Showing papers on "Optical Carrier transmission rates published in 2004"

40 GHz electro-optic polarization modulator for fiber optic communications systems

Abstract: A novel ultrahigh-speed electro-optic polarization modulator is introduced. The modulator uses a mode converter and a static polarization controller to change the output polarization state in a circular path, following a great circle, around the Poincare sphere. Any two states on the Poincare sphere can be connected. The mode converter is constructed using an AlGaAs ridge waveguide combined with slow-wave travelling wave electrodes. The travelling wave electrodes are designed to match the velocity of the electrical modulating signal, the data signal, to the optical carrier signal over a broad frequency range. This modulator demonstrates a 3 dB bandwidth in excess of 40 GHz. The polarization modulator exhibits extremely low differential group delay, on the order of a few 10s of femto-seconds, and low drive voltage, on the order of 5 V.

Method and apparatus for waveform generation

Abstract: A spread spectrum waveform generator has a photonic oscillator and an optical heterodyne synthesizer. The photonic oscillator is 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, where the first laser feeds the multi-tone optical comb generator and the second laser is a single tone laser whose output light provides a frequency translation reference. At least one photodetector is provided for heterodyning the frequency translation reference with the optical output of the photonic oscillator to generate a spread spectrum waveform. A receiver pre-processor may be provided to operate on the spread spectrum waveform.

Precise frequency transfer through a fiber network by use of 1.5-µm mode-locked sources

Abstract: We report the precise transfer of radio-frequency signals by use of the pulse repetition frequency of mode-locked laser sources at 1.5 microm transmitting through a fiber network. The passive transfer instability through a 6.9-km fiber is below 3 x 10(-14) at 1 s, which is comparable with the optical carrier-frequency transfer of a narrow-linewidth cw laser. The instability of the measurement system is below 7 x 10(-15) at 1 s. It is noted that the pulsed mode of operation offers almost an order-of-magnitude improvement in stability at 1 s over that with a sinusoidal amplitude modulation on an optical carrier.

Compensating impairments of optical channel using adaptive equalization

Abstract: An embodiment of the invention is a technique to equalize received samples. An optical to electrical converter (OEC) produces an electrical signal vector representing at least one of amplitude, phase, and polarization information of a modulated optical carrier transmitted through an optical channel with impairments. A signal processor processes the electrical signal vector to compensate the impairments of the optical channel. The signal processor includes at least an adaptive equalizer to generate an equalized output, a decision, and an error. The error is difference between the equalized output and the decision. The adaptive equalizer has an adaptation based on at least the error.

A robust 43-GHz VCO in CMOS for OC-768 SONET applications

Abstract: In this paper, we present a 43-GHz LC-VCO in 0.13-/spl mu/m CMOS for use in SONET OC-768 optical networks. A tuned output buffer is used to provide 1.3 V/sub p-p/ (single-ended) into a 90-fF capacitive load as is required when the VCO is used in typical clock and data recovery (CDR) circuits. Phase noise is -90 dBc/Hz at a 1-MHz offset from the carrier; this meets SONET jitter specifications. The design has a tune range of 4.2%. The VCO, including output buffers, consumes 14 mA from a 1-V supply and occupies 0.06 mm/sup 2/ of die area. Modern CMOS process characteristics and the high center frequency of this design mean that the tank loss is not dominated by the integrated inductor, but rather by the tank capacitance. An area-efficient inductor design that does not require any optimization is used.

Optical-to-wireless WDM converter

Abstract: In a method and apparatus for converting optical wavelength division multiplexed channels to wireless channels, the information carrying optical carriers are first de-multiplexed and each optical carrier is then extracted from the data using an optical channelizing technique. The optical frequency of each of the extracted optical carriers is then shifted by an amount equal to the desired wireless carrier frequencies in the broadband wireless channels. Optical heterodyning of the frequency-shifted extracted lightwave carriers with the original data-containing optical signals, which are mutually in phase coherence, in a photodetector results in a set of wireless carriers each modulated with the data carried by the corresponding optical channel.

High-speed modulation for optical subcarrier

Abstract: PROBLEM TO BE SOLVED: To provide an improved method and a system for transmitting data on an optical subcarrier. SOLUTION: The method for transmitting digital data comprises a process for dividing a coherent optical carrier having subcarriers into a plurality of optical carriers coherent all together, a process for generating an array of phase shifts corresponding to each of the plurality of the optical carriers coherent all together, and a process for interfering the plurality of the optical carriers with each other. The interfering process creates an output optical carrier containing modulated subcarriers in which the modulated subcarriers comprise modulated in-phase and quadrature phase components each having an array of pairs of corresponding values. The pairs of values of modulated in-phase and quadrature phase components made by the interfering process correspond to an array of coordinate pairs concerning signal points of the configurations of 4-PSK 2D, 16-QAM 2D, or 16-PSK 2D. COPYRIGHT: (C)2005,JPO&NCIPI

A 10 Gb/s SONET-compliant CMOS transceiver with low cross-talk and intrinsic jitter

Abstract: A 4:1 SERDES IC suitable for SONET OC-192 and 10-Gb/s Ethernet is presented. The receiver, which consists of a limiting amplifier, a clock and data recovery unit, and a demultiplexer, locks automatically to all data rates in the range 9.95-10.7 Gb/s. At a bit error rate of less than 10/sup -12/, it has a sensitivity of 20 mV. The transmitter comprises a clock multiplying unit and a multiplexer. The jitter of the transmitted data signal is 0.2 ps RMS. This is facilitated by a novel notched inductor layout and a special power supply concept, which reduces cross-coupling between the transmitter and receiver. Integrated in a 0.13-/spl mu/m CMOS technology, the total power consumption from both 1.2- and 2.5-V supplies is less than 1 W.

Metropolitan photonic switch

Abstract: A photonic switch uses a cost-effective DWDM optimized switch architecture allowing the introduction of DWDM into the metro network. In order to implement this architecture cost-effective ways of implementing the optical carrier frequency/wavelength precision required for a Dense Wavelength Division Multiplexing 100 GHz or 50 GHz on-grid solutions are needed. The photonic switch acts as an intermediary between the WDM density of the access portion of the metropolitan photonic network and the DWDM density of the core photonic network. The metro photonic switch introduces optical carriers that are all generated in the photonic layer adjacent to it and allocates them out to the photonic access nodes for modulation. This has the advantage of providing the optical carriers to be modulated from a centralized highly stable and precise source, thereby meeting the requirements for DWDM carrier precision, whilst generating these carriers in relatively close proximity to the modulators. Coarse WDM components can be used in the access portion of the network without adversely affecting the ability of the signal to transit the DWDM portion of the core network, since the optical carrier frequency is fixed at the centralized source and is unaffected by these components.

All-optical ASK/DPSK label-swapping and buffering using Fabry-Perot laser diodes

Abstract: We describe an approach for optical label encoding that allows the realization of all-optical label-swapping in optical packet-switched networks. The proposed method is based on a combination of the amplitude-shift-keying (ASK) modulated payload with the differential phase-shift keying (DPSK) modulated label on the same optical carrier. We demonstrate an implementation using dual-wavelength injection locking (DWIL) of a Fabry-Perot laser diode. Bit-error-rate measurements were performed for the 10-Gb/s payload, and the 2.5-Gb/s label showed the feasibility of the proposed method. An all-optical buffer for the two-level ASK/DPSK optically labeled packets is also described. The buffer is implemented by routing the packet via a delay line if potential contention is predicted. Error-free operation was also achieved.

Optical upconversion techniques for high-sensitivity millimetre-wave detection

Abstract: Millimeter-wave radiation has the unique ability to penetrate atmospheric obscurations such as smoke, fog, and light rain while maintaining the capability for high-resolution imaging. However, suitable technologies for creating high-sensitivity, large pixel-count detectors are a limiting factor in the implementation of such systems. To this end, we present a technique for detecting millimeter-wave radiation based on optical upconversion that promises both high sensitivity and scalability to large pixel arrays. High-speed optical modulation is used to transfer millimeter-wave radiation onto the sidebands of a near-infrared optical carrier frequency. Optical filtering techniques are subsequently used to suppress light at the carrier frequency. The resultant signal is passed to a low-frequency photodetector, which converts the remaining sideband energy to a photocurrent proportional to the incident millimeter wave energy at the modulator input. Utilizing the low noise powers of such photodetectors, high sensitivities may be obtained even accounting for the relatively high signal losses associated with optical upconversion. Since optical upconversion inherently preserves both phase and amplitude information and fiber optics may readily be used for low-loss routing of the modulated signal, such an approach offers promise for high-resolution synthetic aperture imaging. Alternatively, since each of the required components may be fabricated in III-V materials using planar semiconductor processing techniques, integration of multi-pixel arrays is feasible. Herein, we present experimental results obtained using a baseline detector assembled from commercially available fiber-optic components as well as efforts to integrate the desired functionality into a single GaAs substrate. An initial noise equivalent power (NEP) of the proposed detector has been demonstrated at sub-nanowatt levels, with improvements to sub-picowatt NEP's anticipated as the setup is optimized.

Requirements for the sampling source in coherent linear sampling

Abstract: Complex envelope measurement using coherent linear optical sampling with mode-locked sources is investigated. It is shown that reliable measurement of the phase requires that one of the optical modes of the mode-locked laser be locked to the optical carrier of the data signal to be measured. Carrier-envelope offset (CEO) is found to have negligible effect on the measurement. Measurement errors of the intensity profile and phase depend on the pulsewidth and chirp of the sampling pulses as well as the detuning between the carrier frequencies of the data signal and the center frequency of sampling source.

Multirate payload switching using a swappable optical carrier suppressed label in a packet switched DWDM optical network

Abstract: Optical packets with multirate payloads have been demonstrated for optical label switching (OLS) and transport in a multihop dense wavelength-division-multiplexed (DWDM) optical network with over 200 km fiber and a low-power penalty for the first time. The key functions for label generation, swapping, and switching have been successfully realized.

Optical transmission method and system

Abstract: An optical transmitter splits a linear polarization optical carrier into a TE wave and a TM wave. One of the TE wave and the TM wave is phase-modulated with a transmission data so as to generate a phase-modulated signal. The phase-modulated signal and the other one of the TE wave and the TM wave are coupled with a linear polarization and output into an optical transmission line. An optical receiver splits a light input from the optical transmission line into the TE wave and the TM wave. The TM wave or TE wave is converted into the TE wave or TM wave to interfere with the TE wave or TM wave. The interfered signal light is converted into an electric signal for restoration of the data.

Digital optical signal transmission in a seismic sensor array

Abstract: The invention describes a sensor array with digital signals transmitted over an optical fiber for seismic exploration systems. The seismic system includes a transducer for providing digital optical data signals and an optical interrogator for collecting the digital data. The transducer provides data from seismic sensors to the optical interrogator by acting on an optical carrier transmitted along the optical fiber. The system is designed to utilize known electromechanical seismic sensors with fiber optic telemetry.

Shared multi-lambda source for WDM PON

Abstract: Shared optical carrier sources for the OLT's are provided. An apparatus comprises a plurality of optical carrier generators, each optical carrier generator outputting an optical carrier at a different wavelength, an optical multiplexer operable to combine the plurality of optical carriers to form a wave division multiplexed optical carrier, and an optical power splitter having a plurality of outputs, each output connectable to an optical line termination unit, the optical power splitter operable to split the wave division multiplexed optical carrier to form a plurality of wave division multiplexed optical carriers.

Multioctave high dynamic range up-conversion optical-heterodyned microwave photonic link

Abstract: An up-converting microwave photonic link which enables high dynamic range over a multioctave information bandwidth is demonstrated. The improvement in spurious-free dynamic range (SFDR) as compared to conventional links is experimentally demonstrated. The link consists of two heterodyned lasers with one optical carrier modulated by a LiNbO/sub 3/ Mach-Zehnder modulator biased at the null point. This results in strong optical sidebands, minimum even order distortion, and more than /spl sim/40-dB suppression of the optical carrier. The first carrier's two optical sidebands are heterodyned with the second unmodulated optical carrier. The modulated optical carrier is suppressed reducing noise power and enhancing SFDR. An SFDR of 115 dB/Hz/sup 2/3/ was measured. The detected local oscillator power is also suppressed, easing output filtering requirements.

RadSensor: x-ray detection by direct modulation of an optical probe beam

Abstract: We present a new x-ray detection technique based on optical measurement of the effects of x-ray absorption and electron hole pair creation in a direct band-gap semiconductor. The electron-hole pairs create a frequency dependent shift in optical refractive index and absorption. This is sensed by simultaneously directing an optical carrier beam through the same volume of semiconducting medium that has experienced an xray induced modulation in the electron-hole population. If the operating wavelength of the optical carrier beam is chosen to be close to the semiconductor band-edge, the optical carrier will be modulated significantly in phase and amplitude. This approach should be simultaneously capable of very high sensitivity and excellent temporal response, even in the difficult high-energy xray regime. At xray photon energies near 10 keV and higher, we believe that sub-picosecond temporal responses are possible with near single xray photon sensitivity. The approach also allows for the convenient and EMI robust transport of high-bandwidth information via fiber optics. Furthermore, the technology can be scaled to imaging applications. The basic physics of the detector, implementation considerations, and preliminary experimental data are presented and discussed.

Novel all-optical flip-flop using semiconductor optical amplifiers in innovative frequency-shifting inverse-threshold pairs

Abstract: All-optical digital sequential logic reduces the expense and bit rate constraints associated with optical-electronic-optical (OEO) conversion in telecommunications. Two semiconductor optical amplifiers (SOAs) are directly coupled by connecting the output of each to the input of the other. This new configuration provides positive feedback to create a logical NOT or inverse for complete logic. An inverted optical threshold improves the quality of bit modulation. At the same time, frequency shifting allows improvement in the quality of the optical carrier. The SOA pair is analyzed in closed form to show that the positive feedback provides an output-input slope steeper than –1, allowing connection of two pairs to form a flip-flop. Two SOA pairs are cross-connected by connecting the output of each pair to the input of the other, to construct a novel R-S flip-flop. Closed form analysis shows, for the first time, that there is an unstable state and two stable states forming bistability for this configuration. Simulation demonstrates setting and resetting the reset-set (R-S) flip-flop at more than 5 Gbps. Agreement between closed form analysis and numerical simulation provides verification of the validity of the results obtained.

Quaternary optical transmission system combining phase and polarization-shift keying

Abstract: A new optical transmission scheme which combines polarization-shift keying and differential phase-shift keying on the same optical carrier is proposed. Simulations carried out show a considerable tolerance toward different physical impairments, such as polarization-mode dispersion, nonlinear effects, and chromatic dispersion. When compared to other multilevel modulation formats, it shows the advantage of reusing the carrier power, thus, sensitivity is improved.

Coherent demodulation of differential 8-phase-shift keying with optical phase diversity and digital signal processing

Abstract: Demodulation of differential 8-PSK is demonstrated with an optical phase-diversity receiver and a digital signal processing circuit to recover both the phase and amplitude of the optical carrier. The acceptable range of the laser linewidth is also investigated.

Optical carrier‐suppression of microwave signals with stimulated Brillouin scattering in long fiber ring

Abstract: A novel and simple system based on stimulated Brillouin scattering in long fiber ring for optical-carrier suppression is presented. In this system, a large optical carrier reduction can be attained easily at relative low input power. The anti-Stokes wave is inhibited by adjusting the Stokes wave feedback. Experiments are implemented to suppress the optical carrier of a microwave photonics signal. About 35-dB optical carrier reduction and a modulation-gain factor of 27 are achieved. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 258–260, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20436

An optical voltage controlled oscillator for an optical phase locked loop

Abstract: An optical phase locked loop (1), comprising an optical phase detector (2) receiving as inputs an optical signal to be locked ( symbol I ) and a locked optical signal (symbol II ) and providing as its output an electrical error signal (VPD) indicating the phase shift existing between the optical signal to be locked (symbol I ) and the locked optical signal (symbol II ); an electrical loop filter (3) receiving the electrical error signal (VPD) and outputting a filtered electrical error signal (VPDF), and an optical voltage controlled oscillator (4) receiving as an input the filtered electrical error signal (VPDF) and outputting the locked optical signal (symbol II ) The optical voltage controlled oscillator (4) comprises an electrical voltage controlled oscillator (8) receiving as an input the filtered electrical error signal (VPDF) and outputting a modulating electrical signal (VEVCO), an external-cavity semiconductor laser source (9) providing an optical carrier (Soc), and a Mach-Zehnder optical amplitude modulator (10) receiving as an input the optical carrier (Soc) and the modulating electrical signal (VEVCO) and outputting the locked optical signal (symbol II ), which is obtained by amplitude modulating the optical carrier (SOC) with the modulating electrical signal (VEVCO)

Optical channelizer utilizing resonant microsphere coupling

Abstract: In a method and apparatus for converting optical wavelength division multiplexed channels to wireless channels, the information carrying optical carriers are first de-multiplexed and each optical carrier is then extracted from the data using an optical channelizing technique. The optical frequency of each of the extracted optical carriers is then shifted by an amount equal to the desired wireless carrier frequencies in the broadband wireless channels. Optical heterodyning of the frequency-shifted extracted lightwave carriers with the original data-containing optical signals, which are mutually in phase coherence, in a photodetector results in a set of wireless carriers each modulated with the data carried by the corresponding optical channel.

Optical Single-Sideband Modulators and Their Applications

Abstract: We review our recent work in the implementation of optical single-sideband (OSSB) modulation and in the application of this modulation format to microwave photonics and optical testing systems. We have developed an enhanced OSSB modulator for wide-band operation, the so-called bidirectional OSSB modulator, and a simplification of this scheme for narrow-band applications. These OSSB modulators are based on the use of a standard single-electrode Mach-Zehnder electro-optic modulator (MZ-EOM) and passive fiber-optic components. In both designs, the OSSB operation is shown to be independent of the MZ-EOM bias. Therefore, the optical modulation depth at the output of the device can be enhanced using minimum transmission biasing to provide suppression of the optical carrier. Finally, we demonstrate the application of OSSB modulators to the improvement of microwave/millimeter-wave subcarrier multiplexing fiber-optic links and to narrow-band fiber radio systems. In addition, we analyzed the feasibility and the lim...

20Gb/s 0.13/spl mu/m CMOS serial link transmitter using an LC-PLL to directly drive the output multiplexer

Abstract: A 20Gb/s transmitter is implemented in 0.13/spl mu/m CMOS technology. Eight 2.5Gb/s data streams are 4:1 multiplexed, sampled, and retimed into two 10Gb/s data streams. A final 20Gb/s 2:1 output multiplexer, clocked by complementary phases of an LC-VCO (voltage controlled oscillator) in a phase-locked loop, creates 20Gb/s data. The VCO is integrated with the output multiplexer, resonating the load and eliminating the need for clock buffers. Power, active die area, and jitter (RMS/pk-pk) are 165mW, 650/spl mu/m /spl times/ 350/spl mu/m, and 2.37ps/15ps, respectively.

An orthogonal subcarrier based optical tandem single sideband system

Abstract: The authors propose an Optical Tandem Single Sideband (OTSSB) system using orthogonal subcarriers that double bandwidth efficiency by allowing transmission of different channels in the upper and lower sidebands of the same optical carrier. A mathematical model and simulation results are presented to demonstrate this new technique.