Long-distance Soliton Transmission Research Articles

Long-distance soliton transmission through ultralong fiber lasers

We present the first experimental demonstration (to our knowledge) of long-distance unperturbed fundamental optical soliton transmission in conventional single-mode optical fiber. The virtual transparency in the fiber required for soliton transmission, over 15 complete periods, was achieved by using an ultralong Raman fiber laser amplification scheme. Optical soliton pulse duration, pulse bandwidth, and peak intensity are shown to remain constant along the transmission length. Frequency-resolved optical gating spectrograms and numerical simulations confirm the observed optical soliton dynamics.

Optical Solitons in Fibers for Communication Systems

A brief history of attempts to use solitons for optical fiber communications and of the technical developments toward making soliton transmission practical is reviewed. The main problems affecting long-distance soliton transmission, as well as techniques to solve them, are described. Recent developments concerning the use of dispersion management and some of the remarkable properties of dispersion managed solitons are also discussed.

Design of InGaAsP multiple quantum-well Fabry-Perot modulators for soliton control

The use of synchronous optical modulators is effective in reducing the pulse timing jitter in long-distance soliton transmission. The inherently polarization-insensitive characteristics of the Fabry-Perot multiple quantum-well (MQW) electroabsorption modulator make it a potentially suitable device for this application. We investigate the intensity and phase modulation characteristics of symmetric and asymmetric Fabry-Perot modulators, and show that, by positioning the resonant wavelength <30 nm away from the exciton absorption peak to obtain negative chirp operation, both configurations can be used to successfully reduce timing jitter in a 20 Gb/s soliton system.

Performance evaluation of a long-distance soliton transmission system with optical source noise

The effect of carrier phase noise on arrival time jitter, bit error rate (BER) and dispersion tolerance is analyzed. The performance of a soliton system with optical source noise in the presence of fixed filters, synchronous modulators, optical phase conjugation, and dispersion management is also evaluated. The existence of carrier phase noise increases time jitter and BER, reduces dispersion tolerance, and changes the optimum position of optical phase conjugator. With one of the above transmission controls and proper parameter selection, one can still find a dispersion tolerance where BER is less than 10 −9 in a high-speed long-distance soliton system even with carrier linewidth.

The effects of carrier phase noise on long-distance soliton transmission system

The effects of carrier phase noise on the performance of long-distance soliton transmission system are analyzed. The arrival time jitter due to carrier linewidth is derived with initial value perturbation method, optical phase conjugation is used to suppress timing jitter, and a optimum design theory is given for long-distance soliton transmission system with optical source noise. Carrier phase noise increases the total timing jitter, changes the optimum position of conjugator, the optimum dispersion value and choosing range of dispersion in the transmission link. But an optimum dispersion range can still be found for 10 Gb/s, 10000 km soliton system even with optical source noise.

Dispersion-allocated soliton technology with long amplifier spacing and long distance

In order to realize long amplifier spacing, long-distance soliton transmission, dispersion-allocated fiber was optimized. Dispersion-decreasing-allocated fiber is favorable to transmit stable solitons over long distances. Fiber loss plays an important role in stable soliton transmission with the dispersion-allocated fibers. In order to realize soliton bidirectional transmission, symmetrical configuration of the dispersion-allocated fiber within an amplifier spacing must be designed, so the dispersion-decreasing-allocated fiber is not favorable to soliton bidirectional transmission.

A novel sliding-frequency guiding filter for soliton transmission

The Gordon-Haus effect can be substantially reduced by using the sliding-frequency guiding filters. However, a long-distance (such as transoceanic) soliton transmission system may require hundreds of these filters operating at slightly different wavelengths from each other. Thus, it would be difficult in practice to produce and install such a large number of these filters all operating at different wavelengths. In this letter, we demonstrate a novel sliding-frequency guiding filter which automatically offsets its peak wavelength from the wavelength of soliton pulses. Thus, these filters can guide the soliton pulses to slightly different wavelengths continuously, although they are made to be identical.

Solitons in optical communications

The history of the proposal that solitons be used for optical fiber communications and of the technical developments toward making soliton transmission practical is reviewed. The causes of bit errors in long-distance soliton transmission are presented and the methods for reducing them are described. A perturbation theory suited for soliton analysis is developed. Current status and future prospects of long-distance repeaterless fiber communications are stated.

Recent Progress in Long-Distance Soliton Communication.

Current progress on long-distance soliton transmission technologies is summarized, in which the use of erbium-doped fiber amplifiers has been a major breakthrough for the soliton communication. Techniques which can send solitons over unlimited distance are described, in which soliton control in time and frequency domains plays an important role as an optical 3R repeater. Finally, a new soliton transmission technique which employs dispersion allocation is described, which enables us to bring the soliton transmission into a developmental stage.

Long-distance soliton transmission with a nonlinear twin-core fiber

We numerically demonstrate soliton transmission over long distances in a new regime in which the soliton evolves in a two-core fiber over many dispersion lengths between successive amplifications. Shorter pulses than those transmitted in the average soliton dynamics regime are predicted, while a significant drift of the soliton mean frequency owing to the soliton self-frequency shift is observed and controlled by appropriate gain and loss parameters.

Reduction of amplified spontaneous emission from a transmitted soliton signal using a nonlinear amplifying loop mirror and a nonlinear optical loop mirror

The amplified spontaneous emission (ASE) from concatenated erbium-doped fiber amplifiers (EDFA's) in a 10 Gb/s 500 km soliton transmission system has been successfully reduced through the use of a nonlinear amplifying-loop mirror (NALM). By using the NALM the ratio of the signal peak to ASE was improved from 17.4:1 to 24.9:1. A similar result was obtained for a nonlinear optical-loop mirror (NOLM) with a 6:4 directional coupler. It is noted that pulse transmission through the NALM or the NOLM gives rise to frequency chirp, which means that these fiber devices are not appropriate for use at the midpoint of a long-distance soliton transmission. The chirp characteristics caused by the NALM were also described and the optimum condition for nonlinear switching was obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Long-distance soliton transmission with filtering

Filters spaced periodically along a transoceanic cable can affect soliton propagation by changing the random walk-off, the amplitude fluctuations, and the force of attraction and repulsion between solitons. The permissible power range for soliton transmission is significantly increased.

Reduction and suppression of soliton interactions by bandpass filters

We compare a perturbative analysis with a numerical analysis of the reduction of soliton interactions in a long-distance soliton transmission system with lumped amplifiers and filters. We find that soliton interactions may be suppressed by sliding the center frequency of the filters along the line, as devised by Mollenauer et al. [Opt. Lett. 17, 1575 (1992)].

Ultra-short pulse generation for soliton transmission using electroabsorption modulators

Abstract A simple and stable technique of optical short pulse generation for soliton transmission based on external modulation is reviewe.By using nonlinearity of absorption characteristics of an electroabsorption modulator, ultra-short optical pulse trains having a shape close to sech2 shape can be generated just with sinusoidal modulation, without ultra-short driving pulses and ultra-broad bandwidth of the modulator. The pulse width and the repetition rate can be varied by changing the electrical driving conditions. Quasi-transform-limited optical pulseswith time-bandwidth product of 0.32 were successfully generated by the sinusoidally driven InGaAsP electroabsorption modulator with up to 20 GHz repetition rate. An application of a λ/4-shifted DFB laser-electroabsorption modulator integrated light source to a single-chip soliton source is also described. The high quality of the modulator-generator pulses has been proven by long-distance soliton transmission over 6400 km at 2.5 Gb/s using a recirculating...

Limits of long-distance soliton transmission in optical fibers with laser diodes as pulse sources

To employ soliton transmission in practical optical fiber communication systems, it is desired that semiconductor laser diodes (LDs) can be used as the optical soliton sources. The authors show that, when pulses generated by LDs are used for soliton transmission, the large frequency noise of LDs causes jitter in soliton arrival times, and makes a limit on the bit-rate distance product of the soliton transmission system. This limit is shown to be proportional to the square root of the output peak power of the pulses generated by LDs, and has a value of 12800 GHz-km for pulses with an output peak power of 10 mW and a duration of 20 ps. >

Soliton transmission control

The Gordon-Haus limit of long-distance soliton transmission can be partially overcome through the use of linear filters in each amplifier stage. New limits are derived, and they show the possibility of increased bit rates and/or distances of propagation.