Showing papers on "Optical Carrier transmission rates published in 2008"

High-stability transfer of an optical frequency over long fiber-optic links

Abstract: We present theoretical predictions and experimental measurements for the achievable phase noise, timing jitter, and frequency stability in the coherent transport of an optical frequency over a fiber-optic link. Both technical and fundamental limitations to the coherent transfer are discussed. Measurements of the coherent transfer of an optical carrier over links ranging from 38 to 251 km demonstrate good agreement with theory. With appropriate experimental design and bidirectional transfer on a single optical fiber, the frequency instability at short times can reach the fundamental limit imposed by delay-unsuppressed phase noise from the fiber link, yielding a frequency instability that scales as link length to the 3/2 power. For two-way transfer on separate outgoing and return fibers, the instability is severely limited by differential fiber noise.

Optical Millimeter-Wave Signal Generation Using Frequency Quadrupling Technique and No Optical Filtering

Abstract: This letter demonstrates a novel method to generate high-purity optical millimeter-wave signals with carrier suppression by using a frequency quadrupling technique. To the authors' knowledge, this is the first time that a frequency quadrupling system requires only a single integrated Mach-Zehnder modulator without a narrowband optical filter to remove undesired optical sidebands. Since no optical filter is needed, fast frequency tuning is straightforward and this approach will be particularly attractive for optical up-conversion in wavelength-division-multiplexing radio-over-fiber systems. This letter provides both theoretical analysis and experimental demonstration. The generated optical millimeter-wave signals have very high quality with an optical carrier and harmonic distortion suppression ratio of more than 38 and 36 dB at 40 and 72 GHz, respectively.

Optical line terminal, passive optical network and radio frequency signal transmission method

Abstract: An optical line terminal, a passive optical network and a radio frequency signal transmission method in the communication technical field are provided. The passive optical network comprises: OLT, ODN and at least one ONU. The OLT comprises: at least one transmitting unit, which provides one dedicated downlink optical carrier and two dedicated uplink optical carriers for ONU, the downlink radio frequency signal which needs to be transmitted to ONU is modulated on the dedicated downlink optical carrier for the ONU, and after combining the modulated downlink optical carrier and the two dedicated uplink optical carriers, the downlink optical signals are outputted; the two dedicated optical carriers for ONU are configured to bear ONU uplink radio frequency signals; a multiplexing/demultiplexing unit which multiplexes through wavelength division the downlink optical signal outputted from each transmitting unit and transmit it to ONU via ODN, and demultiplexes through wavelength division the uplink optical wave of each ONU which has been multiplexed through wavelength division and is transmitted by ODN, and then output them; and at least one receiving unit which obtains the uplink signal from the demultiplexed uplink optical signal. The bandwidth of wireless access network is enhanced, and the design of ONU is simple.

Frequency-scanned optical time domain reflectometry

Abstract: A frequency-scanned optical time domain reflectometry technique includes launching a plurality of interrogating pulses into an optical fiber at a plurality of optical carrier frequencies. A Rayleigh backscatter signal is detected for each interrogating pulse as a function of time between the launching of the pulse and the detection of the backscatter signal. The time resolved Rayleigh backscatter signal at each optical frequency may then be examined to determine a distribution of a physical parameter along the length of the optical fiber.

Bidirectional Radio-Over-Fiber System With Phase-Modulation Downlink and RF Oscillator-Free Uplink Using a Reflective SOA

Abstract: We propose and demonstrate a bidirectional radio-over-fiber (RoF) system based on a reflective semiconductor optical amplifier (RSOA). In this system, phase-modulated 5.25-GHz radio frequency (RF) carrying 850 Mb/s is used for the downstream signal. Optical envelope detection of 10-GHz RF carrying 850 Mb/s is achieved in an RSOA. Both signals share a single fiber link and the same light source by exploiting optical carrier remodulaiton. Moreover, there is no need to employ RF down-conversion technology for RoF uplink. This makes the proposed system simpler and more cost-effective. The experimental results indicate that after simultaneous transmission of downstream and upstream signals over 25-km fiber, the receiver sensitivities are -22 and -14.5 dBm, respectively.

High-speed optical transceiver for infiniband and ethernet

Abstract: The present invention provides a high-speed 100G optical transceiver for InfiniBand and Ethernet with associated mapping to frame InfiniBand and Ethernet into GFP-T. The optical transceiver utilizes an architecture which relies on standards-compliant (i.e., multi-sourced) physical client interfaces. These client interfaces are back-ended with flexible, programmable Field Programmable Gate Array (FPGA) modules to accomplish either InfiniBand or Ethernet protocol control, processing, re-framing, and the like. Next, signals are encoded with Forward Error Correction (FEC) and can include additional Optical Transport Unit (OTU) compliant framing structures. The resulting data is processed appropriately for the subsequent optical re-transmission, such as, for example, with differential encoding, Gray encoding, I/Q Quadrature encoding, and the like. The data is sent to an optical transmitter block and modulated onto an optical carrier. Also, the same process proceeds in reverse on the receive side.

Generation and Transmission of Optical Carrier Suppressed-Optical Differential (Quadrature) Phase-Shift Keying (OCS-OD(Q)PSK) Signals in Radio Over Fiber Systems

Abstract: We propose and experimentally demonstrate generation of optical carrier suppressed-optical differential phase-shift keying (OCS-oDPSK) modulation format in radio-over-fiber (RoF) systems using one single-drive Mach-Zehnder modulator (MZM). This scheme realizes up-conversion of baseband data for downlink wireless service delivery, generation of remote local oscillator (LO) signal for down-conversion of uplink radio frequency (RF) signal, and remodulation of down-converted uplink data, thus lowering the cost of base stations (BSs) in full-duplex RoF systems. The proposed scheme is expected to be simple and compact due to the use of a single MZM. Furthermore, the OCS-oDPSK generation principle is extended to obtain an OCS-optical differential quadrature phase-shift keying (OCS-oDQPSK) signal by employing a dual-parallel MZM (DPMZM), which is useful to deliver multiple wireless services on the same RF carrier.

Extended-reach PON employing 10Gb/s integrated reflective EAM-SOA

Abstract: A novel integrated reflective EAM-SOA, capable of tolerating optical carrier power variations of up to 13 dB, is operated in a 10 Gb/s, 128-way split, 100 km reach DWDM-TDMA PON.

An Optical Millimeter-Wave Generation Technique Based on Phase Modulation and Brillouin-Assisted Notch-Filtering

Abstract: A novel approach to generate continuously tunable microwave and millimeter-wave (mm-wave) signals is proposed and experimentally demonstrated based on an optical phase modulator and a Brillouin-assisted notch-filtering technique. The strong optical carrier of the phase modulated signal is deeply suppressed by using stimulated Brillouin scattering (SBS) in a dispersion-shifted-fiber ring while the sidebands keep unchanged. Therefore, only even-order electrical harmonics exist at the output of a photodetector. As this SBS-assisted carrier-filter is narrow bandwidth and wavelength-independent, a wavelength-flexible way of optical generation mm-wave signals can be successfully realized.

Gigabit Optical Access Link for Simultaneous Wired and Wireless Signal Transmission Based on Dual Parallel Injection-Locked Fabry–PÉrot Laser Diodes

Abstract: A novel scheme, for the wired and wireless gigabit data transmission in optical access network, is proposed and experimentally demonstrated by using dual parallel injection locked Fabry-Perot laser diodes. In the proposed method, it was able to achieve both the optical carrier suppressed signals with high suppression ratio and high transmission performance for both baseband and 60-GHz signal by injection locking of each sideband and direct modulation of the Fabry-Perot laser diodes, respectively. Using the remodulation technique based on reflective semiconductor optical amplifier, it was possible to accomplish bidirectional 1.25 Gbps 20-km transmission (BER < 10-9) with the receiver sensitivity lower than - 20 dBm.

60-GHz-Band 155-Mb/s and 1.5-Gb/s Baseband Time-Slotted Full-Duplex Radio-Over-Fiber Access Network

Abstract: We demonstrate a time-slotted full-duplex analog/digital hybrid radio-over-fiber access network unit. A reflective semiconductor optical amplifier at the access point is used to erase the downlink 1.5-Gb/s baseband signal for 60-GHz-band 155-Mb/s uplink signal on the reused optical carrier.

Fiber nonlinearity precompensation for long-haul links using direct-detection optical OFDM.

Abstract: The use of nonlinearity precompensation in direct-detection optical orthogonal frequency division multiplexed links is investigated by simulation. Because of the presence of a strong optical carrier its performance is poorer than for coherent systems: with compensation the signal quality is found to vary almost periodically across the signal band. We propose and explain the operation of two optical, one electrical and one computational method of removing this periodic variation. Optical filtering of one sideband at the receiver is most effective, but a substantial improvement can be obtained by a simple modification to the precompensation algorithm.

Optical generation of binary-phase-coded, direct-sequence ultra-wideband signals by polarization modulation and FBG-based multi-channel frequency discriminator.

Abstract: In this paper a novel optical generation approach for binary-phase-coded, direct-sequence ultra-wideband (UWB) signals is experimentally demonstrated. Our system consists of a laser array, a polarization modulator (PolM), a fiber Bragg grating (FBG), a length of single mode fiber, and a photo detector (PD). The FBG, designed based on the superimposed, chirped grating, is used as the multi-channel frequency discriminator. The input electronic Gaussian pulse is modulated on the optical carrier by the PolM and then converted into UWB monocycle or doublet pulses sequence by the multi-channel frequency discriminator. The PolM is used so that the desired binary phase code pattern could be simply selected by adjusting the polarization state of each laser, rather than tuning the laser wavelengths. The desired UWB shape, monocycle or doublet, could be selected by tuning the FBG. Based on our proposed approach, four-chip, binary-phase-coded, DS-UWB sequences with different pulse shapes and code patterns are experimentally demonstrated. The impact of the fiber dispersion on the generated UWB pulses is also discussed in our paper.

Method and arrangement for transmitting an optical OFDM-signal

Abstract: From an real valued OFDM signal (S 0 (t)) is a baseband signal (S B (t)) derived and converted into a complex single sideband modulation signal (n(t)). This is modulated onto an optical carrier (f OC ) to generate a SSB transmission signal (S OT ) having a small bandwidth an carrying the information in the envelope or in the power of the envelope. According to the modulation direct detection is possible. Only a small bandwidth is necessary for the transmission.

Orthogonal frequency division multiple access based optical ring network

Abstract: A fiber optic network transmits data between a hub node and a plurality of local nodes connected by at least one unidirectional fiber ring. Downstream data streams are carried on wavelength-division-multiplexed optical carriers from the hub node to the local nodes. An optical carrier corresponding to a specific wavelength carries downstream data streams to a specific local node. Downstream data streams are multiplexed onto an optical carrier via orthogonal frequency division multiplexing. A parallel signal detector in each local node detects all downstream optical carriers. A signal processing module demultiplexes the data stream from the optical carrier having the specific wavelength corresponding to the local node. An upstream data stream is multiplexed via orthogonal frequency division multiplexing onto an upstream optical carrier having the same specific wavelength and transmitted from the local node to the hub node. Upstream data awaiting transmission is allocated to specific subcarriers and time slots.

Method and arrangement for transmitting signals in a point to multipoint network

Abstract: Bidirectional data signals are exchanged between a central unit and a plurality of network terminals. The optical carrier frequencies of the downstream and upstream signals are chosen so that reflections do not interfere with the selected signal at the optical network unit and not with the received upstream signals at the central unit. The optical network units select their associated downstream signal and generate an associated upstream signal.

Cmos-compatible tunable microwave photonic band-stop filter

Abstract: According to one embodiment, a microwave photonic band-stop (MPBS) filter uses an electrical input signal to drive an optical Mach-Zehnder modulator. A modulated optical carrier produced by the modulator is applied to an optical filter having at least two tunable spectral attenuation bands that are located substantially symmetrically on either side of the carrier frequency. The resulting filtered optical signal is applied to an optical-to-electrical (O/E) converter to produce an electrical output signal.

Switchable delays optical fibre transponder with optical generation of doppler shift

Abstract: The invention concerns an optical modulator, comprising an input suitable to receive an optical carrier, a high- frequency microwave input and an output suitable to transmit an optical signal, the optical modulator comprising two Mach-Zender (1,2) modulators in parallel between the input and output so as to constitute two different optical paths within a third Mach-Zender modulator (3), the optical modulator being characterised in that: - the first Mach-Zender modulator (1) is provided with an electrode suitable to apply two microwave signals (RFl, RF2) obtained by the sum of the two tones fR and fD of equal power, the signals being dephased by pi/2, the modulator (1) being further provided with an electrode (Bias 1) for realising a single side band modulation of the tones fR and fp; - the second Mach-Zender modulator (2) is provided with an electrode (Bias 2) to vary the phase and the amplitude of the optical carrier; the third Mach-Zender modulator (3) comprises an electrode • (Bias 3) suitable to realise the summation of the signals deriving from the first (1) and the second (2) Mach-Zender modulator before the output, so as to suppress the optical carrier and thus obtain only the tones fR and fo in the optical spectrum. The invention further concerns an optical generator of Doppler frequency, an optical link for the generation of a variable optical delay and a transponder, in particular for the calibration, the test and the performances test of a radar, in particular a phased-array radar, that uses the optical modulator according to the invention.

Optimal Phase Lock at Femtowatt Power Levels for Coherent Optical Deep-Space Transponder

Abstract: We report on results of the first tests of an optical phase-lock loop (PLL) with the capabil ity to recover an optical carrier at powers below one picowatt (pW), as required for a deepspace coherent optical transponder. In such an application, a limiting phase variation is due to instability in the (optical) frequency standard that provides a phase reference at the return of the transponded signal, possibly many minutes later. We present results showing a PLL phase-slip rate below one cycle slip per second at powers as low as 40 femtowatts (fW). This phase-slip rate corresponds to a frequency stability of d f /f . 1 × 10 –14 / x , a value better than any frequency standard available today for measuring times equal to a typical two-way delay between Earth and Mars, and the 1100 fW required power allows application at Mars’ farthest distance from Earth with a reasonable transmitter power level (P 15 W). Parameters for a second-order PLL were optimized for the laser-noise and shotnoise levels by use of simulation software. Good agreement was obtained between laboratory measurements and the simulation results. We also report on measurements of the phase noise of the fiber lasers used for the test, analysis of the limitations on PLL performance at low optical power implied by this laser noise level, the results of demonstrations of Doppler signals at fW power levels, and transponder architectures designed to take advantage of this capability to achieve micron-level ranging accuracy with very short measuring times.

Enhanced linearity RF photonic link

Abstract: A method and apparatus for modulating an RF signal. The RF signal is supplied to a grating modulator having a grating, and light of at least a first wavelength is supplied as a first optical carrier to the grating modulator. The first carrier light is modulated by the grating modulator, wherein the first wavelength of the first carrier coincides with a null in the third derivative of a transmittance spectrum of the grating. Optionally, light of at an additional, second wavelength as a second optical carrier, is supplied to the grating modulator which modulates the second carrier light. The second wavelength of the second carrier coincides with another null, but different than the first mentioned null, in the third derivative of a transmittance spectrum of the grating.

Method and system for setting timing of phase modulation of xpsk transmitter

Abstract: A method is provided for setting a timing of phase modulation by a target phase modulator within an optical transmitter which performs 2 n order phase shift keying, n being a natural number equal to or more than two. The method is provided with: feeding a specific pattern to the optical transmitter to allow the xPSK transmitter to emit an optical carrier in accordance with the specific pattern; receiving the optical carrier by a delay interferometer; converting a pair of light signals emitted from constructive and destructive outputs of the delay interferometer into an electrical signal; detecting a peak to peak value of the electrical signal; and setting the timing of the phase modulation by the target phase modulator so as to minimize the peak to peak value of the electrical signal.

Full-Duplex 1.0 Gbit/s Data Transmission Over 60 GHz Radio-on-Fiber Access System Based on the Loop-Back Optical Heterodyne Technique

Abstract: Full-duplex transmission over a 60 GHz radio-on-fiber access system based on the optical heterodyne technique is verified in this paper. With this technique, an optical carrier generator on the transmitting side consolidates the functions of wavelength and polarization control for optical heterodyne detection in uplinks and optical millimeter-wave generation in downlinks, on behalf of each optical transmitter/receiver. Therefore, the whole system configuration can be significantly simplified. A full-duplex 1.0 Gbit/s transmission experiment over 10 km of single-mode fiber, which represents an access network transmission, is demonstrated using the simultaneous modulation/photodetection operation of an electroabsorption modulator (EAM). Bit error rates of less than 10-9 were obtained in both the uplink and downlink without noticeable mutual interference, even though the laser source and the EAM is shared by both links, and no significant dispersion-induced degradation was observed. Moreover, the experimental results showed that an optical link budget of 9.2 dB can be achieved with the experimental configuration.

Gigabits in the home with plugless plastic optical fiber (POF) interconnects

Abstract: We have developed plugless optical transceivers for low cost optical networking with plastic optical fiber (POF). The transmission speed is 125 Mb/s for Ethernet applications and 1.25 Gb/s for Gigabit Ethernet and other high speed applications. The high speed modules for Gigabit transmission are based on a red VCSEL light source for the transmitter that matches the optical attenuation minimum of the plastic fiber media. The devices have demonstrated excellent reliability with more than 850,000 hours of mean-time-to-failure operating life time at elevated temperatures of 40degC. Automotive qualified, rugged resonant cavity LEDs (RCLEDs) are used for the lower speed modules. The plugless transceiver design enables the direct optical connection between the active components and standard POF without the need for special termination of the fiber. Only a simple cutting action is required. This enables low cost field installations.

Systems and methods for optical carrier recovery

Abstract: In one embodiment a system and method pertain to generating a pump from a received optical signal, inputting the generated pump into a phase-sensitive oscillator, and amplifying a carrier component of the pump to generate an optical carrier having the same phase and polarity of an optical carrier of the received optical signal.

Method, system and device for data transfer in an optical network

Abstract: A method for data transfer in an optical network, including: amplitude modulating, by a central office, an optical carrier by a downstream data with a first rate to generate a downstream optical signal carrying the downstream data; sending the downstream optical signal to a user terminal; obtaining, by the user terminal, the downstream data from the downstream optical signal; amplitude modulating, by the user terminal, the downstream optical signal by an upstream data with a second rate to generate an upstream optical signal, wherein the ratio of the first rate to the second rate is greater than 1; sending the upstream optical signal to the central office; and receiving, by the central office, the upstream optical signal, and obtaining, by the central office, the upstream data from the upstream optical signal. Furthermore, the present invention discloses a system and device for data transfer in the optical network. With the invention, the complexity of the system may be effectively reduced, and the cost of the device may be lowered.

Coherent optical orthogonal frequency division multiplexing (OFDM) reception using self optical carrier extraction

Abstract: A method includes producing interference between a received optical OFDM signal and an optical carrier extracted from the received optical OFDM signal to provide optical coherent detection of the received optical OFDM signal. Preferably, producing the interference includes optically splitting the received optical OFDM signal into a first part that is filtered to extract the carrier from the received optical OFDM signal and a second part similar to the received optical OFDM signal.

Direct Detection Frequency Discrimination Optical Receiver for Minimum-Shift Keying Format Transmission

Abstract: An incoherent detection scheme based on frequency discrimination for minimum-shift keying (MSK) optical transmission systems is proposed to significantly extend the reach of uncompensated transmission distance. The receiver consists of dual narrowband optical filters in association with an optical delay line. This photonic front end operates based on frequency discrimination principles of matched filters, rather than relying on the phase of the optical carrier. Hence, its performance is less sensitive to the all-pass quadratic phase transfer function of the fiber transmission medium and is thus less susceptible to fiber chromatic dispersion. The photonic front-end optical receiver for 40-Gb/s optical MSK offers a dispersion tolerance of up to plusmn340 ps/nm for 1-dB power penalty at a bit-error rate of 10-9. This achievement is approximately five to seven times better than that of the existing value based on the Mach-Zehnder delay interferometer (MZDI) optical balanced receiver. Furthermore, the receiver is shown to be robust to polarization-mode dispersion.

Method and system for distributed measurement and compensation of chromatic dispersion in an optical network

Abstract: A method and apparatus for distributed measurement of chromatic dispersion in an optical network is disclosed. The network comprises optical switching nodes interconnected by optical links. An optical link may comprise multiple spans, each span ending in a transport module which comprises signal-processing components. At least one optical switching node has a probing signal generator transmitting an optical probing signal along a selected path in the network. Probing-signal detectors placed at selected transport modules determine chromatic-dispersion values and send results to a processing unit which determines appropriate placement of compensators or appropriate adjustments of compensators placed along the path. A preferred probing signal has the form of wavelength modulated optical carrier which is further intensity modulated by a periodic, preferably sinusoidal, probing tone. Variation in the phase-shift of the probing tone corresponding to variation of the wavelength of the optical probing signal determines chromatic-dispersion characteristics for different spans of the path.