Dispersion Of Transmission Fiber Research Articles

Phase squeezing and dispersion tolerance of phase sensitive amplifier using periodically poled LiNbO_3 waveguide

The phase squeezing property of phase sensitive amplifiers (PSAs) is a useful feature to recover signal quality. Chromatic dispersion of transmission fiber largely affects the performance of PSAs when they are used as in-line amplifiers in long-haul transmission systems. In this work, we demonstrated that phase variation such as chirping can be reduced by phase squeezing in a periodically poled LiNbO3 (PPLN)-based PSA. We also examined the dispersion tolerance of a PPLN-based in-line PSA. Theoretical analysis and experiment revealed that we can relay the received data with negligible power penalty utilizing the phase squeezing capability of the PSA, if the phase variation due to dispersion within the data bandwidth is below π/2.

Information-rate analysis of a fiber-optic transmission system including 2R signal regenerators

Performance of a single-channel fiber-optic transmission system in which signal regenerators are periodically inserted is analyzed in terms of information rate (IR) considering channel memory. Limitations in using regenerators in a system having non-zero residual dispersion between the regenerators are discussed. It is shown that a type of signal impairment caused by the interaction between the transmission-fiber dispersion and the regenerator nonlinearity is pattern-dependent and will be mitigated by the use of sequence estimation after detection at the receiver.

Performance evaluation of reflective electro-absorption modulator based optical source using a broadband light seed source for colorless WDM-PON applications

The performance of reflective electro-absorption modulator (R-EAM) based optical source has been evaluated for the use in high-capacity wavelength-division multiplexed passive optical networks (WDM-PONs). In our measurements, a broadband light source (BLS) was used as a seeding source for the cost-effective implementation of R-EAM based optical source. At first, a bit-error rate (BER) floor at 10(-6) was observed even in a back-to-back configuration with the BLS seeded R-EAM source. This is mainly because of the excess intensity noise (EIN) within BLS and the signal-to-noise ratio (SNR) degradation induced by a high insertion loss of R-EAM. To mitigate both effects of EIN and SNR degradation, a reflective semiconductor optical amplifier (RSOA) was also used for the implementation of our BLS seeded R-EAM source. Then, we have evaluated the impact of various noises, such as EIN, chromatic dispersion of transmission fiber and in-band crosstalk, on the system's performance using our BLS seeded R-EAM optical source. From the results, we have found that a 3-dB bandwidth of the BLS seeded R-EAM optical source should be wider than ~0.8 nm to achieve an error-free transmission of 1.25 Gb/s signal. We have also confirmed that there was a trade-off between the dispersion- and the in-band crosstalk-induced penalties due to the wide source bandwidth of our BLS seeded R-EAM source, like the cases of BLS seeded RSOA and Fabry-Perot laser diode (FP-LD) sources.

Optical Back Propagation With Optimal Step Size for Fiber Optic Transmission Systems

An optical back propagation scheme consisting of an optical phase conjugator, fiber Bragg gratings (FBGs), and highly nonlinear fibers (HNLFs) is investigated. Transmission fiber dispersion is compensated by the FBGs and the nonlinearity is compensated by HNLFs. Several sections of FBGs and HNLFs are concatenated in a way analogous to the split-step Fourier scheme used for solving the nonlinear Schrödinger equation. The optimum accumulated dispersion of each section of the FBG and the optimum nonlinear phase shift of the each section of the HNLF are calculated by minimizing the mismatch between the area under the exponentially increasing nonlinearity profile and its stepwise approximation. The method of Lagrange multipliers is used for optimization. The proposed optimization technique leads to significant performance improvement and/or reach enhancement as compared to uniformly spaced sections, for the given number of sections.

Rapid Reconfigurable OCDMA System Using Single-Phase Modulator for Time-Domain Spectral Phase Encoding/Decoding and DPSK Data Modulation

An optical-code-division-multiple-access (OCDMA) system with a novel modulation scheme for simultaneous generation of time-domain spectral phase encoding/decoding (SPE/SPD) and differential phase-shift keying (DPSK) data modulation that can be potentially rapidly reconfigured using only a single-phase modulator (PM) is proposed and experimentally demonstrated. The time-domain SPE is realized by stretching and compressing the ultrashort optical pulse through two-chirped fiber Bragg gratings with opposite dispersion and a high-speed PM for optical code (OC) generation and data modulation. The SPD has similar configuration as the SPE counterpart but using another PM synchronously driven by the complementary code pattern for OC recognition. Simulation investigation and experimental results both show that the code transition, dispersion mismatch between the encoding and decoding side, and the transmission fiber dispersion have detrimental effect on the en/decoding performance. In the experiment, 16-chip, 40-Gchip/s OC pattern and 2.5-Gb/s DPSK data modulation have been simultaneously generated using a single PM. The 2.5-Gb/s DPSK data have been successfully decoded and transmitted over 34 km fiber with BER <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> for five OCs. The proposed scheme employs similar setup for transmitter and receiver, exhibiting the potential to simplify the architecture of the whole system, and improve the flexibility and confidentiality of OCDMA system.

Impact of various noises on maximum reach in broadband light source based high-capacity WDM passive optical networks

We investigated the effects of various noises on the performance of extended-reach WDM-PONs based on broadband light sources (BLSs). The maximum reach in BLS based WDM-PONs was analyzed by taking into account the impact of relative intensity noise of optical source, chromatic dispersion of transmission fiber and in-band crosstalk. We confirmed that the system's performance of BLS based WDM-PONs would be strongly dependent on the equivalent optical bandwidth of optical source. From the results, we found that the maximum reach in BLS based WDM-PONs operating at 1.25 Gb/s could be increased to be approximately 70 km of single-mode fiber as long as the chirp and relative intensity noise (RIN) of optical source would be suppressed properly.

Analysis of maximum reach in WDM PON architecture based on distributed Raman amplification and pump recycling technique

We analyze the performance of bidirectional WDM PON architecture which utilizes distributed Raman amplification and pump recycling technique. The maximum reach at data rates of 622 Mb/s and 1.25 Gb/s in the proposed WDM PON architecture is calculated by taking into account the effects of power budget, chromatic dispersion of transmission fiber, and Raman amplification-induced noises with a given amount of Raman pump power. From the result, the maximum reach for 622 Mb/s and 1.25 Gb/s signal transmission is calculated to be 65 km and 60 km with a Raman pump power of 700 mW, respectively. We also find that the calculated results agree well with the experimental results which were reported previously.

Effect of transmission fiber on chaos communication system based on erbium-doped fiber ring laser

We report a numerical study on the deterioration of eye opening penalty (EOP) and bit error rate (BER) of the received message from a communication system based on chaos generated in erbium-doped fiber ring laser (EDFRL) under the influence of amplifier noise, transmission fiber dispersion, and nonlinearity. Three different transmission fibers with practical parameters are considered. We find that in order to realize high-bit-rate chaotic communication, the residual fiber dispersion should be kept as small as possible. Furthermore, if the transmission power is optimized to balance the effect of amplifier noise and fiber nonlinearity, a message with bit rate on the order of several gigabits/second can be transmitted over hundreds of kilometers with acceptable BER deterioration. A comparison between open- and closed-loop structures is also conducted. Moreover, we find that the maximum bit rate is limited by the bandwidth of the chaos determined by the nonlinearity of the fiber ring laser and the laser configuration. It is possible to optimize these parameters to provide the maximum chaos bandwidth and hence the maximum message bit rate.

Ultralong lightwave systems with incomplete dispersion compensations

Ultralong nonreturn-to-zero optical transmission systems with incomplete dispersion compensations are studied. The dispersion of transmission fiber is periodically under- or overcompensated. Postdispersion compensation (PDC) at the receiver is used to compensate for the residual dispersion caused by incomplete compensation and to tailor the signal pulse shape. Formulas estimating the change of pulse width in the absence of amplifier noise during signal transmission and after PDC are given. During signal transmission, pulse width may be compressed or broadened by the combined effect of the dispersion and self-phase modulation (SPM). The change of pulse width nearly increases with the square of the distance during signal transmission. With amplifier noise, system performance evaluated by Q factor is studied. Several types of transmission fibers are considered. The Q factor can be significantly improved by proper PDC. Signal pulse is compressed when PDC is optimized. The characteristics of the maximum Q factor and the residual dispersion are studied, in which PDC is optimized. The results show that to achieve the best system performance, fiber dispersion should be undercompensated for positive dispersion parameter and overcompensated for negative dispersion parameter. The optimal fiber dispersion lies in the range from 4 to 10 ps/km/nm for the considered systems, and the optimal ratio of residual dispersion and fiber dispersion is about 1%.

Bi-end dispersion compensation for ultralong optical communication system

Bi-end dispersion compensation (DC) for ultralong nonreturn-to-zero (NRZ) optical transmission system is studied. Both the loss and dispersion of the transmission fiber are periodically compensated. Two dispersive elements are placed at the input and output ends of a compensation period, respectively, to compensate for fiber dispersion. The pulse compression owing to self-phase modulation (SPM) can be adjusted by the compensation ratios of the dispersive elements at the two ends of a compensation period. Therefore, the pulse compression can be optimized and the system performance can be improved to compare with the system with either pre- or postdispersion compensation. The rules to design the system are considered. The transmission system of 10-Gb/s bit rate, 9000-km transmission distance, and 100-km compensation period is taken as an example. The second-order fiber dispersion is assumed to be completely compensated. Wave equation is numerically solved to study the system performance which is represented by Q factor. The relations of several system parameters and Q factor are studied. The system parameters include the compensation ratios of the dispersive elements at the two ends of a compensation period, dispersion of transmission fiber, signal power, and the compensation ratios of third-order fiber dispersion. If the third-order fiber dispersion cannot be completely compensated, it is found that one can use a higher signal power to improve the system performance.

Prechirp technique as a linear dispersion compensation for ultrahigh-speed long-span intensity modulation directed detection optical communication systems

Prechirp technique, as a linear dispersion compensation for intensity modulation direct detection (IM-DD) optical transmission systems, has been investigated theoretically and experimentally. This technique is based on a predistortion technique in an optical transmitter. Implementation to the ordinary IM-DD optical transmitter, which uses an external intensity modulator, is easily realized merely by adding a small injection current modulation to a semiconductor laser diode, allowable optical transmission fiber dispersion will be more than doubled with this technique, modified prechirp technique, which utilizes a time division superimposing prechirped bit streams, has also been investigated to achieve greater dispersion compensation capability. >

A new design arrangement of transmission fiber dispersion for suppressing nonlinear degradation in long-distance optical transmission systems with optical repeater amplifiers

The invention of the erbium-doped fiber amplifier has opened the possibility of constructing long-distance optical transmission systems with 1.5-mm zero-dispersion wavelength shifted fibers. In such systems, nonlinear degradation due to four-wave mixing and self-phase modulation strictly limits the total span of systems and the length of the optical repeater spacing. There are proposals to use slightly normal group velocity dispersion fibers (D<0) through the whole system or to arrange the various sections of different dispersion fiber in the cable for suppressing these nonlinearities. However, these strategies are not so easily applied in real systems. A new arrangement of transmission fiber dispersion which easily suppresses these nonlinearities so as to expand the total span of the system or to increase the repeater spacings is proposed. The feasibility of the proposal has been experimentally confirmed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Prechirp technique for dispersion compensation for a high-speed long-span transmission

Dispersion compensation by the prechirp technique is theoretically investigated, and experimental results are discussed. An improvement of more than two times was observed for dispersion-limited transmission lengths in 5-Gb/s, 150-km and 10-Gb/s, 50-km transmission with a semiconductor electroabsorption external modulator and a normal fiber. An allowable transmission fiber dispersion of 10000 ps/nm and 2.5 Gb/s is estimated by computer simulation with this prechirp technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>