A design method is proposed that yields the optimum remote pre-amplifier (RPRA) parameters considering cable repair, the results of include increased cable loss and insertion position uncertainty. The optimum RPRA location is given by the intersection point of optical SNR (OSNR) vs. RPRA location curves in two cases; the total cable repair loss is assumed to be inserted at the transmitter end and at the receiver end. This RPRA parameter gives the maximum OSNR in the worst loss insertion case by cable repair.

Methodologies for more efficient Raman amplification and a more suitable modulation format for 40 Gbit/s WDM unrepeatered transmission are investigated. Management of the fiber effective area is proposed to realize low noise distributed Raman amplification. An Aeff management technique in which low-Aeff fiber is located in a median section instead of the last section, was confirmed numerically and experimentally to improve the OSNR and Q-factor. Carrier-suppressed-return-to-zero (CS-RZ) modulation has the advantage of reducing fiber-nonlinearity effects and permitting denser multiplexing of the wavelengths. 40 Gbit/s 32-channel unrepeatered WDM transmission over 202 km was demonstrated employing the proposed methodologies.

The term pilot pollution in IS-95 CDMA systems is used to indicate that a large number of equally strong pilot signals is present. Those pilots compete with each other to become the serving one and this causes a very high rotation of pilot leadership at the mobile station. As a consequence, the signaling rate on the traffic channel increases, thus degrading the call quality. We present a method of alleviating the pilot pollution problem by means of repeaters. Simulation studies have been carried out on an actual CDMA network suffering from pilot pollution and the results have been verified by field trials. They indicate that repeaters can effectively improve call quality by altering the spacial distribution of pilot signal strength.

Since the inception of optical networking, a goal has been to create an all-optical network. The rapid breakthrough for WDM in point to point links has brought this prospect considerably closer, however, at the same time, questions regarding the scalability of the all-optical network remain. In this paper, we review our recent research in this area, partly performed within the European Union project METON (METropolitan Optical Network), and discuss the all-optical approach and different optoelectronic alternatives, mainly of the 2R (reamplify and reshape) type.

Since the inception of optical networking, a goal has been to create an all-optical network. The rapid breakthrough for WDM in point to point links has brought this prospect considerably closer, however, at the same time, questions regarding the scalability of the all-optical network remain. In this paper, we review our recent research in this area, partly performed within the European Union project METON (METropolitan Optical Network), and discuss the all-optical approach and different optoelectronic alternatives, mainly of the 2R (reamplify and reshape) type.

Repeaterless transmission system design employing remote pumping in a single fiber is clarified. The design is aimed to realize cost effective submarine transmission systems with easy maintenance. Remote pumping in a single fiber can extend repeaterless transmission distance without decreasing the system capacity per cable. It is applicable for high-count-fiber cable such as the 100-fiber submarine cable already developed. A simple but effective system configuration is presented that uses remote pumping from receiver end; both remote-pre erbium-doped fiber (EDF) amplification and backward pumping Raman amplification are employed. Stable transmission can be obtained without optical isolators, therefore the optical time domain reflectometry (OTDR) method is supported by this system. Three fiber configurations, which consist of dispersion shifted fiber (DSF), pure silica core fiber (PSCF) and a combination of DSF and PSCF, are examined to compare system performance. Remote-pre EDF is optimized in terms of length and location from receiver end by optical SNR (OSNR) calculations. Maximum signal output power is also determined through a waveform simulation based on the split-step Fourier method, in order to avoid waveform distortion caused by the combined effect of self-phase modulation (SPM) and group velocity dispersion (GVD). Through these calculations and simulations, we confirm the proposed repeaterless transmission system performance of 600Mbit/s-451 km with PSCF, 2. 5 Gbit/s-407 km with DSF + PSCF, and 10 Gbit/s-376 km with DSF+PSCF, which include system margin.

This paper proposes a new method for estimating route outage probability in non-regenerative repeater digital microwave radio systems. In this method, the route outage probability is estimated by various means, including path correlation of fading occurrence and C/N degradation corresponding to the number of non-regenerative repeater stations with and without demodulator devices. In the conventional method, the path correlation is treated as 0 and the C/N degradation is taken as a constant value on each path. To confirm the proposed method's effectiveness, a field test is carried out in which 16QAM signals pass through two non-regenerative repeater stations. The results obtained are in good agreement with the estimated outage probability.

This paper proposed a fault localization and supervisory (SV) channel implementation for linear-repeaters (L-Reps) employing optical line amplifiers. In order to successfully introduce L-Reps into a Synchronous Digital Hierarchy (SDH)/Synchronous Optical Network (SONET)-based networks in a smooth, orderly fashion, layering of repeater section and supervisory system design must be taken into consideration. There supervisory techniques, such as linking analog-based and digital-based information, a precedence of digital-based information and an upstream precedence, for locating faulty L-Rep sections are proposed taking into consideration the difference in monitoring capabilities between L-Reps and regenerating-type repeaters (R-Reps). Furthermore, a linear repeater supervisory (LSV) channel configuration for L-Reps is also proposed. Finally, an SV system established in a prototype SDH-based 10-Gbit/s optical transmission system is briefly described.

This paper proposes that a combination of pre-chirping and dispersion compensation is effective in suppressing the waveform distortion due to the self-phase modulation and the group-velocity dispersion in 10 Gb/s repeaterless transmission using 1.3-µm zero-dispersion single-mode fibers (SMF) operating at a wavelength of 1.55µm. The following results were obtained through simulation. 1) Setting the α-parameter of a LiNbO3 optical modulator negative (α1.0) gives a large tolerance of the launched power Pin. 2) For 90-km SMF transmission, the maximum Pin is obtained when the dispersion compensation ratio β is from 50% to 70%. 3) For the allowable β as a function of the transmission distance when a dispersion compensator is located in the receiver (post-compensation scheme), the lower limit of β is determined by the constant residual dispersion value, which agrees well with the dispersion tolerance without dispersion compensation. Our 90-km SMF transmission experiments using a LiNbO3 optical modulator and a dispersion compensating fiber (DCF) confirmed the simulation results regarding the optimum value of β and the large tolerance of the fiber launched power. Based on the above investigations, we achieved a 10-Gb/s repeaterless 140-km SMF transmission with α1.0 and post-compensation.