-tone laser whose output light provides a fequency translation reference.At least one photodetector is provided for heterodyning the frequency translation referencewith the optical output of the photonic oscillator to generate an agile spread spectrum waveform.

Supercontinuum multi-carrier source for WDM systems

Abstract: The paper reported the multiple optical carrier generation (over 1000 channels with 12.5-GHz spacing) from a single supercontinuum source. It was confirmed that these carriers have sufficient SNR to achieve Q-factors above 18.3 dB. The channel spacing is strictly determined by the microwave mode-locking frequency of the source laser and so Hz-level accuracy is possible. A transmission experiment utilizing the SC source was also presented. A 106-channel, 25-GHZ-spaced, 10-Gbit/s transmission over 640 km with Q-factors of greater than 15.6 dB was achieved. The results show that the SC-MCS can be applied to over 100-channel DWDM systems. By improving the flatness of the SC spectrum, over 1000-km transmission is achievable. It is expected that SC-MCS will be a key technology in realizing WDM networks that offer hundreds of wavelengths. A part of this work was supported by Telecommunications Advancement Organization of Japan (TAO).

Microstrip coupled VCOs for 40–GHz and 43–GHz OC–768 optical transmission

Abstract: In this paper, we present 40-GHz and 43-GHz voltage-controlled oscillators (VCOs) for use in SONET / SDH optical transmission systems operating at OC-768 rates. The 40-GHz oscillator has a tuning range of 5 GHz, a single-sideband phase noise power spectral density of -99 dBc/Hz at 1-MHz offset from the carrier, and consumes 363 mW from a 3V supply. The oscillator occupies 0.189 mm2of die area and is implemented in a 120-GHz f T SiGe BiCMOS process.

Optical compensation of PMD-induced power fading for single sideband subcarrier-multiplexed systems

Abstract: We experimentally demonstrate a novel technique for compensating the PMD-induced power fading that occurs in single sideband SCM transmission systems. PMD-induced power fading can be understood in the optical domain as caused by the polarization state of the optical carrier being different from that of the SSB.

Optical transmitter and optical modulator

Abstract: A feature of this invention is to realize a VSB modulation with a simple configuration. A data generating circuit ( 10 ) generates a transmission data composed of an optical pulse with duty factor of 50% according to a clock from a clock generating circuit ( 12 ). An optical source ( 14 ) generates a laser light that functions as an optical carrier to carry the transmission data generated from the data generating circuit ( 10 ) and applies it to a data modulator ( 16 ). The data modulator ( 16 ) intensity-modulates the laser light from the optical source ( 14 ) according to the transmission data from the data generating circuit ( 10 ) and generates an optical signal of an RZ optical pulse train to carry the transmission data. The generated optical pulse train is applied to a phase modulator ( 18 ). According to the clock from the clock generating circuit ( 12 ), a sine wave generating circuit ( 20 ) generates a sine wave signal synchronizing and having the same frequency with the clock. A phase shifting circuit ( 22 ) shifts phase of the sine wave from the sine wave generating circuit ( 20 ) by π/2 and applies it to the phase modulator ( 18 ). A phase modulator ( 18 ) modulates optical phase of each optical pulse in the optical pulse train from the data modulator ( 16 ) according to the sine wave from the phase shifting circuit ( 22 ).

Multiplexed optical transition method and multiplexed optical transmitter

Abstract: A multiplexed optical transmitter according to this invention comprises first spreader which code-spreads first data stream of electrical signal by first spreading-code, first frequency-converter which converts a frequency of the code-spread first data stream into first frequency, and first electrical-optical converter which converts the first data stream into first optical carrier of first optical signal having a predetermined optical wavelength. Furthermore, the multiplexed optical transmitter comprises second spreader which code-spreads second data stream of electrical signal by second spreading-code, second frequency-converter which converts a frequency of the code-spread second data stream into second frequency, and second electrical-optical converter which converts the second data stream into second optical carrier of second optical signal having the predetermined optical wavelength. Then, an optical coupler couples the first optical signal and the second optical signal for generating a multiplexed optical signal having the first optical carrier and the second optical carrier.

Rf power amplification system

Abstract: A RF amplification system which includes a RF modulation unit fed by an optical carrier and an RF input signal, the modulation unit modulating the RF input signal onto the optical carrier to produce a RF modulated optical signal; an array of optical amplifiers coupled to the modulation unit for receiving and amplifying the RF modulated optical signals; and a detecting unit having at least one photodetector coupled to the array of optical amplifiers for receiving and detecting the RF modulated optical signals, the at least one photodetector producing an amplified RF output in response thereto.