Dispersion Compensation Research Papers - Academia.edu (original) (raw)

2004, Optics Express

Ultrahigh-resolution optical coherence tomography uses broadband light sources to achieve axial image resolutions on the few micron scale. Fourier domain detection methods enable more than an order of magnitude increase in imaging speed and sensitivity, thus overcoming the sensitivity limitations inherent in ultrahigh-resolution OCT using standard time domain detection. Fourier domain methods also provide direct access to the spectrum of the optical signal. This enables automatic numerical dispersion compensation, a key factor in achieving ultrahigh image resolutions. We present ultrahigh-resolution, high-speed Fourier domain OCT imaging with an axial resolution of 2.1 µm in tissue and 16,000 axial scans per second at 1024 pixels per axial scan. Ultrahigh-resolution spectral domain OCT is shown to provide a ~100x increase in imaging speed when compared to ultrahigh-resolution time domain OCT. In vivo imaging of the human retina is demonstrated. We also present a general technique for automatic numerical dispersion compensation, which is applicable to spectral domain as well as swept source embodiments of Fourier domain OCT.

2004, Optics Express

We present, for the first time, in vivo ultrahigh resolution (~2.5 µm in tissue), high speed (10000 A-scans/second equivalent acquisition rate sustained over 160 A-scans) retinal imaging obtained with Fourier domain (FD) OCT employing a commercially available, compact (500x260mm), broad bandwidth (120 nm at full-width-at-half-maximum centered at 800 nm) Titanium:sapphire laser (Femtosource Integral OCT, Femtolasers Produktions GmbH). Resolution and sampling requirements, dispersion compensation as well as dynamic range for ultrahigh resolution FD OCT are carefully analyzed. In vivo OCT sensitivity performance achieved by ultrahigh resolution FD OCT was similar to that of ultrahigh resolution time domain OCT, although employing only 2-3 times less optical power (~300 µW). Visualization of intra-retinal layers, especially the inner and outer segment of the photoreceptor layer, obtained by FDOCT was comparable to that, accomplished by ultrahigh resolution time domain OCT, despite an at least 40 times higher data acquisition speed of FD OCT.

2000, Journal of Lightwave Technology

We discuss coherent optical orthogonal frequency division multiplexing (CO-OFDM) as a suitable modulation technique for long-haul transmission systems. Several design and implementation aspects of a CO-OFDM system are reviewed, but we especially focus on phase noise compensation. As conventional CO-OFDM transmission systems are very sensitive to laser phase noise a novel method to compensate for phase noise is introduced. With the help of this phase noise compensation method we show continuously detectable OFDM transmission at 25.8 Gb/s data rate (20 Gb/s after coding) over 4160-km SSMF without dispersion compensation.

1999, IEEE Journal of Quantum Electronics

This paper presents an efficient method for the design of complex fiber Bragg gratings. The method relies on the synthesis of the impulse response of the grating by means of a differential layer-peeling algorithm. The algorithm developed takes into account all the multiple reflections inside the grating, giving an exact solution to the inverse scattering problem. Its low algorithmic complexity enables the synthesis of long fiber gratings. The method is illustrated by designing several filters with interest for optical fiber communication systems: dispersionless bandpass filters and second-and third-order dispersion compensators.

2000, Journal of Lightwave Technology

We present experimental demonstrations using direct-detection and optical-orthogonal frequency division multiplexing (DD-OOFDM) for the compensation of chromatic dispersion in long-haul optical fiber links. Three transmitter designs of varying electrical and optical complexity are used for optical single sideband (OSSB) transmission and the theory behind each design is discussed. The data rates achieved for the three systems are 10, 12, and 20 Gbit/s for fiber distances between 320 and 400 km. A discussion of system overheads is provided together with simulations of the required optical signal-to-noise ratio (OSNR).

2000, Journal of Lightwave Technology

The intensive investment in optical microelectromechanical systems (MEMS) in the last decade has led to many successful components that satisfy the requirements of lightwave communication networks. In this paper, we review the current state of the art of MEMS devices and subsystems for lightwave communication applications. Depending on the design, these components can either be broadband (wavelength independent) or wavelength selective. Broadband devices include optical switches, crossconnects, optical attenuators, and data modulators, while wavelength-selective components encompass wavelength add/drop multiplexers, wavelength-selective switches and crossconnects, spectral equalizers, dispersion compensators, spectrometers, and tunable lasers. Integration of MEMS and planar lightwave circuits, microresonators, and photonic crystals could lead to further reduction in size and cost.

1996, Optics Letters

A theory of optical pulse propagation in cascaded transmission systems that are based on the dispersioncompensating fiber technique is developed. The existence of two scales associated with fiber dispersion and system residual dispersion leads to a simple model for the averaged pulse dynamics. In the particular case of practical importance, the averaged pulse dynamics is governed by the nonlinear Schrödinger equation. The pulse transmission stability is examined.

2000, Journal of Lightwave Technology

We discuss optical multi-band orthogonal frequency division multiplexing (OFDM) and show that by using multiple parallel OFDM bands, the required bandwidth of the digital-to-analogue/ analogue-to-digital converters and the required cyclic prefix can significantly be reduced. With the help of four OFDM bands and polarization division multiplexing (PDM) we report continuously detectable transmission of 10 121.9-Gb/s (112.6-Gb/s without OFDM overhead) at 50-GHz channel spacing over 1,000-km standard single mode fiber (SSMF) without any inline dispersion compensation. In this experiment 8 QAM subcarrier modulation is used which confines the spectrum of the 121.9 Gb/s PDM-OFDM signal within a 22.8 GHz optical bandwidth. Moreover, we propose a digital signal processing method to reduce the matching requirements for the wideband transmitter IQ mixer structures required for PDM-OFDM.

1999, IEEE/OSA Journal of Lightwave Technology

The superprism phenomenon, the dispersion of light 500 times stronger than the dispersion in conventional prisms, was demonstrated at optical wavelengths in photonic crystals (PC's) fabricated on Si. Drastic light-beam steering in the PC's was achieved by slightly changing the incident wavelength or angle. The scanning span reached 50° with only a 1% shift of incident wavelength, and reached 140°

2008

We experimentally demonstrate dispersion compensation in a wavelength selective switch, and characterize the bandwidth-dispersion product. At a channel bit-rate of 80 Gbit/s, we compensate for various amounts of dispersion (up to 60 ps/nm), tunable for each wavelength division multiplexed channel, solely by adjusting the phase front of the optical signal inside the wavelength selective switch. Error-free operation is obtained for all of the channels, and for each output port after propagation over various lengths of dispersive fiber.

2003, Optics Letters

We demonstrate generation of 3.8-fs pulses with energies of up to 15 mJ from a supercontinuum produced in two cascaded hollow fibers. Ultrabroadband dispersion compensation was achieved through a closed-loop combination of a spatial light modulator for adaptive pulse compression and spectral-phase interferometry for direct electric-field reconstruction (SPIDER) measurements as feedback signal.

2000, IEEE Photonics Technology Letters

We compare nonreturn-to-zero (NRZ) with return-to-zero (RZ) modulation format for wavelength-divisionmultiplexed systems operating at data rates up to 40 Gb/s. We find that in 10-40-Gb/s dispersion-managed systems (single-mode fiber alternating with dispersion compensating fiber), NRZ is more adversely affected by nonlinearities, whereas RZ is more affected by dispersion. In this dispersion map, 10-and 20-Gb/s systems operate better using RZ modulation format because nonlinearity dominates. However, 40-Gb/s systems favor the usage of NRZ because dispersion becomes the key limiting factor at 40 Gb/s.

1997, IEEE/OSA Journal of Lightwave Technology

We propose a transmission-based dispersion compensator employing an apodized, unchirped fiber Bragg grating (FBG). A theoretical model for dispersion compensation in transmission based on the dispersive properties of the periodic structure is developed. A figure of merit is defined for optimization of the grating parameters for maximum recompression of dispersion-broadened optical pulses in long-haul communication systems. Numerical examples confirm that nearly perfect compensation with very low insertion losses can be achieved for many practical cases of interest.

1998, IEEE Journal of Quantum Electronics

Her doctoral research focuses on high-speed fiber optic communication systems, including dispersion management, fiber Bragg gratings, and different modulation formats.

2000, IEEE Photonics Technology Letters

We propose a novel dispersion compensating fiber design consisting of two highly asymmetric concentric cores. We show that the fundamental mode of the proposed fiber can have very large negative dispersion values [~-5100 ps/(nm.km)] with... more

2001, Journal of the Optical Society of America B

The problem of matching double-chirped mirrors to the ambient medium, which currently limits the design of ultrabroadband dispersion-compensating mirrors is reconsidered. A design of double-chirped mirror pairs that exhibit high reflectivity and a controlled group-delay dispersion in combination over 1 octave is presented. These mirrors permit the generation of octave-spanning spectra directly from a Ti:sapphire laser oscillator.

Dispersive samples introduce a wavelength dependent phase distortion to the probe beam. This leads to a noticeable loss of depth resolution in high resolution OCT using broadband light sources. The standard technique to avoid this consequence is to balance the dispersion of the sample by arranging a dispersive material in the reference arm. However, the impact of dispersion is depth dependent. A corresponding depth dependent dispersion balancing technique is diffcult to implement. Here we present a numerical dispersion compensation technique for Partial Coherence Interferometry (PCI) and Optical Coherence Tomography (OCT) based on numerical correlation of the depth scan signal with a depth variant kernel. It can be used a posteriori and provides depth dependent dispersion compensation. Examples of dispersion compensated depth scan signals obtained from microscope cover glasses are presented.

2000, Journal of Lightwave Technology

Nonlinear phase noise (Gordon-Mollenauer phase noise) can limit the transmission distance for phase-shift-keyed modulation formats. In this paper, the compensation of nonlinear phase noise by a midlink optical phase conjugation (OPC) is studied. A proof-of-principle experiment is presented showing an over 4-dB improvement in Q factor when OPC is employed in a differential phase-shift-keying (DPSK) system. Also, an ultra long-haul OPC-based differential quadrature phase-shift-keying (DQPSK) transmission experiment is studied to show the impact of self-phase modulation (SPM)-induced impairments, including nonlinear phase noise, in a transmission line. OPC results in a 44% increase in transmission distance when compared to a "conventional" transmission system using dispersion compensating fiber (DCF) for chromatic dispersion compensation.

1988, Optics Letters

We report direct measurements of the frequency dependence of the optical group delay for a number of optical components commonly used in femtosecond optics. IVe have investigated the group-delay errors that occur on reflection from metal... more

2002, Optical Fiber Communication Conference and Exhibit

A photonic band gap fiber has been generated by incorporating a high index fluid into a sol-gel derived microstructured fiber. The band gap positions and widths are tuned by adjusting the temperature.

2000, IEEE Photonics Technology Letters

The effect of nonideal dispersion and reflection characteristics of chirped fiber gratings on the performance of 10-Gb/s nonreturn-to-zero-transmission systems operating over standard fiber is investigated. The system penalty for different amplitude and period ripples are quantified. Analyses of an experimental grating confirm that current fabrication technology can meet the requirements for <1-dB-penalty operation.

2005, IEEE/OSA Journal of Lightwave Technology

Novel photonic devices based on a new type of waveguide, hollow optical fibers (HOF), are described. Utilizing unique three layered structure of HOF, the central air hole, germanosilicate ring core, and silica cladding along with its adiabatic mode transformation capability we demonstrated versatile applications in short-haul, long-haul optical communications, and tunable wavelength selective devices. Detailed design parameters, fabrication arts of the fibers, and operation principles of the devices are discussed.

1998, Optics Communications

Using the variational method, we obtain analytical conditions for stationary propagation of a Gaussian pulse in a fibre with strong dispersion management. We consider both the lossless fibre and the one with losses and periodic amplification. The analytical predictions have been checked against direct numerical simulations, and a good agreement between the two has been demonstrated. In particular, we find that in a certain region of parameters, the average dispersion necessary to Ž . support the stationary propagation is negative normal . We also show that under a certain assumption, the variance of the Gordon-Haus timing jitter for the pulse in a strongly dispersion-managed system approximately equals that for the conventional soliton, reduced by an energy enhancement factor. Using our analytical conditions, we obtain an estimate for this factor. In particular, we show that in the presence of losses and periodic amplification, this jitter suppression factor can be made to be as large as that for the lossless case, by properly choosing the segment lengths in the dispersion map. q 1998 Elsevier Science B.V.

2003

We demonstrate an optical recirculating loop as a tool for performance evaluation of cascades of effects or elements in an optical communication system. We describe the critical issues to operate the recirculating loop properly and we present experimental results on the cascading of a dispersive fiber link and an optical amplifier. Additionally, we conduct a numerical simulation of the recirculating loop experimental conditions. Simulation and experimental results are in good agreement.

1997, Optics Letters

We report efficient frequency doubling of passively mode-locked femtosecond erbium-fiber lasers. Quasiphase-matched second-harmonic generation in periodically poled lithium niobate is used to generate 8.1 mW of 190-fs (FWHM), 90-pJ pulses at 777 nm with a conversion efficiency greater than can be obtained with existing birefringently phase-matched nonlinear materials. A dispersion-compensation-free soliton oscillator generating transform-limited 230-fs (FWHM) pulses at 1554 nm is used as a pump laser.

2003, IEEE/OSA Journal of Lightwave Technology

Binary and multilevel phase-only sampling functions are proposed for the sampled fiber Bragg gratings (FBGs) with high channel count, which require significantly less refractive-index modulation than that does the sampled grating with amplitude sampling. The design using the new simulated quenching optimization with temperature rescaling results in high channel uniformity and minimum energy in the out-of-band channels. The technique can be applied to the sampled FBGs with very high channel count. A five-channel nonlinearly chirped multilevel phase-only sampled FBG for tunable chromatic dispersion compensation is demonstrated.

2000, IEEE Photonics Technology Letters

THz-range optical-frequency conversion of 1 Gb/s-signals is demonstrated, for the first time, through the use of cavity-enhanced highly nondegenerate four-wave mixing (HNDFWM) in an InGaAsP semiconductor laser. This conversion is based on a subpicosecond ultrafast nonlinear gain process in the laser. The possibility of applying this phenomenon to an optical fiber dispersion compensator is also discussed.

2000, Journal of Lightwave Technology

Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set the according digital filtering function. We present different non-data-aided (blind) CD estimation methods for single-carrier transmission under implementation constraint conditions such as bandwidth limitation and sampling rate. The estimation performance for various modulation formats is compared with respect to precision and robustness for a wide range of combined channel impairments.

2000, IEEE Photonics Technology Letters

We carried out an extensive simulative analysis to investigate in depth the potential of electronic dispersion compensation (EDC) in amplified multispan 111-Gb/s wavelength-division-multiplexed systems based on polarization-multiplexed quadrature phase-shift keying modulation with coherent detection, also in the presence of substantial fiber nonlinearity. For typical single-mode and nonzero dispersion-shifted fibers, our results show that the use of inline optical dispersion management is always suboptimal versus using EDC at the receiver.

2006, IEEE Journal of Selected Topics in Quantum Electronics

In this paper, we review the recent progress in transmission experiments by employing optical phase conjugation (OPC) for the compensation of chromatic dispersion and nonlinear impairments. OPC is realized with difference frequency generation (DFG) in a periodically poled lithium-niobate (PPLN) waveguide, for transparent wavelength-division multiplexed (WDM) operation with high conversion efficiency. We discuss extensively the principle behind optical phase conjugation and the realization of a polarization independent OPC subsystem. Using OPC for chromatic dispersion compensation WDM 40-Gb/s long-haul transmission is described. As well, transmission employing both mixed data rates and mixed modulation formats is discussed. No significant nonlinear impairments are observed from the nonperiodic dispersion map used in these experiments. The compensation of intrachannel nonlinear impairments by OPC is described for WDM carrier-suppressed return-to-zero (CSRZ) transmission. In this experiment, a 50% increase in transmission reach is obtained by adding an OPC unit to a transmission line using dispersion compensating fiber (DCF) for dispersion compensation. Furthermore, the compensation of impairments due to nonlinear phase noise is reviewed. An in-depth analysis is conducted on what performance improvement is to be expected for various OPC configurations and a proof-of-principle experiment is described showing over 4-dB improvement in Q-factor due to compensation of nonlinear impairments resulting from nonlinear phase noise. Finally, an ultralong-haul WDM transmission of 22 × 20-Gb/s return-tozero differential quadrature phase-shift keying (RZ-DQPSK) is discussed showing that OPC can compensate for chromatic dispersion, as well as self-phase modulation (SPM) induced nonlinear impairments, such as nonlinear phase noise. Compared to a "conventional" transmission link using DCF for dispersion compensation, a 44% increase in transmission reach is obtained when OPC is employed. In this experiment, we show the feasibility of using only one polarization-independent PPLN subsystem to compensate for an accumulated chromatic dispersion of over 160 000 ps/nm. Index Terms-Dispersion compensation, differential phaseshift keying (DPSK), differential quadrature phase-shift keying (DQPSK), duobinary, fiber-optics communications, nonlinear phase noise, phase conjugation, phase-shift keying, periodically poled lithium niobate (PPLN), spectral inversion.

2010, Southeast Asian International Advances in Micro/Nanotechnology

Optical coherence tomography (OCT) is an imaging technique widely used in various applications especially in biomedical field. It constructs a high resolution 3-D image using multiple cross-sectional views. The axial resolution can be degraded if the sample is dispersive, which is usually true as most of the samples are living tissues. For time-domain OCT, this dispersion is minimized numerically by introducing a compensation filter, which is applied to the obtained signal in Wigner domain, a time-frequency domain. The filter is designed using simulated annealing optimization technique. This paper shows the design of the filter and the results of dispersion compensation.

2000, IEEE Photonics Technology Letters

We propose a tunable dispersion and dispersion slope compensator based on induced strain-chirp in a uniform fiber Bragg grating. A specially designed mechanical rotator concatenated with a metal beam with linear thickness variation along its height was used to induce a quadratic strain gradient along the grating. We successfully demonstrated the dispersion and dispersion slope change by adjusting the rotation angle and feasibility of dispersion and dispersion slope compensation at 160-Gb/s nonreturn-to-zero transmission by simulation.

2005, Optics Express

Orthogonal Frequency Division Multiplexing (OFDM) can provide electronic dispersion compensation of optical paths. However, it requires a high bias to convert bipolar electrical signals to unipolar optical signals, so is inefficient in optical power for a given electrical signal to noise ratio. We present a novel method of transmitting OFDM signals over multimode fibers that increases electrical SNR by 7 dB for a given optical power. Using simulations, we show a 1.8 dB sensitivity benefit over 10 Gbit/s NRZ (Non-Return to Zero) and demonstrate compensation of intermodal dispersion in a 300-m multimode fiber that cannot support NRZ.

2007, IEEE/OSA Journal of Lightwave Technology

We introduce our recent progresses in the design and fabrication of the high channel-count fiber Bragg grating (FBG). We theoretically and experimentally demonstrated the phase-only sampled FBG with channels up to 81, which could be used as the dispersion compensator, the simultaneous dispersion and dispersion-slope compensator, respectively. Moreover, we have presented a novel method for multi-channel FBG design, which enables us to design any kind of multi-channel FBGs where the amplitude or the spectral response of each channel could be either identical or nonidentical. As an example, a novel design for a multi-channel FBG with asymmetrical triangular reflection spectrum has been demonstrated.

1997, Physical Review E

We study a nonlinear process of the formation of a breathing solitary wave in the optical transmission systems with periodic amplification and dispersion compensation. Results of our numerical simulations demonstrate remarkably stable asymptotic propagation of such breathing pulse over long distances. We have derived approximate equations describing pulse amplitude and width oscillations and found that results obtained by this approach are in good agreement with the results of direct numerical modeling on the short and middle distances. It is shown that asymptotic averaged pulses have a form typically close to a Gaussian shape. We have found numerically that an input pulse evolves asymptotically into a stable breathing structure. After the first stage of propagation, the input pulse emits radiation that spreads due to dispersion. The asymptotic structure that is formed realizes a balance between the main pulse and the radiative tail.

2005, Optics Letters

A novel Fourier domain fast scanning optical delay line is proposed in which the walk-off is eliminated by only two passes through a diffraction grating. Working in transmission, the novel delay line is ideal for balanced optical coherence tomography configurations with recirculation of the reference beam. We evaluate theoretically and experimentally its walk-off and dispersion compensation capabilities.

2012, Smart Materials & Structures

A strategy for the localization of acoustic emissions (AE) in plates with dispersion and reverberation is proposed. The procedure exploits signals received in passive mode by sparse conventional piezoelectric transducers and a three-step processing framework. The first step consists in a signal dispersion compensation procedure, which is achieved by means of the Warped Frequency Transform. The second step concerns the estimation of the differences in arrival time (TDOA) of the acoustic emission at the sensors. Complexities related to reflections and plate resonances are here overcome via a wavelet decomposition of cross-correlating signals where the mother function is designed by a synthetic warped cross signal. The magnitude of the wavelet coefficients in the warped distance-frequency domain, in fact, precisely reveals the TDOA of an acoustic emission at two sensors. Finally, in the last step the TDOA data are exploited to locate the acoustic emission source through hyperbolic positioning. The proposed procedure is tested with a passive network of three/four piezo-sensors located symmetrically and asymmetrically with respect to the plate edges. The experimentally estimated AE locations are close to those theoretically predicted by Cramèr-Rao lower bound.

2000, IEEE Photonics Technology Letters

The nonlinear power limit of optical links using optical orthogonal frequency division multiplexing for dispersion compensation can be significantly improved using a simple and computationally efficient nonlinearity precompensation technique that requires no additional optical components. Simulations show that a 2-dB increase in transmission power is possible for 6 ps/nm/km fibers in a 4000-km system, and this increases to 4 dB for 2 ps/nm/km fibers. Alternatively, the bit error ratio can be substantially reduced with precompensation when the systems are operated at an optimum power. Only a single tuning parameter is used to represent the whole link, and the system is robust against variations in this parameter.

2000, Journal of Lightwave Technology

We present a hybrid dense wavelength-division-multiplexed time-division multiple access passive optical network (DWDM-TDMA PON) with record performance in terms of reach (135.1 km of which 124 km were field-installed fibers), number of supported optical network units (ONUs-8192) and capacity (symmetric 320 Gb/s). This was done using 32-, 50-GHz-spaced downstream wavelengths and another 32-, 50-GHz-spaced upstream wavelengths, each carrying 10 Gb/s traffic (256 ONUs per wavelength, upstream operated in burst mode). The 10 Gb/s downstream channels were based upon DFB lasers (arranged in a DWDM grid), whose outputs were modulated using a electro-absorption modulator (EAM). The downstream channels were terminated using avalanche photodiodes in the optical networks units (ONUs). Erbium-doped fiber amplifiers (EDFAs) provided the gain to overcome the large fiber and splitting losses. The 10 Gb/s upstream channels were based upon seed carriers (arranged in a DWDM grid) distributed from the service node towards the optical network units (ONUs) located in the user's premises. The ONUs boosted, modulated, and reflected these seed carriers back toward the service node using integrated 10 Gb/s reflective EAM-SOAs (EAM-semiconductor optical amplifier). This seed carrier distribution scheme offers the advantage that all wavelength referencing is done in the well-controlled environment of the service node. The bursty upstream channels were further supported by gain stabilized EDFAs and a 3R 10 Gb/s burst-mode receiver with electronic dispersion compensation. The demonstrated network concept allows integration of metro and optical access networks into a single all-optical system, which has potential for capital and operational expenditure savings for operators.

2000, IEEE Photonics Technology Letters

We designed and experimentally demonstrated an efficient photonic frequency-tripling technology for 60-GHz radio-over-fiber systems to simultaneously realize millimeter-wave (mm-wave), microwave, and baseband signal generation. The technique utilizes vestigial sideband filtering in combination with optical carrier suppression to generate novel alternate subcarrier modulation for high tolerance of fiber dispersion. Experimental verification of the proposed scheme is presented with generation and error-free transmission of 2.1-Gb/s data on the 63-GHz mm-wave and 21-GHz microwave carriers over 50-km single-mode fiber (SMF-28) without dispersion compensation. The power penalty for both signals is less than 1.0 dB.

2006, Optics Letters

We demonstrate a multiple-wavelength Brillouin comb laser with cooperative Rayleigh scattering that uses Raman amplification in dispersion-compensating fiber. The laser resonator is a linear cavity formed by reflector at each end of the dispersion-compensating fiber to improve the reflectivity of the Brillouin Stokes comb. Multiple Brillouin Stokes generation has been improved in terms of optical signal-to-noise ratio and power-level fluctuation between neighboring channels. Furthermore, the linewidth of the Brillouin Stokes is uniform within the laser output bandwidth.

2002, Optical Fiber Technology

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2004

A novel technique for optical multiplexing of label and payload using optical carrier suppression and separation is proposed and experimentally demonstrated. No power penalty is observed when the payload and label, with signal extinction ratio 11 dB, are transmitted over 60-km standard single-mode fiber with full-dispersion compensation. The technique of the optical label generation offers many advantages compared with previous techniques.

2002, Journal of Lightwave Technology

We present a multichannel tunable dispersion compensator (TDC) based on multicavity all-pass etalons that is capable of operation at 40 Gb/s. The device has a tuning range of +200/ 220 ps/nm with a group delay ripple 5 ps over a channel bandwidth of 80 GHz, an overall loss of 5.2 dB, very low insertion loss ripple, and can operate on any channel on a 200-GHz grid over the C-band. In addition, we present system performance results at 40 Gb/s using NRZ, RZ, and CS-RZ modulation, compensating up to 45 km of nonzero dispersion shifted fiber (NZDSF). Our results show that this device introduces very little excess system penalty with signal frequency drifts of up to 20 GHz when operated near the center of its tuning range. For single channel experiments with fiber, the system penalty increase versus signal detuning is more significant, but can be reduced by dynamically optimizing the device dispersion during detuning. Finally, we demonstrate simultaneous compensation of 4 channels across the C-band over 25 km of NZDSF. Index Terms-Chromatic dispersion, fiber optics communications, integrated optics devices, modulation formats. I. INTRODUCTION C HROMATIC dispersion compensation devices that can accommodate both fixed dispersion slope as well as dynamic dispersion variation in a link are clearly needed as the individual bit rate per channel in WDM systems increases to 40 Gb/s. In addition, there is significant interest in devices that can perform multichannel compensation. Apart from applications where simultaneous compensation of a small band of channels may be needed, even for single channel applications a multichannel device also has the potential to greatly reduce inventory overhead (so-called "colorless" devices), and may be useful in potential future, wavelength agile, networks where terminals themselves may need to be intrinsically colorless.

2000, IEEE Transactions on Instrumentation and Measurement

We have measured wavelength dependent Polarization Dependent Loss (PDL) in chirped fiber Bragg gratings for dispersion compensation, grating filters for wavelength add/drop multiplexing and long period gratings for EDFA gain flattening. The PDL is measured in devices used in reflection and in transmission by applying the Jones matrix method, the Mueller matrix method and the polarization scanning method. A comparison of the experimental results and an analysis of the sources of errors are presented. Index Terms-Fiber Bragg grating, Jones matrix method, long period grating, Mueller matrix method, polarization dependent loss (PDL), polarization-scanning method.

2012, Laser Physics Letters

The free-standing graphite nano-particle located between two FC/APC fiber connectors is employed as the saturable absorber to passively mode-lock the ring-type Erbiumdoped fiber laser (EDFL). The host-solvent-free graphite nanoparticles with sizes of 300 -500 nm induce a comparable modulation depth of 54%. The interlayer-spacing and lattice fluctuations of polished graphite nano-particles are observed from the weak 2D band of Raman spectrum and the azimuth angle shift of -0.32 • of {002}-orientation dependent X-ray diffraction peak. The graphite nano-particles mode-locked EDFL generates a 1.67-ps pulsewidth at linearly dispersion-compensated regime with a repetition rate of 9.1 MHz. The time-bandwidth product of 0.325 obtained under a total intra-cavity groupdelay-dispersion of -0.017 ps 2 is nearly transform-limited. The extremely high stability of the nano-scale graphite saturable absorber during mode-locking is observed at an intra-cavity optical energy density of 7.54 mJ/cm 2 . This can be attributed to its relatively high damage threshold (one order of magnitude higher than the graphene) on handling the optical energy density inside the EDFL cavity. The graphite nano-particle with reduced size and sufficient coverage ratio can compete with other fast saturable absorbers such as carbon nanotube or graphene to passively mode-lock fiber lasers with decreased insertion loss and lasing threshold. Microscope image Cladding Core 980 nm LD Isolator EDFA PC FC/APC 980 nm LD 5% output 1×2 (95/5) coupler SEM 0.5 µm

2000, IEEE Communications Magazine

2008, IEEE/OSA Journal of Lightwave Technology

Orthogonal frequency-division multiplexing (OFDM) can compensate for linear distortions, such as group-velocity dispersion (GVD) and polarization-mode dispersion (PMD), provided the cyclic prefix is sufficiently long. Typically, GVD is dominant, as it requires a longer cyclic prefix. Assuming coherent detection, we show how to analytically compute the minimum number of subcarriers and cyclic prefix length required to achieve a specified power penalty, trading off power penalties from the cyclic prefix and from residual inter-symbol interference (ISI) and inter-carrier interference (ICI). We derive an analytical expression for the power penalty from residual ISI and ICI.