Influence Of Chromatic Dispersion Research Articles

Chromatic dispersion dependence of GAWBS phase noise compensation with pilot tone

We describe experimental and numerical results regarding the influence of chromatic dispersion in optical fibers on guided acoustic-wave Brillouin scattering (GAWBS) phase noise compensation with a pilot tone (PT). We compared the compensation performance for GAWBS phase noise generated in an ultra-large-area fiber (ULAF) where DULAF = 21 ps/nm/km with that in a dispersion-shifted fiber (DSF) where DDSF = -1.3 ps/nm/km and found that the performance depends strongly on chromatic dispersion. The numerical analysis shows that the group delay between the signal and PT caused by chromatic dispersion reduces the GAWBS noise correlation between them, which degrades the compensation performance for GAWBS phase noise. It is clarified that a condition for effective GAWBS compensation is that the group delay between the signal and PT should be less than half the period of the GAWBS phase noise component.

Simultaneous carrier extraction from wavelength-division-multiplexed phase-conjugated twin waves by using sum-frequency generation with second-order optical nonlinear medium for phase-sensitive optical amplifier repeaters

This paper proposes and numerically investigates simultaneous carrier extraction from wavelength-division multiplexed phase-conjugated twin waves (WDM-PCTWs) in optical phase-locked loop (OPLL) for phase-sensitive optical amplifier (PSA) repeaters on optical multi-relay transmission systems. First, it is mathematically derived that the proposed scheme contributes to a signal-to-noise ratio improvement of phase error signals between WDM-PCTWs and a pump wave for PSA. As a result, the quality of the pump wave is improved. Then, the influence of chromatic dispersion in a transmission fiber on the proposed scheme is numerically investigated. When a center optical frequency of WDM-PCTWs is equal to a zero-dispersion optical frequency of an 80 km transmission fiber, the extracted carrier power increases as the number of WDM channels increase. In contrast, an optical frequency difference between the center frequency of WDM-PCTWs and the zero-dispersion optical frequency of a transmission fiber severely impairs the extracted carrier power as the number of WDM channels increase.

Adaptive Compensation of Bandwidth Narrowing Effect for Coherent In-Phase Quadrature Transponder through Finite Impulse Response Filter

Coherent in-phase quadrature (IQ) transponders are ubiquitous in the long-haul and the metro optical networks. During the transmission, the coherent signal experiences a bandwidth narrowing effect after passing through multiple reconfigurable optical add-drop multiplexers (ROADMs). The coherent signal also experiences a bandwidth narrowing effect when electrical or optical components of the coherent IQ transponder experience aging. A dynamic method to compensate the bandwidth narrowing effect is thus required. In the coherent optical receiver, signal bandwidth is estimated from the raw analog-to-digital converter (ADC) outputs. By adaptively adjusting the tap coefficients of the finite impulse response (FIR) filter, simple post-ADC FIR filters can increase the resiliency of the coherent signal to the bandwidth narrowing effect. The influence of chromatic dispersion, polarization mode dispersion, and polarization dependent loss are studied comprehensively. Furthermore, the bandwidth information of the transmitted analog signal is fed back to the coherent optical transmitter for signal optimization, and the transmitter-side FIR filter thus changes accordingly.

A Radio over Fiber (RoF) Based Single Sideband Modulated Passive Optical Network (PON) Using Mach Zender Modulator Based on Different Electrical Phase Shifts

Abstract This research work provides an insight on a radio over fiber (RoF) based passive optical network (RoF-PON) utilizing two diverse electrical phase shifts with optical single sideband modulation (OSSB) by exploiting Mach Zender modulator. The influence of chromatic dispersion (CD) in PONs employing single mode fiber (SMF) is a noteworthy issue and should be limited. The two techniques of OSSB modulation, in view of the two distinct angles of the hybrid coupler are employed for the design and implementation of RoF-PON. The RF signal is partitioned into two ways equally before applying it to the dual drive Mach Zender modulator input, utilizing an electrical hybrid coupler that imparts two discrete phase shifts of 90° and 120° to generate two OSSB signals individually. By utilizing traditional OSSB technique having 90° phase shift, either of the first-order sideband (lower or upper first order) suppression occurs yet second-order harmonics are still existent in the system. As opposed to this, the OSSB technique using 120° phase shift causes the suppression of either lower first order and higher second order sideband or vice versa. When contrasted to the PON based on traditional technique (90° phase shift technique), the suppression of second order sideband in PON using 120° technique lessens the system CD. Hence the PON based on 120° phase shift technique has enhanced functionality in terms of system BER, received power and power losses as compared to that with traditional OSSB technique.

Simultaneous optical signal to noise ratio and symbol rate estimation with blind chromatic dispersion compensation for auxiliary amplitude modulation optical signals

Based on the peak to valley ratio (PTVR) of the average magnitude difference function (AMDF), we present a novel optical signal to noise ratio (OSNR) and symbol rate (SR) estimation method for commonly used auxiliary amplitude modulations (AAMs). Moreover, it is demonstrated that the influence of chromatic dispersion (CD) on the method can be mitigated by maximizing the PTVR of the AMDF with additional tunable dispersion compensators. The results of simulations show that the OSNR estimation error can be kept within 0.8 dB in the wide OSNR range of (12, 32) dB, while the SR estimation error is below 0.079% for four widely used 10 Gsymbol/s AAM signals.

Comparison of Numerical Modelling of Degradation Mechanisms in Single Mode Optical Fibre Using MATLAB and VPIphotonics

Mathematical models for description of physical phenomena often use the statistical description of the individual phenomena and solve those using suitable methods. If we want to develop numerical model of optical communication system based on transmission through single mode optical fibres, we need to consider whole series of phenomena that affect various parts of the system. In the single-mode optical fibre we often encounter influence of chromatic dispersion and nonlinear Kerr effects. By observing various different degradation mechanisms, every numerical model should have its own limits, which fulfil more detailed specification. It is inevitable to consider them in evaluation. In this paper, we focus on numerical modelling of degradation mechanisms in single-mode optical fibre. Numerical solution of non-linear Schroedinger equation is performed by finite difference method applied in MATLAB environment and split-step Fourier method, which is implemented by VPIphotonics software.

Mathematical simulation of an experimental prototype of a high-speed nonreturn-to-zero differentialphase-shift-keying fibre-optic communication system

The influence of chromatic dispersion, optical power, and nonlinear distortions in a fibre-optic communication system on the quality of data transmission based on nonreturn-to-zero differentialphase-shift keying at a rate of 40 Gbit s-1 in one spectral channel have been numerically simulated and experimental studied. The results of direct numerical calculations and estimates based on the quality factor (Q factor) are in qualitative agreement with the experimental data. It is found experimentally that the dependence of the error rate on the accumulated dispersion has a plateau in therange from —50 to 50 ps nm-1; a similar dependence is obtained in the numerical calculation based on the Q factor. The optimal calculated value of the power launched into each of 10 sections of a line with a total length of 1000 km is 2 — 4 dBm; it corresponds to the experimental value of 3 dBm.

Achievement of Subchannel Frequency Spacing Less Than Symbol Rate and Improvement of Dispersion Tolerance in Optical OFDM Transmission

We propose a novel optical orthogonal frequency-division multiplexing (OFDM) transmission, where the frequency spacing of subchannels is less than the symbol rate. We show experimentally that the novel OFDM transmission achieves an optical SNR (OSNR) sensitivity level and dispersion tolerance roughly equivalent to those of the conventional OFDM. We also show the influence of chromatic dispersion from the transmission channel on the OFDM signal. The chromatic dispersion causes a desynchronization of the symbol timing between subchannels and breaks the frequency orthogonality in OFDM. We confirm experimentally that it is possible to mitigate the signal degradation due to the chromatic dispersion by optimizing the symbol timing and orthogonally polarizing the subchannels to the neighboring subchannels.

Experimental Study on the Role of Chromatic Dispersion in Continuous-Wave Supercontinuum Generation

The influence of chromatic dispersion on continuous-wave (CW)-pumped supercontinuum (SC) generation in kilometer-long standard fibers is experimentally investigated. We perform our study by means of a tunable, high-power fiber ring laser pumping a dispersion-shifted fiber in the wavelength range of small and medium anomalous dispersion. Our results show that, at low input powers, chromatic dispersion plays a dominant role on nonlinear pump spectral broadening, giving rise to a broader spectrum when pumping just above the zero-dispersion wavelength of the fiber. At higher input powers, however, the width of the generated SC spectrum is mostly due to the Raman effect, hence more independent of the value of the chromatic dispersion coefficient. We show that, in this case, the optimum pumping wavelengths for SC generation are not so close to the zero-dispersion wavelength of the fiber as in the previous case. In these conditions, as the chromatic dispersion grows, we can obtain square-shaped and high-power density spectra, which seem extremely promising for applications in optical coherence tomography.

Simulating phase coding in quantum cryptography: influence of chromatic dispersion

We demonstrate the impact of chromatic dispersion on the phase coding method in a double Mach-Zehnder implementation of an interferometric system for quantum cryptography. Formulas have been developed to explore detailed studies of the modifications on energy and position spectra which arise if chromatic dispersion is taken into account. Examples demonstrate the shifting of spectra and the appearance of oscillations depending on the wavelength and spectral broadness as well as on the phase shifters, absorbers and the dimensions of the interferometric set-up.

All-optical wavelength-path service with quality assurance by multilayer integration system

In the future all-optical network controlled by generalized multiprotocol label switching (GMPLS), the wavelength path between end nodes will change dynamically. This inevitably means that the fiber parameters along the wavelength path will also vary. This variation in fiber parameters influences the signal quality of high-speed-transmission system (bit rates over 40 Gb/s). Therefore, at a path setup, the fiber-parameter effect should be adequately compensated. Moreover, the path setup must be completed fast enough to meet the network-application demands. To realize the rapid setup of adequate paths, a multilayer integration system for all-optical wavelength-path quality assurance is proposed. This multilayer integration system is evaluated in a field trial. In the trial, the GMPLS control plane, measurement plane, and data plane coordinated to maintain the quality of a 40-Gb/s wavelength path that would otherwise be degraded by the influence of chromatic dispersion. It is also demonstrated that the multilayer integration system can assure the signal quality in the face of not only chromatic dispersion but also degradation in the optical signal-to-noise ratio by the use of a 2R regeneration system. Our experiments confirm that the proposed multilayer integration system is an essential part of future all-optical networks.

Improving frequency response of radio over fibre systems by fibre Bragg grating

A novel scheme to improve the frequency response of radio over fibre systems is proposed. It is based on a narrowband fibre Bragg grating (FBG) as a flattening filter with its spectral slope used to compensate the frequency response declination in the high frequency band. FBG also functions as a tilted filter to suppress one sideband of the double-sideband modulated signals and optical carrier signal for reducing the influence of chromatic dispersion to system performance. Experimental results confirm the effectiveness of the proposed scheme.

Field trial of GMPLS triple plane integration for 40 Gbit∕s dynamically reconfigurable wavelength path network

A field trial of GMPLS triple plane integration for dynamic wavelength path switching has been successfully demonstrated. In the trial, GMPLS control plane, measurement plane and data plane were co-ordinated to ensure the quality of a 40 Gbit/s wavelength path that is degraded by the influence of chromatic dispersion in all-optical rerouting.

Numerical Simulations on Long Haul Soliton Transmission Systems with In-line Control by Intensity Modulators and Filters

The limitations on the product of bit rate and distance can be overcome by placing intensity modulators and filters along the transmission line. For these types of systems, we study through numerical simulations their performances. The results are represented by contour plots for the pairs of filter bandwidth and amplifier output power. These plots show an optimum area and three zones according to their origin of degradation which are analyzed. The influence of chromatic dispersion on the system performances is also investigated.

Rigorous approach to performance modelling of nonlinear, optically amplified IM/DD systems

A method is reported that, through a rigorous treatment of the combined effect of chromatic dispersion, self-phase modulation and in-line amplifier noise, provides a sound basis for quantitative performance analysis in long-haul systems. This is achieved by using a moment generating function based approach in which the effect of intersymbol interference and the randomness of waveform distortion are fully accommodated. Additionally, an improved bound on the bit error rate for optically preamplified receivers is proposed which is tighter than the Chernoff and modified Chernoff bounds and is independent of gain for all gains of practical interest. With the aid of this new bound, the influence of chromatic dispersion, self-phase modulation and in-line amplifier noise as function of various system parameters examined and quantified.

Influence of chromatic dispersion on a dual-wavelength passive-homodyne detection method for fiber-coupled interferometers

The passive-homodyne method is very attractive for demodulating optical signals available at the output of interferometric sensors by the use of coherence multiplexing. Phase measurement and the use of two broadband sources with different central wavelengths permit a resolution of λ/10(5) to be achieved with a 20-µ range-sensor optical path difference. However, dispersive birefringent elements are required in this technique, which has some disturbing effects on the correlation signal position, on its envelope form, and on the measured phase. An analytical treatment of the problem and a numerical validation are described. Experimental evidence of the effects predicted by theory is presented.

Kerr effect and chromatic dispersion in fiber-optic gyroscopes

We investigate the influence of chromatic dispersion on the nonreciprocal phase shift induced by the optical Kerr effect of two beams counterpropagating in a fiber-optic gyroscope.

Influence of chromatic dispersion on degenerate four-wave mixing

We investigate the way in which four-wave mixing in a waveguide is affected by chromatic dispersion. The frequency dependence of the associated phase-conjugate mirror reflectivity turns out not to be influenced by chromatic dispersion itself.